Surface and nanostructural modifications of polytetrafluoroethylene by Au + irradiation for energy harvesting applications

Surface modification of polymers using ion-irradiation is a promising technique to improve their triboelectric performance. In this work, Polytetrafluoroethylene (PTFE) samples were irradiated with 1.5 MeV gold ions (Au +) using Pelletron Accelerator at various doses (1 × 10 13, 5 × 10 13, 1 × 10 14, and 5 × 10 14 ions-cm 2). The X-ray photoelectron spectroscopy results showed a shift in the binding energies of C 1s and F 1s core levels, along with the formation of new oxygen and carbon-containing functional groups in the irradiated samples. The surface roughness and crystallite size of the PTFE were decreased after the irradiation. The Fourier Transform Infrared Spectroscopy (FTIR) revealed attenuation and a shift in the C–F vibrational bands upon irradiation, indicating defluorination and ion-induced chain scission of the polymer. Both pristine and Au + irradiated samples were used for the fabrication of Triboelectric Nanogenerators (TENGs). The Au + irradiated TENG displayed a significant increase in the output voltage as compared to the pristine TENG. The maximum values of the output voltage and power density were found to be ∼112 V and 1.74 Wm -2 respectively, at 5 × 10 14 ions-cm 2. The enhanced triboelectric performance of the TENG is attributed to increased charge trapping on the PTFE surface induced by the Au + irradiation, leading to a notable enhancement in the electrical output.

In recent years, energy harvesting using triboelectric nanogenerators has received tremendous interest worldwide (Li et al., 2019; Yang et al., 2023). The low-frequency mechanical energy from the surrounding environment can be efficiently converted into electrical energy using a triboelectric nanogenerator (TENG). The principle behind this conversion is the combined effect of contact electrification and electrostatic induction (Chen et al., 2020; Wajahat et al., 2024). The TENG offers several advantages, such as high output voltage, simple design, low-cost manufacturing process, and ability to work in diverse environments. These characteristics enable it to power small electronic devices and to act as a self-powered sensor in wearable, environmental, security, and biomedical applications (Fan et al., 2012; Jing and Kar-Narayan, 2018; Wang et al., 2020; Hasan et al., 2021; Khandelwal et al., 2021; Chen et al., 2022; Manchi et al., 2024).

The selection of a material used for the TENG fabrication is of critical importance. Polytetrafluoroethylene (PTFE) is a well-known polymer that has good chemical stability, high electron affinity, excellent dielectric strength, and low surface energy. Due to these properties, a TENG based on PTFE exhibits high surface charge density and shows remarkable performance (Wang R. et al., 2017). However, the inert surface of the PTFE limits its triboelectric performance. Therefore, various surface modification techniques have been employed to increase the charge density and trapping abilities on the PTFE surface. Ahmed and co-workers (Ahmed et al., 2023) treated the PTFE surface with air plasma to enhance its triboelectric performance. The output voltage of the plasma-treated PTFE-TENG was increased due to the formation of surface structures. Mule et al. (2018) developed micro-patterns on the PTFE surface through thermal imprinting lithography using sandpaper as a master mold. The formation of micro-patterns significantly increased its triboelectric performance. Wang M. et al. (2017) reported a high-performance single-electrode triboelectric nanogenerator (S-TENG) employing sponge-like porous PTFE as the triboelectric layer. The porous PTFE S-TENG displayed 1.8 times higher voltage as compared to the non-porous PTFE based S-TENG under similar conditions. Zhang et al. (2019) reported TENG fabrication using expanded PTFE and reported an increase in its triboelectric performance by controlling the expansion ratio. In addition to the above techniques, ion irradiation of polymers is also an effective method to produce a controllable surface modification. Jizhong et al. (2004) demonstrated an increase in the surface roughness and water droplet angle of the aged PTFE by nitrogen ion irradiation. Kwon et al. (2007) found fluorine removal, cross-linking, and carbonizing reactions on the PTFE surface due to 150 keV Ar ions irradiation. Dhillo et al. (2010) demonstrated that defluorination and changes in the crystallinity of the PTFE occurred due to 150 MeV Ni ions. Singh and Kumar reported amorphization and a decrease in the crystallite size and band gap of the PTFE by 50 MeV Li 3+ ions in the dose range of 1 × 10 10 to 1 × 10 12 ions-cm -2 (Singh and Kumar, 2014). Lv and co-workers found an increase in the surface energy and defluorination of the PTFE due to 25 keV proton irradiation (Lv et al., 2015).

