Predictive estimation of vacuum ultraviolet emission intensity in a low-pressure inductively coupled hydrogen plasma based on the branching ratio technique

Vacuum ultraviolet (VUV) emission has recently attracted attention in low pressure processing plasmas because of the possibility of high-energy photon damages on the substrates. To quantify the VUV induced damages during the plasma processes, it is need to use of a VUV spectrometer equipped with vacuum systems not readily available in industries. In this work, therefore, we report a simple method to estimate the VUV emission intensity of hydrogen plasmas utilizing a conventional visible spectrometer widely used in plasma processes. From the measurement of hydrogen emission spectra in the visible wavelength region, the VUV emission line (Lyman-β) was calculated using the branching ratio technique and enabled the estimation of Lyman-α emission intensity based on the Boltzmann relation with given plasma parameters. In addition, it was found that the method could also predict the VUV emission intensity for high density hydrogen plasma cases by considering the self-absorption effect by hydrogen atoms.     

Steady state and time resolved laser-induced fluorescence of garlic plants treated with titanium dioxide nanoparticles

The study involves investigation of the effect of the interaction of titanium dioxide nanoparticles with garlic plant by spectroscopy techniques. For this, garlic plants have been grown in the laboratory under controlled conditions of light flux, temperature, humidity, and nutrient media. The growth and biomass parameters in terms of shoot length, fresh, and dry mass are found to increase upon the treatment of titanium dioxide nanoparticles while a reduction is observed in the root length of the garlic plants. The steady state laser-induced fluorescence, time resolved laser-induced fluorescence, and ultraviolet visible spectra of the control and titanium dioxide nanoparticles-treated plants have been acquired. The curve fitting data reveal that titanium dioxide nanoparticles decrease the intensity and fluorescence intensity ratio of red and far red chlorophyll fluorescence bands indicating increase in the photosynthetic activity and chlorophyll content. The evaluation of life time of the excited chlorophyll molecule shows that life time is effected by the treatment of the titanium dioxide nanoparticles. The results pertaining to ultraviolet visible measurement indicate increase in the concentration of chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, and quercetin in the leaves of garlic plants treated with titanium dioxide nanoparticles.     

Features of radiation-induced changes in the diffuse reflectance spectra of modified titanium-dioxide powders

Changes in the diffuse reflectance spectra of titanium-dioxide micropowders (initial, modified by nanoparticles, treated with oxidants such as potassium peroxoborate and sodium peroxide, or ultraviolet irradiated in an oxygen atmosphere) in the range 0.3–2.1 μm after irradiation with ultraviolet light, electrons, or protons are analyzed. The general and distinctive features of changes in the spectra in the visible and near infrared regions are revealed and an explanation of the obtained data is proposed.     

Calculation of torsional and rotational raman spectra of hydrogen peroxide

We present calculated intensity distributions in torsional, rotational, and torsional-rotational Raman lines in spectra of hydrogen peroxide. Ab initio calculations of polarizability tensor components as functions of internal rotation angle were carried out in the HF/6-311G approximation. It is shown that the structure and transformational properties of the polarizability tensor components of hydrogen peroxide in extended molecular symmetry group G₄(EM) permit formation of purely rotational and torsional and rotational-torsional Raman spectra. Common expressions to calculate Raman line intensities governed by torsional and rotational motions of the non-rigid symmetric top molecule are obtained. The torsional components of the line intensities have been calculated by estimating the appropriate matrix elements. The contribution of rotational components has been calculated using the 3j-symbols technique.     

Optimization of the superconducting phase of hydrogen sulfide

The electron and phonon spectra, as well as the densities of electron and phonon states of the SH₃ phase and the stable orthorhombic structure of hydrogen sulfide SH₂, are calculated for the pressure interval 100–225 GPa. It is found that the I4/mmm phase can be responsible for the superconducting properties of metallic hydrogen sulfide along with the SH₃ phase. Sequential stages for obtaining and conservation of the SH₂ phase are proposed. The properties of two (SH₂ and SH₃) superconducting phases of hydrogen sulfide are compared.     

