Self-assembly of tin oxide nanoparticles: localized percolating network formation in polymer matrix

A novel method to prepare transparent antistatic films by trapping nanoparticles in thin surface layers is proposed, and high performance of the product is demonstrated. Coating solutions consisting of surface-active antimony-doped tin oxide (ATO) nanoparticles, an organic solvent mixture of high affinity with poly(methyl methacrylate) substrate, and an ultraviolet curable resin are used for the film formation. Antistatic property of the layer is obtained at ATO concentrations above the critical concentration for percolation. A scaling analysis of the data shows that the critical concentration (0.004 volume fraction) is extremely low as compared to the value predicted by the percolation theory for randomly packed systems as well as the values in ever developed composite films filled with ATO particles. Microscopic observation of the deposited layers indicates that percolating clusters of ATO particles are localized on the layer surfaces. The excellent electrical and optical properties of the layer are attributed to the characteristic microstructure.     

Optical,electrical, and thermal insulation properties of antimony-doped tin oxide nanoparticles prepared by frozen gel method

Antimony doped tin dioxide (ATO) nanoparticles with different Sb doping contents were prepared by freeze-drying the precursor gel and then calcined procedure. The obtained ATO nanoparticles were characterized by X-ray diffraction, scanning electron microscope, optical and electrical techniques. Results indicated that ATO with 10 mol% Sb doping is optimal, with which had the lowest resistivity and highest transmittance in visible region as well as narrow particle size distribution. Thermal insulation properties of ATO/waterborne polyurethane (WPU) films coating on the glass substrates with different thickness were studied on a DIY heat insulating measurement box and showed that the glass coated with ATO/WPU films possessed better heat-insulating effect than empty glass .     

Revisiting Surface Modification of Graphite: Dual‐Layer Coating for High‐Performance Lithium Battery Anode Materials

Surface modification of electrode active materials has garnered considerable attention as a facile way to meet stringent requirements of advanced lithium‐ion batteries. Here, we demonstrated a new coating strategy based on dual layers comprising antimony‐doped tin oxide (ATO) nanoparticles and carbon. The ATO nanoparticles are synthesized via a hydrothermal method and act as electronically conductive/electrochemically active materials. The as‐synthesized ATO nanoparticles are introduced on natural graphite along with citric acid used as a carbon precursor. After carbonization, the carbon/ATO‐decorated natural graphite (c/ATO‐NG) is produced. In the (carbon/ATO) dual‐layer coating, the ATO nanoparticles coupled with the carbon layer exhibit unprecedented synergistic effects. The resultant c/ATO‐NG anode materials display significant improvements in capacity (530 mA h g^?1), cycling retention (capacity retention of 98.1 % after 50 cycles at a rate of C/5), and low electrode swelling (volume expansion of 38 % after 100 cycles) which outperform that of typical graphite materials. Furthermore, a full‐cell consisting of a c/ATO‐NG anode and an LiNi_0.5Mn_1.5O₄ cathode presents excellent cycle retention (capacity retention of >80 % after 100 cycles). We envision that the dual‐layer coating concept proposed herein opens a new route toward high‐performance anode materials for lithium‐ion batteries.     

Cryo-SEM studies of latex/ceramic nanoparticle coating microstructure development

Cryogenic scanning electron microscopy (cryo-SEM) was used to investigate microstructure development of composite coatings prepared from dispersions of antimony-doped tin oxide (ATO) nanoparticles (approximately 30 nm) or indium tin oxide (ITO) nanoparticles (approximately 40 nm) and latex particles (polydisperse, D(v): approximately 300 nm). Cryo-SEM images of ATO/latex dispersions as-frozen show small clusters of ATO and individual latex particles homogeneously distribute in a frozen water matrix. In contrast, cryo-SEM images of ITO/latex dispersions as-frozen show ITO particles adsorb onto latex particle surfaces. Electrostatic repulsion between negatively charged ATO and negatively charged latex particles stabilizes the ATO/latex dispersion, whereas in ITO/latex dispersion, positively charged ITO particles are attracted onto surfaces of negatively charged latex particles. These results are consistent with calculations of interaction potentials from past research. Cryo-SEM images of frozen and fractured coatings reveal that both ceramic nanoparticles and latex become more concentrated as drying proceeds; larger latex particles consolidate with ceramic nanoparticles in the interstitial spaces. With more drying, compaction flattens the latex-latex particle contacts and shrinks the voids between them. Thus, ceramic nanoparticles are forced to pack closely in the interstitial spaces, forming an interconnected network. Finally, latex particles partially coalesce at their flattened contacts, thereby yielding a coherent coating. The research reveals how nanoparticles segregate and interconnect among latex particles during drying.     

