Ultra-sensitive H2S sensor based on sunflower-like In-doped ZnO with enriched oxygen vacancies.

Metal oxide sensors face the challenge of high response and fast recovery at low operating temperatures for the detection of toxic and flammable hydrogen sulfide (H2S) gases. Herein, novel In-doped ZnO with a sunflower-like structure and tunable surface properties was rationally synthesized. The substitutional In atom in the ZnO crystal can dramatically enhance the concentration of oxygen vacancies (Ov), the In-ZnO sites are responsible for fast recovery, and the formation of sub-stable sulfide intermediates gives rise to the high response towards H2S. As a result, the response of the optimized 4In-ZnO sensor is 3538.36 to 50 ppm H2S at a low operating temperature of 110 °C, which is 106 times higher than that of pristine ZnO. Moreover, the response time and recovery time to 50 ppm H2S are 100 s and 27 s, respectively, with high selectivity and stability. First-principles calculations revealed that 4In-ZnO with rich Ov exhibited higher adsorption energy for the H2S molecule than pristine ZnO, resulting in effortless H2S detection. Our work lays the foundation for the rational design of highly sensitive gas sensors through precise doping of atoms in oxygen-rich vacancies in semiconductor materials.

Advances in Doped ZnO Nanostructures for Gas Sensor.

Gas sensors based on metal oxides semiconductor (MOS) have attracted extensive attention from both academic and industry. ZnO, as a typical MOS, exhibits potential applications in toxic gas detection, owning to its wide band gap, n-type transport characteristic and excellent electrical performance. Meanwhile, doping is an effective way to improve the sensing performance of ZnO materials. In this review, the effects of different types of doping on morphology, crystal structure, band gap and depletion layer of ZnO materials are comprehensively discussed. Theoretical analysis on the strategies for enhancing the sensing properties of ZnO is also provided. This review puts forward the reasonable insight for designing efficient n-type ZnO-based semiconductor oxide sensing materials.

Ultrathin agaric-like ZnO with Pd dopant for aniline sensor and DFT investigation.

Aniline detection is of great importance in many industries, but most of the aniline sensors suffers from tedious and time consuming process. Herein, we present an efficient aniline sensor based on Pd decorated ZnO nanomaterials. Ultrathin ZnO nanosheets were synthesized by a facile one-step hydrothermal method. The nanosheets were corrugated into a unique agaric morphology, endorsing the nanomaterials with high surface area that is ideal for gas sensing applications. The obtained ZnO nanosheets were then uniformly decorated with uniform Pd nanoparticles (Pd NPs) around 5 nm in diameter. Gas sensing experiment on the ZnO decorate with different amount of Pd nanoparticles were systematically evaluated. The sample decorated with 0.3 % Pd NPs (Pd-ZnO-0.3) exhibited the highest sensitivity to aniline, which is about two orders higher than that of the pure ZnO nanosheet. The gas sensor based on Pd-ZnO-0.3 has a detection limit to aniline down to 0.5 ppm, with very short response and recovery times of 29 s and 23 s, respectively to 100 ppm aniline. First-principles DFT study was employed to provide the sensing mechanism. The improved sensing performance could be attributed to the increasing adsorbed oxygen and tunable band alignment for Pd-ZnO materials. This work provides new insights to the design strategy of Pd-decorated ZnO nanomaterials for high performance gas sensors.

Double-platelet Pd@ZnO microcrystals for NO2 chemical sensors: their facile synthesis and DFT investigation.

Double-platelet, single-platelet and spherical ZnO microcrystals were fabricated via a facile and controllable hydrothermal method. The morphology of the ZnO microcrystals and the exposure ratio of the (001) crystal surface were regulated by adjusting the pH of the solution. The ZnO microcrystals were modified with Pd nanoparticle loading by simple calcining, and the interaction of Pd nanoparticles (NPs) on the ZnO crystal surface increased its oxygen vacancy content. A micro-amount (0.05 wt%) of Pd NP-doped ZnO double-platelets (D-ZnO-0.05) enhanced the gas sensing of the sensor to 3.5 times that of pure double-platelet ZnO. The gas sensing results indicate that D-ZnO-0.05 exhibits a high response (71.2 for NO2 with 25 ppm), fast response/recovery (25 s/21 s), and superior long-term stability (remained at around 95.5% after 35 days). The enhancement in the gas sensing could be attributed to the catalysis of Pd NPs and the increase in the number of oxygen vacancies as a result of Pd loading. The band structure of D-ZnO-0.05 could be effectively tuned by introducing Pd nanoparticles, as shown in density functional theory (DFT) calculations. The Pd dopant and oxygen vacancies reduce the band gap of the ZnO(001) crystal materials, resulting in excellent sensor performance. It is believed that the D-ZnO-0.05 microcrystals could provide inspiration for crystal growth studies and high NO2 gas sensing.

