Features of formation of CdSe nanoparticles in aqueous sodium polyphosphate solutions

A study was carried out on the features of formation of stable aqueous colloidal solutions containing CdSe nanoparticles stabilized by sodium polyphosphate resulting from a reaction between cadmium chloride and sodium selenosulfate. The major parameters determining the size of the CdSe nanoparticles are the reaction medium temperature and the ratio of the starting reagent concentrations. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 102–106, March–April, 2006.     

Structure and spectral-optical characteristics of Se,Se/CdS,and Se/Cd<Subscript>0.5</Subscript>Zn<Subscript>0.5</Subscript>S nanoparticles,stabilized in polymer-containing media

A method was proposed for the production of colloidal nanoparticles of selenium stabilized by polymers and surfactants, and their structural and optical characteristics were studied. It was shown that during the deposition of CdS and Cd_0.5Zn_0.5S on the surface of the Se nanoparticles followed by dissolution of the selenium with sodium sulfite it is possible to obtain network “nanoframeworks” with size 30–50 nm, formed by CdS or Cd_0.5Zn_0.5S particles measuring 3–5 nm. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 24–29, January–February, 2007.     

Growth and spectroscopic characterization of CdSe nanoparticles synthesized from CdCl2 and Na2SeSO3 in aqueous gelatine solutions

CdSe nanoparticles were synthesized in comparatively mild conditions from Na₂SeSO₃ and CdCl₂ in aqueous gelatine solutions. Kinetics of the formation and growth of CdSe nanocrystals as well as the effect of various parameters of reacting mixture on the size of CdSe nanocrystals are investigated. Optical properties of thin gelatine films, containing CdSe nanoparticles of different size, are characterized using absorption and Raman spectroscopy.     

Spectral,lifetime and photochemical characteristics of 4-acetoxy-chalcone in viscous media

Both fluorescence and excitation spectra of 4-acetoxy-chalcone (4-AC) are bathochromically shifted as the medium polarity increases. The fluorescence quantum yields are sensitive to medium viscosity and increase sharply as the medium viscosity increases due to prohibition of radiationless deactivation pathways. The fluorescence lifetime of 4-AC in glycerol has been measured as τ = 1.9 ns. The photochemical quantum yields (thought to be a trans-cis photo-isomerization) are also sensitive to medium viscosity with minimum φ_c values obtained in highly viscous solvents. The effect of medium viscosity on the quenching of 4-AC fluorescence using picric acid as a quencher has been studied. A static-type quenching mechanism is proposed to account for the quenching efficiency as the medium viscosity increases.     

Preparation of sodium titanate nanotubes modified by CdSe quantum dots and their photovoltaic characteristics

Sodium titanate nanotubes have been prepared and modified chemically with CdSe quantum dots (QDs) using bifunctional modifiers (HS-COOH). Their photovoltaic characteristics have also been studied. The results indicate that the surface photovoltage response of nanotubes extends to the visible light region, and the intensity of surface photovoltage is enhanced after modification with CdSe QDs. The field-induced surface photovoltage spectroscopy (FISPS) shows that sodium titanate nanotubes have different photovoltaic response before and after modification. That is, the surface photovoltaic re-sponse of pure sodium titanate nanotubes increases with the enhancement of positive applied bias and decreases with the enhancement of negative applied bias. Meanwhile, the surface photovoltaic re-sponse of CdSe modified sodium titanate nanotubes is different from that of the pure sodium titanate nanotubes. The whole spectrum increases with the enhancement of applied bias at the first stage. However, when the applied bias reaches a certain value, the surface photovoltage response keeps in-creasing in some spectrum regions, while decreasing in other spectrum regions. This novel phe-nomenon is explained by using an electric field induced dipole model.     

Raman and photoluminescence investigation of CdS/CdSe quantum dots on TiO2 nanoparticles with multi-walled carbon nanotubes and their application in solar cells

Raman spectroscopy and photoluminescence (PL) were used to investigate the improved short-circuit current density (J_SC) of CdS/CdSe quantum dot (QD)-sensitized solar cells with multi-walled carbon nanotubes (MWCNTs). Raman and PL experiments were carried out in order to explore the hot-electron and cold-electron injections, respectively. The experimental results showed that the concentration of MWCNTs influences the hot-electron and cold-electron injections from CdS/CdSe QDs to TiO₂ nanoparticles. Therefore, the improved J_SC in CdS/CdSe QD-sensitized solar cells can be explained as due to the better electron injections.     

Nanosecond and microsecond decay of photogenerated charges in Cd<Subscript>x</Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S nanoparticles

The luminescent characteristics of Cd_xZn_1−xS nanoparticles were studied. It was shown that the emission is due to the recombination of holes in the valence band with electrons captured by two sorts of traps, of which the traps with lower energy were ascribed to the surface states of the Cd_xZn_1−xS nanoparticles. It was established that the Cd_xZn_1−xS nanoparticles have more pronounced ability than CdS nanoparticles to accumulate excess negative charge under the conditions of pulsed irradiation. It was shown that the consumption of the photogenerated electrons in nanosecond and microsecond time scales involves the participation of one and the same electron traps. It was established that the rate of interaction of the electrons captured by the surface traps with oxygen increases with decrease in the size of the nanoparticles. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 275–281, September–October, 2007.     

