An ensemble and single-molecule fluorescence microscopy investigation of phase-separated monolayer films stained with Nile Red

Phase-separated Langmuir-Blodgett monolayer films prepared from mixtures of arachidic acid (C19H39COOH) and perfluorotetradecanoic acid (C13F27COOH) were stained via spin-casting with the polarity sensitive phenoxazine dye Nile Red, and characterized using a combination of ensemble and single-molecule fluorescence microscopy measurements. Ensemble fluorescence microscopy and spectromicroscopy showed that Nile Red preferentially associated with the hydrogenated domains of the phase-separated films, and was strongly fluorescent in these areas of the film. These measurements, in conjunction with single-molecule fluorescence imaging experiments, also indicated that a small sub-population of dye molecules localizes on the perfluorinated regions of the sample, but that this sub-population is spectroscopically indistinguishable from that associated with the hydrogenated domains. The relative importance of selective dye adsorption and local polarity sensitivity of Nile Red for staining applications in phase-separated LB films as well as in cellular environments is discussed in context of the experimental results.     

Preparation of thin silica films with controlled thickness and tunable refractive index

Silica films with controlled thickness and refractive index have been formed by the sequential adsorption of a cationic polyelectrolyte and silica sols. The conditions used to prepare the sol were varied, and allowed films with refractive indices as low as 1.16 to be obtained. The sequential adsorption technique allows the thickness of these films to be controlled in increments of 5-10 nm, depending on the desired refractive index. Scanning electron microscopy revealed that a low packing density of constituent silica particles was responsible for the low indices of these films. The as-adsorbed films are thermally robust; calcination at 500 degrees C resulted in only very small decreases in film thickness (by < or =1.8%) and refractive index (to as low as 1.14). After calcination, the silica films remained hydrophilic and sorbed water vapor from the atmosphere. As a result, the refractive indices of these films increased with increasing relative humidity (RH). The dependence of the refractive index on RH was eliminated by treating the calcined films with trimethylchlorosilane.     

The synthesis of mesoporous aluminosilicate using microcline for adsorption of mercury(II)

An economical mesoporous aluminosilicate was synthesized with microcline as starting material and the precursor 13X zeolite as seed for crystal structure on mesoporous walls. In this method, a mixture of microcline and Na2CO3 with a molar ratio of 1:1.05 was first calcined at 1093 K for 2.5 h. The calcined materials were mixed with 35 ml C16TMABr aqueous solution (containing 8.2 g C16TMABr) and the precursors of 13X zeolite, resulting in mesoporous aluminosilicate after crystallization of the solution at 378 K for 48 h and calcination of the powder at 823 K for 5 h. The as-synthesized sample has a uniform pore diameter distribution centered at 3.7 nm. The as-synthesized sample had BET surface area of 725 m2/g and BJH mean pore diameter of 3.7 nm. The FT-IR results revealed that the building units of 13X zeolite were inserted into the pore walls of the as-synthesized sample. The adsorption ratio of mercury(II) onto the as-synthesized adsorbent was about 95%. The adsorption process was found to be spontaneous and can be explained by particle diffusion and chemical ion-exchange mechanisms. The equilibrium concentration of mercury(II) using the as-synthesized sample as the adsorbent was under 1 microg/L, making the concentration of mercury meet the limit for drinking water in China as recommended by the World Health Organization.     

Synthesis and spectroscopic properties of silica-dye-semiconductor nanocrystal hybrid particles

We prepared silica-dye-nanocrystal hybrid particles and studied the energy transfer from semiconductor nanocrystals (= donor) to organic dye molecules (= acceptor). Multishell CdSe/CdS/ZnS semiconductor nanocrystals were adsorbed onto monodisperse Sto?ber silica particles with an outer silica shell of thickness 2-23 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the energy transfer efficiency, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of nanocrystals with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with numerically calculated FRET efficiencies and by control experiments confirming attractive interaction between the nanocrystals and Texas Red freely dissolved in solution.     