Despite these advancements, systematic studies focusing on the correlation between ion irradiation parameters and triboelectric performance of PTFE-based TENGs remain limited. The increased performance of a TENG is essential for its large-scale implementation in sustainable energy harvesting and self-powered electronic systems. Since the triboelectric behavior is highly sensitive to surface characteristics, controlled surface engineering offers an effective route to optimize charge generation and retention. In this work, Au + -induced chemical, morphological, and structural modifications of PTFE are investigated at different doses to correlate these modifications with its triboelectric performance. The Au + irradiation of the PTFE could be quite useful for its surface modification because of the high electrical conductivity and high electron affinity of Au (Grzelczak et al., 2008). This can effectively tailor the morphological, chemical, and nanostructural properties of the PTFE to enhance its performance for the energy harvesting application. The literature survey shows that the Au + irradiation of the PTFE has not been given much attention in the past. This work aims to investigate Au + irradiation-induced surface and nanostructural modifications of the PTFE and their effects on the performance of Al-PTFE based TENG. This work not only advances the fundamental understanding of ion–polymer interactions but also offers a viable pathway for the development of high-performance, durable, and scalable triboelectric energy harvesting systems.

Preparation of samples

A polytetrafluoroethylene (PTFE) sheet of 1 mm thickness was used in the present work. The samples of PTFE were cut into 2 × 2 cm 2 pieces and cleaned before the ion irradiation. The samples were ultrasonically cleaned in ethanol, isopropanol, and deionized water for 15 min to remove surface contamination and impurities. After ultrasonic cleaning, the samples were dried in air at room temperature. The cleaned samples were used for ion irradiation using a Pelletron Accelerator.

Ion irradiation of samples

PTFE samples were subjected to gold ions (Au +) irradiation at room temperature using the Pelletron Accelerator (Figure 1a). The Pelletron Accelerator is an electrostatic accelerator that uses a chain of metal pellets to transport charge from one terminal to another. The Au + ions were produced by the Au SNICS source and were accelerated towards the accelerator tank, where the charge stripping process occurred. These were then directed onto the target material (Masood et al., 2023). The ion energy was kept fixed at 1.5 MeV, whereas the ion dose was adjusted to 1 × 10 13, 5 × 10 13, 1 × 10 14, and 5 × 10 14 ions-cm -2 by changing the beam current. All samples were uniformly irradiated by the Au + at room temperature. The range of Au + inside the PTFE was about 385 nm, found using the SRIM software. The SRIM results of the depth distribution and energy loss of the Au + in the PTFE are shown in Figures 1b–d.

Characterizations of samples

The pristine and Au + implanted samples were characterized by various techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy.

Fabrication of triboelectric nanogenerator

For the fabrication of a triboelectric nanogenerator (TENG), a 50 μm-thick aluminum (Al) foil tape was fixed on the rear side of the PTFE. The PTFE served as a tribo-negative material due to its strong electron affinity, whereas the Al foil acted as a tribo-positive material due to its tendency to donate electrons during contact electrification. The experimental setup for measuring the TENG output is shown in Figure 2. The Al–PTFE TENGs were operated in contact–separation (C–S) mode using a mechanical exciter to provide controlled cyclic loading and unloading conditions. The applied mechanical force was monitored continuously by a force sensor to ensure stability of the excitation conditions. The output voltage (V) of the TENG was directly measured using a digital oscilloscope across external load resistors (R), whereas the corresponding load current (I) was then calculated using the relation I = V/R. The voltage obtained from the TENG was utilized to charge a capacitor and to turn ON a light-emitting diode rectified using a full-wave bridge rectifier, confirming the device’s potential for mechanical-to-electrical energy conversion in low-power applications.