Elimination effects of toxic trans-crotonaldehyde in mitochondria of glioma by lithocholic acid

The purposes of this study were to explore the factors contributing to the generation of the toxic trans-crotonaldehyde in mitochondria of glioma and to look for the elimination effects of the toxic trans-crotonaldehyde by the lithocholic acid. Ultraviolet-visible absorption spectroscopy and mitochondrial isolation and extraction from glioma were used in this study. Research findings showed that the factors contributing to the generation of the toxic trans-crotonaldehyde were hydrogen peroxide, mitochondria of glioma, and their appropriate interaction, respectively. The appropriate quantity of the toxic trans-crotonaldehyde could be induced by hydrogen peroxide (0.16?mmol), mitochondria of glioma (3?mg protein/ml), and 30?min of their interaction, respectively. The most suitable conditions for the lithocholic acid to eliminate the toxic trans-crotonaldehyde were the weakly alkaline of mitochondria of glioma (pH 8.0), the lithocholic acid (0.15?mmol), and 15?min of interaction, respectively. The conclusion was that the lithocholic acid efficiently eliminated the toxic trans-crotonaldehyde in mitochondria of glioma in real time and opened up a new way to treat glioma.     

The amounts of hydroxyl radicals generated by titanium dioxide and 3.5% hydrogen peroxide under 405-nm diode laser irradiation

A new bleaching agent consisting of a titanium dioxide photocatalyst and 3.5% hydrogen peroxide has recently been developed for in-office bleaching and has proven to react well with irradiated light around a wavelength of 400 nm. This study was conducted to evaluate the efficacy of dental bleaching with a 405-nm diode laser irradiation on titanium dioxide and 3.5% hydrogen peroxide by measuring the generation of hydroxyl radicals. The amount of hydroxyl radicals generated from a titanium dioxide and 3.5% hydrogen peroxide irradiated by a 405-nm diode laser were measured using electron spin resonance spin-trapping techniques. The irradiation conditions of the laser were a spot size of 1 mm, output powers of 100, 200, 400 mW, and 600 mW, and irradiation times of 10, 20, 30, and 60 s. Nonirradiated samples were used as controls. DMPO-OH adduct spectra and DMPO-O ₂ ^? adduct spectra were observed when the bleaching agent was irradiated by laser light. The amount of hydroxyl radicals generated changed in accordance with adjustments in the irradiation power and irradiation time. In the nonirradiated controls, hydroxyl radicals were generated in far smaller amounts. The 405-nm diode laser is effective in inducing the generation of hydroxyl radicals and shows promise as a bleaching light source for use in combination with bleaching agents composed of titanium dioxide and low concentrations of hydrogen peroxide.     

Immobilization of redox mediators on functionalized carbon nanotube: A material for chemical sensor fabrication and amperometric determination of hydrogen peroxide

Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) on graphite electrode was achieved by gently rubbing the electrode surface on carbon nanotubes supported on a glass slide. The electrochemical behaviour of the modified electrodes was investigated by cyclic voltammetry. The SWNT-modified electrodes showed excellent electrocatalytic effect for the reduction of hydrogen peroxide. A decrease in overvoltage was observed as well as an enhanced peak current compared to a bare graphite electrode for the reduction of hydrogen peroxide. The catalytic current was found to be directly proportional to the amount of hydrogen peroxide taken.     

The effect of hydrogen peroxide on polishing removal rate in CMP with various abrasives

The effect of hydrogen peroxide in chemical mechanical planarization slurries for shallow trench isolation was investigated. The various abrasives used in this study were ceria, silica, alumina, zirconia, titania, silicon carbide, and silicon nitride. Hydrogen peroxide suppresses the polishing of silicon dioxide and silicon nitride surfaces by ceria abrasives. The polishing performances of other abrasives were either unaffected or enhanced slightly with the addition of hydrogen peroxide. The ceria abrasives were treated with hydrogen peroxide, and the polishing of the work surfaces with the treated abrasive shows that the inhibiting action of hydrogen peroxide is reversible. It was found that the effect of hydrogen peroxide as an additive is a strong function of the nature of the abrasive particle.     