Synthesis and characterization of low-melting ferrocenyl salts: a study of thermal and photochemical redox reactions

Abstract

The syntheses of bis(trifluoromethane) sulfonimide N-(ferrocenylmethyl) N,N,N-trimethyl ammonium salt 1 and bis(trifluoromethane) sulfonimide N′,N-bis(ferrocenylmethyl) inmidazolium salt 2 are reported. The compounds show low melting points, 76° and 125?°C, respectively, and were characterized by spectroscopic techniques ¹H-NMR, mass spectrometry, FT-IR spectroscopy, cyclic voltammetry, and XRD crystallographic analysis. Cyclic voltammetry results demonstrate that both salts have a quasi-reversible electrochemical behavior, similar to the reversible one shown by ferrocene under the same conditions. In the case of 1, a coupled chemical reaction was detected at slow scan rates after the oxidation. Transient species in the redox processes were investigated using flash photolysis and pulse radiolysis. In both cases, transient spectra of the products were similar to transient spectra observed for ferrocene. The decay kinetics of the oxidized and reduced transients were examined and mechanistic information was obtained. The experimental results show the potential uses of the two complexes as catalytic materials for electrochemical applications.     

Photophysical and photochemical processes of riboflavin (vitamin B_2) by means of the transient absorption spectra in aqueous solution

Using time-resolved techniques of 337 and 248 nm laser flash photolysis, the photo-physical and photochemical processes of riboflavin (RF, vitamin B2) were studied in detail in aqueous solution. The excited triplet state of riboflavin (3RF*) was produced with 337 nm laser, while under 248 nm irradiation, both 3RF* and hydrated electron (eaq) formed from photoionizationcould be detected. Photobiological implications have been inferred on the basis of reactivity of 3RF* including energy transfer, electron transfer and hydrogen abstraction. The RF.+ was generated by oxidation of SO4.- radical with the aim of confirming the results of photolysis.     

Photophysical and photochemical processes of riboflavin (vitamin B2) by means of the transient absorption spectra in aqueous solution

Using time-resolved techniques of 337 and 248 nm laser flash photolysis, the photo physical and photochemical processes of riboflavin (RF, vitamin B₂) were studied in detail in aqueous solution. The excited triplet state of riboflavin (³RF^*) was produced with 337 nm laser, while under 248 nm irradiation, both³RF^* and hydrated electron (e_aq) formed from photoionization could be detected. Photobiological implications have been inferred on the basis of reactivity of³RF^* including energy transfer, electron transfer and hydrogen abstraction. The RF^·+ was generated by oxidation of SO₄ ^·-radical with the aim of confirming the results of photolysis.     

水相中荧光CdSe纳米晶的优化合成与表征

Ⅱ-Ⅵ族半导体纳米粒子（也称半导体量子点（semiconductor quantum dots）简称NCs）由于其独特的光学、光化学、电化学以及非线性光学性质已逐渐引起人们的广泛关注。而Ⅱ-Ⅵ族NCs最诱人的 潜在应用是作为荧光探针应用于生物体系,在生命科学研究中起到定性和定量标记分子和细胞的作用。     

Evaluating the Conservation State of Naturally Aged Paper with Raman and Luminescence Spectral Mapping: Toward a Non-Destructive Diagnostic Protocol

Micro-Raman and luminescence spectroscopy were combined with morphological analysis to study the conservation state of differently degraded paper samples, dated from 1873 to 2021. The aim of the work reported in this paper was to obtain ageing markers based on variations of Raman and fluorescence spectral features. Raman and luminescence spectra were acquired by scanning non-printed areas of books, and Raman and fluorescence maps were built by contrasting spectral parameters point by point, obtaining a micron-scale space resolved imaging of the degradation pattern. Complementary information on paper morphology and surface compactness were obtained by high-resolution scanning electron and atomic force microscopy. The proposed non-destructive procedure is particularly interesting for precious and ancient samples to analyze their degradation processes and to evaluate the performance and effectiveness of restoration treatments.     

高质量CdSe量子点的水相制备与表征

以巯基丁二酸为稳定剂, 亚硒酸钠为硒源, 制备了高质量水溶性CdSe量子点. 研究了反应时间、 镉与硒的摩尔比及镉与巯基丁二酸的摩尔比等实验条件对CdSe量子点光谱性能的影响. 分别用紫外-可见光谱、 荧光光谱、 X射线粉末衍射和透射电子显微镜等对量子点进行表征. 结果表明, 采用这种方法制得的CdSe量子点为立方晶型, 量子点的荧光发射峰在518～562 nm范围内连续可调, 并且发射峰的半峰宽始终保持在35 nm左右, 荧光量子产率可达21%.     