X-ray photoelectron spectroscopy

The X-ray photoelectron spectroscopy (XPS) of the PTFE was carried out to examine the chemical changes that occurred on its surface due to Au + irradiation. Figure 3 shows the results of C 1s, F 1s, and O 1s spectra of the pristine and Au + irradiated samples. The C 1s spectrum of the pristine PTFE shows two peaks: one is CF 2 peak at 292.6 eV, and the other is the C–C peak at 284.6 eV, as shown in Figure 3a. The CF 2 peak corresponds to the repeating–CF 2 – units in the PTFE polymer (Ahmed et al., 2023; Yu et al., 2026), whereas the C-C peak is associated with the surface adventitious carbon contamination resulting from exposure to the atmosphere (Piwowarczyk et al., 2019). After irradiation of the PTFE with Au + at 1 × 10 13 ions/cm 2, the CF 2 peak broadens and becomes less intense. In addition, the C–O and C-F peaks occur at 286.5 eV and 289.7 eV, respectively, indicating the formation of oxygen and carbon containing functional groups (Ohkubo et al., 2018). The C-C peak could not be observed, which may be due to the removal of surface adventitious carbon contamination by Au + irradiation. Increasing ion dose to 5 × 10 13 ions/cm 2, intensity of the CF 2 peak was significantly reduced, indicating an extensive defluorination of the polymer due to chain scission (Yu et al., 2026). The carbon ion separated from CF 2 due to the chain scission of the PTFE formed carbon-rich and oxygen-containing species in the form of C–O, C-F, and C-C peaks. Similarly, at a dose of 1 × 10 14 ions/cm 2, the XPS spectrum was dominated by the C–C, C–O, and C-F peaks, and only a minor CF 2 peak was observed due to substantial defluorination of the PTFE. When the Au + dose was increased to 5 × 10 14 ions/cm 2, the CF 2 peak exhibited high intensity, while a CF 3 peak at 293.8 eV also appeared, indicating changes in the chemical bonding environment of the PTFE (Lee et al., 2004). The high-dose Au + irradiation can result in the formation of thermal spikes in addition to chain scission, which can result in structural rearrangements and localized crosslinking, thus forming the CF 2 peak (Popok, 2019). The results of F 1s spectra of the PTFE are shown in Figure 3b. The pristine PTFE exhibits a peak at ∼ 690 eV, corresponding to fluorine atoms bonded to carbon in the CF 2 unit. This peak reflects high fluorine content and stability in the pristine PTFE. After Au + irradiation at 1 × 10 13 ions/cm 2, the CF 2 peak is slightly shifted to 689.5 eV, indicating a partial defluorination of the sample. With increasing ion dose to 5 × 10 13 ions/cm 2, three peaks CF, CF 2, and CF 3 were observed in the XPS spectrum at 687.1 V, 689.7 eV, and 692.7 eV, respectively. The formation of CF and CF 3 demonstrates the chain scission of the polymer (Ahmed et al., 2023). At 1 × 10 14 ions/cm 2, similar peaks (C-F, CF 2 and CF 3) were found with slight variation in their binding energies (Fujitani et al., 2023). At 5 × 10 14 ions/cm 2, the F 1s spectrum exhibited CF 2 and CF 3 peaks at 690.9 eV and 694.3 eV, respectively.

