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Optical properties of chiral single-walled carbon nanotubes thin films
摘要： This work contains experimental results of optical properties for thin films containing Single-Walled Carbon Nanotubes. Thin films concerning 0.5, 1 and 2 mg of low dimension chiral (10,6) Single-Walled Carbon Nanotubes dispersed in low concentration aqueous sodium dodecyl sulfate solution (2 mL) were successfully fabricated by spin-coating technique on transparent substrates at ambient atmosphere. Optical properties of these thin films were examined using Transmission, Raman and Photoluminescence Spectroscopies. We find that investigated chiral Single-Walled Carbon Nanotubes show transmission and emission bands not only in infrared range but also ultraviolet and visible range.
关键词： Absorbance,Single-walled carbon nanotubes,Raman spectra,Photoluminescence,Decay time of photoluminescence,Quantum yield
更新于2025-09-11 14:15:04
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The phenomenon of fluorescence in immunosensors
摘要： The phenomenon of fluorescence in immunosensors is described in this paper. Both structure and characteristics of biosensors and immunosensors are presented. Types of immunosensors and the response of bioreceptor layers to the reaction with analytes as well as measurements of electrochemical, piezoelectric and optical parameters in immunosensors are also presented. In addition, detection techniques used in studies of optical immunosensors based on light-matter interactions (absorbance, reflectance, dispersion, emission) such as: UV/VIS spectroscopy, reflectometric interference spectroscopy (RIfs), surface plasmon resonance (SPR), optical waveguide light-mode spectroscopy (OWLS), fluorescence spectroscopy. The phenomenon of fluorescence in immunosensors and standard configurations of immunoreactions between an antigen and an antibody (direct, competitive, sandwich, displacement) is described. Fluorescence parameters taken into account in analyses and fluorescence detection techniques used in research of immunosensors are presented. Examples of immunosensor applications are given.
关键词： absorbance,UV/Vis,fluorescence,immunosensor,biosensor
更新于2025-09-11 14:15:04
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Janus Group-Ⅲ Chalcogenide Monolayers and Derivative Type-Ⅱ Heterojunctions as Water Splitting Photocatalysts with Strong Visible Light Absorbance
摘要： Search for two-dimensional (2D) water splitting photocatalysts is crucial to solve energy crises and environmental problems. In this research, we study the electronic and photocatalytic properties of single-layer Ga2X1X2 (Ga2SeTe, Ga2STe and Ga2SSe) and newly proposed α-Ga2S3/Ga2SSe-A, α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C van der Walls heterojunctions using first-principles calculations. Theoretical results indicate Ga2X1X2 monolayers present suitable band edges. 2D α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C belong to type-Ⅱ heterojunctions, and under biaxial strains embody suitable band edges. Comparisons of the valence band maximum (VBM) charge and electric dipole of α-Ga2S3/Ga2SSe-A and α-Ga2S3/Ga2SSe-B demonstrate it is possible to achieve suitable band edges for water splitting by switching electric dipoles. Especially, the three Ga2X1X2 monolayers, α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C heterojunctions absorb a large amount of visible light, promising they are photocatalysts for water splitting. More importantly, we find the optical absorption coefficients of 2D monolayers and heterojunctions in previous calculations are several times underestimated because the effective volume is not taken into consideration. To obtain reliable absorption coefficients, the real and imaginary parts of dielectric function must be renormalized.
关键词： visible light absorbance,van der Waals heterojunctions,two-dimensional (2D) materials,Janus group-Ⅲ chalcogenide monolayers,water splitting photocatalysts,first-principles calculations
更新于2025-09-10 09:29:36
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Micromachined optical flow cell for sensitive measurement of droplets in tubing
摘要： Here a micromachined flow cell with enhanced optical sensitivity is presented that allows high-throughput analysis of microdroplets. As a droplet flows through multiple concatenated measurement points, the rate of enzymatic reaction in the droplet can be fully characterized without stopping the flow. Since there is no cross-talk between the droplets, the flow cell is capable of continuously measuring biochemical assays in a droplet flow and thus is suitable to be used for continuous point-of-care diagnostics monitoring. This paper describes the design and operation of the device and its validation by application to the accurate and continuous quantification of glucose concentrations using an oxidase enzymatic assay. The flow cell forms an important component in the miniaturization of chemical and bio analyzers into portable or wearable devices.
