ZnS Nanobelt Research Articles

A novel SERS substrate: Wrinkled ZnS nanobelt film coated with Ag nanoparticle

Wrinkled ZnS nanobelt film was used as a template for Ag sputtering deposition as a surface-enhanced Raman scattering (SERS) substrate. The substrate exhibits excellent SERS performance because of its unique structure and possesses the great potential in trace-detecting persistent organic pollutants in the environment.

Concentrated second‐harmonic generation from a single Al‐covered ZnS nanobelt

AbstractHere we report on the hybrid nanostructures where a single ZnS nanobelt was half‐covered with an aluminum (Al) film, which is an ideal platform for studying the second‐harmonic generation (SHG) enhancement effects of the Al coating. It was fabricated by the lift‐off process and allowed for the accurate comparison of the SHG intensity between the Al‐covered and the same bare ZnS nanobelt under consistent test conditions. The results indicate that the Al coating in the hybrid nanostructures not only confines the pumping laser in the ZnS effectively, but also concentrates the emitted SHG signal greatly, increasing the signal collection efficiency. By the combination of these two effects, ∼60 times enhancement of the SHG intensity is achieved at the optimized geometry size (width and thickness) of the ZnS nanobelts. The Al‐based hybrid nanostructures open up new possibilities for low‐cost, highly efficient and directional coherent nanolight sources at short wavelengths. image

Raman selection rule for surface optical phonons in ZnS nanobelts.

We report Raman scattering results for high-quality wurtzite ZnS nanobelts (NBs) grown by chemical vapor deposition. In the Raman spectrum, the ensembles of ZnS NBs exhibit first order phonon modes at 274 cm(-1) and 350 cm(-1), corresponding to A1/E1 transverse optical and A1/E1 longitudinal optical phonons, in addition to a strong surface optical (SO) phonon mode at 329 cm(-1). The existence of the SO band is confirmed by its shift with different surrounding dielectric media. Polarization dependent Raman spectra were recorded on a single ZnS NB and for the first time a SO phonon band has been detected on a single nanobelt. Different selection rules for the SO phonon mode are shown from their corresponding E1/A1 phonon modes, and were attributed to the breaking of anisotropic translational symmetry on the NB surface.

New UV‐A Photodetector Based on Individual Potassium Niobate Nanowires with High Performance

A new UV‐A photodetector based on K2Nb8O21 nanowire is successfully fabricated for the first time. The potassium niobate is synthesized using a facile molten method. The K2Nb8O21 nanowire photodetectors exhibit an excellent sensitivity and wavelength selectivity with respect to UV‐A light. Furthermore, the photodetectors show great advantages in response time compared with other sensors based on single‐oxide semiconductor nanostructures, and, especially, the responsivity is much better than that of single ZnS nanobelt photodetectors. The mechanism of conductivity is explained from the viewpoints of field emission and thermionic field emission for the change of light intensities.

Determination of the mechanical constants of ZnS nanobelt by combining nanoindentation test and finite element method

The single nanobelt simplified as transversely isotropic is modeled by three dimension element during the modeling of finite element method (FEM), and the mechanical constants of ZnS nanobelt are obtained by combining nanoindentation test and FEM. In the forward analysis, the numerical loading curves at the appropriate penetration depth are simulated by using the purely mechanical indentation (PMI) and piezoelectric indentation (PI) modes to extract the numerical maximum indentation load and numerical loading curve exponent, and they are used to establish the dimensionless equations related with the mechanical constants of nanobelt by fitting the mechanical constants vs numerical maximum indentation load and numerical loading curve exponent curves. In the reverse analysis, the experimental indentation curve performed on ZnS nanobelt is fitted as the power function to obtain the maximum indentation load and the loading curve exponent and they are substituted into the dimensionless equations to solve the mechanical constants of the nanobelt. In order to verify the validity, the mechanical constants are inputted into ABAQUS software to obtain the computational loading curves under PMI and PI modes, and they are in good agreement with the experimental indentation curve of ZnS nanobelt. The combination solutions of mechanical constants under PMI mode is of larger total error than those under PI mode, and it indicates that the piezoelectric effect should be reasonably considered into the developed method, which is effective to determine the mechanical property of single nanobelt.

Width-to-thickness ratio dependence on photoplastic effect of ZnS nanobelt

Photoplastic effect (PPE) of individual ZnS nanobelt with different width-to-thickness (w/t) ratios was investigated by using a nanoindenter in conjunction with an incident ultraviolet light source system. The results show that the positive and negative PPEs are observed for the w/t ratios 4.9–9.6 and 3.2–4.1. At the peak indentation loads 20–50 μN, the positive and negative PPEs occur for the w/t ratios 4.9 and 3.2, however, they disappear at 60 μN. PPE is determined by w/t ratio not peak indentation load, and it is interpreted by the competing mechanisms of increase of Peierls barrier and radiation enhanced dislocation glide.

