WO2009062038A2 - Method for performing electrostatically induced redox chemistry on a dielectric surface - Google Patents

Abstract

A method for inducing a redox reaction is provided which comprises (a) providing first and second distinct dielectric materials; (b) imparting an electrostatic charge to the first dielectric material by contacting it with the second dielectric material; and (c) inducing a chemical reaction by immersing the first dielectric material in a solution.

Description

METHOD FOR PERFORMING ELECTROSTATICALLY INDUCED REDOX CHEMISTRY ON A DIELECTRIC SURFACE

Technical Field of the Invention

The present disclosure relates generally to redox chemistry, and more specifically to methods for performing electrostatically induced chemistry on a dielectric surface.

Background Art

It is well known that electrostatic charges may be produced by bringing two dissimilar dielectric materials, such as glass and silk, into contact with each other and then separating them. However, although this phenomenon has been known for thousands of years, the nature of the charges involved, and the mechanisms that govern them, have been poorly understood. Consequently, to date, this phenomenon has persisted primarily as a laboratory curiosity having few practical applications.

Disclosure of the Invention

In one aspect, a method for inducing a redox reaction is provided which comprises (a) providing first and second distinct dielectric materials; (b) imparting an electrostatic charge to the first dielectric material by contacting it with the second dielectric material; and (c) utilizing the electrostatic charge to induce a chemical reaction.

In another aspect, a method for inducing a redox reaction is provided which comprises (a) providing first and second distinct dielectric materials; (b) imparting an electrostatic charge to the first dielectric material by contacting it with the second dielectric material; and (c) inducing a chemical reaction by immersing the first dielectric material in a solution.

In a further aspect, a method for plating a metal on a dielectric material is provided which comprises (a) providing a first dielectric material; (b) imparting an electrostatic charge to the first dielectric material; and (c) immersing the first dielectric material in a liquid medium containing metal ions.

In another aspect, a method for generating hydrogen gas is provided which comprises (a) providing a proton-containing solution; (b) providing a first dielectric material; (c) imparting an electrostatic charge to the first dielectric material; and (d) generating hydrogen gas by contacting the charged first dielectric material with the proton-containing solution. In yet another aspect, the present invention provides a method of generating light by using electrochemical (faradaic) reactions to produce highly reactive species at the surface of an electrode by providing a first dielectric material and imparting an electrostatic charge to the first dielectric material and inducing a chemical reaction by immersing the first dielectric material in a liquid medium.

Description of the Drawings

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

FIGURE 1 is an energy dispersive X-ray spectroscopy graph of the copper film on polytetrafluoroethylene.

FIGURE 2 is a graph of the optical absorbance of a CuSO₄ solution before (top) and after (bottom) contact with charged polytetrafluoroethylene.

FIGURE 3 is a graph of a cyclic voltammogram with a glass-encased Pt ultramicroelectrode in water containing Fe(CN)₆ ^3- and KCl.

FIGURE 4 is a plot of the relative electrostatic chemiluminescence intensity as a function of time.

FIGURE 5 is a schematic of a reaction mechanism for electrostatic chemiluminescence.

FIGURE 6 is a plot of the relative electrostatic chemiluminescence intensity generated by charged polytetrafluoroethylene as a function OfNa₂S₂O₈ concentration. FIGURE 7 is a plot of the reproducibility of charged polytetrafluoroethylene generated chemiluminescence .

FIGURE 8 is a graph of the electrostatic charge on Teflon surface.

FIGURES 9a-9d are images of the interaction of an unintentionally treated TEFLON® surface.

FIGURE 10 is a cyclic voltammogram before and after the contact with PMMA-rubbed PE disks.

FIGURE 11 is a graph of the relative intensity of chemiluminescence as a function of time.

FIGURES 12a-12c are optical images showing Cu deposited on the surface.

Description of the Invention

It has now been found that the electrostatic charges produced through the contact of dissimilar dielectric materials may be effectively utilized to carry out a variety of useful chemical reactions. The identity of the charge carriers (electrons, holes or ions) and the absolute density of the charges on a surface or interface may be precisely determined based on the mechanisms of the relevant chemical reactions and the concentration change of reactant or product, respectively. Consequently, this approach provides a means for performing high precision redox chemistry on dielectric materials with a single electrode, and without the need for counter and reference electrodes or an external power supply.

The methodologies disclosed herein have many potential applications. These applications include, but are not limited to, their use in various chemical reactions such as hydrogen generation reactions, metal plating reactions, and chemiluminescent (CL) reactions. The methodologies disclosed herein have applications in various fields, including clinical analyses, chemical plating techniques, and the calibration of charges and energy levels on dielectric materials.

In comparison to existing methodologies known to the art, the methodologies disclosed herein offer a new approach for synthesizing many chemical compositions and for implementing a variety of useful chemical reactions. In many cases, desired products may be synthesized by these routes without the formation of by-products. By contrast, most synthetic techniques currently known to the art unavoidably yield unwanted, and sometimes harmful, by-products which must be separated from the desired product through additional and costly procedures. The methodologies disclosed herein also offer a means for determining the identity of electrostatic charges, something not possible with conventional techniques. In particular, the methodologies disclosed herein provide a method for accurately determining the absolute charge (electron or hole) density on dielectric surfaces. Previously, such charge densities could only be estimated using conventional technologies.

The methodologies disclosed herein also offer an unprecedented means for effecting surface redox chemistry. This type of redox chemistry has applications in fields as diverse as nanotechnology and clinical analysis (e.g., CL reactions). In many cases, applications in these fields are constrained by the spacing limitations of the electrochemical processes currently available.

The methodologies disclosed herein also offer a means for plating metals onto dielectric surfaces (including polymeric surfaces) which have been intentionally charged, thus inducing a charge transfer chemical reaction in solution. By contrast, present technologies typically require such substrates to be maintained in a vacuum (for sublimation processes) or air (for spin coating processes), and thus do not permit the use of wet chemistries.

The methodologies and devices disclosed herein may be further understood with respect to the following particular, non-limiting examples.

EXAMPLE 1. Hydrogen generation. A series of experiments were carried out involving the immersion of charged TEFLON^® polytetrafluoroethylene substrates into an acidic solution to determine the effect of the immersion on pH and on the formation of hydrogen gas. As part of the experimental methodology, 37 pieces of Teflon septa (12 mm in diameter) were placed on a LUCITE^® polymethylmethacrylate plate, were rubbed with polymethylmethacrylate disks, and were then briefly and consecutively immersed into 3 mL of a 0.1 mM HCl solution. The solution pH was found to increase from 4 (before the immersion) to 6.2 (after the immersion).

Three portions of polytetrafluoroethylene tape were then charged using the foregoing methodology, and were consecutively immersed in 3 mL of an HCl solution having an initial pH of 3.1. The pH of the solution was observed to change in succession after the immersions from 3.1 to 4.1, 5.2 and 7.3.

