MgZnO/ZnO p–n junction UV photodetector fabricated on sapphire substrate by plasma-assisted molecular beam epitaxy

We have investigated the spectral response of back- and front-surface-illumination MgZnO/ZnO p–n ultraviolet photodetector fabricated by plasma-assisted molecular beam epitaxy on sapphire substrate. The current–voltage measurements show that the device has a rectifying behavior with a turn-on voltage of 4.5 V. The detector exhibits a broad spectral response which covers the visible and UV spectra regions (from 275 to 375 nm) and has a maximum peak response at the wavelength of 330 nm. At a reverse bias of 5 V, the visible rejection (R330 nm/R500 nm) was more than two orders of magnitude. The peak responsivity at 330 nm for the device under back-illumination is about four times larger than that of the device under front-illumination under the same reverse bias. The response mechanisms of the device under back- and front-illumination are discussed.     

pH对玫瑰红色素紫外和荧光光谱的影响

玫瑰是蔷薇科蔷薇属落叶丛生灌木,品种繁多,其花色、香、形具美,有极高的观赏和经济价值,我国玫瑰资源丰富,古代人们就将玫瑰用于染色、食品和药用等领域,现在玫瑰主要用于商品花卉和提取玫瑰精油.     

N-(4-羟基苯基)马来酰亚胺的合成及其光谱分析

利用对氨基酚和马来酸酐反应制取N-(4-羟基苯基)马来酰亚胺(HPM),并采用红外光谱及核磁光谱对其结构进行了表征.研究了HPM在甲醇、四氢呋喃及二氯甲烷3种溶剂中的紫外光谱.结果发现,在这3种溶剂中,HPM在210～250 nm范围内的吸收峰对溶剂极性及溶液浓度敏感;而275 nm左右的吸收峰在各种极性不同溶剂中位置...     

Identification of compounds and specific functional groups in the wavelength region 168-330 nm using gas chromatography with UV detection

A GC-UV instrumental set up with two different GC units has been used for determination of specific functional groups and compounds in complex mixtures. Separations have been made using a micro gas chromatograph built into a gas flow cell and by means of an external capillary gas chromatograph linked to the same gas flow cell. Four various applications (cigarette smoke, petroleum, dust, flavour) have been performed in order to demonstrate the potential of the GC-UV method. Gas phase UV spectra have been recorded in the region of 168-330 nm. Based on a gas phase spectrum reference library the identification of unknowns as well as the determination of specific functional groups have been achieved. A table showing the spectral shapes and positions of the absorption bands for 50 specific functional groups is presented. The advantage of using derivative spectra in order to amplify spectral details and improve selectivity is discussed. Regarding sensitivity, it has been found that identifications can be made in the mid-pg range and limit of detection for naphthalenes are at a level of 0.5-3 pg/s.     

ULTRAVIOLET QUANTUM YIELDS OF PHOTOPHOSPHORYLATION IN Halobacterium halobium*

Quantum yields of photophosphorylation in Halobacterium halobium were determined for ultraviolet spectral bands between 276 and 365 nm, and at 565 nm wavelength, based on integral spectral cell absorptance, bacteriorhodopsin-specific cell absorptance and the corresponding quantum dose rates. In the ultraviolet, there is an almost linear decline of the quantum yields of photophosphorylation from 365 to 276 nm wavelength, despite the peak absorption of bacteriorhodopsin at 280 nm. The cycling quantum yield for 276 nm excitation of bacteriorhodopsin was determined as 4.5 ± 1.8%, which is about one fourth of the value of 19% for solubilized bacteriorhodopsin. Threshold energy fluence rates of 20 W m^?2 for UV-B radiation typify the photophosphorylation as three orders less sensitive than the sensory UV-B avoidance response that needs 0.02 W m^?2 as the threshold. Thus, UV-B avoidance appears as the dominating strategy for survival of the archaic bacterium H. halobium, rather than possible photoenergetic use of UV-B radiation and photorepair of UV-damage.     