The O 1s XPS spectra (Figure 3c) illustrate the evolution of oxygen-containing functional groups on the PTFE surface due to air contamination. In the pristine sample, two distinct peaks (532.1 eV, attributed to C-O bond and 533.7 eV, corresponding to O-C=O bond) were observed. These oxygen-related species are most likely introduced by surface oxidation resulting from unavoidable exposure to the atmosphere, even in pristine PTFE. The Au + irradiation at the lower ion dose (1 × 10 13 ions cm -2) resulted in the formation of three distinct peaks, such as C=O, C-O and O-C=O at 531.2 eV, 532.8 eV and 534.5 eV, respectively (Ahmed et al., 2023). At 5 × 10 13 ions cm -2 and 1 × 10 14 ions cm -2, the XPS spectra exhibit two dominant peaks corresponding to C-O and O-C=O. At 5 × 10 14 ions cm -2, the XPS graph shows C=O and O-C=O peaks. The O-C=O peak is higher in intensity as compared to the C=O peak. The changes that occurred at the PTFE surface are attributed to ion-induced bond scission and structural rearrangements within the C–F chain, which generate active sites capable of incorporating oxygen from the surrounding environment.

The analysis of results shows that the ion irradiation induces significant structural and electronic modifications, including chain scission, defluorination, carbon-rich defect formation, and localized oxidation, as evidenced by the C 1s and F 1s spectra. The carbon-containing functional groups and unsaturated carbon dangling bonds on the PTFE surface may act as efficient charge-trapping centers, facilitating the transfer of electrons from Al to PTFE during the physical contact. Therefore, the modified surface electronic structure is beneficial to enhance the triboelectric performance of the PTFE (Ahmed et al., 2023).

Scanning electron microscopy

The surface morphology results of the PTFE, obtained using scanning electron microscopy (SEM), are shown in Figures 4a–d. A higher-magnification view of the PTFE surface is presented in the inset of each figure. The micrograph of the pristine PTFE shows no significant morphological features (Figure 4a). Irradiation of the PTFE by Au + at 5 × 10 13 ions-cm -2 resulted in the formation of surface structures containing protrusions, micro-voids, cavities, and grooves (Kitamura et al., 2009). The formation of such structures is attributed to the breaking of polymer chains (C-F and C-C bonds) due to Au + irradiation (Figure 4b). At 1 × 10 14 ions-cm -2, the nanoscale structures became small and irregular in shape due to partial re-deposition of the polymer fragments (Figure 4c). At a dose of 5 × 10 14 ions cm -2, the surface exhibited uniformly distributed small micro-voids and protrusions (Figure 4d). Further, agglomeration of these protrusions was also observed. The changes in surface morphology of the PTFE occurred due to ion irradiation-induced C–F and C–C bond scission, defluorination, chain rearrangement, and localized crosslinking (Lee, 1999; Ohkubo et al., 2017). The Au + interacts with the PTFE surface via electronic and nuclear collisions and lose their energy. Electronic energy loss induces ionization and excitation of the polymer chains, while nuclear collisions transfer momentum to the constituent atoms, resulting in C–C and C–F bond scission and free-radical formation. The irradiation-induced radicals subsequently undergo recombination due to thermal spikes, leading to localized crosslinking and structural reorganization of the polymer chains. This modifies the near surface region of the PTFE, giving rise to changes in its surface morphology (Popok, 2019).

Atomic force microscopy

To study the nanoscale surface topography of the pristine and Au + irradiated PTFE, atomic force microscopy (AFM) images of the samples were acquired over 5 μm × 5 µm scan area. The AFM images of the pristine and Au + irradiated PTFE at different doses are shown in Figure 5. The AFM image of the pristine sample shows coarse surface morphology in the form of mountains and valleys and pronounced height variations across the sample’s surface, causing its high surface roughness. In the case of pristine PTFE, the rms surface roughness was found to be 68 nm. After Au + irradiation at 1 × 10 13 ions/cm 2, the particles became small, and the value of the surface roughness was noted to be 42 nm. Upon increasing the ion dose to 5 × 10 13 and subsequently 1 × 10 14 ions/cm 2, the surface roughness of the PTFE was decreased to 20.7 nm and 19.7 nm, respectively. With further increase of the ion dose to 5 × 10 14 ions/cm 2, the roughness was increased to 33.1 nm. Overall, the Au + irradiated samples exhibited lower surface roughness as compared to the pristine sample.