水体细菌微生物多波长透射光谱快速准确获取方法研究

为实现水体细菌微生物快速在线监测,搭建了多波长透射光谱快速测量实验系统,利用该系统分别测量了重铬酸钾标准溶液紫外波段及中性滤光片可见波段的透射光谱,并与紫外-可见分光光度计测得的透射光谱进行对比分析,验证了实验系统测量透射光谱的准确性;以水体中常见的金黄色葡萄球菌作为研究对象,利用搭建的实验系统获取金黄色葡萄球菌溶液在220～900 nm波段的前向小角度透射光谱,进一步验证了实验系统测量细菌微生物透射光谱的准确性和快速性。结果表明,由实验系统和紫外-可见分光光度计测得的重铬酸钾标准溶液,与中性滤光片紫外波段及可见波段透射光谱的线性拟合相关系数分别为0.999 7和0.999 5,光密度误差分别在5.00%和4.58%以内,说明两个系统测量光谱的一致性较好,所搭建的实验系统测量标准样品紫外-可见透射光谱准确度较高;对于金黄色葡萄球菌,实验系统测得的透射光谱经过校正后,与紫外-可见分光光度计测得的透射光谱线性拟合的相关系数为0.999 97,两者相比的光密度误差在0.74%以内;系统重复30次细菌光谱信号采集获得平均透射光谱单次测量时间为15 s,说明该实验系统相对于紫外-可见分光光度计能够快速准确获取水体细菌微生物多波长透射光谱,在保证测量结果准确的同时缩短了光谱测量时间,为水体细菌微生物快速检测提供技术支持。     

Study on the photocatalytic activity of K2La2Ti3O10 doped with zinc(Zn)

The layered perovskite type oxides, K₂La₂Ti₃O₁₀ and zinc(Zn)-doped K₂La₂Ti₃O₁₀ were prepared by sol-gel method and were characterized by power X-ray diffraction, UV-vis diffuse reflectance and X-ray photoelectron spectroscopy. The photocatalytic activity for water splitting of the catalyst powders was investigated with I⁻ as electron donor under ultraviolet and visible light irradiation respectively. The electronic structure of the powders has been analyzed by the first principles calculation, which reveals the photo responses in the visible region and the improvement of the photocatalytic activity of K₂La₂Ti₃O₁₀. Conclusions were made that zinc(Zn)-doped K₂La₂Ti₃O₁₀ exhibited higher reactivity for hydrogen production. When I⁻ was used as electron donor, the optimum doping concentration of zinc(Zn) was found to be 0.015:1 (n_Zn:n_Ti). The average hydrogen production rates were 126.6 μmol/(gcat h) under ultraviolet irradiation and 55.5 μmol/(gcat h) under visible light irradiation which were raised by 131% and 251% compared with undoped K₂La₂Ti₃O₁₀ photocatalyst, respectively.     

Catalytic activity of copper (II) oxide prepared via ultrasound assisted Fenton-like reaction

Copper (II) oxide nanoparticles were synthesized in an ultrasound assisted Fenton-like aqueous reaction between copper (II) cations and hydrogen peroxide. The reactions were initiated with the degradation of hydrogen peroxide by ultrasound induced cavitations at 0 °C or 5 °C and subsequent generation of the OH radical. The radical was converted into hydroxide anion in Fenton-like reactions and copper hydroxides were readily converted to oxides without the need of post annealing or aging of the samples. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis. Catalytic activity of the nanoparticles for the hydrogen peroxide assisted degradation of polycyclic aromatic hydrocarbons in the dark was tested by UV–visible spectroscopy with methylene blue as the model compound. The rate of the reaction was first order, however the rate constants changed after the initial hour. Initial rate constants as high as 0.030 min⁻¹ were associated with the high values of surface area, i.e. 70 m²/g. Annealing of the products at 150 °C under vacuum resulted in the decrease of the catalytic activity, underlying the significance of the cavitation induced surface defects in the catalytic process.     