Kinetic modeling of adsorption of di-2-pyridylketone salicyloylhydrazone on silica gel

The kinetics of DPKSH (di-2-pyridylketone salicyloylhydrazone) adsorption onto silica gel has been investigated at (25+/-1) degrees C and pH 1 and 4.7. The kinetics of adsorption of DPKSH is discussed using three kinetic models, the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. The adsorption of DPKSH, at pH 1 and 4.7, onto silica gel proceeds according to the pseudo-second-order model and the correlation coefficients were very close to 1. The intraparticle diffusion of DPKSH molecules within the silica gel particles was identified as the rate-limiting step. The parameters of the pseudo-second-order model are q(max,calc)=1.02 x 10(-4) and 1.5 x 10(-4) g DPKSH/g silica; k(2)=3.01 x 10(4) and 9.67 x 10(4) h(-1)g silica/g DPKSH, respectively, for pH 1 and 4.7.     

Coulombic interactions on the deposition and rotational mobility distributions of dyes in polyelectrolyte multilayer thin films

We employed negatively charged fluorescein (FL), positively charged rhodamine 6G (R6G), and neutral Nile Red (NR) as molecular probes to investigate the influence of Coulombic interaction on their deposition into and rotational mobility inside polyelectrolyte multilayer (PEM) films. The entrapment efficiency of the dyes reveals that while Coulombic repulsion has little effect on dye deposition, Coulombic attraction can dramatically enhance the loading efficiency of dyes into a PEM film. By monitoring the emission polarization of single dye molecules in polyethylenimine (PEI) films, the percentages of mobile R6G, NR, and FL were determined to be 87 +/- 4%, 76 +/- 5%, and 68 +/- 3%, respectively. These mobility distributions suggest that cationic R6G enjoys the highest degree of rotational freedom, whereas anionic FL shows the least mobility because of Coulombic attraction toward cationic PEI. Regardless of charges, this high percentage of mobile molecules is in stark contrast to the 5-40% probe mobility reported from spun-cast polymer films, indicating that our PEI films contain more free volume and display richer polymer dynamics. These observations demonstrate the potential of using isolated fluorescent probes to interrogate the internal structure of a PEM film at a microscopic level.     

Functionalisation of the template-free and template-structured silica films synthesised on glass substrates by sol–gel technique

Possibility of the post-synthesis functionalisation of the template-free and template-structured silica films of ca. 200 nm thickness on glass slides was evaluated. The films were prepared by dip-coating from TEOS sol–gel precursor in the absence or presence of CTAB template. It has been found out that the template-structured silica films can be functionalised with Ag nanoparticles via [Ag(NH₃)₂]NO₃ ion-exchange or with adsorbed Methylene Blue (MB) cationic dye due to the presence of the well-organised mesopores after template removal. In contrast, only the external geometric surface of the template-free silica films appeared to be accessible for modifier molecules. Possibility of functionalisation of the multi-layered template-structured silica film depends on the sequence of dip-coating and calcination steps upon their preparation. When preparation includes reiteration of dip-coating and calcination steps, only the latest top silica film appears to be accessible to modifier molecules. When preparation includes successive dip-coating cycles accomplished by calcination of the final multi-layered film, all pores appear to be accessible since their formation occurs via simultaneous removal of the template molecules over the whole thickness of the multi-layered template-structured silica film.     

Comparative study of guest charge-charge interactions within silica sol-gel

We investigated the effect of charge-charge interactions on the mobilities of rhodamine 6G (R6G), Nile Red, sulforhodamine B, and Oregon Green 514 (ORG) guest molecules within a silica sol-gel host as the guest charge progressed from positive to neutral to negative. Through classification of the mobility as fixed, tumbling, or intermediate behavior, we were able to distinguish differences in surface attraction as the guest charge was varied. On the basis of our results, an attractive charge (as tested by cationic R6G) does not contribute significantly to mobility within dry films. However, an increase in the cationic influence is observed in water-equilibrated environments. A comparison of ORG in dry and water- and phosphate-buffer-equilibrated films indicates that charge repulsion does significantly increase dye rotational mobility (to a maximum of 24 +/- 3% tumbling molecules). However, in view of the percentage of tumbling molecules found, charge-charge interactions do not appear to be the dominant force controlling guest mobility.     

