Highly Sensitive and Stable SERS Substrate Fabricated by Co-sputtering and Atomic Layer Deposition.

In this study, we develop a facile method to fabricate highly sensitive and stable surface-enhanced Raman scattering (SERS) substrate, which is realized by combining co-sputtering with atomic layer deposition technology. To accomplish the SERS substrate preparation, we firstly utilized co-sputtering silver and aluminum on glass slides to form uniform discontinuous Ag film by removing Al later, which acted as SERS active moiety and presented high sensitivity in glycerin detection. After coating an ultrathin TiO2 layer via atomic layer deposition (ALD), the samples could further enhance the Raman signal due to the chemical effect as well as the long-range effect of the enhanced electromagnetic field generated by the encapsulated Ag nanoparticles (NPs). Besides, the coated sample could maintain the significant enhancement in air condition for more than 30 days. The high stability is induced by TiO2 layer, which efficiently prevents Ag NPs from surface oxidation. This highly sensitive and stable SERS substrate might highlight the application of interface state investigation for exploring novel liquid lubricating materials.

Highly Enhanced Visible-Light-Driven Photoelectrochemical Performance of ZnO-Modified In2S3 Nanosheet Arrays by Atomic Layer Deposition.

Photoanodes based on In2S3/ZnO heterojunction nanosheet arrays (NSAs) have been fabricated by atomic layer deposition of ZnO over In2S3 NSAs, which were in situ grown on fluorine-doped tin oxide glasses via a facile solvothermal process. The as-prepared photoanodes show dramatically enhanced performance for photoelectrochemical (PEC) water splitting, compared to single semiconductor counterparts. The optical and PEC properties of In2S3/ZnO NSAs have been optimized by modulating the thickness of the ZnO overlayer. After pairing with ZnO, the NSAs exhibit a broadened absorption range and an increased light absorptance over a wide wavelength region of 250-850 nm. The optimized sample of In2S3/ZnO-50 NSAs shows a photocurrent density of 1.642 mA cm-2 (1.5 V vs. RHE) and an incident photon-to-current efficiency of 27.64% at 380 nm (1.23 V vs. RHE), which are 70 and 116 times higher than those of the pristine In2S3 NSAs, respectively. A detailed energy band edge analysis reveals the type-II band alignment of the In2S3/ZnO heterojunction, which enables efficient separation and collection of photogenerated carriers, especially with the assistance of positive bias potential, and then results in the significantly increased PEC activity.

Hierarchically ZnIn2S4 nanosheet-constructed microwire arrays: template-free synthesis and excellent photocatalytic performances.

Hierarchically ZnIn2S4 nanosheet-constructed microwire arrays (NCMAs) on a zinc substrate have been synthesized for the first time through a one-step solvothermal method without using any template or surfactant. The as-synthesized ZnIn2S4 microwires are constructed by vertical nanosheets preferentially exposing (006) facets, which are about 1-5 µm in diameters and larger than 10 µm in average length. Experimental results demonstrate that the hierarchically ZnIn2S4 NCMAs are converted from intermediate components of single crystalline indium nanowires, which are generated along the direction of (101) planes by a displacement reaction between Zn and In3+ during the initial synthesis process. This conversion of indium nanowires to hierarchically ZnIn2S4 NCMAs has been explained by a novel corrosion-exchange-self-assembly mechanism, which might indicate a novel strategy for preparing other ternary sulphide nano-microwire arrays. The prepared ZnIn2S4 NCMAs are used as photocatalysts, demonstrating effective photocatalytic degradation activity for diverse organic pollutants including different dyes, tetracycline and 2,4,6-tribromophenol (2,4,6-TBP). This efficient photocatalytic activity is ascribed to the strong absorption of ZnIn2S4 NCMAs in a wide range from ultraviolet to visible light as well as the preferentially exposed (006) facets of ZnIn2S4 nanosheets.

In situ preparation of Ag nanoparticles on silicon wafer as highly sensitive SERS substrate.

An intensive surface enhanced Raman scattering (SERS) effect is realized by ordered Ag nanoparticles (NPs) in situ grown on silicon wafer directly using (3-aminopropyl) trimethoxysilane (APS) as both the surface modifier and reducing agent. The as-prepared ordered Ag NPs based SERS substrate shows excellent performance in detecting glycerin (an important integration in liquid super lubricating system) as well as conventional Rhodamine 6G (R6G, a kind of dye organic pollutant). The enhancement factor (EF) achieves 4-fold for glycerin and 10-fold for R6G (allowing for detecting as low as 10-11 M aqueous R6G), confirming the high sensitivity. The limited relative standard deviations (RSD) of the enhancement factors are within 15% for both glycerin and R6G, indicating the excellent uniformity. This remarkable progress is ascribed to the advantages of APS in improving adsorption and modulating distribution of Ag NPs on silicon, which results in a large local electric field to enhance the Raman signals. The SEM and UV-visible absorption spectrum characterization verified the contribution of APS in SERS improvement by investigating the influence of APS content and reduction time during the preparation process. All these advances imply that the SERS substrates prepared by Ag NPs in situ grown on silicon wafer have great potential application in real-time interface state tracing and sensitive detection.

Controlled growth of vertically aligned ultrathin In2S3 nanosheet arrays for photoelectrochemical water splitting.

This paper reports a facile solvothermal method for the in situ growth of vertically aligned In2S3 nanosheet arrays (NSAs) on fluorine-doped tin oxide substrates. The as-synthesized two-dimensional graphene-like In2S3 nanosheets show an ultrathin thickness down to 3.7 nm consisting of the duodenary interplanar spacing of the (222) plane and a tunable bandgap varying from 2.32 to 2.58 eV. The film thickness and nanosheet density of the In2S3 NSAs can be adjusted by varying the reaction time and precursor concentration. The In2S3 NSAs with a higher film thickness exhibit relatively higher photocurrent due to their stronger light absorption as well as larger surface area for sufficient charge separation and redox reaction. The photoelectrochemical performance of the In2S3 photoanodes can be greatly enhanced by constructing an effective heterojunction with ZnO to promote the photocarrier separation. The In2S3/ZnO NSAs have demonstrated an optimal photocurrent density of 349.1 µA cm-2 at 1.2 V vs. RHE and a maximum incident photon to current efficiency of 10.26% at 380 nm, which are 13.5 and 38 times higher than those of the pristine In2S3 counterparts, respectively.

A spot laser modulated resistance switching effect observed on n-type Mn-doped ZnO/SiO2/Si structure.

In this work, a spot laser modulated resistance switching (RS) effect is firstly observed on n-type Mn-doped ZnO/SiO2/Si structure by growing n-type Mn-doped ZnO film on Si wafer covered with a 1.2 nm native SiO2, which has a resistivity in the range of 50-80 Ω∙cm. The I-V curve obtained in dark condition evidences the structure a rectifying junction, which is further confirmed by placing external bias. Compared to the resistance state modulated by electric field only in dark (without illumination), the switching voltage driving the resistance state of the structure from one state to the other, shows clear shift under a spot laser illumination. Remarkably, the switching voltage shift shows a dual dependence on the illumination position and power of the spot laser. We ascribe this dual dependence to the electric filed produced by the redistribution of photo-generated carriers, which enhance the internal barrier of the hetero-junction. A complete theoretical analysis based on junction current and diffusion equation is presented. The dependence of the switching voltage on spot laser illumination makes the n-type Mn-doped ZnO/SiO2/Si structure sensitive to light, which thus allows for the integration of an extra functionality in the ZnO-based photoelectric device.