By itself, the foregoing result does not conclusively establish that the negative charges present on the tape were attributable to electrons rather than being ionic in nature. Indeed, it is to be noted that H⁺ could adsorb onto charged polytetrafluoroethylene. Similarly, it is conceivable that adsorbed anions, such as hydroxide anions (OH-), could be transferred to the surface during charging, and could subsequently leach into the solution to cause a pH change. However, UHV mass spectrometry has revealed the presence of hydrogen in the gas phase. Since there is no evident means by which adsorbed ions can generate hydrogen gas, the presence of hydrogen gas strongly suggests that the charge carriers on the polytetrafluoroethylene tape are electrons.

As part of the experimental procedure, D₂O was used and samples were prepared inside a glove box. Charged polytetrafluoroethylene tape was introduced through a TEFLON^® tube into a glass reactor with 50 mL D₂O solution containing 1.5 mL DCl (35%). The reactor, which was equipped with a metal joint, was then connected to a stainless steel tube sealed with a valve. Note that some tape stayed above the DCl solution; careful shaking and tilting of the reactor was necessary to bring the tape into full contact with the solution.

The reactor was then removed and connected to a UHV system (1.5^χ 10^~9 Torr). Liquid nitrogen was used to freeze the reactor solution and the gas was first introduced into a sample transfer chamber before it reached the main UHV chamber. A clear D₂ peak appeared in the mass spectrum. By contrast, a control carried out under the same conditions without contact to charged polytetrafluoroethylene (that is, in the control experiment, the step of rubbing the polytetrafluoroethylene with polymethylmethacrylate disks was omitted) showed only a flat baseline.

Further verification of the presence of hydrogen gas was provided through potentiometric measurements. In these measurements, a Pt wire was touched to a charged polytetrafluoroethylene surface immersed into a 1 M HCl solution, and the potential between the Pt wire and a saturated calomel electrode (SCE) was determined. This potential was found to be about -236 mV, which is consistent with the expected value if H₂ on the polytetrafluoroethylene surface fixed the potential of the Pt wire.

The occurrence of hydrogen generation in the experimental procedure strongly suggests that energetic electrons were present on the polytetrafluoroethylene surface and caused a reduction process. Such a process should be faradaic in nature as in conventional electrochemistry:

2H⁺ + 2e → H₂ (REACTION I)

In this process, unlike comparable processes which utilize a typical dual-electrode electrochemical cell, the solution becomes negatively charged with excess anions. If the entire change in pH can be ascribed to proton reduction, then the observed change in pH may be used as an accurate means for determining the electrostatic charge density on a dielectric substrate.

Indeed, when the total number of H⁺ ions removed from the solution is divided by the geometric polytetrafluoroethylene surface area involved in the treatment, an average electron density of the order of 10¹⁵/cm² was found. This was obviously an overestimation, since the actual surface area of the rubbed polytetrafluoroethylene must be significantly larger than the apparent one. Nevertheless, it still appears to be a higher charge density by contact electrification than that usually reported on a polymer surface. The skilled artisan knows that the present invention depends on surface area and the magnitude of the effect on a per gram basis can greatly increase by using nanoparticles of dielectrics.

It is not clear if electrons at such a high density have some mobility, even in an insulator such as polytetrafluoroethylene, especially considering that charges distributed more than 10 μm deep into the bulk on some polymers (including polytetrafluoroethylene) have been found after electron beam deposition. Note that the determination of the true charge density is a longstanding problem in contact electrification, since it is very difficult to access all areas on a surface that is rough or porous. Soft rubber and mercury have been used to increase the contact area for more accurate measurements. Indeed, mercury contact achieved elementary charge densities on some polymers up to 10¹²/cm², significantly higher than that produced with a conventional rigid solid contact. This density, however, was still over 10 times smaller than that obtained on an atomically smooth mica surface where a good contact could be made.

EXAMPLE 2. Metal deposition. The present invention also provides faradaic metal electrodeposition with charged dielectric materials. FIGURE 1 is an energy dispersive X-ray spectroscopy graph of the copper film on polytetrafluoroethylene that was rubbed with polymethylmethacrylate and then briefly immersed into a ImM CuSO₄ solution. The EDS image includes Cu peak 2 seen on each spot (not shown) examined and no Cu was noted on uncharged polytetrafluoroethylene. The insert is an optical microscope image of a copper film on polytetrafluoroethylene that was rubbed with polymethylmethacrylate and then briefly immersed into a ImM CuSO₄ solution, causing the reaction Cu²⁺ + 2e → Cu and a small amount of Cu²⁺ was reduced and deposited as Cu metal on the surface leaving the solution negatively charged with excess SO₄ ^2- ions. A series of studies was conducted to determine the possibility of faradaic metal electrodeposition using charged dielectric materials in accordance with the methodologies described herein. When a charged polytetrafluoroethylene rod was briefly immersed in an aqueous solution containing 1 mM CuSO₄, small amounts of Cu²⁺ were reduced and deposited as Cu metal on the surface (see FIGURE 1). The Cu deposits appeared only on a few isolated areas where the deposited Cu atoms might aggregate.

The polytetrafluoroethylene surface was carefully examined before and after the deposition so that Cu spots could be correctly identified as confirmed by energy dispersive X-ray spectroscopy (EDS) (see FIGURE 1). A Cu peak in EDS was seen on each spot examined. By contrast, no Cu was noted on control samples of uncharged polytetrafluoroethylenewhich had been immersed in the CuSO₄ solution. The F and C peaks in FIGURE 1 originate from the area beneath the Cu spot that was thin enough for the electron beam to penetrate, since the scanned area for the EDS was smaller than the Cu spot. The peak height of F relative to C appeared much larger in EDS scans obtained on bare TEFLON® compared to the Cu deposited one, suggesting that F was possibly deficient beneath the Cu spot. The O peak shown in FIGURE 1 suggests that the Cu in the analyzed portion of the substrate might be partially oxidized. However, a small O peak in EDS was also seen with a bare polytetrafluoroethylene surface.

When a small drop of 1 mM CuSO₄ was intentionally placed on polytetrafluoroethylene and dried, the EDS obtained from that spot showed strong S and O peaks in addition to Cu, F and C, confirming that the Cu film described above was the result of Cu²⁺ reduction by electrons on polytetrafluoroethylene. A hydroxide adsorption mechanism could also be excluded here since the expected product of Cu(OH)₂ would dissolve into solution, while the observed Cu deposits on polytetrafluoroethylene did not wash away with water. In addition, the color of Cu(OH)₂ could not be confused with of the sample shown in FIGURE 1.

FIGURE 2 is an optical image of Cu lines formed by electroless deposition on polytetrafluoroethylene. It was also found that the optical absorbance of Cu²⁺ in the solution decreased upon immersion and removal of the polytetrafluoroethylene, as shown in FIGURE 2. The concentration change after polytetrafluoroethylene contact corresponded to an average charge density of about 8^χ10¹⁴/cm² (geometric area), which is slightly smaller than, but of the same order of magnitude as, the charge density calculated from the pH change. It is also possible that some H⁺ reduction occurs in the experimental process and consumes a fraction of the available electrons.

