碳纳米管@SiO_2@Ag纳米复合材料的制备及其表面增强拉曼效应

本文以SiO2为中间层,在多壁碳纳米管(MWCNTs)表面负载Ag纳米粒子,制备出CNTs@SiO2@Ag纳米复合材料,并采用TEM、XRD、UV-Vis、XPS等对纳米复合材料的结构、形貌和成分进行了表征,同时对该纳米复合材料的表面增强拉曼散射(Surface-enhanced Raman scattering,SERS)效应进行了研究。结果显示,Ag纳米颗粒有效提高了CNTs的SERS活性,纳米复合材料的拉曼峰强度是单纯CNTs拉曼峰强的近5倍。进一步研究了吸附罗丹明6G生物染料分子的SERS光谱,结果表明R6G分子的拉曼信号的质量与强度得到显著提高。因此,所制备的CNTs@SiO2@Ag纳米复合材料有望作为SERS的活性基底,应用于生物无损检测领域。     

碳纳米管@SiO2@Ag纳米复合材料的制备及其表面增强拉曼效应

本文以SiO₂为中间层,在多壁碳纳米管(MWCNTs)表面负载Ag纳米粒子,制备出CNTs@SiO₂@Ag纳米复合材料,并采用TEM、XRD、UV-Vis、XPS等对纳米复合材料的结构、形貌和成分进行了表征,同时对该纳米复合材料的表面增强拉曼散射(Surface-enhancedRamanscattering,SERS)效应进行了研究。结果显示,Ag纳米颗粒有效提高了CNTs的SERS活性,纳米复合材料的拉曼峰强度是单纯CNTs拉曼峰强的近5倍。进一步研究了吸附罗丹明6G生物染料分子的SERS光谱,结果表明R6G分子的拉曼信号的质量与强度得到显著提高。因此,所制备的CNTs@SiO₂@Ag纳米复合材料有望作为SERS的活性基底,应用于生物无损检测领域。     

Endohedral complexes of fullerene-like silica molecules with H2O, CH4, and CH3NH2 molecules

The possibility of formation of (SiO₂)₆₀@H₂O, (SiO₂)₆₀@CH₄, and (SiO₂)₆₀@CH₃NH₂ endohedral complexes was studied by the density functional (DFT) method (B3LYP exchange correlation functional, 6-31G** basis). The penetration of these molecules into the cavity of fullerene-like silica molecules is hindered by high activation barriers, which ensures the stability of the complexes formed during the synthesis of these molecules.     

Structure and optical characteristics of the polymer-dye composites prepared via solvent crazing

Optical characteristics of the composites based on an amorphous polymer and a luminescent dye [poly(vinyl chloride)-Rhodamine 6G] prepared via solvent crazing are studied. After annealing at temperatures above glass transition temperature T _g, the samples show a dramatic increase in the intensity of absorption and luminescence bands of Rhodamine Y and a marked decrease in light scattering. The observed changes are due to the diffusion of dye molecules in the polymer matrix and healing of the porous structure of crazes. The above processes are independent and proceed simultaneously. As a result, transparent composites with a low level of light scattering and with a uniform distribution of dye molecules in the polymer matrix are formed. When the PVC-Rhodamine 6G samples are annealed at temperatures above T _g, dramatic changes in their spectral luminescent characteristics and color allow the above composites to be considered specific photochromic materials.     

Study of optical,dimensional, and catalytic properties of nanodispersed CdS–Na<Subscript>2</Subscript>SiO<Subscript>3</Subscript> powders

Composite powders of the CdS–Na₂SiO₃(SiO₂) type were synthesized. It was found that varying the amount of Na₂SiO₃ introduced in the synthesis stage affects both the texture characteristics of the powders obtained and their optical and photocatalytic properties. All the powders absorb electromagnetic radiation in the visible spectral range (~420–620 nm). It was shown for the example of photodestruction of Nile Blue and Rhodamine C dyes that the powders exhibit good photocatalytic properties under exposure to visible light (λ ≥ 410 nm). One of important advantages of the composites used as photocatalysts is that the transfer of cadmium ions under photoirradiation, characteristic of CdS particles, does not occur.     