Highly enhanced photocatalytic H2 evolution of Cu2O microcube by coupling with TiO2 nanoparticles.

A Cu2O/TiO2 p-n heterojunction composite was created via a facile, controllable, one-pot hydrothermal method based on cubic Cu2O and TiO2 nanoparticles in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The TiO2 nanoparticles with an average edge length of ∼10.1 nm were uniformly distributed on the crystal surface of a Cu2O cube {100}. The photocatalytic performance of the composite was effectively tuned by controlling the amount of TiO2. The Cu2O/TiO2 (60 wt%, labeled as CT-60) exhibits the highest enhanced photocatalytic activity in hydrogen production with H2 evolution of 3002.5 µmol g-1. The yield remained around 92.6% after three cycles. Hydrogen production of the CT-60 is 103 and 8.5 fold higher than the cubic Cu2O and TiO2 nanoparticles, respectively. The improvement in photocatalytic performance could be attributed to the formation of p-n heterojunction. Furthermore, the interface effect of Cu2O and TiO2 caused a broader absorbance in the visible-light region and the lower recombination of photogenerated electron-hole pairs. It is believed that the Cu2O/TiO2 p-n heterojunction composites could provide an alternative method to design highly efficient photocatalysts for solar energy.

Gamma knife radiosurgery for brainstem cavernous malformations.

OBJECTIVE: The goal of this retrospective study was to evaluate the efficacy and safety of gamma knife radiosurgery (GKS) for the treatment of brainstem cavernous malformations (CMs). METHODS: Between January of 2009 and December of 2014, 43 patients (20 males and 23 females) with brainstem CMs were treated at the West China Hospital, Sichuan University, Gamma Knife Center. The mean age of these patients was 41.7 years. All of the patients experienced 1 or more episodes of symptomatic bleeding (range 1-4) before undergoing GKS. The mean volume of the malformations at the time of GKS was 442.1mm3, and the mean prescribed marginal radiation dose was 11.9Gy. The mean follow-up period after radiosurgery was 36 months (range 12-120 months). RESULTS: Before GKS, 50 hemorrhages (1.2 per patient) were observed (25.0% annual hemorrhage rate). Three hemorrhages following GKS were observed within the first 2 years (3.92% annual hemorrhage rate), and 1 hemorrhage was observed in the period after the first 2 years (1.85% annual hemorrhage rate). In this study of 43 patients, new neurological deficits developed in only 1 patient (2.32%; permanent paresthesia on the left side of the face and the right lower limb of the patient). There were no deaths in this study. CONCLUSION: GKS is a favorable alternative treatment for brainstem CMs. Using a low marginal dose treatment might reduce the rate of hemorrhage and radiation-induced complications.

[Correlation analysis between nutritive components of Whitmania pigra and Bellamya purificata].

The dried Whitmania pigra is used for the treatment of cardiovascular and cerebrovascular diseases in traditional Chinese medicine. Bellamya purificata is widely distributed in the Chang Jiang River basin, it is natural diets of W. pigra. Current study was conducted to compare and analyze the nutritional ingredient in W. pigra, body fluid and flesh of B. purificata. Results showed that the contents of protein, crude fat and total sugar in W. pigra, body fluid and flesh of B. purificata were significantly different (P < 0.05). Protein content in W. pigra accounts up to 65.01%. The contents of inorganic elements and amino acid were abundant in W. pigra, body fluid and flesh of B. purificata. The content of essential amino acids in them were 32.6, 221.59, 40.78 mg x g(-1), respectively. The content of flavor amino acid in them were 27.51, 14.5, 32.03 mg x g(-1), while the coresponding content of antioxidant amino acid were 8.81, 5.91, 9.73 mg x g(-1), respectively. The individual amino acids of high content in them were Glu, Asp and Leu. Macro elements Ca, P, Mg and trace elements Zn, Si, Fe were abundant. It could be speculated that W. pigra may be a promising novel food, and the present results provide a foundation to develop artificial feed for W. Pigra.