It has also been found that the Cu deposition effect may be amplified by using the available charge on polytetrafluoroethylene in an electroless deposition mode. This is demonstrated by the following experiment. After a polytetrafluoroethylene surface was rubbed with the edge of a polymethylmethacrylate rod or machined with a cutting tool in a lathe in a pattern of lines, it was briefly dipped in a saturated PdCl₂ solution. This produced Pd metal particles that appeared dark and could act as catalysts for Cu deposition. It was then washed and immersed into a Cu electroless plating bath containing CuSO₄, KNaC₄H₄O₆, NaOH, and HCHO. Cu was deposited on polytetrafluoroethylene in the same pattern as shown in the insert of FIGURE 2. Although this approach was not explored in detail, it suggests that one can charge the polytetrafluoroethylene surface in a designed pattern and then metallize it to form a desired structure, polytetrafluoroethylene has a low dielectric constant and good thermal stability, which are desirable properties for microelectronic applications and other end uses. Similar metal deposition occurred on polytetrafluoroethylene after being rubbed with a KleenGuard Powder- Free Blue Nitrile Glove.

EXAMPLE 3. Reduction of Fe(CN)₆ ^3- to Fe(CN)₆ ^4-. To further verify if charges on polytetrafluoroethylene were indeed electrons instead of ions, charged polytetrafluoroethylene was immersed into a solution containing Fe(CN)₆ ^3-. FIGURE 3 is a graph of a cyclic voltammogram with a glass-encased Pt ultramicroelectrode in water containing Fe(CN)₆ ^{3 -} and NaCl before (top) and after (bottom) the immersion of polytetrafluoroethylene tapes charged with polymethylmethacrylate by rubbing. The formation Of Fe(CN)₆ ^4- in the bulk solution would provide strong evidence of a redox reaction. As shown in FIGURE 3, a single steady state current plateau corresponding to Fe(CN)₆ ^3- appeared in the cyclic voltammogram for the initial solution. However, the height of the plateau decreased, and an anodic one appeared, after the solution had contacted charged polytetrafluoroethylene tape. This new plateau corresponded to Fe(CN)₆ ^4- in the solution, and clearly indicated that the reduction reaction of Fe(CN)₆ ^3- to Fe(CN)₆ ^4- took place on charged polytetrafluoroethylene. Note that some Fe(CN)₆ ^4- might also adsorb on the Teflon, since the current for Fe(CN)₆ ^4- oxidation appears smaller than the current decrease in Fe(CN)₆ ^3- reduction (see FIGURE 3).

In a well controlled experiment, 16 pieces of polytetrafluoroethylene septa (the same as those used for the pH experiment) were charged with polymethylmethacrylate and were then immersed briefly and consecutively into 1 mL of an aqueous solution containing 0.2 mM Fe(CN)₆ ^3- and 0.1 M KCl. The current plateau for Fe(CN)₆ ^3- reduction dropped by 23%. This corresponds to an electron density of 7.7× 10¹⁴/cm² (geometric area) on charged polytetrafluoroethylene septa, assuming 100% reaction efficiency. Such a density is essentially the same as that obtained from Cu deposition. Notably, contacting the solution with uncharged polytetrafluoroethylene never showed production of Fe(CN)₆ ^4-. In all the experiments, more Fe(CN)₆ ^3- molecules were reduced to Fe(CN)₆ ^4- with more charged polytetrafluoroethylene immersion, independent of the shape, size and brand of the polytetrafluoroethylene. This result again suggests that electrons were involved in the charging/discharging process.

EXAMPLE 4. Electrostatic Chemiluminescence (ESCL). Electrogenerated chemiluminescence (ECL) is a method of generating light by using electrochemical (faradaic) reactions to produce highly reactive species at the surface of an electrode. Such species can produce excited states in energetic electron transfer reactions. ECL is a highly sensitive method of determining very low levels of species in solution (e.g., at the pM level) and, hence, of detecting small amounts of charge. ECL is thus well suited to studying electronic charges on insulator surfaces. Indeed, as shown by the experiments described below, use of charged insulators for generating light provides a new and completely different approach to this type of analysis, which we have called electrostatic chemiluminescence (or ESCL).

When a charged polytetrafluoroethylene rod is immersed into an acetonitrile (MeCN)/water (1 :1, v/v) mixture, a transient luminescence at the few nA level was detected with a photomultiplier tube operated under a bias of -750 V (compared to a background level of 0.2 nA). This represents a very low-level discharge or chemiluminescent background process.

A mixture of typical ECL reagents, namely, 0.25 mM tris(2,2'-bipyridine)ruthenium (II) perchlorate [Ru(bpy)3(Clθ4)₂] and 2.5 mM tetra-n-butylammonium peroxydisulfate ((TBA)₂S₂O₈) in MeCN/water was used in the studies. When the charged TEFLON® rod was introduced, a strong ESCL emission was detected, at about the niA level (~10⁶ times higher than background). This emission saturated the detection system. Without wishing to be bound by theory, this emission is ascribed to the well-known ECL process where available electrons on polytetrafluoroethylene reduce Ru(bpy)₃ ²⁺ and S₂O₈ ^2- to generate the light producing species. This process is described in further detail below.

FIGURE 4 is a plot of the relative electrostatic chemiluminescence intensity as a function of time when a charged polytetrafluoroethylene disk at the bottom of a rod was gradually introduced into a MeCN/H₂0 mixture containing S₂O₈ ^2- and Ru(bpy)₃ ²⁺. Notably, when either of these reagents was present in the solution by itself, the luminescence was not above the background level upon charged polytetrafluoroethylene introduction. In order to monitor the process of ESCL, the charged polytetrafluoroethylene rod was slowly and manually introduced into the mixture, section by section, so that the luminescence could be measured at a lower level over a longer period of time as shown in FIGURE 5. In this case, a fraction of the charged polytetrafluoroethylene rod was first immersed into the mixture and held there for a moment (point 1 in FIGURE 4), upon which the ESCL quickly increased to over 1 μA and then dropped rapidly as electrons were consumed. Before the ESCL decayed to baseline, fresh polytetrafluoroethylene was gradually introduced into the solution (point 2) and a near steady state ESCL was seen for about 1 minute.

At point 3, the polytetrafluoroethylene rod was moved more rapidly into the solution, leading to an ESCL spike followed by a slow movement (point 4) and decay. When the rod was moved out of the solution at point 5 in FIGURE 4, the ESCL dropped to baseline, confirming that the detected luminescence was indeed produced by the charges on polytetrafluoroethylene. The ESCL reappeared when a fresh portion of the charged polytetrafluoroethylene was immersed into the solution again (point 6). Such a process could be repeated at points 7 and 8. ESCL was always observed as long as the electrons on the polytetrafluoroethylene were not fully depleted. Finally, polytetrafluoroethylene was removed from the solution (point 9), and the ESCL disappeared.