不同pH值下合成的双中孔和六方中孔SiO_2的表征(英文)

在相同的反应体系中当ｐｈ值从约９．５调变至１１时分别合成出双中孔ＳｉＯ２和六方中孔ＳｉＯ２材料,并用ＸＲＤ、Ｎ２吸附、ＴＥＭ、ＴＧ／ＤＴＡ和ＦＴＩＲ等测试手段对合成产物进行了表征。实验结果表明,双中孔ＳｉＯ和六 方中孔ＳｉＯ２是合成中必然出现的两种不同的中孔物相。与六方中孔ＳｉＯ２相比,双中孔ＳｉＯ２也具有典型中孔 材料的特征ＸＲＤ谱图,虽然仅呈现一个易让人产生不完全晶化误解的相对较宽的单ＸＲＤ衍射峰（ｄ＝５．２ｎｍ）,但它却给出一种独特的Ｎ２吸附等温线和窄的双峰中孔孔径分布曲线。由于孔壁的无定形及表面活性剂分子与ＳｉＯ２骨架间相似的相互作用,两类材料给出类似的ＦＴＩＲ谱图和ＴＧ／ＤＴＡ曲线。然而,在双中孔ＳｉＯ２的ＦＴＩＲ谱图中９６０ｃｍ处峰强度的微小变化可能意味着在锻烧脱除模板剂后双中孔ＳｉＯ２较六方中孔ＳｉＯ２具有更高的骨架聚合度。     

Removal of Reactive Red 141 Dye from Aqueous Solution by Titanium Hydroxyapatite Pellets

The adsorption of Reactive Red 141 over the pressed and calcined pellets of TiHAp and HAp was investigated by using continuous reflux system. Langmuir isotherm model was found to be the best model to describe the equilibrium data, with maximum adsorption capacity of 20.62 and 28.41 (mg g^?1) for HAp and TiHAp, respectively. Kinetics data was best described by the pseudo-second-order model and intraparticle diffusion determined as sole controlling step of adsorption process. Possible mechanisms of the adsorption dye on the HAp and TiHAp were discussed.     

Enhancement of electron transport in nano-porous TiO2 electrodes by dye adsorption

Influence of dye adsorption on electron transport in nano-porous TiO₂ electrodes filled with electrolytes is studied with various TiO₂ films and electrolytes. Electron diffusion coefficient in the electrodes is derived from pulsed laser induced current transients. It is found that dye adsorption increases the diffusion coefficients in the electrodes regardless of the difference of electrolytes and TiO₂ electrodes. The degree of the increases scales with the surface area of the nano-porous electrodes. Based on trapping model, these observations can be interpreted with that the charge traps located on the electrode surface are removed by the dye adsorption. However, dependency of electron diffusion coefficients on light intensity is not affected by dye adsorption, implying that the traps are located not only on the surface but also inside the electrodes.     

Adsorption of Acid Dyes from Aqueous Solutions by Calcined Alunite and Granular Activated Carbon

Dyestuff production units and dyeing units have always had a pressing need for techniques that allow economical pretreatment for color in the effluent. The effectiveness of adsorption for dye removal from wastewaters had made it an ideal alternative to other expensive treatment options. This paper deals with an investigation on alunite, existing wide reserves in Türkiye and in the world, for dye removal. Calcined alunite was utilized for this study and its performance evaluated against that of granular activated carbon (GAC). The use of calcined alunite for the removal of Acid Blue 40 and Acid Yellow 17 (AB 40 and AY 17) from aqueous solution at different calcination temperature and time, particle size, pH, agitation time and dye concentration has been investigated. The adsorption followed by Langmuir and Freundlich isotherms. The process follows first order adsorption rate expression and the rate constant was found to be 7.65 × 10^–2 and 5.74 × 10^–2 min^–1 for adsorption of AB 40 and AY 17 on calcined alunite, and 8.41 × 10^–2 and 10.04 × 10^–2 min^–1 for adsorption of AB 40 and AY 17 on GAC, respectively. The equilibrium saturation adsorption capacities were 212.8 mg dye/g calcined alunite and 151.5 mg dye/g calcined alunite for AB 40 and AY 17, respectively. The adsorption capacities were found to be 57.47 mg and 133.3 mg dye per g of GAC for AB 40 and AY 17, respectively. The results indicate that, for the removal of acid dye, calcined alunite was most effective adsorbent, although comparable dye removals were exhibited by GAC.     

