Facile synthesis of C-doped hollow spherical g-C3N4 from supramolecular self-assembly for enhanced photoredox water splitting

A facial, template-free and green strategy was developed to prepare C-doped hollow spherical g-C₃N₄ derived from supramolecular self-assembly of melamine, glucose and cyanuric acid. Especially, the precursors were tightly connected by hydrogen bonds, wherein glucose was served as a source of doped carbon. Spectroscopic and electrochemical analysis confirmed that the endmost nitrogen was replaced by the doped carbon to combine two melon parts, leading to the possible existence of the delocalized big π bonds in the system. Moreover, the GCN-x not only maintained the excellent properties of the hollow sphere, such as high surface area, moderate porosity and short charges diffusion distance, but also overcame the drawbacks of low visible light response and high electron-holes recombination rate from bulk g-C₃N₄. Thereby, the visible light utilization rate and the photogenerated electron-holes separation efficiency of the catalyst were improved. The highest hydrogen yield of 305  μmol h⁻¹ from GCN-0.2 was 28.5 times that of bulk g-C₃N₄. Finally, a possible mechanism underlying the photocatalytic performance of C-doped g-C₃N₄ hollow spheres was proposed tentatively.     

ECR plasma etch fabrication of C-doped base InGaAs/InP DHBT structures: A comparison of CH4/H2/Ar vs BCl3/N2 plasma etch chemistries

We compare ECR plasma etch fabrication of self-aligned thin emitter carbondoped base InGaAs/InP DHBT structures using either CH₄/H₂/Ar or BCl₃/N₂ etch chemistries. Detrimental hydrogen passivation of the carbon doping in the base region of our structure during CH₄/H₂/Ar dry etching of the emitter region is observed. Initial conductivity is not recovered with annealing up to a temperature of 500°C. This passivation is not due to damage from the dry etching or from the MOMBE growth process, since DHBT structures which are ECR plasma etched in BCl₃/N₂ have the same electrical characteristics as wet etched controls. It is due to hydrogen implantation from the plasma exposure. This is supported with secondary ion mass spectroscopy profiles of structures which are etched in CH₄/D₂/Ar showing an accumulation of deuterium in the C-doped base region.     

氮气流量对磁控溅射C掺杂TiO2薄膜光学性能的影响

采用磁控溅射法制备了C掺杂TiO₂薄膜,并研究了氮气引入溅射过程对薄膜光学性能的影响。利用X射线衍射仪、拉曼光谱仪、X射线光电子能谱仪、分光光度计和原子力显微镜分析了不同氮气流量下薄膜的微结构、元素价态、透光性能和表面形貌。结果表明,沉积的薄膜主要是非晶结构,拉曼光谱中存在少量锐钛矿相,且随着氮气流量增大,锐钛矿特征峰强度减弱,意味着晶粒出现细化。当氮气流量增大为4cm³/min时,C掺杂TiO₂薄膜内氮元素含量为3.54%,其光学带隙从3.29eV变化至3.55eV,可见光区的光学透过率明显提高。可见改变氮气流量可实现对C掺杂TiO₂薄膜光学带隙和光吸收率的有效调控。     

碳掺杂氮化硼纳米管吸附气体小分子的DFT计算

采用密度泛函理论研究了氮化硼纳米管(Boron nitride nanotubes,BNNTs)及碳掺杂氮化硼纳米管对O2、NO2、F2气体小分子的气敏特性。计算了三种气体小分子吸附在氮化硼纳米管及碳掺杂氮化硼纳米管表面不同位置时的吸附能、相互作用距离,同时还计算得到了气体分子分别吸附在碳掺杂BNNTs不同位置时的电子态密度。研究结果表明,氮化硼纳米管对O2、NO2、F2气体分子比较敏感,碳掺杂氮化硼纳米管可以明显地改变其表面的化学反应活性,增强气体分子与氮化硼纳米管之间的相互作用。     

