Silver and gold nanoparticles in silica matrices: synthesis,properties, and application

Methods of synthesis, optical characteristics, morphology, and catalytic and bactericidal characteristics of composite materials based on silica (films and powders) containing nanoparticles of silver, gold, and their binary compounds with alloy or core–shell structure are examined. The photochemical reduction of Au³⁺ and Ag⁺ with a photocatalyst (a film of SiO₂ with adsorbed benzophenone) makes it possible to generate stable nanoparticles of gold and silver in solutions for subsequent introduction into adsorbents and catalysts. Examples of the use of nanosized composites in catalysis and in microbiological experiments are presented.     

Silver nanodisks: size selection via centrifugation and optical properties

Silver nanodisks, having two different sizes, and spherical particles are synthesized by soft chemistry. By using centrifugation, nanodisks are mainly selected. The experimental absorption spectra of these nanodisks with different sizes are compared to those simulated using the discrete dipole approximation method. For small nanodisk sizes, the nanodisk shape is neglected and the simulated spectra closest to the experiments are obtained by assuming a spheroidal particle. Conversely, for larger nanodisks, the precise geometries represented by snip and aspect ratio are needed for good agreement between experiments and simulations.     

Squaraine dyes: The hierarchical synthesis and its application in optical detection

Squaraine dyes, a four-membered ring system with structural rigidity, possess unique photoelectrical properties and are marked by their exceptionally sharp and intense absorption associated with a strong fluorescent emission in solution. These favorable characteristics have prompted their exploitation in a number of state of the art applications including photoconductivity, data storage, light-emitting field-effect transistors, solar cells and fluorescent histological probes. In this review, we first summarize the recently proposed novel methods in the synthesis of these versatile derivatives. Subsequently, their extensive applications in the prevalent optical detection of the surrounding medium such as ions, pH, thiol-based compounds, biomolecules and cell over the past decades are covered and discussed. In addition, different categories for the synthesis and sensing mechanisms for various squaric acid-based chemo-/bio- sensors are illustrated. Finally, the challenges and opportunities in the synthesis and application of these derivatives are also briefly discussed.     

Core-tetrasubstituted naphthalene diimides: synthesis, optical properties, and redox characteristics

2,3,6,7-tetrabromonaphthalene dianhydride has been synthesized by the bromination of naphthalene dianhydride with dibromoisocyanuric acid in excellent yield. The condensation of this dianhydride with 2,6-diisopropylaniline yielded the corresponding tetrabromo-substituted naphthalene diimide (NDI), which is a versatile precursor for the synthesis of core-tetrafunctionalized NDIs. Nucleophilic substitution of tetrabromo NDI with alkoxy, alkylthio, and alkylamino nucleophiles afforded a series of core-tetrasubstituted NDI chromophores that complete the series of previously reported di- and trifunctionalized NDI derivatives. The effects of electronic nature and number of core substituents on the optical and electrochemical properties of NDIs have been investigated by UV-vis and fluorescence spectroscopy and cyclic voltammetry. The absorption maxima (629-642 nm) of tetraamino NDIs are strongly bathochromically shifted compared to those of other core-functionalized NDIs.     

Trihydrazone functionalized cyanopyridine discoids: synthesis,mesogenic and optical properties

A new series of trihydrazone functionalized cyanopyridine derivatives (CPTH-D_m) carrying 3,4-dialkoxyphenyl groups was designed and synthesized successfully as discotic columnar liquid crystals. These new discoid mesogens display hexagonal columnar phase with a wide mesophase range from ambient temperature to 110 °C and the observed columnar assembly is due to the presence of intermolecular hydrogen bonds and π–π interactions in them. Their optical studies reveal that the compounds are good blue light emitters and hence they are potential candidates for OLED device fabrication.     

Oxasmaragdyrin-ferrocene and oxacorrole-ferrocene conjugates: synthesis, structure, and nonlinear optical properties

