Chuang Yue

Ag nanoparticle/ZnO hollow nanosphere arrays: large scale synthesis and surface plasmon resonance effect induced Raman scattering enhancement

ZnO hollow nanosphere (HNS) arrays decorated with Ag nanoparticles (NPs) were fabricated on silicon substrates using self-assembled monolayer polystyrene (PS) nanospheres as the template. The O2 plasma etching was introduced to manipulate the diameters of the ZnO HNSs. This fabrication method has the advantages of simplicity, large scale production, easy size and shape manipulations, low cost and bio-compatibility. Scanning electron microscopy (SEM) images show that the obtained Ag NP–ZnO HNS hybrid structures are hexagonally arranged, with the uniform size and shape, and the X-ray diffraction (XRD) pattern shows that the ZnO HNS arrays are of high crystal quality and have a dominant orientation of direction. Resonant Raman scattering spectra reveal the multiphonon A1 (LO) modes of ZnO hollow nanospheres at 574, 1147 and 1725 cm−1. Enhanced resonant Raman scattering from the Ag NP modified ZnO HNSs was observed, indicating a strong energy coupling effect located at the metal/semiconductor interface. Surface enhanced Raman scattering (SERS) application for the Ag NP decorated ZnO HNS arrays was verified using a Rhodamine 6G (R6G) chromophore as a standard analyte, which is proved to be an effective SERS template for Raman signal detection. SERS substrates with different structures have been compared, and the Ag NP modified ZnO HNS system exhibits superior Raman scattering enhancements induced by the local surface plasmon resonance (LSPR) effect. The SERS mechanism was well explained by theoretical calculation results. This study is helpful to fabricate controllable Ag NP arrays using the ZnO HNS as the supporting structure and to understand the mechanism of bio-sensing enhancements due to the LSPR effect originated from the metal NPs and metal/semiconductor interface.

The Effects of Different Core-Shell Structures on the Electrochemical Performances of Si-Ge Nanorod Arrays as Anodes for Micro-Lithium Ion Batteries

Connected and airbag isolated Si-Ge nanorod (NR) arrays in different configurations have been fabricated on wafer scale Si substrates as anodes in micro-lithium ion batteries (LIBs), and the impacts of configurations on electrochemical properties of the electrodes were investigated experimentally and theoretically. It is demonstrated that the Si inner cores can be effectively protected by the connected Ge shells and contribute to the enhanced capacity by ∼68%, derived from an activation process along with the amorphization of the crystalline lattice. The first-principles calculations further verify the smaller forces on the Si layers at the atomic level during the restricted volume expansion with the covering of Ge layers. This work provides general guidelines for designing other composites and core-shell configurations in electrodes of micro-LIBs to accomplish higher capacities and longer cycle lives.

Si/Ge core-shell nanoarrays as the anode material for 3D lithium ion batteries

The rapid development of small scale electronic devices, such as M/NEMS devices, smart dust, micro or nano bio-sensors and so on, is leading to the urgent need for micro or nano power sources with the possibility for integration. In this work, 3D Si/Ge composite nanorod (NR) arrays were fabricated on wafer-scale Si substrates as anode materials in micro or nano Li ion batteries (LIBs) by a low cost, simple and Si-compatible process. Significantly improved capacities and cycling performances were accomplished in the optimized 3D Si/Ge composite NR array electrode by successfully addressing the volume expansion and conductivity issues. Further theoretical calculations gain more insights into the origins of the improved electrochemical properties by considering the adsorption and diffusion energies of Li ion in Si and Si/Ge unit cells. This study technically and fundamentally provides a perspective idea for practical applications of wafer-scale Si substrates in LIBs with the aim of supplying integrated power for micro or nano scale electronic devices.

Multi-hot spot configuration on urchin-like Ag nanoparticle/ZnO hollow nanosphere arrays for highly sensitive SERS

Urchin-like Ag nanoparticle (NP)/ZnO hollow nanosphere (HNS) arrays were fabricated employing a simple, low cost and wafer scale method consisting of nanosphere lithography (NSL) and solution processes. This three-dimensional (3D) multi-hot spot decorated nanocomposite presents an as high as 108 Raman enhancement using Rhodamine 6G (R6G) as the probe with the concentration down to 10−10 M. The high density hot spots in a unit area and strong field intensity around each individual hot spot in 3D layout are believed to be the major reasons for this high sensitivity Raman phenomenon, which is further proved by the theoretical simulation results. Given its high Raman sensitivity and good reproducibility in a large area, this urchin-like Ag NP/ZnO HNS hybrid nanoarray can be reasonably proposed to be used as a SERS substrate in practical applications, including bio-sensing, materials characterization, environmental science and so on.

Effect of the surface-plasmon–exciton coupling and charge transfer process on the photoluminescence of metal–semiconductor nanostructures

The effect of direct metal coating on the photoluminescence (PL) properties of ZnO nanorods (NRs) has been investigated in detail in this work. The direct coating of Ag nanoparticles (NPs) induces remarkable enhancement of the surface exciton (SX) emissions from the ZnO NRs. Meanwhile, the charge transfer process between ZnO and Ag also leads to notable increment of blue and violet emissions from Zn interstitial defects. A thin SiO2 blocking layer inserted between the ZnO and Ag has been demonstrated to be able to efficiently suppress the defect emission enhancement caused by the direct contact of metal-semiconductor, without weakening the surface-plasmon-exciton coupling effect. A theoretical model considering the type of contacts formed between metals, ZnO and blocking layer is proposed to interpret the change of the PL spectra.

