High-Throughput Electrospinning System| Carbon Quantum Dot Functionalized Nanofiber-BasedTriboelectric Nanogenerator With Boosted Output andFluorescence Function

 Prof. Zi Yunlong at HKUST: Carbon Quantum Dot Functionalized Nanofiber-Based Triboelectric Nanogenerator With Enhanced Output and Fluorescence Function

In recent years, triboelectric nanogenerators (TENGs) based on the coupling of triboelectrification and electrostatic induction effects have provided a new energy supply solution by harvesting low-frequency mechanical energy from the environment. Researchers have explored various material strategies to improve the output performance of nanofiber-based TENGs or expand their functional applications. Recently, the luminescent properties of triboelectric materials have offered a simple means of information transmission and show promise for integration with TENGs, opening new avenues for interactive signal visualization in wearable electronics.

Recently, Prof. Zi Yunlong's team at Hong Kong University of Science and Technology (Guangzhou) proposed a composite nanofiber material based on carbon quantum dots/polyvinylidene fluoride (CDs/PVDF) as a highly negative material to enhance the output performance of TENGs. The related research was published in Interdisciplinary Materials under the title "Carbon Quantum Dot Functionalized Nanofiber‐Based Triboelectric Nanogenerator With Boosted Output and Fluorescence Function." Dr. Guo Ru from The Chinese University of Hong Kong is the first author, with Prof. Zi Yunlong as the corresponding author. Prof. Luo Xing and Prof. Zhou Xuefan from Central South University are co-corresponding authors.

Nano-sized and surface-functionalized CDs act as nucleating agents to promote the polarization-induced β-phase transformation of PVDF polymer. The CDs/PVDF nanofiber membrane generates more negative surface charge density through β-phase PVDF polarization, resulting in a greater electrostatic potential difference that enhances charge transfer. In addition to reducing bead defects, it produces a more uniform fiber morphology that increases the effective contact area. Furthermore, the CDs/PVDF composite nanofibers exhibit unique multicolor fluorescence effects, showing broad application prospects in visual displays and sensing.The fabricated TENG achieves a short-circuit current density of ~61.8 mA/m² and a maximum peak power density of ~11.7 W/m², surpassing most reported nanofiber-based TENGs to date. As a demonstration of application potential, the TENG shows energy harvesting capabilities for charging capacitors, powering 125 green LEDs, and serving as a self-powered sensor for human motion monitoring. This work provides insights for developing novel triboelectric materials for high-output TENGs with broad potential in biomechanical energy harvesting and self-powered sensing.

Figure 1. Schematic illustration of the electrospinning process for fluorescent CDs/PVDF nanofiber composites and conceptual demonstration of nanofiber-based TENG for energy harvesting and self-powered sensing.

Figure 2. Characterization of quantum dot powder and CDs/PVDF nanofiber membranes.

Figure 3. (A-E) SEM images of electrospun CDs/PVDF nanofibers with different CD concentrations. (F) Hydrophobicity of CDs/PVDF nanofibers. LSCM images of electrospun CDs/PVDF nanofibers under (G) 389 nm, (H) 458 nm, and (I) 488 nm excitation. (J) PL spectra and (K) CIE diagram of CDs/PVDF nanofibers under 389, 458, and 488 nm excitation.

Figure 4. (A) Schematic of CDs/PVDF-Nylon66 TENG in vertical contact-separation mode. (B) Working mechanism of TENG. (C) COMSOL-simulated potential distribution. Electrical output performance: (D) Isc, (E) Voc, and (F) σsc of CD/PVDF nanofibers with different CD contents. (G) Isc and (H) Voc under 10-90 N contact forces. (I) Isc and (J) Voc at 1-9 Hz operating frequencies. (K) Stability test over 12,000 cycles.

Figure 5. Output enhancement mechanism. (A) Single-molecule electrostatic potential distribution and surface potential histogram: (i) Nylon66, (ii) α-PVDF, (iii) β-PVDF. (B) Contact interface potential distribution: (i) Nylon66/α-PVDF and (ii) Nylon66/β-PVDF. (C) KPFM topography and surface potential of pristine PVDF vs. 8 wt% CDs/PVDF nanofiber membranes. (D) Schematic of contact potential difference. (E) Surface DC voltmeter tests of LPPS-NFC membranes with different CD contents before/after contact-separation. (F) Surface potential variation over time.

Figure 6. Application demonstrations of CDs/PVDF-Nylon66 TENGs. (A) Output current/voltage. (B) Power density vs. external resistance. (C) Performance comparison with reported works [17,43-51]. (D) Rectifier circuit for capacitor charging. (E) Charging curves of capacitors. (F) 125 green LEDs powered by rectified TENG. (G) Self-powered wearable biosensor detecting body movements. (H) Demonstration of CDs/PVDF nanofiber membrane functionality.

In summary, CDs/PVDF composite nanofibers are demonstrated as a highly negative triboelectric material. Specifically, the incorporation of CDs promotes the formation of polarized β-crystalline phases, benefiting from their nano-size and surface functionalization. Moreover, the surface morphology of CDs/PVDF nanofibers is significantly improved by reducing bead defects during electrospinning, yielding more uniform nanofibers. Most notably, CDs/PVDF nanofibers exhibit the unique advantage of color-tunable photoluminescence properties, making them promising for visual displays and wearable electronics sensing.

Compared with PVDF-Nylon66, the TENG using Nylon66-8 wt% CDs/PVDF shows 2.4× and 2.0× enhancements in output voltage and current, respectively. The enhancement mechanism confirms that increased β-phase polarization in PVDF enlarges the energy level difference with positively charged Nylon66 through strengthened dipole-dipole interactions and electrostatic coupling effects, facilitating charge transfer during contact electrification.Under optimized operating force and frequency, the CDs/PVDF-Nylon66 TENG demonstrates exceptional output performance with a short-circuit current density of ~61.8 mA/m² and a maximum peak power density of ~11.7 W/m², exceeding many recently reported nanofiber-based TENGs. For practical applications, the energy harvesting capability of CDs/PVDF-Nylon66 TENGs is demonstrated by efficiently charging commercial capacitors and rapidly illuminating 125 green LEDs. Additionally, self-powered wearable sensors constructed with CDs/PVDF nanofibers enable real-time detection of body movement signals.This work establishes a paradigm for developing novel triboelectric materials in high-output TENGs and provides sustainable, eco-friendly energy solutions for self-powered wearable electronics.