Impact of PS/SiO2 morphologies on the SERS activity of PS/SiO2/Ag nanocomposite particles

To understand the relationship between the morphology of carboxyl-functionalized polystyrene/silica (PS/SiO₂) nanocomposite microspheres and the surface-enhanced Raman scattering (SERS) performance of PS/SiO₂/Ag nanocomposite particles, core-shell and raspberry-like PS/SiO₂ composite microspheres were used as templates to prepare PS/SiO₂/Ag nanocomposite particles. The core-shell and raspberry-like structured PS/SiO₂ templates were prepared via in situ sol-gel reaction by hydrolysis tetraethyl orthosilicate (TEOS) in alkali solution. Silver nanoparticles (10–50 nm) were loaded on the PS/SiO₂ templates’ surface by chemical reduction. The morphology and structure of the PS/SiO₂/Ag particles were characterized by TEM, SEM, X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. Rhodamine 6G (R6G) was selected as a model chemical to study the enhancement performance of substrate constructed by PS/SiO₂/Ag nanocomposite. Results indicated that the PS/SiO₂/Ag nanocomposite prepared based on the core-shell templates showed higher SERS activity. The beneficial effect was associated with a lower specific area of core-shell structure and the larger average diameter of nanosilvers than that of the raspberry-like templates.     

Characterisation of a new sol-gel precursor for a SiO<Subscript>2</Subscript>-rhodamine 6G hybrid class II material

The entrapment of organic dyes in inorganic solids offers several advantage for solid-state laser applications with respect to the use of liquid or polymer hosts. Among the various inorganic hosts, silica is preferred for its superior mechanical, thermal and optical properties. Organic dyes, such as Rhodamine 6G (Rh6G), can be immobilised in SiO₂ both physically (materials of class I), and by covalent bonds (class II materials). In the past years Rh6G-SiO₂ class I hybrids were prepared. In this work we propose, for the first time, a Rh6G-SiO₂ class II hybrids. We describe the preparation of a suitable sol-gel Rh6G precursor verified by FT-IR analysis and report the characterization of the hybrid materials by means of thermal and porosimetric analysis and optical spectroscopy measurements. The precursor is thermally stable up to ∼250°C, and its optical characteristics (UV-VIS absorbance and photoluminescence, PL) do not change with respect to those of the pristine dye molecule. The PL spectra of the final hybrids show that they are promising candidates for applications in solid state dye lasers.     

Evolution of Laser Plume upon Graphite Ablation in Vacuum and Nitrogen

The propagation of carbon laser plasma during its expansion in vacuum and in a nitrogen atmosphere was studied with the use of an Nd : YAG laser (λ = 532 nm, τ = 15 ns). The presence of C₂, C₃, and CN molecules was detected in emission spectra, and the space and time characteristics of their propagation were determined. The vibrational temperatures of C₂ and CN molecules were calculated.     

Extending Surface-Enhanced Raman Spectroscopy to Liquids Using Shell-Isolated Plasmonic Superstructures

Plasmonic superstructures (PS) based on Au/SiO₂ were prepared for Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) in liquid phase applications. These superstructures are composed of functionalized SiO₂ spheres with plasmonic Au nanoparticles (NPs) on their surface. Functionalization was performed with (3-aminopropyl)trimethoxysilane, (3-mercaptopropyl)trimethoxysilane and poly(ethylene-imine) (PEI). Of these three, PEI-functionalized spheres showed the highest adsorption density of Au NPs in TEM, UV/Vis and dynamic light scattering (DLS) experiments. Upon decreasing the Au NP/SiO₂ sphere size ratio, an increase in adsorption density was also observed. To optimize plasmonic activity, 61 nm Au NPs were adsorbed onto 900 nm SiO₂-PEI spheres and these PS were coated with an ultrathin layer (1–2 nm) of SiO₂ to obtain Shell-Isolated Plasmonic Superstructures (SHIPS), preventing direct contact between Au NPs and the liquid medium. Zeta potential measurements, TEM and SHINERS showed that SiO₂ coating was successful. The detection limit for SHINERS using SHIPS and a 638 nm laser was around 10⁻¹² m of Rhodamine (10⁻¹⁵ m for uncoated PS), all with acquisition settings suitable for catalysis applications.     