Synthesis of a novel polyester-ether copolymer and its derivatives as antistatic additives for thermoplastic films

Development of antistatic thermoplastic elastomer composites is gaining much interest in scientific and industrial aspects. In this contribution, a novel type of polyester-block-ether copolymer (PEBE), PEBE with ionic liquid (PEBE-IL) and quaternized PEBE (PEBE-Q) were synthesized, characterized and compounded with a commercial bottle grade polyester (PET) resin. It was found that the surface resistivity of the PET composite films was around 10⁹–10¹⁰ Ω/sq. The addition of the PEBE copolymers as an antistatic agent into PET matrix resulted in almost 10⁶ times enhancement in surface resistivity compared to neat PET film. Among the PET films with an antistatic agent, it was emphasized that PEBE-IL and ionic liquid doping to PET matrix led to a relatively lower crystallization degree, surface resistivity, contact angle and breaking force with a translucent appearance compared to neat PET film. Furthermore, it was illustrated that antistatic PET films with fine-tune physical, mechanical and morphological properties can be achieved by choosing appropriate antistatic agent type and amount.     

柔性透明自支撑氧化锡锑电纺纳米纤维膜的制备与表征

以四氯化锡和三氯化锑为前驱体,通过静电纺丝技术制备了柔性透明的自支撑氧化锡锑(ATO)纳米纤维膜.研究结果表明,该柔性ATO纤维膜具有四方相金红石晶体结构,且呈无规的纤维网状分布.当前驱体煅烧温度分别为520℃和700℃时,纤维的平均直径为200和150 nm;组成纤维的颗粒的平均粒径为10和19 nm;可见光透过率为72%和80%;电阻率为5.23和2.20Ω·cm.该自支撑ATO纳米纤维膜还显示出优异的柔韧性,在弯曲500次后其电阻率基本不变.     

基于氧荧光猝灭速率法的生化需氧量检测

利用氧荧光猝灭速率的方法,结合自行构建的BOD光纤传感装置进行海水中生化需氧量(BOD)含量检测。考察了四种筛选的海洋耗氧菌种在四甲基硅氧烷(TMOS)、二甲基二甲氧基硅烷(Di Me-DMOS)和聚乙烯醇(PVA)包埋固定情况下,对不同浓度的葡萄糖-谷氨酸(GGA)标准溶液的荧光响应情况。BOD敏感膜的荧光响应在0·2~30mg/L浓度范围内呈良好的线性关系,对2mg/L标准溶液测定的相对标准偏差为2·5%(n=6),响应时间(t95%)为4·0min,BOD敏感膜使用寿命大于12个月。实际海水样品检测表明,利用BOD敏感膜检测得到的结果与国标BOD5方法之间存在较好的一致性。     

Thermo-responsive Hercosett/Poly(N-isopropylacrylamide) films: a new, fast, optically responsive coating

Poly(N-isopropylacrylamide) (PNIPAM) is a common thermo-responsive, water-soluble polymer, while Hercosett is a cationic resin commonly employed in the paper industry. In this paper, Hercosett? and poly(N-isopropylacrylamide) (PNIPAM) nanoparticles were used to prepare composite films that show thermo-responsive behavior and swelling–shrinking properties in water. First, size-controlled PNIPAM hydrogel nanoparticles were synthesized. These were then embedded within a matrix of the cationic resin Kymene 577H by film casting. The distribution of nanoparticles in the resin film was investigated. The thermo-responsive properties of the as-synthesized PNIPAM hydrogel nanoparticles and of the composite films were characterized together with the repeatability of the swelling–shrinking cycles. The presence of nanoparticles endowed the film with highly enhanced water retention (in comparison with resin-only films) and, most importantly, thermo-responsiveness. A very fast optical and morphological response was in fact observed. Due to the dual (optical and morphological) response, this new system is suitable for applications in optical or morphological actuation and gating.     