Ferrocenyl macrocyclic conjugates involving 22 pi oxasmaragdyrins and 18 pi oxacorroles have been synthesized and characterized. The direct covalent linkage of the ferrocenyl moiety to the meso position of the macrocycle is achieved by simple oxidative coupling of appropriate precursors with trifluoroacetic acid as catalyst. The electronic coupling between the ferrocenyl moiety and the macrocyclic pi system is apparent from: a) the red shifts (293-718 cm(-1)) of the Soret and Q-bands in the electronic absorption spectra of ferrocenyl conjugates; b) the shift of oxidation potentials (50-130 mV) of both the ferrocene and the corrole rings to the positive potentials; and c) considerable shortening of the C-C bond which connects the ferrocene and the meso-carbon atom of the macrocycle. The single-crystal X-ray structure of oxasmaragdyrin-ferrocene conjugate 9 reveals the planarity of the 22 pi skeleton with very small deviations of the meso-carbon atoms. The meso-ferrocenyl substituent has a small dihedral angle of 38 degrees, making way for mixing of the molecular orbitals of the ferrocene and the macrocycle. However, the other two meso substituents are almost perpendicular to the mean plane, defined by the three meso carbon atoms. Classical C-H...O and nonclassical C-H...pi interactions lead to a two-dimensional supramolecular network. Ferrocene-smaragdyrin conjugate 9 bonds to a chloride ion in the protonated form and a rhodium(i) ion in the free base form. Nonlinear optical measurements reveal a larger nonlinear refractive index (-5.83 x 10(-8)cm(2)W(-1)) and figure of merit (2.28 x 10(-8)cm(3)W(-1)) for the rhodium smaragdyrin-ferrocene conjugate 19 than for the others, suggesting its possible application in optical devices.     

BiOBr hierarchical microspheres: Microwave-assisted solvothermal synthesis, strong adsorption and excellent photocatalytic properties

Two kinds of BiOBr nanosheets-assembled microspheres were successfully prepared via a facile, rapid and reliable microwave-assisted solvothermal route, employing Bi(NO(3))(3)·5H(2)O and cetyltrimethylammonium bromide (CTAB) as starting reagents in the absence or presence of oleic acid. The phase and morphology of the products were characterized by powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). Experiments indicated that the formation of these building blocks of microspheres could be ascribed to the self-assembly of nanoparticles according to mesocrystal growth mode. Interestingly, both samples exhibited not only strong adsorption abilities, but also excellent photocatalytic activities for methyl orange (MO), rhodamine B (RhB) and phenol. The resulting BiOBr hierarchical microspheres are very promising adsorbents and photocatalysts for the treatment of organic pollutants.     

GaN taper rods: Solid-phase synthesis, crystal defects, and optical properties

Wurtzite GaN taper rods assembled from highly oriented nanoparticles were synthesized using NaNH₂ and the as-synthesized GaOOH prismatic rods as reactants at 600 °C for 5 h. The lengths of the GaN taper rods are in the range of 4–6 μm and the diameters are about 0.5–1.5 μm. It was found that a slow heating rate (1 °C min⁻¹) was beneficial to keeping the one-dimensional (1D) skeleton of GaN, otherwise only GaN nanoparticles were obtained with a quick heating rate (10 °C min⁻¹). Selected area electron diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) observations revealed that the GaN taper rods assembled from highly oriented nanoparticles and there were crystal defects in the GaN structure. The GaN taper rods displayed luminescence emission in the blue-violet region, which may be related to crystal defects.     

Luminescent silicate core-shell nanoparticles: synthesis, functionalization, optical, and structural properties

SiO(2)/Zn(2)SiO(4):Mn(2+) core-shell nanoparticles with mean diameters in the range of 55-220 nm were prepared by a modified Pechini sol-gel method followed by lyophilization and annealing at temperatures of 800-1100°C. The as-synthesized nanoparticles were characterized by transmission electron microscopy, X-ray diffraction analysis, and photoluminescence spectroscopy. The results demonstrate that the crystal structure of the shell and the optical properties can be tuned by the annealing temperature and a variation of the concentration of doping ions. Under UV excitation, the samples emit green luminescence with its maximum at 525 nm, typical for the Mn(2+) ions in α-Zn(2)SiO(4). The resulting nanoparticles were successfully modified with amine and carboxyl functions with respect to a later attachment of biological moieties.     

Excellent blue fluorescent trispirobifluorenes: synthesis, optical properties and thermal behaviors

Tetraiodotrispirobifluorene (1) was synthesized through cyclization of 2,7-diiodofluorene with pentaerythrityl tetrabromide under base condition. Subsequent treatment of 1 with arylboronic acid or arylacetylene under Pd-catalyzed coupling condition led to corresponding tetraaryl trispirobifluorenes (3–8). These trispirobifluorene derivatives exhibited bright-violet to blue photoluminescence (PL) with excellent quantum efficiencies and showed high thermal stabilities. ‘Green-emission tail’ could not be detected for those tetraaryl substituted trispirobifluorenes (3–8) annealed both in N₂ and in air.     