A simple strategy for constructing acylhydrazone photochromic system with visible color/emission change and its application in photo-patterning

As a potential photochromic system, acylhydrazones exhibit many outstanding advantages including low cost, simple synthesis and high modifiability compared with some classic photochromic systems. However, the absorption wavelengths of acylhydrazones usually locate in ultraviolet region, which makes the band separation between the absorbance maxima of its irradiated and unirradiated forms cannot be observed by naked eyes and greatly limits their practical applications. In this work, a simple strategy for constructing acylhydrazone photochromic system with visible color/emission change is provided. Rhodamine 6G hydrazine-2-aldehyde-pyridine Schiff base (compound 3) is designed and synthesized by combining acylhydrazone with Rhodamine 6G structure. The introduction of Rhodamine 6G moiety to 3 not only makes it remain all the advantages of acylhydrazone photochromic system but also exhibits visible photo-induced color/emission changes both in solution and in a solid matrix. Moreover, 3 exhibits reversible photochromic property with good fatigue resistance, which makes it an excellent candidate for photo-patterning.     

Formation of nano‐dots of phenylazomethine dendrimers with Rhodamine 6G on mica

The phenylazomethine dendrimer (DPA) is associated with Rhodamine 6G in chloroform, which results in the chemical shift attributed to the aromatic protons of phenylazomethine being moved upfield in the ¹H‐NMR spectrum by increasing the Rhodamine 6G. The shift is saturated at the ratio of 1 : 1. On the basis of the NMR analysis, the association constant K of phenylazomethine with Rhodamine 6G was determined to be 1.4 × 10⁴ (l/mol) in CDCl₃ at 20°C. The association is also confirmed by UV‐vis spectroscopy, in which the absorption around 450 and 527 nm changes during the addition of Rhodamine 6G. The fluorescence intensity of the 1 : 1 complex of Rhodamine 6G and DPA G4 is stronger than that of the solution dissolved only in Rhodamine 6G at greater than 1 mM though it is generally known that the intermolecular interaction quenches the dye fluorescence in a concentrated solution. The association of DPA G4 with Rhodamine 6G suppresses the quenching at higher concentrations. Homogenous nano‐dots were observed on mica by casting the DPA G4 complex with Rhodamine 6G, in which the height and average area were 1.5–3 nm and 1.6 × 10³ nm² (the standard deviation σ = 3.7 nm²), respectively. Copyright © 2004 John Wiley & Sons, Ltd.     

A fragmentation study of the Rhodamine 610 cation using visible‐laser desorption ionization

The fragmentation of a potential visible matrix‐assisted laser desorption ionization: Rhodamine 610 was studied under 532 nm visible irradiation, as a function of anion counter ion. It was found that at a fixed fluence, the chloride salt produced fewer fragments than those formed with ClO₄^? or BF₄^?. Evidence presented suggests that the degree of fragmentation is inversely proportional to the strength of the contact ion pair in the solid state; that is, more energy is deposited into the radical cation which can lead to fragmentation when less energy is required to separate the ion pair. Similar results were found for salts of Rhodamine 6G. Copyright © 2010 John Wiley & Sons, Ltd.     