关键词： Enzymatic assays,Droplet microfluidics,Optical detections,Microfluidics,Real-time monitoring,Continuous measurement,Absorbance,Point-of-care diagnostics
更新于2025-09-10 09:29:36
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Photophysical and photocatalytic properties of corrophyll and chlorophyll
摘要： Tetrapyrrolic macrocycles are well known photosensitizers, absorbing light in the ultraviolet and visible region. The quantum e?ciency of these naturally occurring compounds in optical processes, and the possibility of altering their behavior by modifying its constituent features, make them promising candidates for applications as Dye Sensitized Solar Cells (DSSC) and photocatalytic reactions. The time-dependent density-functional theory (TD-DFT) were used to study the optical and redox properties of chlorophyll and corrin-related molecules (corrophyll). The in?uence of the substituents and metallic atoms in their properties have been investigated. Our results show lower reduction potentials for corrophyll molecules compared with chlorophyll. The optical absorbance spectra of corrophyll without a metallic atom at their central rings shows a signi?cant blue-shift, as compared to their chlorophyll counterparts. The presence of Co(I) ion species at the corrophyll core leads to oxidation potentials below than that of water, which puts corrophyll ahead of traditional chlorophyll pigments as photocatalysts. We show that the substituents and the ions coordinated to the macrocycles play an important role in this phenomena. These ?ndings show the great potential of tuning the spectroscopic and reactive properties of tetrapyrrole macrocycles for applications in photocatalysis and optoelectronic devices, while keeping their essential structural features intact.
关键词： Corrole,Photophysics,Porphyrin,Electronic structure,TD-DFT,Optical absorbance,Photocatalysis
更新于2025-09-10 09:29:36
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Beer’s law - why absorbance depends (almost) linearly on concentration
摘要： Beer’s law assumes a strictly linear dependence of the absorbance from concentration. Usually, chemical interactions and instrumental imperfection are made responsible for experimental deviations from this linearity. In this contribution we show that even in the absence of such interactions and instrumental errors, absorbance should be only approximately proportional to concentration. This can be derived from the quadratic dependence of the complex refractive index, and, by that, of the molar attenuation coefficient, from the dielectric constant and its frequency dispersion. Following dispersion theory, it is the variation of the real and the imaginary part of the dielectric function that depends linearly on concentration in the absence of interactions between the oscillators. We show that this linear correlation translates into a linear dependence of the absorbance for low concentrations or molar oscillator strengths based on an approximation provided by Lorentz in 1906. Accordingly, Beer’s law can be derived from dispersion theory.
关键词： Dispersion,Absorbance,Beer’s law
更新于2025-09-04 15:30:14
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Paracetamol micro-structure analysis by optical mapping
摘要： Domain structure of paracetamol - popular antipyretic analgesic - was investigated by infrared (IR) spectroscopy using synchrotron radiation. Absorbance and retardance maps reveal molecular orientation inside the micro-domains of the paracetamol form II which has a better water solubility and compressibility compared to the commercially used forms I. The developed method of analysis representing orientation of optical slow(fast)-axis is compared with azimuthal orientation of the absorbance at several specific IR bands using vector maps. High brightness of synchrotron radiation and hyper-spectral mapping of structural domains in paracetamol clearly reveals the domain boundaries and can potentially be used to observe in situ intra-phase transformations of paracetamol forms-I, II, III and melting, which are important for making medical tablets and powders by an industrial process.
关键词： Paracetamol,Water solubility,Retardance,Orientational anisotropy,Absorbance
更新于2025-09-04 15:30:14
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Polarons, bipolarons, and absorption spectroscopy of PEDOT
摘要： Electronic structure and optical absorption spectra of poly(3,4-ethylenedioxythiophene) (PEDOT) for different oxidation levels were studied using density functional theory (DFT) and time-dependent DFT. It is shown that the DFT-based predictions for the polaronic and bipolaronic states and the nature of corresponding optical transitions are qualitatively different from the widely used traditional picture based on semi-empirical pre-DFT approaches that still dominate the current literature. Based on the results of our calculations, the experimental Vis/NIR absorbance spectroscopy and the electron paramagnetic resonance spectroscopy are re-examined and a new interpretation of the measured spectra and the spin signal which is qualitatively different from the traditional interpretation is provided. The findings and conclusions concerning the nature of polaronic and bipolaronic states, band structure and absorption spectra presented for PEDOT, are generic for a wide class of conducting polymers (such as polythiophenes and their derivatives) that have similar structure of monomer units.
关键词： Vis/NIR absorbance spectroscopy,PEDOT,conducting polymers,Polarons,electron paramagnetic resonance spectroscopy,bipolarons
更新于2025-09-04 15:30:14
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UV-SPECTROPHOTOMETRIC DETERMINATION OF ROSUVASTATIN AND NIACIN INDIVIDUALLY AND COMBINED TABLET DOSAGE FORM BY SIMULTANEOUS EQUATION AND ABSORBANCE RATIO METHOD
摘要： Two UV-spectrophotometric methods were developed and validated for quantitative determination of Rosuvastatin and niacin in combined tablet dosage form .Method I is based on the simultaneous equation and method II is based on the absorbance ratio method. The absorbance maxima were found to be at 241and 262nm in water for the Rosuvastatin and niacin respectively. Beer’s law is obeyed in the concentration range 5-40μg/ml with correlation coefficient within range of0.998 for both the drugs. The accuracy of the methods was assessed by recovery studies and found to be 98-105%for Rosuvastatin and niacin respectively.
关键词： Rosuvastatin and niacin,absorbance ratio method,Simultaneous equation
更新于2025-09-04 15:30:14