Because this study was carried out by hand in a dark room, it is difficult to quantify the area of polytetrafluoroethylene rod immersed at the point when each of the above points was recorded. Note that it was the charges on polytetrafluoroethylene rather than simply polytetrafluoroethylene itself that triggered the luminescence, since no ESCL was detected when uncharged or fully discharged polytetrafluoroethylene was immersed into the same solution. Interestingly, similar results had been obtained when Mg powder was introduced into the same system. The identical effect generated from both charged polytetrafluoroethylene and a strong reductant, such as Mg powder, in the same system is clear evidence that the luminescence observed was indeed a result of an electron transfer reaction, rather than a spark from an electrostatic discharge. Such a conclusion was also supported by the fact that both Ru(bpy)3²⁺ and S₂O₈ ^2- must coexist in the MeCN/H₂O mixture to produce a strong luminescence.

FIGURE 5 is a schematic of the reaction mechanism for Electrostatic chemiluminescence based on earlier studies in ECL from this system at metal electrodes. The electronic excited-state of Ru(bpy)3^{2 *}, responsible for luminescence, was produced through an electron transfer reaction from Ru(bpy)₃ ⁺ to SO₄-· radical, generated by reduction of Ru(bpy)₃ ²⁺ and S₂O₈ ^2- on the charged TEFLON® surface. SO₄-· radical could also be made by the reaction

S₂O₈ ^2- + Ru(bpy)₃ ⁺ → Ru(bpy)₃ ²⁺ + SO₄ - + SO₄ ^2- (REACTION 2)

Another path leading to the excited state involves generation of Ru(bpy)₃ ³⁺ by reaction of SO₄-· with Ru(bpy)₃ ²⁺, followed by reaction with Ru(bpy)³⁺. Note that the first steps for the luminescence generation in this system involve the reduction of both reactant Ru(bpy)₃ ²⁺ and co- reactant S₂O₈ ^2- to trigger the series of reactions. Therefore, ESCL obtained here is again consistent with the proposition that the charges on polytetrafluoroethylene were electrons.

FIGURE 6 is a plot of the relative electrostatic chemiluminescence intensity generated by charged polytetrafluoroethylene as a function Of Na₂S₂O₈ concentration in MeCN/H₂O solution (1 :1 by volume) with 1 nM Ru(bpy)₃ ²⁺. In order to study possible analytical applications, the ESCL dependence on the concentrations of Ru(bpy)₃ ²⁺ and S₂O₈ ^2- was studied, similar to previous ECL studies. For 1 nM Ru(bpy)₃ ²⁺, the ESCL increased with S₂O₈ ^2-concentration up to roughly 100 nM (FIGURE 6), and then the emission dropped off sharply, probably due to quenching of Ru(bpy)₃ ^2+* by S₂O₈ ^2- as reported earlier. Similar results were obtained for different concentrations of Ru(bpy)₃ ²⁺ over a range of 5 orders of magnitude.

FIGURE 7 is a plot of the reproducibility of charged polytetrafluoroethylene generated chemiluminescence in MeCN/H₂0 solution (1 :1 by volume) containing 1 nM Ru(bpy)₃ ²⁺ and 100 nM Na₂S₂O₄. TABLE I shows the maximum ESCL response at a given Ru(bpy)₃ ²⁺ concentration from separate measurements for each mixed with 4 to 5 different concentrations of S₂O₈ ^2-. At 0.1 nM Ru(bpy)₃ ²⁺, a clear ESCL signal was seen that was well above the background level. Since the electrostatic charges on the polytetrafluoroethylene surface were generated through rubbing with polymethylmethacrylate, reproducibility of these measurements was a concern. A series of measurements showed that the ESCL intensities did not vary significantly over 10 separate experiments (two different solutions with the same composition and polytetrafluoroethylene rods of the same size and shape, 5 new rubbings for each) with 1 nM Ru(bpy)₃ ²⁺ and 100 nM S₂O₈ ^2- and yielded an averaged signal of 49 nA with a standard deviation of 5.8 nA (see FIGURE 7).

The foregoing experiments demonstrate that electrons are involved in insulator contact electrification. The change in pH, Cu²⁺, or Fe(CN)₆ ^4- concentration due to a faradaic reaction can provide a new approach to measurement of charge on insulators. The calculated charge density, ~10¹⁵ charges/cm² geometric area, even assuming a roughness factor of 10 is still about an order of magnitude larger than that reported for smooth mica charged against silica, and is much larger than previous reports of contact charged polymers. However, the roughness factor corrected value is equivalent to about 16 μC/cm², typical of the electronic charge on metal electrodes (and about that for a monolayer of adsorbate).

ESCL with Charged Lucite. Although the studies described so far have concentrated on Teflon, which is negatively charged, oxidation reactions at the charged Lucite initiated by oxidized centers ("holes") should also be possible. When a Lucite disk (~2 cm in diameter) charged by rubbing with TEFLON® was immersed into a MeCN solution containing 0.2 mM Ru(bpy)3²⁺, presumably producing some of the +3 species by oxidation, no ESCL was detected, as expected, since no reduced species, like Ru(bpy)₃ ⁺ was available for the electron transfer reaction that generates the excited-state Ru(bpy)3^2+*. However, after the same solution had first been exposed to charged TEFLON® tapes, strong ESCL, at the μA level, was then produced following the immersion of charged Lucite. In this case, Ru(bpy)₃ ²⁺ was reduced by electrons on TEFLON® to Ru(bpy)3⁺ , which is stable in MeCN. Upon immersion of the Lucite, Ru(bpy)3³⁺ was formed in an oxidation reaction by positive charges on the Lucite. The +1/+3 annihilation led to the formation of Ru(bpy)₃ ²⁺* through an electron transfer reaction with the generation of ESCL. This is analogous to ECL experiments in which the potential is stepped between potentials where the reduction and oxidation processes occur. To test the remote possibility that the negative charges on TEFLON® were OH and positive charges on Lucite were H⁺ and the conditions near the insulator surfaces promoted electron transfer reactions with adventitious impurities causing reduction and oxidation of Ru(bpy)₃ ²⁺, this system was tested by injecting 1 mL of a 10 M H₂SO₄ solution containing 0.5 mM Ru(bpy)₃ ²⁺ into 1 mL 10 M NaOH. However, no emission was detected, suggesting that an ion transfer mechanism does not produce the ESCL.

Tri-n-propylamine (TPrA) is a known coreactant for the oxidative ECL reaction with Ru(bpy)₃ ²⁺. (see J. B. Noffsinger, N. D. Danielson, Anal. Chem. 59, 865 (1987) and J. K. Leland, M. J. Powell, J. Electrochem. Soc. 137, 3127 (1990)). Upon electrochemical oxidation, TPrA decomposes to form a strongly reducing intermediate that can produce the electron transfer reaction and excited Ru(bpy)3²⁺ at an electrode surface. Therefore, it appeared possible for positively charged Lucite to oxidize both species in a solution to produce ESCL. With a phosphate buffer (pH 7.8) containing 1 mM Ru(bpy)₃ ²⁺ and 50 mM TPrA, the ESCL generated was too weak to be distinguished from the background. However, when the concentration of TPrA was increased to 200 mM and that of Ru(bpy)₃ ²⁺ decreased to 50 μM, ESCL at -100 nA was measured. We suspect that at the higher concentration of Ru(bpy)₃ ²⁺, a proper balance of the two needed intermediate reacting species might not be attained to achieve a reasonable efficiency in ESCL generation, since the total number of charges on Lucite was limited. As expected, when either Ru(bpy)₃ ²⁺ or TPrA alone was used at these concentration levels, no ESCL above the baseline level of a few nA was observed.