氧化锌纳米晶体的光谱分析

采用沉淀法并通过控制前驱体的煅烧温度来制备粒径不同的氧化锌(ZnO)纳米晶体,对粒子的透射电镜照片进行分析,结果表明,制备出的纳米粒子分散性好、形貌一致、粒径分布集中。样品的X射线衍射光谱分析表明,随着前驱体煅烧温度增加,晶体粒径增大、结晶度提高;样品的紫外-可见吸收光谱的峰位随粒径减小而发生蓝移,这一实验结果表明ZnO纳米晶体呈现出较明显的量子限域效应;红外吸收光谱测量结果表明,用沉淀法制备的ZnO纳米晶体的表面会吸附一小部分残余的离子,对红外吸收光谱中的ZnO特征振动峰随粒径减小发生宽化和红移的现象进行了理论分析;光致发光光谱测量结果表明,ZnO纳米晶体在紫外区(360 nm)存在一较弱的发光峰,而在可见区(468 nm)存在一较强的发光峰,与理论计算结果进行比较后,认为锌空位点缺陷是导致ZnO纳米晶体可见区发光的主要原因。     

Electron paramagnetic resonance of hydrogen in silicon

A review of the investigations by means of electron paramagnetic resonance (EPR) of hydrogen and hydrogen-related defects in crystalline silicon is presented. The main features of the EPR center Si-AA9 (bond-centered hydrogen), which is known as the hydrogenic analogue of the anomalous muonium (Mu^*) in silicon, are discussed. It was found that the process of annealing the AA9 center is characterized by an activation energy, E = 0.48 ± 0.04 eV with a second-order pre-exponential factor, K₀ = (1.25 ± 2.5) × 10^-7 cm³/s.

A detailed investigation by EPR of the defect (Si-AA1), which we identify as the hydrogen-related shallow donor in a positive charge state, is also presented. In particular it is shown that the H-related shallow donor is a helium-like center and its wave function has C_2v symmetry. Moreover, the main features of the series of EPR spectra in silicon characteristic for the implantation of hydrogen are presented.     

Effects of hydroxyl groups and hydrogen passivation on the structure,electrical and optical properties of silicon carbide nanowires

The effects of hydrogen and hydroxyl passivation on the structure, electrical and optical properties of SiCNWs were investigated. The passivation performance of different atoms (groups) were discussed by analyzing the distribution of electronic states and the polarity of chemical bonds. The results show that passivation can improve the stability of SiCNWs structure, and the effect of hydroxyl is better than hydrogen passivation. And hydrogen and hydroxyl passivation both increase the band gap of SiCNWs, and the changing trend of band gap is relevant to the polarity of the covalent bond formed by the passivation of surface atoms. Moreover, passivation enhances the stability of the optical properties of SiCNWs, resulting in narrowing of light absorption, photoconductivity and other spectra, and the response peak shifts to the deep ultraviolet region, which means that hydrogen or hydroxyl passivation of SiCNWs is likely to be a candidate material for deep ultraviolet micro-nano optoelectronic devices.     

Effects of hydrogen flow on properties of hydrogen doped ZnO thin films prepared by RF magnetron sputtering

The hydrogen doped ZnO (ZnO:H) thin films were deposited on quartz glass substrates by radio frequency magnetron sputtering. The doping characteristics of ZnO:H thin films with varied hydrogen flow ratio were investigated. At low hydrogen flow ratio (H₂/(H₂+Ar)≤0.02), the ZnO:H thin films exhibited dominant (002) peaks from X-ray diffraction and the lattice constants became smaller. The particles were mainly a columnar structure. The particles’ size became smaller, and the island-like structure appeared on the thin films surface. In addition, the low resistivity properties of ZnO:H thin films was ascribed to the increase of the carriers concentration and carriers mobility; When the hydrogen flow ratio was more than 0.02 (M≥0.02), two absorption bands at 1400–1800 cm^?1 and 3200–3900 cm^?1 were observed from the FT-IR spectra, which indicated that the ZnO:H thin films had typical Zn–H bonding, O–H bonding (hydroxyl), and Zn–H–O bonding (like-hydroxyl). The scanning electron microscope (SEM) results show that a large number of hydroxyl agglomeration formed an island-like structure on the thin films surface. The absorption peak at about 575 cm^?1 in the Raman spectra indicated that oxygen vacancies (V_O) defects were produced in the process of high hydrogen doping. In this condition, the low resistivity properties of ZnO:H thin films were mainly due to the increasing electron concentration resulted from V_O. Meanwhile, the Raman absorption peaks at approximately 98 cm^?1 and 436 cm^?1 became weaker, and the (002) XRD diffraction peak quenched and the lattice constants increased, which shows that the ZnO:H thin films no longer presented a typical ZnO hexagonal wurtzite structure. With the increasing of hydrogen flow ratio, the optical transmittance of ZnO:H thin films in the ultraviolet band show a clear Burstein–Moss shift effect, which further explained that electron concentration was increased due to the increasing V_O with high hydrogen doping concentration. Moreover, the optical reflectance of the thin films decreased, indicating the higher roughness of the films surface. It was noteworthy that etching effect of H plasma was obvious in the process of heavy hydrogen doping.     