Photophysical processes in aromatic polyimides. Studies with model compounds

Emission mechanism in an aromatic polyimide, PI(BPDA/PDA), derived from biphenyltetracarboxylic dianhydride and p-phenylene diamine were studied with ultraviolet visible absorption and fluorescence spectra of a series of the model compounds. The excitation spectrum of the intermolecular charge-transfer (CT) fluorescence peaking around 550 nm of PI(BPDA/PDA) thin film was completely consistent with the absorption spectrum, indicating that the intermolecular CT fluorescence emission of PI(BPDA/PDA) film is not caused by direct excitation of the CT absorption band, but by light absorption due to structural units in the polymer backbone. The UV-vis. absorption spectra of the model compounds corresponding to the structural units in PI(BPDA/PDA) showed that the longest wavelength absorption band is due to the biphenylbisimide moiety. The band was assigned as π, π* transition with the polarization spectrum of the model compound. The fluorescence spectra of the model compounds changed sensitively depending on the conformation around N-phenyl bond. The lifetime measurement for the model compounds suggested that intramolecular CT process occurs very rapidly. © 1993 John Wiley & Sons, Inc.     

Studies on photoprotection and photo-oxidation in polystyrene with various wavelength regions

The photoprotection of styrene-2,2,6,6-tetramethyl-4-piperidinyl methacrylate copolymer (PDS) as an ultraviolet absorbent and the photo-oxidation in polystyrene (PS) film with various wavelength region irradiations have been studied. It was found that the photoprotection of PDS as the hindered amine for PS film was effective. In the full wavelength region irradiation, the Yellowness Index (YI) as the characterizing parameter was only 20%, corresponding to an exposure period as long as 80 hr. The results have proved that the photoprotection behavior of PDS was more effective a wavelength of 274 nm than of 318.5 nm, and the increment of the YI was proportional to the intensity absorbed by PS film. The infrared and ultraviolet spectra of PS film undergoing photooxidation have shown that (a) the dominant contribution to the increment of the ultraviolet characteristic absorption peak A (274 nm) of PS film belonged to the wavelength region (200–320 nm) rather than the singlet, and that (b) the infrared shifting of the wide-peak A (274 nm) could be considered as the relative changes of the constants of carbonyl compounds with the conjugating and non-conjugating structures from the end-products of the photo-oxidation process.     

CO2 和C2 H4 光催化合成丙烯酸的Cu/ZnO-TiO2 催化剂

The metallic Cu modified n-p coupled semiconductor Cu/ZnO-TiO2 was prepared by the sol gel method, and its surface structure, absorptivity of ultraviolet light, chemisorption properties and photocatalytic behaviors were investigated by techniques of X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), BET surface area (BET), Infrared absorption spectra (IR), UV-visible diffused reflectance spectra (UV-vis) and photo stimulated surface catalytic reaction. The results show that the main crystal structure of the catalyst is anatase TiO2 with the particle size about 10 nm. The Zn-O-Ti bond is formed and the absorption intensity in the wavelength region of 250～400 nm is enhanced through the coupling of ZnO and TiO2, while the absorption region is expanded to visible light with the UV absorbance limit shifting to the shorter wavelength region after Cu supported on the coupled semiconductor ZnO-TiO2. The adsorption states of reactants are important factors influencing the results of photocatalytic reaction, while the bridge adsorption state of CO2 formed on Cu and Lewis acid sites Ti4+ and undissociated of C2H4 formed on Cu and Lewis base sites bridge-O are the effective intermediates to synthesize the crylic acid with the selectivity over 87% under the temperature of 100℃.     