The decrease in the surface roughness of the Au + irradiated PTFE can be attributed to irradiation-induced nanostructural changes on its surface. As discussed above, the surface morphology of the Au + irradiated PTFE changes due to bond scission and structural reorganization. The development of nanoscale features on the PTFE surface indicates that the ion irradiation redistributes the surface material and smooths the larger surface asperities present in the pristine PTFE, resulting in a decrease in the surface roughness. This is in accordance with the recent investigation on the air-plasma treated PTFE in which the surface roughness was decreased with the increase of plasma treatment time (Ahmed et al., 2023). In contrast, a few previous studies reported an increase in the surface roughness of the PTFE upon irradiation with low-energy Ar and O ions (Lee et al., 2004; Atta et al., 2013). The formation of nanoscale features and decreased surface roughness is beneficial to enhance the contact area between the two materials used for the formation of triboelectric nanogenerators.

Fourier transform infrared spectroscopy

The Fourier Transform Infrared Spectroscopy (FTIR) results of the pristine and Au + implanted PTFE samples are shown in Figure 6. The FTIR spectrum of the pristine sample shows strong characteristic absorption bands at 1,201 cm -1 and 1,145 cm -1 corresponding to asymmetric and symmetric stretching vibrations of C-F bonds in the CF 2 groups (Satulu et al., 2016). In addition, the bands observed at 554 cm -1 and 638 cm -1 show the deformation vibrations of the CF 2 groups. The absorption bands at 719 cm -1 and 784 cm -1 are related to the vibrations of molecular chains in the amorphous phase of the PTFE (Kim et al., 2017; Mei et al., 2025), while the band at 740 cm -1 shows CF = O species, indicating the oxidation of the PTFE (Satulu et al., 2016). The band at 2,360 cm -1 is a combination band of two modes associated with CF 2 backbone (Atta et al., 2013). Irradiation of the PTFE with Au + at different doses produces a noticeable change in the FTIR spectra of the samples. We clearly see that the intensity of the characteristic’s bands at 1,201 cm -1 and 1,145 cm -1 is reduced after the ion irradiation. This behavior is attributed to chain scission induced by Au + irradiation, resulting in the defluorination of the PTFE. Similarly, the bands at 554 cm -1 and 638 cm -1 also become less intense due to the ion-induced structural modifications. In addition to these changes, a new absorption band appeared at 984 cm -1 in the irradiated samples, which was absent in the pristine PTFE. This band is attributed to the formation of CF 3 due to the chain scission of the PTFE. Lappan et al. observed a similar band at 985 cm -1 corresponding to the CF 3 in the electron beam irradiated PTFE and found an increase of its intensity with increasing irradiation dose (Lappan et al., 1999). Similarly, a new band at 1,650 cm -1 is also observed in the irradiated samples, which is assigned to C=C stretching, indicating the formation of unsaturated carbon species. The FTIR results of this work are in agreement with the previous literature (Lappan et al., 1999; Satulu et al., 2016; Mohammadian-Kohol et al., 2018; Mei et al., 2025). The observed changes in the FTIR spectra after Au + irradiation indicate significant modifications in the chemical structure of the PTFE resulting from ion–matter interactions. The formation of new bands after irradiation occurs due to the chain scission and defluorination of the PTFE. As a result, the CF 2 bands at 1,145 and 1,201 cm −1 weaken with increasing Au + dose and new bands appear. Simultaneously, the appearance of a new CF 3 band in the irradiated samples shows the formation of a new fluorocarbon group through molecular rearrangements. The FTIR analysis revealed that the surface and nonstructural changes depend on the ion dose, indicating bond scission and subsequent molecular reorganization of the irradiated PTFE.