Donor/acceptor-substituted anthradithiophene materials: synthesis, optical and electrochemical properties

The synthesis and characterization of two new anthradithiophene (ADT) derivatives bearing electron donating (triphenylamine) or accepting (5-formylthiophen-2-yl unit) moieties have been performed to assess their potential as materials for organic photovoltaics. Optical spectroscopy was used to evaluate the effect of electron rich/poor substituents on the visible absorption spectrum and on the stability towards photo-oxidation. The results are interpreted with the assistance of quantum-chemical calculations and cyclic voltammetry experiments.     

Hierarchical CdSe-gold hybrid nanocrystals: synthesis and optical properties

The synthesis of hybrid nanostructures with controlled size, shape, composition and morphology has attracted increasing attention due to the fundamental and applicable interest. Here, we demonstrate the synthesis and optical properties of hierarchical CdSe-Au hybrid nanostructures with zinc blende (ZB) CdSe nanocrystals (NCs). For 3.5 nm ZB CdSe NCs, one Au cluster was deposited on each CdSe NC. Nevertheless, several Au clusters were selectively deposited on the apexes of 5 nm and 8 nm ZB CdSe NCs, resulting from the different reactivity of crystal facets. Furthermore, hierarchical CdSe-Au nanostructures with complex morphology were organized with the isolated CdSe-Au hybrid NCs by the coalescence of Au domains on the CdSe-Au hybrid NCs. UV-Vis spectra revealed a red tail upon the deposition of Au clusters. The chemical joint of Au on CdSe NCs was further confirmed by fluorescence quenching. The optical limiting performance of CdSe-Au hybrid NCs dispersed in toluene was investigated at 532 nm using a Nd:YAG laser with the pulse width of 8 ns.     

Organometal halide perovskite quantum dots: synthesis,optical properties,and display applications

In recent two years, organometal halide perovskites quantum dots are emerging as a new member of the nanocrystals family. From the chemical point of view, these perovskites quantum dots can be synthesized either by classical hot-injection technique for inorganic semiconductor quantum dots or the reprecipitation synthesis at room temperature for organic nanocrystals. From a physical point of view, the observed large exciton binding energy, well self-passivated surface, as well as the enhanced nonlinear properties have been of great interest for fundamental study. From the application point of view, these perovskites quantum dots exhibit high photoluminescence quantum yields, wide wavelength tunability and ultra-narrow band emissions, the combination of these superior optical properties and low cost fabrication makes them to be suitable candidates for display technology. In this short review, we introduce the synthesis, optical properties, the prototype light-emitting devices, and the current important research tasks of halide perovsktie quantum dots, with an emphasis on CH₃NH₃PbX₃ (X=Cl, Br, I) quantum dots that developed in our group.     

Highly polarized dithiafulvenes: synthesis and nonlinear optical properties

Push-pull dithiafulvenes with reduced bond length alternation (BLA) and high optical nonlinearities have been prepared. The interplay between the proaromaticity of the donor and the structural and optical properties of these merocyanines is discussed. The donor ability of dithiafulvenes can reach that of ferrocene or dialkylaminophenyl groups.     

Controlled hydrothermal synthesis and optical properties of 3D hierarchical CeO2 microspheres assembled by many loosened nanocubes

Russian Journal of Applied Chemistry - The 3D hierarchical CeO2 microspheres assembled by many loosened nanocubes with a porous structure and an edge length of 300–600 nm have been...     

Silver nanodisks: optical properties study using the discrete dipole approximation method

The simulated optical properties of silver nanodisks are presented. The extinction, absorption, and scattering efficiencies are calculated using the discrete dipole approximation. The influence of the nanodisk size, truncature (snip), aspect ratio, and environment on the plasmon resonance bands is investigated. In particular, the dipolar and multipolar resonance peak positions have been related to the specific features of the nanodisk geometry. An interpretation of the origins of each multipolar mode is proposed for the first time taking into account this geometry.     

Silicon-containing polyimides: synthesis,properties, and application as optical fiber light guide coatings

Russian Chemical Bulletin - Organosoluble polyimides with tetramethyldisiloxane fragments in the main chain were synthesized by one-step high-temperature polycondensation and their properties were...     

ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450–750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.     

Configurationally defined sexi- and octinaphthalene derivatives: synthesis and optical properties

The copper mediated oxidative coupling of optically active quaternaphthalenes having a 2-hydroxynaphthyl moiety gave configurationally defined optically active octinaphthalenes. The absolute configuration was determined by comparison with products of [6+2] coupling. The CD spectra of bi-, ter-, quater-, sexi- and octinaphthalenes suggested that the absolute configuration of the chiral axis could be deduced from the intensity of their Cotton effects.