The skilled artisan will recognize that the other dielectrics may be used. For example, a representive listing is provided in Journal of Electrostatics 62 (2004) 277-290 which is incorporated by reference. A represent list of other dielectrics that may be used appears in TABLE 2 below. TABLE 2 is a comparison of the published dielectric series (also referred to as triboelectric due to the triboelectric effect which is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated, e.g., through rubbing). In TABLE 2 ref [3] refers to Tribo- series published by Coehn in 1898, ref [4] refers to Hersh and Montgomery published in 1955, ref [5] refers to Henniker published in 1962, ref [6] refers to Adams published in 1987. In the table the polymeric materials that are common to each series are lined up horizontally to provide cross comparisons.

The skilled artisan recognizes that the present invention uses a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). Often the polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties. For example common materials include (listed from most positively charged) human, skin, leather, rabbit's fur, glass, quartz, mica, human hair, Nylon, wool, lead, cat's fur, silk, aluminum, paper (small positive charge), to no charge materials like cotton (no charge), steel (no charge), to negatively charged materials like wood (small negative charge), Lucite, amber, sealing wax, acrylic, polystyrene, rubber balloon, resins, hard rubber, nickel, copper, sulfur, brass, silver, gold, platinum, acetate, Rayon, synthetic rubber, polyester, styrene (Styrofoam), Orion, Saran wrap, polyurethane polyethylene (like scotch tape), polypropylene, vinyl (pvc), silicon, Teflon, silicone rubber, ebonite with most negative charges.

Generally, materials are often listed in order of the polarity of charge separation when they are touched with another object. A material towards the bottom of the series, when touched to a material near the top of the series, will attain a more negative charge, and vice versa. The further away two materials are from each other on the series, the greater the charge transferred. Materials near to each other on the series may not exchange any charge, or may exchange the opposite of what is implied by the list. This depends more on the presence of rubbing, the presence of contaminants or oxides, or upon properties other than on the type of material. Lists vary somewhat as to the exact order of some materials, since the charge also varies for nearby materials.

Furthermore the skilled artisan will recognize that as particle size gets smaller the surface area/volume or surface area/mass ration increases and the present invention depends on surface area. Therefore the magnitude of the effect on a per gram basis can increase greatly the by using nanoparticles of dielectric.

While questions remain about the molecular nature of the charge, their energies and distributions, the electrochemical approach described herein of studying the effects with different redox couples that span a range of potentials, has the possibility of addressing these questions. A table based on reducing/oxidizing power of electrostatic charges on different insulators may then be constructed. Such an approach may also find applications as a new type of redox chemistry, equivalent to "single electrode electrochemistry" without a counter electrode and power supply. As ESCL, this approach may also find use in analytical applications, e.g., for clinical analysis of species labeled with a luminescent molecular tag which is different from, but which complements, the widely-used ECL techniques. TEFLON^® and polymethylmethacrylate (rods, disks and plates) were the primary materials used in the studies described herein. Different kinds of polytetrafluoroethylene were used, including septa with a diameter of 12 mm (Alltech Associates, Inc., Applied Science Labs, Deerfield, IL), tapes, disks, rods, and plates of different sizes and shapes. All of these samples showed similar results. The polytetrafluoroethylene surface was rubbed by hand with another substance such as metal, glass, nylon and polymethylmethacrylate, and in all cases became negatively charged as determined with an electrometer (Model 6517, Keithley Instruments, Cleveland, OH). After rubbing with polytetrafluoroethylene, the polymethylmethacrylate surface became positively charged and could be measured in the same way. Experiments were always carried out by rubbing the polytetrafluoroethylene and polymethylmethacrylate for about 10 s by hand without high pressure and separating these for use in the experiments (rather than rubbing them while immersed in the test solutions). This was designed to avoid the possible occurrence of "tribochemistry (that) deals with the relation between mechanical work and mass transformation," such as can be found during milling. All other chemicals used were reagent grade. MiIIiQ deionized water was used to prepare all solutions. For the pH experiment, polytetrafluoroethylene septa (12 mm in diameter) or tapes were placed on polymethylmethacrylate plates (18 cm><18 cm) and rubbed by hand for about 10 s with polymethylmethacrylate disks (2.5 cm in diameter and 1.2 cm in height) and then briefly immersed into solution for few seconds. A pH meter (Orion Research, model 701A) was used.

For hydrogen generation, the sample was prepared in a glove box (Terra Universal) with continuous N₂ flow. D₂O (D, 99 atom %, Aldrich) and DCl (35 wt % in D₂O, Aldrich) were used to avoid any H₂ background. For Cu deposition, polytetrafluoroethylene rods (9.5 mm in diameter) were charged by rubbing with a polymethylmethacrylate plate by hand for about 10 s and the deposited Cu spots were inspected with an optical microscope (Olympus). To examine a particular spot with a scanning electron microscope (LEO 1530), orienting marks were placed on the area under an optical microscope before the sample was mounted in the SEM chamber.

For reduction of Fe(CN)₆ ^3- to Fe(CN)₆ ^4-, polytetrafluoroethylene septa or tapes were charged in the similar way as described above. Cyclic voltammetry was obtained with a 23 μm Pt ultramicroelectrode. A Model 100a Electrochemical Analyzer (Bioanalytical Systems, West Lafayette, IN) was used to analyze the solution composition change following the treatment with charged polytetrafluoroethylene.

All ESCL measurements were performed in a black box located inside a double-door dark room to minimize effects of stray background radiation, polytetrafluoroethylene rods (2.1 cm in diameter) were rubbed at one end by hand with a piece of polymethylmethacrylate plate and ESCL was determined with a photomultiplier tube (PMT, Hamamatsu R4220P). We attempted to use a Faraday cup approach to measure the charge on the end of a polytetrafluoroethylene rod rubbed with polymethylmethacrylate. When the rod was perpendicularly introduced through a hole into a Faraday cup with about half of its (uncharged) length outside, the charge measured clearly increased with firm contact to the cup by pushing the polytetrafluoroethylene rod by hand from the outside. However, when the pressure was removed, and the rod was just lightly resting under its own weight on the bottom of the cup, the measured charge decreased by over 10%. polytetrafluoroethylene is soft and easily deformable, thus the charged area is much larger than the apparent one as opposed to a hard surface, where the contact charged area might only be a fraction of the geometric area.