X-ray diffraction

The results of X-ray diffraction (XRD) of the PTFE are shown in Figure 7a. The main diffraction peak of the PTFE appeared at 18.2°, corresponding to the (100) plane (Jinglong et al., 2016). In addition, two more peaks associated with (110) and (200) planes were observed at 31.6° and 36.8°, respectively. The high intensity and low full width at half maximum (FWHM) of the (100) peak reflect the crystalline nature of the PTFE. Au + irradiation at different doses caused a variation in the intensity and FWHM of the diffraction peaks, indicating changes in the material’s crystallinity. The (100) peak remained dominant in intensity in all the samples. The XRD pattern of the PTFE irradiated with Au + at 5 × 10 14 ions-cm -2 shows a low intensity Au peak in addition to the PTFE peaks. This validates the implantation of Au + in the material (Krishnamurthy et al., 2014). The Au peak could not be detected at lower doses due to the lower number of implanted ions. A magnified view of the Au peak is shown in Figure 7b. The PTFE crystallite size was found using the Debye–Scherrer equation D = k λ β ⁡ cos ⁡ θ (Masood et al., 2023); Here, k indicates the shape factor with a value 0.9, λ represents wavelength of X-rays, and FWHM of the peak is represented by β (in radians). The crystallite size was plotted against ion dose, as shown in Figure 7c. The crystallite size decreased with increasing dose. The decrease in the crystallite size indicates the nanostructural modifications of the PTFE due to irradiation-induced chain scission, defect formation, and degradation of crystalline regions (Dhillo et al., 2010). During ion irradiation, Au + transfers energy to the PTFE matrix via nuclear (elastic) and electronic (inelastic) interactions, leading to bond breakage (chain scission) and defect generation. These processes disrupt the long-range order of the polymer chains, causing partial amorphization, which results in the formation of smaller crystallite domains. At higher doses, overlapping of collisional cascades further enhances structural disorder and prevents the reformation of larger crystallites. Consequently, the crystallite size decreases progressively as the ion dose increases. The reduction in crystallite size increases due to evolution of the PTFE towards a more disordered state. This is consistent with Jinglong et al. results, in which the crystallite size of the PTFE decreased with an increase in electron beam dose (Jinglong et al., 2016). On the contrary, there is an enhancement in the microstrain (Figure 7C) and dislocation density (Figure 7d) with an increase in the ion dose. This indicates that the crystalline volume became destabilized and partially converted into the defect-rich amorphous phase.

Triboelectric nanogenerator

A schematic diagram of the triboelectric nanogenerator (TENG) in contact-separation mode is shown in Figure 8. When a tribo-positive material such as Al is pressed onto a tribo-negative material (PTFE in the present case) and then separated, a voltage is developed between the two materials, resulting in the flow of current through the external circuit. Similarly, pressing Al again onto the triboelectric material causes current to flow in the opposite direction. Repeating this process generates the triboelectric nanogenerator’s output voltage across the external load resistance. As shown in Figure 2, the force is applied to the material via a mechanical exciter, powered through an amplifier and driven by the function generator. The output voltage is recorded on the attached oscilloscope.

The triboelectric output voltage pulses of both pristine and Au + irradiated PTFE-based TENG, measured at a constant applied force of 6 N are presented in Figure 9a. The maximum voltage measured for each type of irradiated sample is shown in Figure 9b. The figure shows an increase in the output voltage of the PTFE-TENG with the increase in ion dose. The voltage rises from ∼20 V for pristine PTFE to nearly 112 V for the sample irradiated at 5 × 10 14 ions-cm -2. This significant enhancement in the voltage is primarily attributed to surface and structural modifications induced by energetic Au + irradiation.