Synthesis and thermal properties of antimony doped tin oxide/waterborne polyurethane nanocomposite films as heat insulating materials

The waterborne polyurethane (WPU) was synthesized from the polycondensation between isophorone diisocyanate (IPDI) and polyoxypropylene glycol (N‐210) and then dispersed into water. Subsequently, the WPU emulsion was modified with antimony doped tin oxide (ATO) nanoparticle by ultrasonic dispersion. The ATO/WPU emulsion was cast onto Teflon molds. After being dried, ATO/WPU films were prepared. TEM indicated that the ATO nanoparticles were homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the ATO/WPU nanocomposites displayed increased glass transition temperatures compared to the control WPU. The mechanical properties of the films were characterized by dynamic‐mechanical analysis (DMA). The higher glass transition temperature and storage modulus indicates the superior mechanical properties of WPU modified by ATO nanoparticles over the conventional unmodified WPU. The thermal behaviors of the films were evaluated by thermogravimetric analysis (TGA). It could be found that the incorporation of ATO into WPU can improve the thermal stability dramatically. The results from UV–visible–near infrared spectra indicated that the ATO/WPU films could decrease the infrared transmission effectively. The heat‐insulation measurements showed that glass coated with ATO/WPU films possessed better heat‐insulating effect than empty glass. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation of ZnO nanoparticles and characteristics of dye-sensitized solar cells based on nanoparticles film

ZnO nanoparticles were synthesized by hydrolization method and the effects of zinc nitrate concentration and reaction temperature on the resulted particle properties were studied. The transmission of the as-prepared and calcined films and their optical band gaps are measured and calculated respectively. Furthermore, as an application of the ZnO nanoparticles film, dye-sensitized solar cells based on it were successfully fabricated and the cell performances were characterized. The short circuit current for ZnO nanoparticles film DSSCs is 1.35 mA cm^?2, which indicates good value of the prepared film using this technique.     

Foam films in the presence of functionalized gold nanoparticles

Dry aqueous foams made of anionic surfactant (SDS) and spherical gold nanoparticles are studied by small angle X-ray scattering and by optical techniques. To obtain stable foams, the surfactant concentration is well above the critical micelle concentration. The specular reflectivity signal obtained on a very thin film (thickness 20 nm) shows that functionalized nanoparticles (17 nm typical size) are trapped within the film in the form of a single monolayer. In order to isolate the film behavior, investigations are made on a single film confined in a tube. The film thinning according to the ratio of functionalized nanoparticle and SDS micelles (1:1, 1:10, 1:100) is mainly governed by the structural arrangement of SDS micelles. In thick films, nanoparticles tend to form aggregates that disappear during drainage. In particular self-organization of nanoparticles (with different surface charge) inside the film is not detected.     

Wet Chemical Deposition of Crystalline,Redispersable ATO and ITO Nanoparticles

A new wet chemical concept to produce coatings by dip, spin or spray processes is presented. It is based on the preparation of solutions made of crystalline nanoparticles fully redispersable in a solvent. It is exemplified for the preparation of SnO₂ : Sb (ATO) and In₂O₃ : Sn (ITO) transparent conducting coatings. The process combines the advantages of using particles having already a low resistivity and the possibility to sinter the coatings at low temperature. The particles are prepared using an in-situ monitoring of the surface energy to control the growth of the particles and to avoid their agglomeration. The dried powders can be fully redispersed in alcohol (ITO) or water (ATO). Single layers with thickness up to 200 nm (ATO) and 400 nm (ITO) have been fabricated. The sheet resistance of the coatings decreases with the sintering temperature. Typical values are 430 for ATO (550°C) and 380 for ITO (550°C). Sols made by redispersing the powders in organosilanes allow to produce coatings at low temperature with antistatic (R > 100 k) and anti-glare properties (R > 100 k, 60 to 80 gloss units).     

Highly transparent and conductive thin films fabricated with nano-silver/double-walled carbon nanotube composites

This study develops a technique for enhancing the electrical conductivity and optical transmittance of transparent double-walled carbon nanotube (DWNT) film. Silver nanoparticles were modified with a NH(2)(CH(2))(2)SH self-assembled monolayer terminated by amino groups and subsequent surface condensation that reacted with functionalized DWNTs. Ag nanoparticles were grafted on the surface of the DWNTs. The low sheet resistance of the resulting thin conductive film on a polyethylene terephthalate (PET) substrate was due to the increased contact areas between DWNTs and work function by grafting Ag nanoparticles on the DWNT surfaces. Increasing the contact area between DWNTs and work function improved the conductivity of the DWNT-Ag thin films. The prepared DWNT-Ag thin films had a sheet resistance of 53.4 Ω/sq with 90.5% optical transmittance at a 550 nm wavelength. After treatment with HNO(3) and annealing at 150 °C for 30 min, a lower sheet resistance of 45.8 Ω/sq and a higher transmittance of 90.4% could be attained. The value of the DC conductivity to optical conductivity (σ(DC)/σ(OP)) ratio is 121.3.     