In another embodiment, PE rod, plate and tubing with different shape and size as well as structure including ultra high molecular weight and low density were employed. All the PEs with or without additives did not appear to make a big difference. Glass vial PE plugs were also used in some experiments and shown the same result. Nylon 6 rods and plates as well as Nylon 11 tubing were used. Polymers were purchased from both U.S. plastics Corp. and local stores. Polymers were rubbed against each other by hand in the same way as reported earlier. Following rubbing, the polymers were always separated and only one charged material was dipped into a solution to carry out chemical reactions. Contact without rubbing generated the same charge on each polymer, but with a lower charge density. Thus, all the studies in this work were carried out with rubbed polymers. All other chemicals were regent grade. MiIIiQ deionized water was used to prepare the solutions. An electrometer (Model 6517, Keithley Instruments) was used to measure the charge on polymer surface and current as well as voltage in other experiments. Cyclic voltammetry was obtained with a 23 μm diameter Pt ultramicroelectrode controlled by an Electrochemical Analyzer (Model 100a, Bioanalytical Systems, West Lafayette, IN). All the luminescence experiments were performed in a black box located inside a double-door dark room with a photomultiplier tube (PMT, Hamamatsu R4220P). Solution was mixed inside the dark room to avoid possible photochemical reactions. Contact angle was measured with a Rame-Hart goniometer (Mountain Lakes, NJ).

Electrostatic charges on a polymer: PE and TEFLON® surface became negatively charged after being rubbed with Nylon or Lucite, which both were found to be charged positive after separation as determined with an electrometer. In the measurement, a BNC male plug directly touched the polymer surface and the contact in the center sensed the charge. When the BNC plug was held at one particular spot, charge density there as a function of time could be measured; and charge distribution over a polymer could be mapped when BNC plug was moved around over the surface.

FIGURE 8 is a graph of the electrostatic charge on TEFLON® surface produced by rubbing with a PMMA plate as a function of time at 6 separate spots. FIGURE 8 shows relative charge density against time at 6 separate locations on Lucite -rubbed TEFLON® as the BNC plug was kept in a stop-and-go mode, i.e., stayed at one spot for a while and then moved to next spot. Here the spot 5 and 6 showing relatively higher charge density were obtained near an edge of the TEFLON® rod. Although the charge density varied from spot to spot, it appeared quite stable during measurement at each location for many minutes. Charged polymers could easily pick up a Kimwipe or carbon power located about 1 cm away due to electrostatic induction. The surface was not uniformly decorated with carbon power as the degree of darkness clearly varied from spot to spot. FIGURE 9a-9d are images of the interaction of an unintentionally treated TEFLON® surface. FIGURE 9a is an optical image of a water drop resting on a PMMA rubbed TEFLON® showing a contact angle of 63°. FIGURE 9b is an optical image of a water drop on an unintentionally treated TEFLON® surface showing a contact angle of 105°. FIGURE 9c is a schematic diagram showing small water drops flying to a charged Teflon surface after rubbing with PMMA. FIGURE 9d is an optical image of a PMMA rubbed Teflon rod pulling water up from a pool that was dyed with black ink for easy visualization. Interestingly, when a charged Teflon disk was placed at least 5 mm away both horizontally and vertically from a syringe filled with water as shown in FIGURE 9c, small water drops spontaneously came out and flew one after another from the syringe needle toward separated spots on TEFLON® and firmly stuck there without rolling over the surface as often seen on an uncharged TEFLON® to which a water drop was introduced from an angle. Those spots may have a higher charge density comparing to other area and thus exert a stronger attracting force for the water drops to overcome the surface tension and gravity. Water drop flying stopped when the empty portion of the needle became so large that charges on Teflon were no longer able to overcome the surface tension. However, when the syringe was pushed slightly to fill the needle to the end, water drops started to fly again. As expected, they all landed on new spots and no two drops ever came to the same location. When a metal blade was placed on top of the TEFLON® and a bias voltage of 1000 V was applied between the blade and the metal needle, no water drop flying was seen even after the syringe was pushed so that a small water drop came out and suspended at end of the needle. When the blade was moved closer to about 1 mm away from the suspended drop, still no flying was seen. Instead, the water drop started to slowly moving toward the blade and briefly touched its edge and then separated. Such a touch and separation repeated every few seconds for many times and the drop never escaped from the needle, suggesting that for a water drop to fly to a metal electrode as it did to charged TEFLON®, the bias voltage should be much higher than 5 kV. Note that water drop flying was not seen with unintentionally charged TEFLON®. Moreover, contact angle measured from those drops that flew and adhered to Teflon was only about 63-70° in contrast to 100-105° for a water drop on Teflon surface without intentional contact charging, because the electrostatic charges improved the water spreading on Teflon surface similar to electro wetting. In addition, the edge of a charged Teflon rod was able to pull water up by about two mm high as shown in FIGURE 9d. These results clearly demonstrated that the charge density on TEFLON® surface was indeed significantly high as reported earlier. Obviously, the highly hydrophobic Teflon surface became more hydrophilic following contact electrification. The same phenomenon was also observed with other polymers including LUCITE®, Nylon and PE.

Fe(CN)₆ ^3- reduction: Since electrons cannot be distinguished from negatively charged ions by an electronic probe, here the identity of charge carrier on a polymer surface was determined by a chemical method in which charged polymers were brought into a solution containing some reducible species. A chemical reaction could occur upon contact if the charge carriers were electrons analogous to a faradaic process on a cathode in conventional electrochemistry. On the other hand, no reduction reaction should happen when negative ions touched the same solution. Analysis of the chemical composition in the solution before and after the immersion of a charged polymer should provide an unambiguous answer to the identity of the charge carrier. Here, Fe(CN)₆ ^3- was used as an indicator. Just as with TEFLON®, the PE surface became negatively charged by rubbing with LUCITE® or Nylon and those negative charges were able to reduce Fe(CN)₆ ^3- to Fe(CN)₆ ^4-. For example, after 0.13 mL aqueous solution consisting of 0.2 mM Fe(CN)₆ ^{3 -} and 0.2 M KCl contacted one after another with 10 PE disks (19 mm in diameter) that had been charged through rubbing on PMMA plates (18xl8cm²), about 15% Fe(CN)₆ ^3- molecules in the solution were reduced to Fe(CN)₆ ^4- as determined by an electrochemical analyzer with a 23 μm glass-encased Pt ultramicroelectrode.

FIGURE 10 is a cyclic voltammogram (10mV/s) at a 23 μm glass-encased Pt ultramicroelectrode in water containing 0.2 mM Fe(CN)₆ ^" and 0.2 M KCl before (a) and after (b) the contact with PMMA-rubbed PE disks. FIGURE 10 shows the cyclic voltammograms of the solution before and after the contact with the charged PE disks. It can be seen that the steady state cathodic current plateau corresponding to Fe(CN)₆ ^3- reduction dropped and a new anodic plateau corresponding to Fe(CN)₆ ^4- oxidation appeared following the treatment with charged PE disks. The decrease and increase in Fe(CN)₆ ^3- and Fe(CN)₆ ^4- concentration respectively appeared well balanced. The generation of Fe(CN)₆ ^4- species in a Fe(CN)₆ ^3- solution clearly indicated that a reduction reaction took place on PE surface upon contact to the solution just like a regular cathodic process occurred in a conventional electrochemical cell. The same results were obtained with glass vial PE plugs that were charged in the same way. Such a faradaic reaction proved that the negative charges on PE surface were indeed electrons rather than ions. This chemical measurement also provided an accurate way to determine the electron density on a polymer surface that has been another longstanding challenge in the studies of electrostatics, since a physical probe is unable to precisely sense all the charges on a rough surface that was often the case for a polymer. When the total number of reaction products, i.e., Fe(CN)₆ ^4- species, divided by the apparent surface area of all the PE disks involved in the treatment, an average electron density of 7.9x10¹³/cm² (geometric area) on charged PE was obtained assuming 100% reaction efficiency. This density is over 10 times smaller than that on charged TEFLON® since PE is often listed above TEFLON® in triboelectric series. Another factor could be surface roughness since PE is smoother than Teflon and therefore has a relatively smaller real surface area.