Silver containing sol–gel derived silica thin films: effect of aluminum incorporation on optical,microstructural and bactericidal properties

Silver containing silica (Ag–SiO₂) thin films with and without aluminum (Al) were prepared on soda-lime-silica glass by spin coating of aqueous sols. The coating sol was formed through mixing tetraethyl orthosilicate [Si(OC₂H₅)₄]/ethanol solution with aqueous silver nitrate (AgNO₃) and aluminum nitrate nonahydrate [(AlNO₃)₃·9H₂O] solutions. The deposited films were calcined in air at 100, 300 and 500 °C for 2 h and characterized using x-ray diffraction, UV-visible and x-ray photoelectron spectroscopy. The effect of Al incorporation and calcination treatment on microstructure and durability of the films, and chemical/physical state of silver in the silica thin film have been reported. The bactericidal activity of the films was also determined against Staphylococcus aureus via disk diffusion assay studies before and after chemical durability tests. The investigations revealed that the optical, bactericidal properties and chemical durability of Ag–SiO₂ films can be improved by Al addition. The Al-modified Ag–SiO₂ thin films do not exhibit any coloring after calcination in the range of 100–500 °C, illustrating that silver is incorporated within the silica gel network in ionic form (Ag⁺). Al incorporation also improved the overall durability and antibacterial endurance of Ag–SiO₂ thin films.     

Study of the spectrophotometric analysis of protein solution with p-iodochlorophosphonazo as adsorbate by the microphase adsorption-spectral correction technique

A microphase adsorption-spectral correction (MPASC) technique was established, which consists of Langmuir adsorption and the spectral correction technique. The hypothesis of a microelectric field formed in macromolecules is proposed, the existence of which results in the adsorption and aggregation of dye molecules in macromolecules. This paper describes the spectrophotometric analysis of protein solution with p-iodochlorophosphonazo (p-ICPA) dye. The results showed that the adsorption ratios of p-ICPA to proteins (bovine serum albumin, ovalbumin, myoglobin and gamma-globulin) at pH 2.56 were 54, 25, 14 and 90, respectively, their adsorption constants 2.86 x 10(5), 1.42 x 10(6), 2.38 x 10(5) and 1.09 x 10(5) and their absorptivities 8.00 x 10(5), 4.02 x 10(5), 1.77 x 10(5) and 1.15 x 10(6) l mol-1 cm-1 at 620 nm. The analysis of practical samples showed that the recovery of protein was between 92.3 and 108% and the relative standard deviation was 4.7%.     

Direct formation of thermally stabilized amorphous mesoporous Fe2O3/SiO2 nanocomposites by hydrolysis of aqueous iron III nitrate in sols of spherical silica particles

Nanocomposite materials containing 10% and 20% iron oxide/silica, Fe2O3/SiO2 (w/w), were prepared by direct hydrolysis of aqueous iron III nitrate solution in sols of freshly prepared spherical silica particles (St?ber particles) present in their mother liquors. This was followed by aging, drying, calcination up to 600 degrees C through two different ramp rates, and then isothermal calcinations at 600 degrees C for 3 h. The calcined and the uncalcined (dried at 120 degrees C) composites were characterized by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption techniques, and scanning electron microscopy as required. XRD patterns of the calcined composites showed no line broadening at any d-spacing positions of iron oxide phases, thereby reflecting the amorphous nature of Fe2O3 in the composite. The calcined composites showed nitrogen adsorption isotherms characterizing type IV isotherms with high surface area. Moreover, surface area increased with the increasing of the iron oxide ratio and lowering of the calcination ramp rate. Results indicated that iron oxide particles were dispersed on the exterior of silica particles as isolated and/or aggregated nanoparticles. The formation of the title composite was discussed in terms of the hydrolysis and condensation mechanisms of the inorganic FeIII precursor in the silica sols. Thereby, fast nucleation and limited growth of hydrous iron oxide led to the formation of nanoparticles that spread interactively on the hydroxylated surface of spherical silica particles. Therefore, a nanostructured composite of amorphous nanoparticles of iron oxide (as a shell) spreading on the surface of silica particles (as a core) was formed. This morphology limited the aggregation of Fe2O3 nanoparticles, prevented silica particle coalescence at high temperatures, and enhanced thermal stability.     

