Chao-Yu Li

Highly transparent and flexible triboelectric nanogenerators: performance improvements and fundamental mechanisms

Transparent, flexible and highly efficient power sources are essential components of mobile electronics and optoelectronic devices. Here, based on the first generation of the transparent triboelectric nanogenerator (TENG), we demonstrate a simple and innovative design that can simultaneously improve the output performance and transmittance of the TENG. The improved TENG gives a maximum output up to 200 V and 7 μA at a current density of ∼0.78 μA cm−2. The TENG shows a high transmittance of ∼78%. To deeply understand the nature of the triboelectric effect, we investigated the influence of the UV–ozone treatment, surface properties, and surrounding environment on the output performance. Integrating the characterization results, we conclude that the tribocharge generation of the PDMS surface is probably due to the bond breaking of Si–O–Si groups, and is closely related to the surface properties and surrounding environment.

In Situ Monitoring of Electrooxidation Processes at Gold Single Crystal Surfaces Using Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

Identifying the intermediate species in an electrocatalytic reaction can provide a great opportunity to understand the reaction mechanism and fabricate a better catalyst. However, the direct observation of intermediate species at a single crystal surface is a daunting challenge for spectroscopic techniques. In this work, electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (EC-SHINERS) is utilized to in situ monitor the electrooxidation processes at atomically flat Au(hkl) single crystal electrode surfaces. We systematically explored the effects of crystallographic orientation, pH value, and anion on electrochemical behavior of intermediate (AuOH/AuO) species. The experimental results are well correlated with our periodic density functional theory calculations and corroborate the long-standing speculation based on theoretical calculations in previous electrochemical studies. The presented in situ electrochemical SHINERS technique offers a unique way for a real-time investigation of an electrocatalytic reaction pathway at various well-defined noble metal surfaces.

Au+-cetyltrimethylammonium bromide solution: A novel precursor for seed-mediated growth of gold nanoparticles in aqueous solution

AbstractThe appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal-especially Au-nanoparticles. In the present work, Au seeds (prepared by the reduction of Au3+ solution with NaBH4 in the presence of cetyltrimethylammonium bromide (CTAB)) have been used to initiate the growth of Au nanoparticles from two different Au precursors. When an aqueous Au+ solution prepared in the presence of CTAB micelles was treated with ascorbic acid in the presence of the gold seeds, a high yield (up to 92%) of gold nanoparticles was obtained. By varying the volume of the seed solution with a fixed amount of Au+, we can effectively control the morphological transformation of the resulting Au nanoparticles from cubes to octahedra. When an aqueous Au3+ solution was prepared in the presence of CTAB micelles and treated with ascorbic acid in the presence of the gold seeds, smaller yields of Au nanoparticles were obtained. A preliminary growth mechanism has been proposed based on the changes induced by varying the amount of ascorbic acid and the ratio of the concentration of Au+ to the number of seeds.

Plasmon-Enhanced Ultrasensitive Surface Analysis Using Ag Nanoantenna

Raman scattering and fluorescence spectroscopy permeate analytic science and are featured in the plasmon-enhanced spectroscopy (PES) family. However, the modest enhancement of plasmon-enhanced fluorescence (PEF) significantly limits the sensitivity in surface analysis and material characterization. Herein, we report a Ag nanoantenna platform, which simultaneously fulfills very strong emission (an optimum average enhancement of 105-fold) and an ultrafast emission rate (∼280-fold) in PES. For applications in surface science, this platform has been examined with a diverse array of fluorophores. Meanwhile, we utilized a finite-element method (FEM) and time-dependent density functional theory (TD-DFT) to comprehensively investigate the mechanism of largely enhanced radiative decay. PES with a shell-isolated Ag nanoantenna will open a wealth of advanced scenarios for ultrasensitive surface analysis.

Plasmon‐Enhanced Spectroscopies with Shell‐Isolated Nanoparticles

Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), due to its versatility, has been able to break the long-term limitations of the material- and substrate-specific generalities in the traditional field of surface-enhanced Raman spectroscopy. With a shell-isolated work principle, this method provides an opportunity to investigate successfully in surface, biological systems, energetic materials, and environmental sciences. Both the shell material and core morphology are being improved continuously to meet the requirements in diverse systems, such as the electrochemical studies at single crystal electrode surfaces, in situ monitoring of photoinduced reaction processes, practical applications in energy conversion and storage, inspections in food safety, and the surface-enhanced fluorescence. Predictably, the concept of shell-isolated nanoparticle-enhancement could be expanded to the wider range for the performance of plasmon-enhanced spectral modifications.

Shell-Isolated Tip-Enhanced Raman and Fluorescence Spectroscopy

Tip-enhanced Raman spectroscopy can provide molecular fingerprint information with ultrahigh spatial resolution, but the tip will be easily contaminated, thus leading to artifacts. It also remains a great challenge to establish tip-enhanced fluorescence because of the quenching resulting from the proximity of the metal tip. Herein, we report shell-isolated tip-enhanced Raman and fluorescence spectroscopies by employing ultrathin shell-isolated tips fabricated by atomic layer deposition. Such shell-isolated tips not only show outstanding electromagnetic field enhancement in TERS but also exclude interference by contaminants, thus greatly promoting applications in solution. Tip-enhanced fluorescence has also been achieved using these shell-isolated tips, with enhancement factors of up to 1.7×103 , consistent with theoretical simulations. Furthermore, tip-enhanced Raman and fluorescence signals are acquired simultaneously, and their relative intensities can be manipulated by changing the shell thickness. This work opens a new avenue for ultrahigh resolution surface analysis using plasmon-enhanced spectroscopies.

Decorating gold nano-spheres, -rods and -cubes with gold nanodots

We have developed a simple solution method to decorate gold nanodots (7–10 nm) on gold nano-spheres, -cubes and -rods, in a solution composed of cetyltrimethyl-ammonium bromide (CTAB), gold salt, thioctic acid (TOA) and ascorbic acid (AA). When gold nanoparticles with about 1.5 nm diameters grew in the decorating solution, cauliflower-like nanoparticles were obtained. Several experimental parameters affecting the morphology of gold nanoparticles were investigated. Nanodots were also decorated on gold nanocubes or nanorods. The optical properties of these gold nanoparticles are drastically influenced by nanodots decorated. The growth mechanism of nanodots on gold nanoparticles is discussed.