Study the damage of DNA molecules induced by three kinds of aqueous nanoparticles

In this paper, the interaction of DNA molecules with aqueous CdTe quantum dots (CdTe QDs), CdTe/SiO₂ composite nanoparticles (CdTe/SiO₂ NPs), and Mn-doped ZnSe quantum dots (Mn:ZnSe d-dots) was studied with ethidium bromide as a probe. The purpose of this work was to study the damage of DNA molecules induced by these three kinds of water-soluble nanoparticles. It was found that ionic strength, pH value and UV irradiation influenced the PL emission properties of CdTe QDs, CdTe/SiO₂ NPs and Mn:ZnSe d-dots, and also influenced the interaction of DNA molecules with them. Among the three kinds of nanoparticles, DNA molecules were most easily damaged by CdTe QDs whether in the dark or under UV irradiation. The CdTe/SiO₂ NPs led to much less DNA damage when compared with CdTe QDs, as a silica overcoating layer could isolate the QDs from the external environment. Mn:ZnSe d-dots as a new class of non-cadmium doped QDs demonstrated almost no damage for DNA molecules, which have great potentials as fluorescent labels in the applications of biomedical assays, imaging of cells and tissues, even in vivo investigations.     

Characterization of rhodamine 6G aggregates intercalated in solid thin films of laponite clay. 2 Fluorescence spectroscopy

The photoluminescence response of Rhodamine 6G (R6G) laser dye intercalated into solid thin films of Laponite (Lap) clay is studied as a function of dye loading. Fluorescence spectroscopy (steady-state and time-resolved techniques) was used to characterize the R6G species adsorbed into the solid films. For very diluted R6G loadings (40% CEC), with a reminiscent fluorescence band at around 600 nm.     

Structure of Na2O–MgO–CaO–SiO2 glasses by combined Raman spectroscopy and thermodynamic modeling approach

The present contribution deals with the Raman spectra and structure of Na₂O–MgO–CaO–SiO₂ glasses. Six glasses with the trisilicate overall composition 15Na₂O·xMgO·(10–x)CaO·75SiO₂ (x = 0, 2, 4, 6, 8, 10) were studied. The structure of studied glasses was described by the thermodynamic model of Shakhmatkin and Vedishcheva. From the 27 components with the stoichiometry given by the composition of stable crystalline phases, only eight were found in significant abundance in the studied glasses—namely: SiO₂, 2MgO·SiO₂ (M2S), MgO·SiO₂ (MS), Na₂O·3CaO·6SiO₂ (NC3S6), Na₂O·CaO·5SiO₂ (NCS5), Na₂O·MgO·4SiO₂ (NMS4), Na₂O·SiO₂ (NS), and Na₂O·2SiO₂ (NS2). The correlation analysis points out that the strong positive correlations between the equilibrium molar amounts of: {M2S–MS–SiO₂}, {NC3S6–NCS5}, and {NMS4–NS–NS2}. From the components of significant abundance, only the content of MS and NC3S6 change significantly within the studied compositional series. These two components were identified with the result of the principal component analysis of Raman spectra that indicated the presence of two independent spectral components. Using the method of Malfait the partial Raman spectra of MS and NC3S6 components were found. The obtained results very well reproduce the experimental Raman spectra and confirmed in such way the thermodynamic model.     

Desorption of Physisorbed Molecules from the Sapphire Surface by Yttrium–Aluminum Garnet Laser Second-Harmonic Radiation

Energy fluence dependences for the laser-enhanced desorption of physisorbed NO, SO₂, CO₂, NH₃, and C₆H₆molecules from the sapphire surface by second-harmonic radiation of a pulse neodymium-doped yttrium–aluminum garnet (YAG) laser were experimentally studied. It was shown that the one-photon absorption of radiation at the second-harmonic wavelength ( = 532 nm) by adsorbed NO molecules was so low that their desorption was accomplished via two-photon absorption. Nonlinear energy fluence dependence with a nonlinearity index of greater than 4 was observed for polyatomic molecules. The desorption of these molecules did not occur at the YAG laser emission wavelength ( =1064 nm), thus suggesting that the long-wavelength edge of their one-photon absorption lies within the range 1064–532 nm.     