Optical spectra and kinetic characteristics of radicals formed upon the photolysis of aqueous solutions of a FeOH<Subscript>aq</Subscript><Superscript>2+</Superscript> complex and phenol

The nature, optical spectra, and kinetic characteristics were determined for intermediate radicals formed upon the photolysis of aqueous solutions of a FeOH_aq ²⁺ complex with phenol additives. The primary radical ^·OH reacts with phenol to form ortho- and para-isomers of the Ph(OH)₂ ^· radical. The Ph(OH)₂ ^· radical eliminates a water molecule to form a phenoxyl radical PhO^·. The latter disappears in the reactions with Fe^III complexes, recombination, and disproportionation. The final products of photochemical transformations were determined. Among them, o-quinone and diphenoquinones were identified.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2605–2612, December, 2004.     

液相OH•, NO3•和SO4•-与二甲基硫反应机理

利用激光闪光光解技术研究了液相二甲基硫(DMS)与OH^•, NO₃^•和SO₄^•-自由基的微观反应机理. 实验结果表明: 在pH 5～9时, OH^•氧化DMS生成DMSOH^•, DMSOH^•会与DMS反应生成(DMS)₂⁺; 而NO₃^•和SO₄^•-;会直接氧化DMS生成DMS^＋, 生成的DMS^＋会与DMS反应生成(DMS)₂⁺.(DMS)₂⁺与氧气的反应很慢, 它的衰减受pH影响较大.     

Electrochemical determination of mesoscopic phenomena, defect states in CdSe nanocrystals and charge carrier manipulability

The review gives an overview of cyclic voltammetry measurements performed on CdSe nanocrystals (so called Quantum Dots). Data of relevant publications is gathered and newly interpreted to give complete insights in charge transfer processes at QD surfaces. In specific, it is focused on the size-dependent electronic properties (Quantum-Size-Effect), the characterisation of surface defects, and the characterisation of hybrid nanocrystal/conducting polymer composites. First two authors contribute equally to this work Correspondence: Thomas Nann, School of Chemical Sciences and Pharmacy, University of East Anglia (UEA), Norwich NR4 7TJ, U.K.     

Two Spectroscopies in One: Interference of Circular Dichroism and Raman Optical Activity

Previously, we and other laboratories have reported an unusual and strong Raman optical activity (ROA) induced in solvents by chiral dyes. Various theories of the phenomenon appeared, but they were not capable of explaining fully the observed ROA band signs and intensities. In this work, an analysis based both on the light scattering theory and dedicated experiments provides a more complete understanding. For example, double-cell magnetic circular dichroism and magnetic ROA experiments with copper-porphyrin complex show that the induced chirality is observed without any contact of the solvents with the complex. The results thus indicate that a combination of electronic circular dichroism (ECD) with the polarized Raman scattering is responsible for the effect. The degree of circularity of solvent vibrational bands is a principal molecular property participating in the event. The insight and the possibility to predict the chirality transfer promise future applications in spectroscopy, chemical analysis and polarized imaging.     

Cuttlebone-derived organic matrix as a scaffold for assembly of silver nanoparticles and application of the composite films in surface-enhanced Raman scattering

Biologically derived materials provide a rich variety of approaches toward new functional materials because of their fascinating structures and environment-friendly features, which is currently a topic of research interest. In this paper, we show that the cuttlebone-derived organic matrix (CDOM) is an excellent scaffold for the one-step synthesis and assembly of silver nanoparticles (AgNPs), which can be further used as substrate for surface-enhanced Raman scattering (SERS). Formation of AgNPs–CDOM composite was accomplished by the reaction of CDOM with AgNO₃ and NH₃·H₂O solution at 80 °C without using any other stabilizer and reducing agents. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs can be partly regulated by changing incubation time; the concentration of NH₃·H₂O is critical to the formation rate of AgNPs. As a proof of principle, we show that the AgNPs–CDOM composite can be employed in trace analysis using SERS.     

某些液相纳米微粒的光谱特性研究及分析应用

介绍了液相纳米微粒的吸收、荧光和共振散射光谱特性研究现状及纳米微粒在共振散射光谱分析中的应用,引用文献125篇．     

SERS and FDTD simulation of gold nanoparticles grafted on germanium wafer via galvanic displacement

Uniform and dense Au nanoparticles grown on Ge (Au/Ge) were fabricated by a facile galvanic displacement method and employed as surface‐enhanced Raman scattering (SERS) substrates. The substrates exhibited excellent reproducibility in the detection of rhodamine 6G aqueous solution with a relative standard deviation of <20%. The substrate showed a high Raman enhancement factor of 3.44 × 10⁶. This superior SERS sensitivity was numerical confirmed by the three‐dimensional finite‐difference time‐domain method, which demonstrated a stronger electric field intensity (|E/E₀|²) distribution around the Au nanoparticles grown on Ge. This facile and low‐cost prepared Au/Ge substrate with high SERS sensitivity and reproducibility might have potential applications in monitoring in situ reaction in aqueous solution. Copyright © 2014 John Wiley & Sons, Ltd.