Fabrication of 3D hexagonal bottle-like Si–SnO2 core–shell nanorod arrays as anode material in on chip micro-lithium-ion-batteries

Three-dimensional (3D) Si–SnO2 composite core–shell nanorod arrays were fabricated as the anode material in lithium ion micro-batteries by nanosphere lithography (NSL) combined with inductive coupled plasma (ICP) dry etching technology. The hexagonal bottle-like Si NR arrays in wafer scale with homogeneous morphology and good mechanical structure provide enough space to accommodate the volume expansion during Li ion insertion/de-insertion processes, while the additionally deposited SnO2 thin film was prepared to successfully improve the capacities and cycle performance by configuring the 3D Si–SnO2 NR composite electrode arrays. This fabrication method has the advantages of simplicity, large scale production, easy size and shape manipulations, low cost and Si-process compatibility. This work will facilitate the configuration of solid state micro-batteries for power supply in micro-electronic devices, such as MEMS devices or smart IC chips.

Plasmonic-enhanced self-cleaning activity on asymmetric Ag/ZnO surface-enhanced Raman scattering substrates under UV and visible light irradiation

Two different asymmetric Ag/ZnO composite nanoarrays were fabricated. These nanoarrays are proposed as highly sensitive and uniform surface-enhanced Raman scattering (SERS) substrates with plasmonic-enhanced UV-visible photocatalytic properties for self-cleaning. The asymmetric nanostructures are composed of Ag nanoparticles hanging inside or capping on the top of ZnO hollow nanospheres, which allows the generation of a strong local electric field near the contact area owing to the asymmetric dielectric environment. Experimental and simulation results showed that these asymmetric structures are favorable for achieving high photocatalytic activity under UV and visible light irradiation, in addition to improving the SERS performance. The electron transfer model based on band gap alignment was employed to further illustrate the mechanisms of the photocatalytic activity, which was dependent on the wavelength of the irradiation. Given the dramatically improved photocatalytic performance, together with the reproducible and uniform SERS signals verified by the Raman mapping results, the large area ordered asymmetric metal/semiconductor nanoarrays have been demonstrated to be suitable for further applications in multifunctional photoelectrochemical chips.

ZIF-8 Cooperating in TiN/Ti/Si Nanorods as Efficient Anodes in Micro-Lithium-Ion-Batteries

Zeolite imidazolate framework-8 (ZIF-8) nanoparticles embedded in TiN/Ti/Si nanorod (NR) arrays without pyrolysis have shown increased energy storage capacity as anodes for lithium ion batteries (LIBs). A high capacity of 1650 μAh cm(-2) has been achieved in this ZIF-8 composited multilayered electrode, which is ∼100 times higher than the plain electrodes made of only silicon NR. According to the electrochemical impedance spectroscopy (EIS) and (1)H nuclear magnetic resonance (NMR) characterizations, the improved diffusion of lithium ions in ZIF-8 and boosted electron/Li(+) transfer by the ZIF-8/TiN/Ti multilayer coating are proposed to be responsible for the enhanced energy storage ability. The first-principles calculations further indicate the favorable accessibility of lithium with appropriate size to diffuse in the open pores of ZIF-8. This work broadens the application of ZIF-8 to silicon-based LIBs electrodes without the pyrolysis and provides design guidelines for other metal-organic frameworks/Si composite electrodes.

High Stability Induced by the TiN/Ti Interlayer in Three-Dimensional Si/Ge Nanorod Arrays as Anode in Micro Lithium Ion Battery

Three-dimensional (3D) Si/Ge-based micro/nano batteries are promising lab-on-chip power supply sources because of the good process compatibility with integrated circuits and Micro/Nano-Electro-Mechanical System technologies. In this work, the effective interlayer of TiN/Ti thin films were introduced to coat around the 3D Si nanorod (NR) arrays before the amorphous Ge layer deposition as anode in micro/nano lithium ion batteries, thus the superior cycling stability was realized by reason for the restriction of Si activation in this unique 3D matchlike Si/TiN/Ti/Ge NR array electrode. Moreover, the volume expansion properties after the repeated lithium-ion insertion/extraction were experimentally investigated to evidence the superior stability of this unique multilayered Si composite electrode. The demonstration of this wafer-scale, cost-effective, and Si-compatible fabrication for anodes in Li-ion micro/nano batteries provides new routes to configurate more efficient 3D energy storage systems for micro/nano smart semiconductor devices.

Synthetic preparation of novel 3D Si/TiO2–Ti2O3 composite nanorod arrays as anodes in lithium ion batteries

A three dimensional (3D) Si/TiO2–Ti2O3 composite has been synthetically prepared on micro-fabricated Si nanorod arrays (NRs) by a solvothermal method. Improved electrochemical performances were achieved with this composite as the anode in lithium ion batteries compared to the individual Si NRs electrode, which benefited from the volume alleviating effect in the TiO2 thin sheath and better conductivity in Ti2O3 grains. This novel nanostructured composite presents great potential in applications in micro/nano-electro-mechanic systems (M/NEMS), photovoltaic and photocatalytic devices.