Aqueous latex/ceramic nanoparticle dispersions: colloidal stability and coating properties

The effect of pH on the colloidal stability of aqueous dispersions containing antimony-doped tin oxide (ATO) or indium tin oxide (ITO) nanoparticles and poly(vinyl acetate-acrylic) copolymer (PVAc-co-acrylic) latex particles was investigated using experimental observations and Derjiaguin, Landau, Verwey and Overbeek (DLVO) theory. The microstructure, electrical properties and optical properties of composite coatings prepared from various dispersions were also studied. Zeta potential measurements revealed that the isoelectric point (IEP) of ATO nanoparticles was below pH 2.0, that of ITO nanoparticles was at pH approximately 6.0 and that of PVAc-co-acrylic latex was at pH approximately 2.0. ATO/PVAc-co-acrylic dispersions prepared at pH 3 were stable, but those prepared at pH 1.5 formed aggregates, which settled quickly with time. DLVO theory predictions are in accord with these results. Stable ITO/PVAc-co-acrylic dispersions are obtained at a pH of 3.0 and 11.0, but dispersions are not stable at a pH of 6.0, the IEP of ITO. At a pH of 3.0, DLVO results predict attraction between ITO particles and latex particles. Dispersion pH affected the microstructures and properties of ATO (or ITO)/PVAc-co-acrylic coatings. Suspensions that formed aggregates produced coatings with lower percolation thresholds and lower transparencies than those produced from stable suspensions.     

Structural and spectroscopic investigation of ZnS nanoparticles grown in quaternary reverse micelles

ZnS nanoparticles were synthesized in four component "water in oil" microemulsions formed by a cationic surfactant (cetyltrimethylammonium bromide, CTAB), a cosurfactant (pentanol or butanol), n-hexane and water. The effect of various parameters (nature of cosurfactant, water/surfactant W(0), and alcohol/surfactant P(0)) on the formation and stability of ZnS nanoparticles was investigated thoroughly. UV-Vis spectroscopy was employed to directly follow the formation of ZnS systems in the microemulsions. Thus, particle size was estimated from the position of the first excitonic transition by employing an approximate finite-depth equation and an empirical correlation, giving average diameters in the ranges 2.3-2.5 and 3.0-3.5nm, respectively. Stable ZnS nanoparticles were obtained by employing low water and high cosurfactant amounts. This suggests that at high concentration the cosurfactant molecules act as capping agents on the surface of the inverse micelles, while low water amounts are needful to obtain water droplets with a radius close to that of the interfacial film spontaneous curvature. HRTEM analysis showed that the samples are formed by a few crystalline ZnS nanoparticles of spherical shape, embedded in and amorphous organic matrix, with a coherent scattering domain between 2 and 4nm.     

Stable aqueous nanoparticle film assemblies with covalent and charged polymer linking networks

The construction of highly stable and efficiently assembled multilayer films of purely water soluble gold nanoparticles is reported. Citrate-stabilized nanoparticles (CS-NPs) of average core diameter of 10 nm are used as templates for stabilization-based exchange reactions with thioctic acid to form more robust aqueous NPs that can be assembled into multilayer films. The thioctic acid stabilized nanoparticles (TAS-NPs) are networked via covalent and electrostatic linking systems, employing dithiols and the cationic polymer poly(L-lysine), respectively. Multilayer films of up to 150 nm in thickness are successfully grown at biological pH with no observable degradation of the NPs within the film. The characteristic surface plasmon band, an optical feature of certain NP film assemblies that can be used to report the local environment and core spacing within the film, is preserved. Growth dynamics and film stability in solution and in the air are examined, with poly(L-lysine) linked films showing no evidence of aggregation for at least 50 days. We believe these films represent a pivotal step toward exploring the potential of aqueous NP film assemblies as a sensing apparatus.     