Chemiluminescence(CL) can be generated through a "reductive oxidation" process in a solution containing a coreactant and a luminophore molecule, when both of them were first reduced at an electrode. The reduced coreactant decomposes to form a highly oxidizing species that in turn produced an oxidized form of the luminophore. Consequently, an annihilation reaction occurred when both reduced and oxidized luminophore molecules meet each other leading to excited state production. This is another system to further verify the identity of the charges on PE following rubbing with PMMA and Nylon. If the negative charges on PE were indeed electrons rather than ions as proved in the Fe(CN)₆ ^{3 -} reduction, then CL could be generated by those electrostatic electrons in a well studied system consisting of tris(2,2'-bipyridine)ruthenium (II) perchlorate [Ru(bpy)s(Clθ₄)₂] and a coreactant of sodium persulfate, Na₂S₂O₈ similar to the studies of charged Teflon as reported earlier ^{Error! Bookmark not defined.} Indeed, a strong CL was detected with charged PE.

In the studies, a PE rod first rubbed with PMMA and then immersed into an acetonitrile (MeCN)/water (1 :1, v/v) mixture containing typical ECL reagents, i.e., 0.25 mM Ru(bpy)₃(C10₄)₂ and 2.5 mM Na₂S₂O₈, a CL at μA level was obtained as shown in FIGURE 11. FIGURE 11 is a graph of the relative intensity of chemiluminescence as a function of time when a PMMA-rubbed PE rod was dipped into a MeCN/H₂O (1 :1, v/v) mixture containing 2.5mM S₂O₈ ^2- and 0.25mM Ru(bpy)₃ ²⁺. Insert shows the reaction mechanism. Available electrons on PE reduced Ru(bpy)₃ ²⁺ and S₂O₈ ^2- to generate the light producing species as mentioned earlier. The CL signal decayed over time as the number of electrons diminished. Note that some air bubbles were trapped at the PE/solution interface and blocked some charged area. As those bubbles moved around and eventually escaped, more electrons became available and generated the irregular CL spikes in FIGURE 4. As expected, when either of these reagents alone was present in the solution, the CL was barely seen from the background upon charged PE introduction on the same scale. This result proved again that charges on PE are electrons instead of ions consisting with our early work with PMMA rubbed TEFLON®. Note that same result was also obtained with Nylon rubbed TEFLON® and PE. Since the same reduction reaction could be carried out by those charges generated through rubbing each other with all the couples of PE/Nylon, PE/PMMA, TEFLON® /PMMA and TEFLON® /Nylon, it appears clear that electron production during contact electrification between two polymers is probably a general process not tied to a specific material or couple.

Metal deposition: Electron transfer reaction induced by electrostatic charges on a polymer surface could be visualized through metal plating. When PMMA or Nylon rubbed PE materials with different size, shape, branching and density (low density, high density, ultra high molecular weight etc) were immersed briefly into a solution containing ImM Ag₂SO₄, saturated PdCl₂ or ImM CuSO₄ followed by a thorough wash with deionized water, the metals Ag, Pd or Cu were plated on PE surface, respectively. Under an optical microscope, about 10 μm size metal films were clearly seen on isolated spots. Just like PMMA, Nylon rubbed Teflon was also able to cause these metal depositions. Note that Cu deposition could be significantly amplified and accelerated with Pd that is known to be a good catalyst for electronless Cu deposition. For example, following the plating of Pd in the way described above, a PE rod was washed and then placed into a Cu plating bath containing CuSO₄, KNaC₄H₄O₆, NaOH, and HCHO.

FIGURE 12a is an optical image showing Cu deposited on the untreated inner surface of a Nylon tube. No Cu was seen on the PE rubbed outer surface and end. FIGURE 12b is an optical image showing Cu deposited on the end of a PMMA-rubbed PE rod and no Cu plated on the surface that was not rubbed. FIGURE 12c enlarged optical image (0.8 x 0.43 mm²) of the Cu film on Nylon inner surface. A large amount of Cu deposition was visually observed easily, as shown on the top right of Figure 5. Many bubbles were formed and almost all the Cu²⁺ available in the bath was consumed in hours as the blue color of the plating bath completely disappeared. Although at least 5 mm long PE rod was immersed into the plating solutions, Cu was deposited just at the end surface, which was the only area initially charged through rubbing with PMMA. These results again clearly demonstrated that electrons could be produced on both Teflon and PE surface through rubbing with other polymers including PMMA and Nylon, and those electrons were able to carry out faradaic reactions firmly proving the concept of "single electrode electrochemistry" using a polymer electrode without a power supply. Note that an ion, e.g. hydroxide, adsorption model proposing an exclusive ion transfer mechanism in contact electrification does not easily explain any of the above faradaic reactions. For example, OH^" will not reduce Pd²⁺, Ag⁺, and Cu²⁺ in a solution leading to a metal deposition. Moreover, the expected product of Cu(OH)₂ has a pale blue color that is sharply different from the color shown in FIGURE 12.

When metal ions were reduced and deposited on a rubbed polymer surface by electron transfer, the solution became negatively charged because of the presence of uncompensated anions; these could be directly measured. In the experiment, an electrometer was connected to two identical cells, fabricated from aluminum foil, containing the same solution of ImM CuSO₄. The cells were well insulated from ground. The voltage was initially zero between those two cells as expected. After a Teflon or PE rod rubbed on a PMMA plate was dipped briefly into one cell, a stable voltage over 100V was appeared, with the electrometer clearly indicating the cell that was contacted with the charged polymer had become negatively charged.

Origin of the charge transfer: All the above reduction chemical reactions suggest that the identity of the charge carriers on the PE surface are electrons just like that of PMMA- rubbed Teflon. The next question is how those electrons were produced during the contact electrification. The two existing mechanisms, electron vs. ion transfer, could explain equally well why one material charged negatively while another positively since the electric effect is identical between the transfer of a positive ion from a surface and an electron transferred to that surface to neutralize the ion. To answer this longstanding debate, we wish to demonstrate again that chemical measurement is indeed able to determine which theory is validated. For example, if one assumes an ion transfer mechanism between Nylon and PE during contact, then Nylon must be either a negative ion donor or positive ion acceptor since Nylon became positively charged after contact with PE. On the other hand, electron transfer theory predicts that electrons were transferred from Nylon to PE, that is, Nylon is an electron donor. These two assumptions were tested by briefly dipping a Nylon tube that had not been contact with other materials before into a solution containing reducible chemical species such as Ag²⁺, Pd²⁺ and Cu²⁺. While an electron donor would have a chance to reduce the metal ions in the solution to cause a metal deposition on its surface, a negative ion donor or positive ion acceptor, however, will require a mechanism that transduces ionic charge to electronic charge in a way yet to be discovered. Indeed, metal deposition on Nylon surface did occur as verified with an optical microscope.