Preparation and thermal stability of fluoroalkyl end‐capped vinyltrimethoxysilane oligomeric silica/boric acid nanocomposites‐encapsulated a variety of low molecular weight organic compounds

Fluoroalkyl end‐capped vinyltrimethoxysilane oligomer [R_F‐(VM)_n‐R_F] reacted with boric acid to afford the corresponding fluorinated oligomeric silica/boric acid nanocomposite [R_F‐(VM? SiO₂)_n‐R_F/B(OH)₃] fine particles with mean diameter: 36–105 nm. The obtained R_F‐(VM? SiO₂)_n‐R_F/B(OH)₃ nanocomposites were applied to the encapsulation of low molecular weight organic compounds such as diphenylsilanediol, 1,1′‐bi‐2‐naphthol, 4,4′‐biphenol, bisphenol A, bisphenol F, bisphenol AF, biphenyl, dibenzyl, and pentaerythritol into these nanocomposite cores to provide the corresponding fluorinated oligomeric silica/boric acid nanocomposites—encapsulated these organic molecules. Interestingly, the obtained nanocomposites were found to exhibit no weight loss behavior corresponding to the contents of these guest molecules even after calcination at 800 °C, although these nanocomposites were isolated through no purification process. The R_F‐(VM? SiO₂)_n‐R_F nanocomposites—encapsulated these organic guest molecules were prepared under similar conditions. However, it was demonstrated that these nanocomposites can provide the clear weight loss corresponding to the contents of these guest molecules in the nanocomposites after calcination at 800 °C. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3835–3845     

Hybrid Gels as Host Matrices of Perfumed Essences

The variety of SiO₂-gel structures allows the use of sol-gel derived materials as host matrices for prolonged release of chemicals. In this work, the release of perfumed essences is studied in the case of hybrid SiO₂ materials obtained from alkyl-modified silicon alkoxides. Thermogravimetric analysis in isothermal conditions at various temperatures provide data on the kinetic release process. The effects of physical parameters (porosity reduction, vapour pressure) and chemical interactions (organic molecules with matrix) are discussed for the interpretation of the results.     

Effects of the Sol-Gel Processing on the Fluorescence Properties of Laser Dyes in Tetraethoxysilane Derived Matrices

Two fluorescent dyes were incorporated into sol-gel derived SiO₂ matrices. The dye was added to SiO₂ precursors of different degrees of pre-condensation and the spectroscopic properties of the immobilized dye were measured at various aging and drying stages of the resulting gels. The significant influence of the processing parameters on the spectroscopic properties is manifested in the relative intensity of a second red shifted emission band (550–560 nm), which was observed besides the typical coumarin emission band (495 nm). The appearance of this long wavelength emission might be attributed to dye aggregation or to other reactions with the ambient matrix forced by micro porosity phenomena.     

Photoluminescent and oxygen sensing properties of core–shell nanospheres based on a covalently grafted ruthenium(II) complex

SiO₂ nanospheres coated with silica chemically doped with a ruthenium complex [Ru(Bphen)₂Phen? Si]Cl₂ (denoted as Ru, there Bphen = 4,7‐diphenyl‐1,10‐phenanthrolin, Phen? Si = modified 1,10‐phenathroline) were prepared using a simple solution‐based method. Field‐emission scanning electron microscopy (FE‐SEM) showed that the pure SiO₂ nanospheres with a mean diameter of ～185 nm were successfully coated with Ru complex–chemically doped SiO₂ shell with a thickness of ～45 nm. The obtained core‐shell nanosphere materials exhibited bright red triplet metal‐to‐ligand charge transfer (³MLCT) emission, and their photoluminescent intensity was sensitive to oxygen concentration. These properties make them promising candidates for biomarkers and optical oxygen sensors, which can measure the O₂ concentration in biological fluids. Copyright © 2010 John Wiley & Sons, Ltd.