Heteroe-Pitaxial Growth and Optical Properties of SnO<sub>2</sub> Nanowires on ZnS Nanobelts

The authors present the results of hetero-epitaxial growth of ultrafine SnO2nanowires on ZnS nanobelt substrates by a simple thermal evaporation method. ZnS/SnO2hetero-nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM) to obtain the morphology and structural information. Comparing with ZnS nanobelts and SnO2nanowires respectively, the optical properties of ZnS/SnO2hetero-nanostructures are studied by Raman scattering and photoluminescence (PL) spectroscopy at room temperature.

Synthesis, characterization and optical properties of ZnS nanobelt/ZnO nanoparticle heterostructures

In this study, we present the synthesis and characterization of ZnS nanobelt/ZnO nanoparticle heterostructures by the metal organic chemical vapor deposition (MOCVD) method. On the basis of TEM results, the ZnO nanoparticles epitaxially grew on the (100) surface of the ZnS nanobelts, sharing the same orientation with the ZnS nanobelt along [210] and [001] directions, respectively. The as-prepared ZnS/ZnO nano-heterostructures exhibit an important feature of single-crystallinity. At room temperature, the ZnS nanobelt/ZnO nanoparticle heterostructures show one strong green emission and two weak violet emissions, which come from the ZnS and ZnO component, respectively. This study will give us some inspiration for the construction of high quality nano-heterostructures.

Tracking the Interface of an Individual ZnS/ZnO Nano-Heterostructure

Understanding and controlling the electronic structure in semiconductor heterostructures is of foremost importance in order to achieve their promise in broad applications. Here we report the chemical mapping and the electronic structure of a single ZnS nanobelt/ZnO nanorod heterostructure by scanning transmission X-ray microscopy. It is the first time that nanoscaled spectroscopy across the interface between the ZnS and ZnO nanocomponents is studied in detail. Nano-X-ray absorption near edge structure at both O K-edge and Zn L3,2-edge indicates that ZnO was anchored underneath the side surfaces of ZnS nanobelt. The threshold shift of the edge energy across the ZnS/ZnO interface illustrates an upward movement of the unoccupied states of O character in the conduction band of ZnO and a downward movement of the unoccupied states of S character in the conduction band of ZnS, revealing the effect of the interface on band alignments of the ZnS/ZnO nanocomposite.

Structure and optical properties of individual hierarchical ZnS nanobelt/ZnO nanorod heterostructures

Here, we report the synthesis and characterization of high-quality hierarchical ZnS nanobelt/ZnO nanorod heterostructures by a simple two-step vapor-phase transport method. On the basis of TEM results, ZnO nanorods epitaxially grew on the side surfaces of ZnS nanobelt along ±[001] directions, resulting in the hierarchical ZnS/ZnO nano-heterostructures having an important feature of single crystallinity. Cathodoluminescence(CL) studies of single ZnS nanobelt and ZnS/ZnO nano-heterostructures reveal that the bandgap emission of the ZnS component was almost totally quenched after the growth of ZnO nanorods on ZnS nanobelt. In addition, high-spatial resolution CL results indicate that the ZnS component contributes more to the green emission of ZnS/ZnO nano-heterostructures than the ZnO component.

An Efficient Way to Assemble ZnS Nanobelts as Ultraviolet‐Light Sensors with Enhanced Photocurrent and Stability

AbstractAlthough there has been significant progress in the fabrication and performance optimization of one‐dimensional nanostructure‐based photodetectors, it is still a challenge to develop an effective and low‐cost device with high performance characteristics, such as a high photocurrent/dark‐current ratio, photocurrent stability, and fast time response. Herein an efficient and low‐cost method to achieve high‐performance ‘visible‐blind’ microscale ZnS nanobelt‐based ultraviolet (UV)‐light sensors without using a lithography technique, by increasing the nanobelt surface areas exposed to light, is reported. The devices exhibit about 750 times enhancement of a photocurrent compared with individual nanobelt‐based sensors and an ultrafast time response. The photocurrent stability and time response to UV‐light do not change significantly when a channel distance is altered from 2 to 100 µm or the sensor environment changes from air to vacuum and different measurement temperatures (60 and 150 °C). The photoelectrical behaviors can be recovered well after returning the measurement conditions to air and room temperature again. The low cost and high performance of the resultant ZnS nanobelt photodetectors guarantee their highest potential for visible‐blind UV‐light sensors working in the UV‐A band.

A photoconductive semiconductor switch based on an individual ZnS nanobelt

A photoconductive semiconductor switch (PCSS) based on an individual ZnS nanobelt (NB) was investigated. Under ultraviolet light (280 nm), the current–voltage curve shows that this PCSS is of high photosensitivity (∼10 4 ), and the response time spectrum shows that this PCSS has a fast response (typical rise time 0.07 s and decay time 0.12 s) and a high-voltage response (6.7 V). Oxygen chemisorption is responsible for the improved photoconductive properties. This PCSS is a promising candidate for future integration.

Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

Millimeter-long single-crystalline hexagonal ZnS nanobelts were grown on specific locations on a wafer scale. This is the first time that the millimeter-scale ZnS nanobelt has been synthesized. The longest nanobelts are about 3 mm. The as-grown nanobelts were characterized by means of field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. The results indicate that the ultra-long nanobelts are pure single-crystalline hexagonal ZnS. There are two kinds of ZnS nanobelts existing in the products. One is the nanobelts that have two smooth sides and grow along the [0 0 1] longitudinal direction, and the other is the nanobelts that have one smooth side and one saw-teeth-like side, namely nanosaws, and grow along the [2 1 0] longitudinal direction. A vapor–liquid–solid mechanism is suggested for the lengthwise growth of the ZnS nanobelts (nanosaws) and a vapor–solid mechanism for the side direction growth of the saw-teeth of the nanosaws.

Fabrication and Field-Emission Performance of Zinc Sulfide Nanobelt Arrays

Large-scale, well-aligned, and oriented wurtzite ZnS nanobelt arrays have been synthesized by a simple template-free solvothermal reaction and subsequent heat-treatment process. The ZnS nanobelts grow along the [0001] direction perpendicularly on a zinc substrate, which have a thickness of about 30 nm, widths of several hundreds of nanometers, and uniform length up to 4 μm. The selection of Zn foil as the substrate is crucial for the formation of ZnS nanostructured arrays. The concentration of Zn ions, the pH value in the initial precursor solution, and the reaction temperature also have an important influence on the morphology of the final arrays. The formation of the nanobelt arrays are attributed to the structural compatibility of the substrate with ZnS and the growth-rate-dependence of morphology. Importantly, such nanostructured arrays show good field-emission properties with low turn-on fields (3.8 Vμm-1) and high field-enhancement factors (1839). This is attributed to the top edges and corners of t...

Room-temperature oxygen sensitivity of ZnS nanobelts

Room-temperature oxygen sensing is realized from individual ZnS nanobelts. Under UV illumination the current through ZnS nanobelt increases from 0.265to2.26nA as the oxygen pressure decreases from 1×105to3×10−3Pa. The conductance of ZnS nanobelt exhibits a logarithmic dependence on oxygen pressure, which is in agreement with theoretical prediction. The sensing is based on the enhanced modulation of ZnS nanobelts conductance by adsorbed oxygen under illumination. These results demonstrate an approach to in situ precisely detect oxygen at room temperature.

Crystal orientation-ordered ZnS nanobelt quasi-arrays and their enhanced field-emission

Crystal orientation-ordered ZnS nanobelt quasi-arrays were fabricated using a non-catalytic and template-free thermal evaporation process; field-emission measurements show that these novel arrays are decent field emitters possessing a current density more than 20 times higher than that of randomly-oriented ZnS nanobelt ensembles at a macroscopic field of 5.5 V microm(-1).

Well-aligned zinc sulfide nanobelt arrays: Excellent field emitters

Large-scale, well-aligned and oriented wurtzite ZnS nanobelt arrays are fabricated by a simple solvothermal reaction and subsequent heat treatment. The nanobelts grow along the [0001] direction perpendicularly on a zinc substrate, which are about 30nm in thickness, several hundreds of nanometers in width, and up to 4μm in length. Importantly, such nanostructured arrays show a good field emission property with low turn-on field (3.8Vμm−1) and high field enhancement factor (∼1800), which is ascribed to the top edges and corners of the freestanding and well aligned nanobelts, and good electric contact with the conducting substrate where they grow.

Oriented Assemblies of ZnS One‐Dimensional Nanostructures

Oriented ZnS nanobelt arrays and ZnS multicore microcables consisting of oriented nanowire bundles with sheaths (see Figure) have been synthesized via a controlled thermal process. Both the ZnS nanowires and nanobelts are single crystals grown along the [001] axis. The special structures of the oriented assemblies of ZnS one‐dimensional nanostructures may have potential applications in nanoelectronics and photonics.

Straight ZnS nanobelts with wurtzite structure synthesized by the vapour phase transportprocess and their crystallization and photoluminescence properties

Single-crystalline wurtzite ZnS nanobelts were synthesized by the VPTprocess for the first time in the presence of Au catalyst on the Sisubstrates. Each ZnS nanobelt is fairly straight. The ZnS nanobelts are50–100 µm in length, 150–600 nm in width and 3–10 in ratio of the width to the thickness. Thecrystalline directions along the length and the width dimensions of the ZnS nanobelts areperpendicular to and make angles within the range0°–15° to and [0001] crystalline directions, respectively. Strong near-band-edge emission at 344 nmwas detected.

Self-Assembled Growth of ZnS Nanobelt Networks

By using a H2-assisted thermal evaporation approach, ZnS nanobelts were grown on a Si substrate and self-assembled into a network structure. A vapor-solid process coupled with vapor−liquid−solid process is proposed for the formation of the ZnS nanobelts and their assembly. This functional structure may be well applied in the study of the electronic properties of ZnS nanobelts and other devices.