A new strategy for quality control and qualitative analysis of Yinhuang preparations by HPLC-DAD-MS/MS

A combinative method using fingerprint analysis (FA) and multi-ingredients quantification (MIQ) was developed and validated for the quality control of Yinhuang (YH) preparations including granule, capsule, and lozenge by high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). Common peaks with or without standard references in FA were confirmed or identified by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The chromatographic separations were achieved on a Sepax GP-C(18) column (250?mm?×?4.6?mm i.d., 5?μm) with a gradient elution using a mixture of 0.1?% formic acid methanol solution and 0.1?% formic acid water solution. In quantitative analysis, nine bioactive constituents (chlorogenic acid, caffeic acid, luteoloside, baicalin, luteolin, wogonoside, baicalein, wogonin, and oroxylin A) were simultaneously determined. The detection wavelength was set at 275?nm, 320?nm, and 350?nm according to the absorption properties of the nine quantified compounds. The linearity, recovery, intraday and interday precision, accuracy, limit of detection (LOD) and quantification (LOQ), repeatability and stability were all tested and good results were obtained. In the FA, 320?nm was selected. The correlation coefficients of similarity were determined on the basis of the relative retention time (RRT) and relative peak area (RPA) of 20 common peaks in chromatographic fingerprints. Results indicated that both the RRT and RPA of 20 common peaks shared a close similarity. From the 20 common peaks, 18 compounds, including the nine quantified compounds, were identified or tentatively characterized by comparing their retention times, UV spectra, and MS spectra with those of standard compounds or literature data. The study not only presents a powerful and reliable analytical tool for the quality control of YH preparations, but also provides the chemical evidence for revealing the material basis of their therapeutic effects.     

Studies on fluorescein-V The absorbance of fluorescein in the ultraviolet, as a function of pH

The ultraviolet absorption spectum of an aqueous solution of highly-purified yellow fluorescein at ionic strength 0.10 has been measured at various pH values in the range from 0.15 to 8.70. The maxima at 227, 249 and 295 nm change little with pH, but the maximum found at 437 nm in acid medium changes greatly in absorbance and position on addition of alkali, resolving first into two maxima, at 455 and 475 nm, and finally becoming a single large maximum (at pH 8) at 490 nm. A unique feature of the absorption at 437 nm is that all four prototropic forms of fluorescein, H(3)Fl(+), H(2)Fl, HFl(-) and Fl(2-), absorb at this wavelength. The total absorbance at this wavelength first falls rapidly as the pH rises from 0.15, reaching a minimum at pH 3.63, then increases to a maximum at pH 5.3, and finally falls to steady value at pH > 8.0. The absorbance as a function of pH is defined by seven constants: three dissociation constants (K(H(3)Fl) = 6.61 x 10(-3), K(H(2)Fl) = 3.98 x 10(-5), K(HFl) = 4.36 x 10(-10)) and four molar absorptivities ((H(3)Fl) = 4.94 x 10(-4), (H(2)Fl) = 1.20(5) x 10(4), (HFl) = 2.16 x 10(4) and (Fl) = 7.61 x 10(3) 1.mole(-1).cm(-1)). Solutions of yellow fluorescein in water undergo rapid deterioration on exposure to daylight or fluorescent lighting but are stable in the dark.     

双波长叠加吸收光谱法测定药物中的酒石酸美托洛尔

建立了快速、准确测定药物中酒石酸美托洛尔的双波长叠加可见吸收光谱法。在pH 4.55的酸性Tris-盐酸介质及586~740 nm波长范围内,偶氮氯膦Ⅲ与酒石酸美托洛尔反应生成具有两个明显正吸收峰的离子缔合物,最大正吸收波长位于614 nm,次大正吸收波长位于664 nm,表观摩尔吸光系数(κ)分别为6.03×10~4L/(mol·cm)(614 nm)和5.37×10~4L/(mol·cm)(664 nm),酒石酸美托洛尔的质量浓度在0.2~8.6 mg/L范围内服从朗伯-比尔定律,检出限为0.13 mg/L(614 nm)和0.15 mg/L(664 nm)。当采用双波长叠加法测定时,其表观摩尔吸光系数(κ)可达1.14×10~5L/(mol·cm),检出限为0.072 mg/L。该文同时探讨了显色反应的适宜条件、共存物质的影响及吸收光谱特征。实验发现,该反应体系的单波长及双波长叠加吸收光谱法的表观摩尔吸光系数可达5.37×10~4~1.14×10~5L/(mol·cm),方法可用于市售药物中酒石酸美托洛尔含量的测定,加标回收率为98.0%~101%,相对标准偏差(n=6)为1.8%~2.3%。     

Absorption spectra of viral components of Sendai virus in the wavelength region from 130 to 320 nm.