The ion–solid interactions generate defects, microvoids, and localized charge-trapping sites within the near-surface region of the PTFE, which collectively contribute to the improved triboelectric performance. These modifications promote greater charge accumulation during contact electrification and, consequently, improve triboelectric performance (Fan et al., 2021). Although a slight reduction in surface roughness and crystallite size was observed, the formation of nanoscale features and microvoids increases the effective contact area between the Al and PTFE surfaces, facilitating more efficient charge transfer. As a result, the progressive increase in the defect-related active sites with the ion dose results in a systematic enhancement of the TENG output voltage. Figure 9c presents the variation of output voltage and current of the Al–PTFE device implanted with Au + at 5 × 10 14 ions cm -2 as a function of external load resistance. The voltage increases whereas the current decreases exponentially on increasing the load resistance, demonstrating their complementary behavior. The increase in voltage can be attributed to higher resistance limiting charge flow, thereby allowing greater accumulation of triboelectric charges at the electrodes. Conversely, the reduction in charge transport at larger resistance values leads to a corresponding decrease in the current, consistent with the RC-type response typically observed in triboelectric systems. The load-dependent power density of both pristine and Au + irradiated samples is shown in Figure 9d, where the power density is calculated using P = IV/A, with I the load current, V the voltage, and A the device’s active area (2 × 2 cm 2). Maximum power densities of 0.14 Wm −2 for the pristine PTFE and 1.74 Wm −2 for the Au + irradiated samples are achieved at 5 MΩ. Beyond this resistance, power density decreases. Although the voltage continues to rise with increasing resistance, the current (I=V/R) decreases more rapidly, leading to an overall decline in power at high resistances. This shows that maximum power transfer occurs when the external load matches the TENG’s internal impedance. The occurrence of maximum power density at a relatively low load resistance suggests reduced effective internal impedance of the ion-irradiated TENG. This is advantageous for directly powering low-impedance electronic devices or energy management circuits with reduced impedance-matching requirements. A comparison of the output parameters of the TENG obtained in this work with those reported in previous studies is presented in Table 1 (Xia et al., 2017; Prada et al., 2022; Ahmed et al., 2023; Min et al., 2023; Ejaz et al., 2023).

The schematic diagram for charging a capacitor using the obtained voltage is shown in Figure 10a. The charging behavior of 10 μF and 47 µF capacitors connected to the TENG is shown in Figure 10b. The 10 µF capacitor reaches about 2.3 V in approximately 100 s, whereas the 47 µF capacitor reaches only 1.2 V. The 10 µF capacitor was chosen as an energy-storage device to power an LED. The schematic diagram of the full-wave rectifier circuit is shown in Figure 10c. The reason for this phenomenon is the relationship between charge and voltage (Q = C × V), where a lower capacitance results in the accumulation of less charge to achieve a higher voltage level. Hence, the faster growth of the attained voltage for the same amount of tribo-charge is observed. The results of this study demonstrate that controlled modification of the surface and structural properties of the PTFE can effectively enhance its performance for energy harvesting applications.

An Al–PTFE triboelectric nanogenerator (TENG) was successfully fabricated, and its triboelectric performance was effectively enhanced through the surface modification of the PTFE by Au + ion irradiation at different doses. Irradiation of the PTFE with 1.5 MeV Au + in the dose range of 1 × 10 13 to 5 × 10 14 ions-cm −2 causes chain scission and defluorination of the polymer, resulting in the formation of unsaturated carbon bonds and oxygen-containing functional groups on the PTFE surface. The Au + irradiation induces the formation of microvoids and decreases the surface roughness of the PTFE. These nanoscale features and chemical modifications collectively enhance the TENG output voltage and power density compared with the pristine PTFE. The maximum values of the output voltage and power density of the Al-PTFE TENG were found to be ∼112 V and 1.74 Wm −2 respectively at 5 × 10 14 ions-cm 2. The power density value of the irradiated sample is higher than that of the pristine sample (0.14 W/m 2) by a factor of ∼12. This power density is sufficient to charge capacitors and drive small electronic devices such as a light-emitting diode.