Cathodic electrochemiluminescence of luminol in aqueous solutions based on C-doped oxide covered titanium electrode

In the present work, a novel sensor for luminol electrochemiluminescence (ECL) was constructed on the base of a C-doped titanium oxide amorphous semiconductor electrode. The morphology, structural and electrochemical properties of the electrode was characterized by X-Ray diffraction, X-Ray photoelectron spectroscopy and electrochemical methods. The ECL behavior of luminol excited by hot electrons injected from C-doped oxide film-covered electrodes in aqueous medium has been investigated in B-R buffer solution (pH = 9) when linear sweep cyclic voltammetry (CV) was applied. Two ECL peaks were observed at −1.0 V (vs. Ag/AgCl, reduction process) and −0.75 V (vs. Ag/AgCl, oxidation process). The possible mechanism was discussed. The C-doped Ti oxide electrode shows excellent properties for sensitive determination of luminol with good reproducibility and stability. The linear response of luminol was in the range of 1 × 10⁻⁸ to 9 × 10⁻⁸ mol/L with the detection limit of 3 × 10⁻⁹ mol/L (S/N = 3). Since luminol is one of the most useful ECL probe, many bioactive compounds which can be labeled by luminol are able to be detected by using the proposed method.     

C掺杂WO_(3-x)的制备及其光解水活性研究

通过溶胶-凝胶法制备了单斜WO3-x及C掺杂WO3-x,采用SEM、XRD、DRS、XPS等对样品进行了表征,考察了样品光解水析氧催化活性。结果表明,C掺杂在一定程度上改变了WO3的晶体结构,并导致晶体缺陷和氧空位增加,使催化剂表面W5+和氧空位含量增加,增强了WO3-x的光吸收性能和电子传输性能。在紫外和可见光照射下,C掺杂WO3-x的光解水析氧速率分别为90.0μmol/(L.g.h)和26.6μmol/(L.g.h),比未掺杂样品提高了91%和52%。     

C-doped WO3 microtubes assembled by nanoparticles with ultrahigh sensitivity to toluene at low operating temperature

Novel C-doped WO₃ microtubes (MTs) were successfully synthesized by a facile infiltration and calcination process using the cotton fibers as templates. The prepared MTs were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), N₂ adsorption and desorption measurements and ultraviolet-visible spectroscopy. XPS spectra show the carbon was doped into the lattice of the WO₃ phase, resulting in a decrease of the band gap of the C-doped WO₃ MTs from 2.45 eV to 2.12 eV. Moreover, the WO₃ MTs were assembled by nanoparticles in size of ca. 40 nm and had larger specific surface area (21.3 m²/g) due to existence of meso/macro-pores inside them. At low operating temperature of 90 °C, the gas sensor based on the C-doped WO₃ MTs had a detected limit of 50 ppb to the toluene gas (response of 2.0). The enhancement of toluene sensing performance of C-doped WO₃ MTs was attributed to a larger surface area and higher porosity, which arises from its unique MTs. Furthermore, the band gap reduction and a new intragap band formation for C-doped WO₃ MTs were proposed as the reason for the decrease in optimal operating temperature.     

重掺碳GaAs层的MOCVD生长及特性研究

采用 CCl4 作为碳掺杂源 ,进行了重掺碳 Ga As层的 L P- MOCVD生长 ,并且对掺杂特性进行了研究 ,研究了各生长参数对掺杂的影响。CCl4 流量是决定掺杂浓度的主要因素。减小生长温度、减小 / 比、降低生长压力 ,都能较大的提高掺杂浓度。通过改变 CCl4 流量 ,在生长温度为5 5 0～ 6 5 0℃、 / 比为 15～ 4 0 ,生长压力在 1× 10 4 ～ 4× 10 4 Pa的范围内 ,均能得到高于 2× 10 19/cm3 的掺碳 Ga As外延层 ,最高掺杂浓度为 8× 10 19/ cm3