Using synchrotron radiation as a light source, the absorption spectra of purified viral components of the Sendai virus, i.e. messenger RNA, lipids, spike (envelope) proteins, reconstructed envelopes, core proteins and whole virions, were obtained in the wavelength region 130-320 nm by measuring the transmission of thin films. Viral (messenger) RNA two peaks at 260 and 190 nm, and a large increase below 160 nm. The absorption spectrum of lipids exhibited a broad peak at 190 nm and a very sharp increase below 160 nm. With spike proteins, a slight peak at 280 nm and a shoulder at 230 nm were observed in addition to a sharper peak at 190 nm and a rather slow increasing absorption below 160 nm. Reconstructed envelopes showed the features of a combination of lipids and proteins. The absorption spectra of core proteins and whole virions exhibited similar characteristics to spike proteins. Conventional UV data were also obtained in the wavelength range 210-320 nm with RNA and lipids. The UV and synchrotron radiation data were in good agreement in terms of the mass absorption coefficients. The molecular splitting of spike proteins was also examined. Proteins gave more diffuse reflection than their subunits, causing a reduction in absorption. This was explained by a loss of transparency with increasing molecular weight.     

Ultraviolet molar absorptivities of aqueous hydrogen peroxide and hydroperoxyl ion

Molar absorptivities are measured at 11 wavelengths between 200 and 300 nm for H₂O₂(aq) with an average error of 8.5% (95% confidence limit), and at 10 wavelengths in the same range for HO₂^? (aq), from absorbance vs. concentration plots. Results are compared to previous measurements of both aqueous and vapor-phase molar absorptivities.     

Equilibrium constants from spectrophotometric data: dimer formation in gaseous Br2

The equilibrium constant for the dimerization reaction, 2Br 2(g) right arrow over left arrow Br 4(g), is estimated using the classic spectrophotometric method with precise data and a multiwavelength fitting approach. The analysis is very sensitive to small errors in the data, requiring that parameters for the baseline absorption be included at each wavelength. To that end spectra for 18 Br 2 pressures in the range 6-119 Torr are augmented by six baseline scans to facilitate estimation of three baseline constants and two molar absorptivities at each wavelength, yielding K c = 2.5 +/- 0.4 L/mol at 22 degrees C. This value is more than double the only previous estimate, which was based on analysis of PVT data. With adoption of a literature estimate of Delta H degrees = -9.5 kJ/mol, the new K implies Delta S degrees = -51 J mol (-1) K (-1) (ideal gas, 1 bar reference). The spectra for monomer absorption (peak 227 nm) and dimer absorption (205 nm) are obtained with unprecedented precision.     

Fluorescence Labeling and Determination of Pepsin with CdSe Quantum Dots

Based on the solid phase/liquid deposition CdSe quantum dots (QD) were synthesized using selenium and cadmium‐salt as precursor at room temperature. The average diameter of CdSe QD estimated from the high resolution transmission electron microscopy (HRTEM) graph and absorption spectra was ca. 3–3.5 nm. The mercaptoacetic‐acid stabilized CdSe QD exhibited ultraviolet absorption at 350 and 380 nm and strong fluorescence emission at 481.6 nm, respectively. When conjugated with pepsin, the fluorescence peak intensity of CdSe QD decreased considerably and the fluorescence peak shifted to 467.2 nm. Under optimal conditions, a concentration in 5–50 mg· L^?1 of pepsin could be determined on the basis of fluorescence decrease ratio of CdSe QD, with a detection limit 3δ of 0.36 mg·L^?1 (n=10). The proposed method was applied to detection of the concentration of pepsin in human gastric juice.     