Diffusion of oriented single molecules with switchable mobility in networks of long unidimensional nanochannels

Single dye molecules incorporated into a mesoporous matrix can act as highly sensitive reporters of their environment. Here, we use single TDI molecules incorporated as guests into hexagonal mesoporous films containing highly structured domains. The dye molecules allow us to map the size of these domains which can extend to over 100 microm. Investigation of the translational and orientational dynamics via single molecule fluorescence techniques gives structural as well as dynamical information about the host material. In an air atmosphere, the guest molecules show no movement but perfect orientation along the pore direction. The diffusion of the TDI molecules can be induced by placing the mesoporous film in a saturated atmosphere of chloroform. In single molecule measurements with very high positioning accuracy (down to 2-3 nm) the movement of molecules could be observed even between neighboring channels. This reveals the presence of defects like dead ends closing the pores or small openings in the silica walls between neighboring channels, where molecules can change from one channel to the next. A statistical analysis demonstrates that the diffusion of TDI in the mesoporous film cannot be described with a 1D-random diffusion but is more complicated due to the presence of adsorption sites in which the TDI molecules can be occasionally trapped.     

Dynamics of molecular diffusion of rhodamine 6G in silica nanochannels

We describe a method to study diffusion of rhodamine 6G dye in single silica nanochannels using arrays of silica nanochannels. Dynamics of the molecules inside single nanochannel is found from the change of the dye concentration in solution with time. A 10(8) decrease in the dye diffusion coefficient relative to water was observed. In comparison to single fluorescent molecule studies, the presented method does not require fluorescence of the diffusing molecules.     

Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.     

Surfactant Templated Silica Xerogels as Adsorbents for Rhodamine 6G

A series of silica xerogels was synthesized by using TEOS as the silica precursor and a non ionic surfactant Triton X100 (TX100) and a cationic surfactant Hexadecyltrimethylammonium Bromide (CTAB) as templates. The xerogels were synthesized through 2‐way catalysis using ultrasonic radiations for homogeneous mixing of the precursors and template. The surfactant template was later removed through calcination at 550 °C. It was found out that gels having CTAB as the template had higher surface area (612.08 m²/g) than the gels templated by TX100 (539.6 m²/g). High surface area xerogels were used in adsorption experiments for aqueous solutions of Rhodamine 6G (R6G). UV visible spectroscopy was used to find out the concentrations of dye solutions. The adsorption data of both the types of xerogels was found to follow Freundlich's adsorption model pointing towards the possibility of adsorption of the dye molecules on the heterogeneous surface of the adsorbent.     

pH响应的介孔二氧化硅纳米颗粒的制备及可控释放

选择带负电荷且溶解度和分子结构对pH值非常敏感的聚丙烯酸作为封堵分子, 采用静电吸附的修饰方法, 制备了pH响应的MCM-41型介孔二氧化硅纳米颗粒. 利用高倍透射电子显微镜(TEM)、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)及比表面积分析等手段表征了介孔二氧化硅纳米颗粒的物理化学性质. 以联钌吡啶染料分子作为模式客体分子, 研究了pH调控下的模式客体分子在介孔二氧化硅纳米颗粒中的包裹及释放行为. 结果表明, 该介孔二氧化硅纳米颗粒对pH具有很好的响应性; 在近中性条件下, 带正电的二氧化硅纳米颗粒通过静电吸附作用吸附带负电的聚丙烯酸, 导致介孔封堵, 使包载的染料分子几乎无释放; 客体分子的释放率随着pH值的降低而升高, 当pH≤5时, 染料分子显著释放, pH=1时客体分子的释放率高达98％, 可以实现对包载客体分子的控制释放. 该pH响应的介孔二氧化硅纳米颗粒载体具有制备简便、 价格低廉和包载量大等优点, 有望应用于药物的控制释放.