Pulsed Sisyphus scheme for laser cooling of atomic (anti)hydrogen

We propose a laser cooling technique in which atoms are selectively excited to a dressed metastable state whose light shift and decay rate are spatially correlated for Sisyphus cooling. The case of cooling magnetically trapped (anti)hydrogen with the 1S-2S-3P transitions by using pulsed ultraviolet and continuous-wave visible lasers is numerically simulated. We find a number of appealing features including rapid three-dimensional cooling from ～1 K to recoil-limited, millikelvin temperatures, as well as suppressed spin-flip loss and manageable photoionization loss.     

Control of optical absorption edge of TiO2 through co-doped acceptors: The chemical trend

Tuning the optical adsorption edge of TiO₂ is attracting increasing attention as a potential solution to the worldwide energy shortage. A possible strategy to achieve high efficiency photocatalysis with TiO₂ is through dopants to modulate chemical composition. Based on first-principles calculations, we propose a hole-strain-mediated coupling mechanism between co-doped acceptors in anatase TiO₂. When the dopant complex on neighboring oxygen sites contains a large radius atom, and the doped system has at least one net hole, the dopants will strongly couple to form a pair through the local lattice strain induced by the large dopant. The coupling results in bandgap narrowing due to the appearance of the fully occupied mid-gap states, leading to a much more effective band gap reduction than that induced by mono-doping or conventional donor–acceptor codoping. The calculated absorption spectra show that acceptor–acceptor codopings could shift the absorption edge to the visible light region.     

An approach to hybrid inorganic nanoparticles in reactive PS-b-PMSMA amphiphilic copolymers

A series of well-defined amphiphilic poly(styrene)-block-poly 3-(trimethoxysilyl) propyl methacrylate (PS-b-PMSMA) copolymers with controlled molecular weight and block length were prepared by the atom transfer free radical polymerization. The cadmium sulfide (CdS) nanoparticles were fabricated in the spherical micelles self-assembled from these prepared PS-b-PMSMA copolymers. Then, the CdS/PS-b-PMSMA films were obtained by spin coating the CdS/PS-b-PMSMA solution on silicon wafer. The experimental results showed the addition of Cu(II) could decrease the value of polydispersity index for the prepared copolymers. Nuclear magnetic resonance and Fourier transform infrared spectra showed the synthesis of PS-b-PMSMA copolymer. The average roughness and mean square roughness of the prepared CdS/PS-b-PMSMA films obtained from the atomic force microscopy analysis were 3.0–3.4 nm and 1.7–2.0 nm, respectively, indicating the excellent surface planarity. On the other hand, the ratio of block length between PS and PMSMA had a great influence on the micelle size. The larger ratio of PS to PMSMA block length resulted in the larger size of micelles and CdS nanoparticles that caused a red-shift of ultraviolet–visible and photoluminescence spectra. The red-shift of spectra was explained by the quantum confinement effect associated with the tiny size of the CdS nanoparticles.     

Detection of hydrogen peroxide with graphyne

The effect of hydrogen peroxide on the electronic properties of graphyne has been investigated to explore the possibility of using graphyne based biosensor. We have used density functional theory to study the electronic properties of γ-graphyne in the presence of different number of hydrogen peroxide. The optimal adsorption position, orientation, and distance of hydrogen peroxide adsorbed on the graphyne sheet have been determined by calculating adsorption energy. It is found that γ-graphyne which is an intrinsic semiconductor becomes an n-type semiconductor due to the presence of hydrogen peroxide. The energy band gap of γ-graphyne is decreased by increasing the number of hydrogen peroxide. The results demonstrate that γ-graphyne is a promising candidate for biosensor application because of its electrical sensitivity to hydrogen peroxide.