To prove further that those electrons donated from Nylon and responsible for the metal deposition were had the same reducing power as those that appeared on PE surface following contact, the ability to cause the amplified plating on the Nylon was investigated. The outer surface and the end of a Nylon tube were first rubbed with a PE plate and the Nylon was then immersed into a Pd(II) solution, followed by washing and immersion in the electroless Cu plating bath. No metal was deposited on the parts of the Nylon that were previously rubbed with PE, suggesting that that charge at those location was depleted during charging. However normal deposition still occurred on the tube's inner wall that had never touched PE as shown on top left in FIGURES 12a-c, in which Pd was deposited first followed by a catalytic electroless Cu deposition as described above. Note that Nylon tubing is not very transparent, leading to a fuzzy appearance of the Cu film when looking from outside. However structures such as small Cu particles could be clearly seen when looking directly at the Cu film surface (FIGURES 12a-c). This result clearly indicated that Nylon acted as an electron donor that is capable of transferring electrons to a solid such as PE or a solution containing chemical species upon contact, and those electrons whether residing on Nylon or transferred to PE had the same capability to reduce metal ions leading to the metal deposition on either Nylon or PE, respectively as shown in the top two images in FIGURES 12a-c. This supports an electron rather than ion transfer mechanism. The same conclusion was drawn from separate studies of Nylon/Teflon and PMMA/PE contacts, consistent with earlier results with the PMMA/TEFLON^® couple.

Similar to PMMA, Nylon is also listed near top in triboelectric series, meaning that it is among the readiest to donate electrons to other materials or solutions containing reducible species upon contact based on the electron transfer mechanism as demonstrated above. Indeed, untreated Nylon that had never contacted with other objects was able to carry out other chemical reactions. For example, Fe(CN)₆ ^3- was reduced to Fe(CN)₆ ^4- when a Fe(CN)₆ ^3- solution was passed through a fresh Nylon tube as determined by an electrochemical analyzer as described earlier. The average density of the electrostatic charge on Nylon was 1.3xlO¹²/cm², about two times the density determined by a metal contact on Nylon in a vacuum in which the contact area could not be measured accurately. Moreover, fresh Nylon could also generate CL just like PMMA in the same system as described before. Since the charge density is over 30 times less than that on a PMMA surface, the CL signal induced by Nylon was much weaker, as expected.

A variety of faradaic reactions including metal deposition, Fe(CN)₆ ^3- reduction and chemiluminescence clearly demonstrated that electron instead of ion transfer occurred during contact electrification between two dissimilar polymers such as PE/Nylon, PE/PMMA, TEFLON^®/Nylon and TEFLON^®/PMMA. Those electrons produced through rubbing were able to carry out conventional electron transfer reactions and therefore supported the concept of polymer electrostatic electrochemistry using a single polymer electrode without a power supply.

Although the studies described in this paper have concentrated on polytetrafluoroethylene, which is negatively charged, oxidation reactions at the charged polymethylmethacrylate were also obtained and will be reported separately.

The above description of the present invention is illustrative, and is not intended to be limiting. It will thus be appreciated that various additions, substitutions and modifications may be made to the above described embodiments without departing from the scope of the present invention. Accordingly, the scope of the present invention should be construed in reference to the appended claims.

Claims

CLAIMS:

1. A method for inducing a redox reaction, comprising: providing first and second distinct dielectric materials; imparting an electrostatic charge to the first dielectric material by contacting it with the second dielectric material; and utilizing the electrostatic charge to induce a chemical reaction.

2. The method of claim 1, wherein the chemical reaction is induced without a counter electrode.

3. The method of claim 1, wherein the chemical reaction is induced without a reference electrode.

4. The method of claim 1, wherein the chemical reaction is induced without a power supply.

5. The method of claim 1 , wherein the chemical reaction is a metal plating reaction.

6. The method of claim 1, wherein the chemical reaction is a hydrogen generation reaction.

7. The method of claim 1, wherein the chemical reaction is a chemiluminescent reaction.

8. The method of claim 1, wherein the chemical reaction is utilized to calibrate charges or energy levels on a dielectric material.

9. The method of claim 1, wherein the chemical reaction is utilized to perform clinical analyses.

10. The method of claim 1, wherein the first dielectric material comprises polytetrafluoroethylene.

11. The method of claim 1 , wherein the second dielectric material comprises polymethyl methacrylate.

12. The method of claim 1, wherein the electrostatic charge is imparted to the first dielectric material by repeatedly rubbing it against the second dielectric material.

13. The method of claim 1, further comprising immersing the first dielectric material in a liquid medium, wherein the liquid medium is a solution containing a chemical species capable of undergoing an electroluminescence reaction through an electron transfer reaction.

14. The method of claim 1, further comprising immersing the first dielectric material in a liquid medium, wherein the liquid medium is a plating bath solution.

15. The method of claim 14, wherein the plating bath solution contains metal ions capable of undergoing reduction through an electron transfer reaction.

16. The method of claim 1, wherein the first and second dielectric materials are chemically distinct.

17. A method for inducing a redox reaction, comprising: providing a first dielectric material; imparting an electrostatic charge to the first dielectric material; and inducing a chemical reaction by immersing the first dielectric material in a liquid medium.

18. The method of claim 17, wherein the liquid medium contains a material capable of undergoing a chemiluminescent reaction.

19. The method of claim 17, wherein the liquid medium contains a plating solution.

20. The method of claim 17, wherein the electrostatic charge is imparted to the first dielectric material by contacting it with a second dielectric material, and wherein the first and second dielectric materials are distinct.

21. A method for plating a metal on a dielectric material, comprising: providing a first dielectric material; imparting an electrostatic charge to the first dielectric material; and immersing the first dielectric material in a liquid medium containing metal ions.

22. The method of claim 21 , wherein the liquid medium is a metal plating bath solution.

23. The method of claim 21 , wherein the metal is copper.

24. The method of claim 21, wherein the electrostatic charge is imparted to the first dielectric material by repeatedly rubbing the first dielectric material against a second dielectric material, and wherein the first and second dielectric materials are distinct.

25. A method for generating hydrogen gas, comprising: providing a hydrogen-containing material; providing a first dielectric material; imparting an electrostatic charge to the first dielectric material; and generating hydrogen gas by contacting the charged first dielectric material with the proton-containing solution.

26. The method of claim 25, wherein the proton-containing solution is an acidic solution.

27. The method of claim 25, wherein the first dielectric material is immersed in the solution.