Highly improved dielectric behaviour of ferronematic nanocomposite for display application

We report the investigation of influence of nickel zinc ferrite magnetic nanoparticles (NZFO (Ni_0.5Zn_0.5Fe₂O₄)) on phase transition, optical and dielectric properties in a nematic liquid crystal (NLC). The interaction of NZFO nanoparticles with NLC was confirmed by the formation of ferronematic droplets due to the transfer of magnetic orientational effect onto the underlying NLC matrix. The doping results in shift of nematic to isotropic transition to low-temperature region. An enhancement in the value of refractive index is observed in the nematic region after the addition of NZFO nanoparticles. The dielectric constant of NLC was remarkably enhanced by 10 times after doping, which is found to be maximum at 0.1 wt% concentration of NZFO nanoparticles. The decrease in the value of dissipation factor in low-frequency region shows that the magnetic nanoparticles are able to trap ionic impurities effectively. The obtained results suggest that the optimum amount of doping concentration is 0.1 wt% of NZFO nanoparticles in NLC due to high dielectric constant with low dissipation factor and high refractive index with high dispersive power at room temperature.     

The green synthetic approach to prepare PbS/chitosan nanocomposites and its new optical sensing active properties for 2-isonaphthol

PbS nanoparticles were successfully synthesized in the presence of chitosan (CS) through an in situ method. This method is an effective, simple, and green synthetic approach to preparing nanomaterial films. The structure, morphology, and stability of the materials were examined via Fourier transform infrared spectroscopy, and the characteristic peak of the NH₂ group shifted from 1554 to 1598 cm^-1 after PbS was formed in the film. The Pb–S bond exhibited a vibrational absorption peak at 605 cm^-1, which further confirmed the generation of PbS nanoparticles. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) procedures were performed as well; well-defined nanoparticles were detected in the CS matrix by SEM. As per DSC findings, the thermal stabilities of the PbS/CS film were 50°C higher than those of pure CS. Moreover, the fluorescence emission of the films was sensitive to the presence of 2-isonaphthol. The effect of 2-isonaphthol concentration on the emission of films increases significantly with an increase in this concentration. The concentration-dependent fluorescence can be described by a correlation equation when 2-isonaphthol concentration ranges from 0 to 12.56 mg/L, and fluorescence results revealed that the PbS/CS nanoparticles were sensitive to 2-isonaphthol in the liquid phase. The proposed method may be applied to detect 2-isonaphthol in the environment and in the chemical industry.     

Analysis of electro-optical and dielectric parameters of TiO2 nanoparticles dispersed nematic liquid crystal

The present investigation is focused on to find out the role of TiO₂ nanoparticles (NPs) on altering the dielectric and electro-optical parameters of nematic liquid crystal (NLC). In addition to this, we also optimized the concentration of dopant (0.25 wt%) for a saturation value of permittivity and dielectric anisotropy in the doped system. Dielectric spectroscopy has been performed with the variation of frequency and temperature to investigate the various dielectric parameters, which demonstrate that the investigated NLC is of positive dielectric anisotropy; the observed result shows a decrement in the value of relative permittivity and dielectric anisotropy; however, the permittivity value increases for higher concentration of dopant but remains less than that of pure NLC. Electro-optical measurements have also been performed to compute the optical response of pure and dispersed NLC. It is found that optical response decreases for the NP-doped systems. This optimized concentration of NPs in NLC matrix can have various credential applications in the field of active matrix display and holography.     

纳米氧化锡锑改性水性聚氨酯的制备与表征

以异佛尔酮二异氰酸酯(IPDI)、聚醚二醇（N-210）、二羟甲基丙酸（DMPA）、一缩二乙二醇（DEG）、三羟甲基丙烷（TMP）及纳米氧化锡锑（ATO）浆料为主要原料,制备了稳定的纳米ATO改性水性聚氨酯(APU)乳液。 粒径测试及透射电子显微镜（TEM）观察显示,纳米ATO在水性聚氨酯中分散较好,乳液粒径均小于100 nm; FTIR分析表明,纳米ATO粒子与水性聚氨酯(WPU)间可能存在化学键; 热重分析(TGA)测试显示,随纳米ATO添加量的增加,胶膜最大热分解温度逐渐提高,最大提高了约20 ℃;紫外-可见-近红外吸收及保温性能测试表明,随着纳米ATO添加量的提高,胶膜在800~2500 nm的透过率逐渐降低,但涂层在可见光区透过率均超过70%,热阻率由1.34×10-2 m2·℃/W提高至3.17×10-2 m2·℃/W。