Fading Spectrophotometric Method for the Determination of Polyvinylpyrrolidone with Eosin Y

在弱酸性HC1-NaAc缓冲介质中,曙红Y（EY）在可见光区有强烈的光吸收,其最大吸收波长(lmax)位于517 nm处,而聚乙烯吡咯烷酮(PVP)在250-700 nm之间无光吸收,当EY与PVP反应形成结合产物时,EY发生明显的褪色作用,最大褪色波长仍位于517 nm,并在545 nm处出现一个较小的吸收峰。其褪色程度（DA）与PVP浓度在0.40~3.20 µg mL-1范围成线性关系,此褪色反应的灵敏度高,摩尔吸光系数(ε)是6.4 × 106 L mol-1 cm-1,对PVP的检出限为0.12 µg mL-1。并研究了反应的影响因素,结果表明方法具有较好的选择性,据此发展了一种曙红Y褪色分光光度法测定PVP的新方法。方法简便快速,可用于啤酒中PVP的定量测定。     

The dependence of DNA luminescence on excitation wavelength in the UV/VUV region

Luminescence emission and excitation spectra have been obtained for DNA films at 77 K under vacuum ultraviolet excitation (150–280 nm). The emission spectra, which cover the wavelength range 310 to 490 nm, consists of two components, a short-lived component around 350 nm which is attributed to fluorescence and a longer-lived component around 410 nm believed to be phosphorescence. The excitation spectra, as functions of emission wavelength, are similar in profile with a fairly broad peak around 9240–260 nm) with a shoulder around 200 nm followed by a gradual but constant decrease into the vacuum ultraviolet region of the spectrum. No evidence of autoionization was seen in the region investigated.     

Core-extended terrylene diimide on the bay region: synthesis and optical and electrochemical properties

Two novel core-extended terrylene diimides on the bay region (CETDIs) were synthesized via annulation of the four additional ethylene units or benzene units on the bay region of the terrylene diimide core. The optical and electrochemical properties of the two compounds were investigated. These CETDIs exhibited broad absorption spectra with high extinction coefficients, which span a wide range in the ultraviolet and visible spectrum from 300 to 700 nm. Furthermore, the redox process of the CETDIs increased from two waves to four waves, and the lowest unoccupied molecular orbital (LUMO) levels were enhanced from -4.00 to -3.59 eV.     

UV spectroscopy of monosubstituted derivatives of 1,2-dihydro-C60-fullerenes

UV spectroscopy is used to determine the molar absorption coefficients of C₆₀ fullerene and monosubstituted 1,2-dihydro-C₆₀-fullerenes in different solvents. It is found that the extinction coefficient of C₆₀ at 330 nm (the main absorption band most frequently used for qualitative and quantitative determination of the C₆₀ content) is independent of the nature of the solvent and is ～54400 M^?1·cm^?1. The molar absorption coefficients of a series of monosubstituted 1,2-dihydro-C₆₀-fullerenes are practically independent of the chemical structure and the length of the substituent and are 35700 M^?1·cm^?1 (λ ～ 328 nm) and 115250 M^?1·cm^?1 (λ ～ 257 nm). It is shown that the substitution in fullerene proceeds via the double 6,6 bond, as evidenced by the absorption band at 424 nm in the spectra of these compounds, which is characteristic of monosubstituted methanofullerenes.     

Determination of mercury in environmental samples by cold vapour generation and atomic-absorption spectrometry with a gold-coated graphite furnace

Mercury is determined at below the pg/ml level by a combination of cold vapour generation, trapping in a gold-coated graphite furnace and atomic-absorption detection. The mercury is reduced to the element by stannous chloride, stripped from solution by a stream of nitrogen and collected on a gold-coated porous graphite disk in a graphite furnace. It is then atomized by increasing the graphite furnace temperature and detected by an atomic-absorption spectrophotometer. The absolute detection limit and the characteristic mass were found to be 5 and 20 pg for 0.0044 absorbance, respectively. The concentration limit of detection was 0.1 pg/ml for a 50-ml sample, and the linear dynamic range covered three orders of magnitude. The precisions of the measurements were 2.7% for 0.1 ng and 2.6% for 2 ng of mercury. Analyses of NBS and NIES reference materials showed quantitative recovery. Analytical results obtained by the technique are presented for natural waters, marine biota and sediments.