A comparison of nitrogen-doped sonoelectrochemical and chemical graphene nanosheets as hydrogen peroxide sensors

Nitrogen-doped graphene nanosheet (N-SEGN) with pyrrolic nitrogen and 5-9 vacancy defects has been successfully prepared from a hydrothermal reaction of tetra-2-pyridinylpyrazine and sonoelectrochemistry-exfoliated graphene nanosheet, with point defects. Additionally, based on the same reaction using chemically reduced graphene oxide, nitrogen-doped chemically reduced graphene oxide (N-rGO) with graphitic nitrogen was prepared. The N-SEGN and N-rGO were used as a non-enzymatic H₂O₂ sensors. The sensitivity of the N-SEGN was 231.3 μA·mM⁻¹·cm⁻², much greater than 57.3 μA·mM⁻¹·cm⁻² of N-rGO. The N-SEGN showed their potential for being a H₂O₂ sensor.     

Sulfur dioxide molecule sensors based on zigzag graphene nanoribbons with and without Cr dopant

Structure, electronic, and transport properties of sulfur dioxide (SO₂) molecule adsorbed on pure and Cr doped zigzag graphene nanoribbons (ZGNRs) are investigated by means of first principle density functional theory and nonequilibrium Greenʼs function computations. It is found that Cr doped ZGNR is more sensitive to SO₂ molecule than pure ZGNR. The pure ZGNRs with and without SO₂ molecule show similar I–V curves, but the current of Cr doped ZGNR will significant increase after SO₂ molecule adsorption.     

硅基底石墨烯器件的现状及发展趋势

石墨烯是一种由单层碳原子紧密排列而形成的具有蜂窝状结构的二维晶体材料,特殊的结构赋予了其优异的性能,如高载流子迁移率、电导率、热导率、力学强度以及量子反常霍尔效应.由于石墨烯优异的特性,迅速激起了人们对石墨烯研究以及应用的热情.石墨烯沉积或转移到硅片后,其器件构建与集成和传统硅基半导体工艺兼容.基于石墨烯的硅基器件与硅基器件的有机结合,可以大幅度提高半导体器件的综合性能.随着石墨烯制备工艺和转移技术的优化,硅基底石墨烯器件将呈现出潜在的、巨大的实际应用价值.随着器件尺寸的纳米化,器件的发热、能耗等问题成为硅基器件与集成发展面临的瓶颈问题,石墨烯的出现为解决这些问题提供了一种可能的解决方案.本文综述了石墨烯作为场效应晶体管研究的进展,为解决石墨烯带隙为零、影响器件开关比的问题,采用了量子限域法、化学掺杂法、外加电场调节法和引入应力法.在光电器件研究方面,石墨烯可以均匀吸收所有频率的光,其光电性能也受到了广泛的关注,如光电探测器、光电调制器、太阳能电池等.同时,石墨烯作为典型的二维材料,其优越的电学性能以及超高的比表面积,使其作为高灵敏度传感器的研究成为纳米科学研究的前沿和热点领域.     

N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry media under ultrasound irradiation

N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate catalyzed efficiently the synthesis of xanthene derivatives under ultrasonic irradiation at room temperature, which has prompted various concerns involving cost and environmental persistence. This methodology shows the effect of presence of anion hydrogen sulfate as an important and effective factor on the promotion of the one-pot multi-components and condensation reactions. The catalyst can be recovered by simple filtration and used for several times without a significant loss of catalytic activity.     

In situ sonochemical reduction and direct functionalization of graphene oxide: A robust approach with thermal and biomedical applications

The rapid, robust, scalable and non-hazardous sonochemical approach for in situ reduction and direct functionalization of graphene oxide has been developed for non-toxic biomedical applications. The graphene oxide (GrO) was directly functionalized with tryptamine (TA) without using any hazardous acylating and coupling reagents. The reaction was completed within 20 min. An impact of ultrasound was inferred for a direct functionalization with other conventional methods. The evolved electronic states were confirmed with near edge X-ray absorption fine structure (NEXAFS). The direct covalent functionalization and formation of f-(TA) GrO was proven with FTIR, ¹³C solid state NMR, XPS, XRD, Raman‚ HRTEM, AFM and TGA. The total percentage weight loss in TGA confirms an enhanced thermal stability of f-(TA) GrO. The f-(TA) GrO was further explored for an investigation of in vitro antimicrobial activity to ensure the health and environmental safety. An outstanding antibacterial activity of f-(TA) GrO was found against gram positive Staphylococcus aureus at MIC 128 mg mL⁻¹. It confirms a suitability of f-(TA) GrO for thermally stable antibacterial coating. The f-(TA) GrO showed 39.14–48.9% antioxidant activities, evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. The inherent cytotoxicity of f-(TA) GrO was evaluated with SRB assay to living cells, MCF-7 and Vero. The estimated cell viabilities were >80% upon addition of f-(TA) GrO over a wide concentration range of 10–80 μg mL⁻¹. The high cytocompatibility of f-(TA) GrO confirms the low toxicity and an excellent biocompatibility. The morphological effect on Vero cell line, evidently confirmed the biocompatibility of f-(TA) GrO. Therefore, f-(TA) GrO was emerged as an advanced functional biomaterial for thermal and biomedical applications.     

Catalyst free rutile phase TiO2 nanorods as efficient hydrogen sensor with enhanced sensitivity and selectivity

Using a low-cost hydrothermal method, we demonstrated the fabrication of phase pure rutile phase high-density vertically aligned TiO₂ nanorods-based catalyst-free hydrogen (H₂) gas sensor. The synthesized TiO₂ nanorods on FTO are decorated with the aluminum interdigitated electrode pattern for electrical measurements. TiO₂ nanorods-based hydrogen sensor showed the optimum response of ∼53.18% at 150 ppm H₂ concentration relative to air at 100 °C. The measured response and recovery time of TiO₂ nanorods are 85 and 620 s, respectively. The TiO₂ nanorods-based H₂ gas sensor showed a relatively better response, good reproducibility, and stability at moderate temperatures, i.e., 50 and 100 °C. The electrochemical impedance measurements showed a small variation in the surface characteristics of TiO₂ nanorods before and after exposing H₂ gas. The carrier lifetime at 50 °C and 100 °C at 150 ppm are 5 μs and 3 μs, respectively. Interestingly, H₂ selectivity is also observed against H₂S, CO, and NH₃ gases, suggesting that high-density vertically aligned TiO₂ nanorods can be a good candidate for efficient hydrogen sensing at relatively low temperatures.