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[Display omitted] • Flower-like C-ZnO microspheres assembly from nanoneedles were prepared using carbon spheres as templates. • C-ZnO nanoneedle is single crystal with exposed nonpolar {1010} facets. • Doping ZnO with C results in the production of oxygen vacancies. • Flower-like C-ZnO microspheres exhibited high photoreactivity and excellent stability towards MO degradation. In this work, carbon spheres (CSs) derived from glucose by simple eco-friendly process were used to create a multiphase environment for precipitation reaction to obtain flower-like C-doped ZnO (C-ZnO) nanoneedles assembly. It was found that the presence of carbon spheres can affect the crystal orientation and morphology of ZnO. When the additive amount of carbon spheres was 13 wt%, one-dimensional (1D) needle-like single crystal C-doped ZnO were obtained, which exposed with higher proportion of nonpolar {1010} facets (51%) than that of pristine ZnO (46%), and C-Zn and C-O-Zn bonds were formed. Compared with pristine ZnO prepared by direct precipitation method (ZnO-DPM) without carbon spheres, carbon doped ZnO exhibited higher light absorption ability and smaller band gap width due to the formation of surface defects. The photocatalytic degradation rate of methyl orange over 13 %C-ZnO was 99.98% for 3 h under the irradiation of UV lamp (15 W), almost 1.3 times higher than that of pristine ZnO-DPM. Even after repeating use for 3 times, the degradation rate of methyl orange can be kept as high as 99%. The present study offers a new preparation method for high photoreactive ZnO with exposed nonpolar {1010} facets by precipitation reaction. [ABSTRACT FROM AUTHOR]

Abstract: Pd2+-doped ZnO nanotetrapods were prepared and studied for the humidity detection application. The humidity sensors developed were featured by combination of a quartz crystal microbalance (QCM) as a transducer and Pd2+-doped ZnO nanotetrapods as a sensing element. The ZnO nanotetrapods were synthesized by evaporating highly pure zinc pellets (99.999%) at 900°C in air and PdCl2 was doped on by traditional solution mixing process. Then the mixed solution distributed onto the electrode surfaces of the quartz crystal at room temperature. Pd2+-doped ZnO nanotetrapods were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results indicated that the response of the sensors varied with the different dosage PdCl2. Linear regression algorithm was used for evincing the highly linear behavior of the Pd2+-doped ZnO nanotetrapods sensor. In this humidity sensing system, the Pd2+-doped ZnO nanotetrapods sensing material coated on the gold electrode of QCM showed good sensitivity (∼74.24324Hz/%RH (relative humidity)), reproducibility, linearity (R 2 =−0.98834), short response and recovery time (less than 5s). [Copyright &y& Elsevier]

Semiconductor heterostructures based on transition metal dichalcogenides provide a broad platform to research two-dimensional nanomaterials and design atomically thin devices for fundamental and applied interests. The MoS 2 /WS 2 heterostructure was prepared on SiO 2 /Si substrate by chemical vapor deposition (CVD) in our research. And the optical properties of the heterostructure was characterized by Raman and photoluminescence (PL) spectroscopy. The similar 2 orders of magnitude decrease of PL intensity in MoS 2 /WS 2 heterostructures was tested, which is attribute to the electrical and optical modulation effects are connected with the interfacial charge transfer between MoS 2 and WS 2 films. Using MoS 2 /WS 2 heterostructure as channel material of the phototransistor, we demonstrated over 50 folds enhanced photoresponsivity of multilayer MoS 2 field-effect transistor. The results indicate that the MoS 2 /WS 2 films can be a promising heterostructure material to enhance the photoresponse characteristics of MoS 2 -based phototransistors. [ABSTRACT FROM AUTHOR]

AlGaAs materials are used in a variety of cutting-edge devices and the band gap states after the surface oxidization is found with Fermi level pinning. With first-principle calculations, we explore the formation of gap states during the initial stage of native-oxide growth on Al 0.5 Ga 0.5 As (001) surface. The results indicate that oxygen adsorption at the bridge sites of Al (Ga)-As satisfies the bond saturation and doesn't lead to any effect on the surface gap states. The breaking of As-As dimer results in the defect states in band gap with Fermi level pining due to the replacement of oxygen. In the oxidization process, it is found that the As-As dimer is very easy to be broken. In addition, the defect states in band gap maybe disappear after the full oxidization of surface with the elimination of unsaturated As on surface. With these gap states, some absorption peaks are found to appear in the range of 0–1 eV in the absorption spectra. [ABSTRACT FROM AUTHOR]

• Stone-Wales defects can upgrade the SO 2 -sensing performance of arsenene. • It is highly appreciated because point defects especially Stone-Wales defect generate much easier on arsenene than other common 2D material. • Most of gas sensor based on 2D material have a slow recovery. • The external electric field can greatly adjust the SO 2 -sensing performance on arsenene with Stone-Wales defects. • This makes it possible to substantially accelerate the recovery of the arsenene with Stone-Wales defects. • Both biaxial strain and external electric field can further enhance the SO 2 -sensing performance of arsenene with Stone-Wales defects. Reported here is a first-principle study of the adsorption of four SF 6 decomposition products on pristine arsenene and arsenene with Stone-Wales defects (SW). The results revealed that pristine arsenene exhibited high sensitivity and selectivity to SO 2 , and Stone-Wales defects enhanced the SO 2 -sensing performance. The presence of ambient O 2 , H 2 O, and SF 6 only slightly affected the adsorption on both pristine and SW arsenene. We also investigated the effect of biaxial strain and an external electric field on the SO 2 detection of SW arsenene. The SO 2 adsorption strength on SW arsenene was drastically enhanced or weakened, depending on the direction of the electric field, which is desirable for realizing the ultra-sensitive adsorption and desorption of SO 2. [ABSTRACT FROM AUTHOR]

• High selectivity and sensitivity of GeP monolayer to nitrogen oxides. • The variation of work function change can be used to distinguish NO 2 and NO. • Compressive strain improve sensitivity of GeP to NO 2 without raising recovery time. • Applied negative electric field can greatly enhance response of GeP monolayer to NO 2. The sensing properties of GeP monolayer to small gas molecule (CO, CO 2 , O 2 , H 2 O, NH 3 , NO and NO 2) have been investigated by performing first-principle calculations. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that GeP monolayer is the most sensitive to NO 2 and NO molecules, and all gas molecules act as acceptors to gain electrons from GeP monolayer. The adsorption energy of NO 2 is smaller than that of NO molecule, which implies that NO 2 is more easily desorbed from GeP. And different work function changes also indicate the possibility to identify NO 2 and NO in an oxygen-free environment. Moreover, we apply uniaxial and biaxial strains to GeP monolayer and find that a small biaxial compressive strain can effectively enhance the sensitivity of work function type sensor based GeP to NO 2 molecule without increasing recovery time. We also discuss the effect of external vertical electric field on the adsorption performance of NO 2 molecule. The negative electric field can significantly increase the adsorption strength, charge transfer and work function change of NO 2 -GeP system. Our results indicate that GeP monolayer is a potential candidate for NO 2 gas sensor. [ABSTRACT FROM AUTHOR]