Preparation of nitrogen doped zinc oxide nanoparticles and thin films by colloidal route and low temperature nitridation process

Nitrogen doped zinc oxide (ZnO) nanoparticles have been synthesized using a colloidal route and low temperature nitridation process. Based on these results, 200 nm thick transparent ZnO thin films have been prepared by dip-coating on SiO₂ substrate from a ZnO colloidal solution. Zinc peroxide (ZnO₂) thin film was then obtained after the chemical conversion of a ZnO colloidal thin film by H₂O₂ solution. Finally, a nitrogen doped ZnO nanocrystalline thin film (ZnO:N) was obtained by ammonolysis at 250 °C. All the films have been characterized by scanning electron microscopy, X-ray diffraction, X-Ray photoelectron spectroscopy and UV–Visible transmittance spectroscopy.     

A general approach to mesoporous metal oxide microspheres loaded with noble metal nanoparticles

Catalytic microspheres: A general approach is demonstrated for the facile preparation of mesoporous metal oxide microspheres loaded with noble metal nanoparticles (see TEM image in the picture). Among 18 oxide/noble metal catalysts, TiO(2)/0.1?mol?% Pd microspheres showed the highest turnover frequency in NaBH(4) reduction of 4-nitrophenol (see picture).     

Nanorods of transition metal oxalates: A versatile route to the oxide nanoparticles

A versatile route has been explored for the synthesis of nanorods of transition metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates using reverse micelles. Transmission electron microscopy shows that the as-prepared nanorods of nickel and copper oxalates have diameter of 250 nm and 130 nm while the length is of the order of 2.5 μm and 480 nm, respectively. The aspect ratio of the nanorods of copper oxalate could be modified by changing the solvent. The average dimensions of manganese, zinc and cobalt oxalate nanorods were 100 μm, 120 μm and 300 nm, respectively, in diameter and 2.5 μm, 600 nm and 6.5 μm, respectively, in length. The aspect ratio of the cobalt oxalate nanorods could be modified by controlling the temperature.The nanorods of metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates were found to be suitable precursors to obtain a variety of transition metal oxide nanoparticles. Our studies show that the grain size of CuO nanoparticles is highly dependent on the nature of non-polar solvent used to initially synthesize the oxalate rods. All the commonly known manganese oxides could be obtained as pure phases from the single manganese oxalate precursor by decomposing in different atmospheres (air, vacuum or nitrogen). The ZnO nanoparticles obtained from zinc oxalate rods are ～55 nm in diameter. Oxides with different morphology, Fe₃O₄ nanoparticles faceted (cuboidal) and Fe₂O₃ nanoparticles (spherical) could be obtained.     

Peptide nucleic acid stabilized perovskite nanoparticles for nucleic acid sensing

Nanostructural hybrid organic-inorganic metal halide perovskites offer a wide range of potential applications including photovoltaics, solar cells, and light emitting diodes. Up to now the surface stabilizing ligands were used solely to obtain the optimal properties of nanoparticles in terms of dimensionality and stability, however their possible additional functionality was rarely considered. In the present work, hybrid lead bromide perovskite nanoparticles (PNP) were prepared using a unique approach where a peptide nucleic acid is used as a surface ligand. Methylammonium lead bromide perovskite colloidal nanoparticles stabilized by thymine-based peptide nucleic acid monomer (PNA-M) and relevant trimer (PNA-T) were prepared exhibiting the size below 10 nm. Perovskite structure and crystallinity were verified by X-ray powder diffraction spectroscopy and high resolution transmission electron microscopy. PNP-PNA-M and PNP-PNA-T colloidal dispersions in chloroform and toluene possessed green-blue fluorescence, while Fourier-transform infrared spectroscopy (FT-IR) and quantum chemical calculations showed that the PNA coordinates to the PNP surface through the primary amine group. Additionally, the sensing ability of the PNA ligand for adenine nucleic acid was demonstrated by photoluminescence quenching via charge transfer. Furthermore, PNP thin films were effectively produced by the centrifugal casting. We envision that combining the unique, tailored structure of peptide nucleic acids and the prospective optical features of lead halide perovskite nanoparticles could expand the field of applications of such hybrids exploiting analogous ligand chemistry.     

A simple route to ordered metal oxide nanoparticle arrays using block copolymer thin films

Oxide nanoparticles arrays are easily synthesized in a 3-steps method including (i) the deposition of poly(styrene)-b-poly(4-vinylpyridine) (PS-b-PVP) thin films, (ii) the selective deposition of inorganic precursors and (iii) the synthesis of oxide nanoparticles and the elimination of the polymer scaffold by thermal annealing. The specific staining of the PVP domains by inorganic precursors is obtained in this study thanks to a simple and fast spin coating process using an alcoholic solution of the precursors. This simple lab-procedure is used to synthesize a wide range of metallic (silicon, titanium, cerium, ruthenium, zinc and manganese) oxides, showing that this method can be extended to the synthesis of all kinds of oxides with all kinds of precursors as long as the precursor is soluble in P4VP solvent. It is shown that this strategy can be extended to the synthesis of oxide nanorods.     

A fast route to obtain manganese spinel nanoparticles by reduction of K-birnessite

The K-birnessite (K_xMnO₂·yH₂O) reduction reaction has been tested in order to obtain manganese spinel nanoparticles. The addition of 0.25 weight percent of hydrazine hydrate, the reducing agent, during 24 hours is efficient to transform the birnessite powder in a hausmanite Mn₃O₄ powder. Well crystallised square shape nanoparticles are obtained. Different birnessite precursors have been tested and the reaction kinetics is strongly correlated to the crystallinity and granulometry of the precursor. The effects of aging time and hydrazine hydrate amount have been studied. Well crystallised Mn₃O₄ is obtained in one hour. The presence of feitknechtite (MnO(OH)) and amorphous nanorods has been detected as an intermediate phase during birnessite conversion into hausmanite. The conversion mechanism is discussed.     

Photoreactive surfactants: a facile and clean route to oxide and metal nanoparticles in reverse micelles

A new class of photoreactive surfactants (PRSs) is presented here, consisting of amphiphiles that can also act as reagents in photochemical reactions. An example PRS is cobalt 2-ethylhexanoate (Co(EH)(2)), which forms reverse micelles (RMs) in a hydrocarbon solvent, as well as mixed reversed micelles with the standard surfactant Aerosol-OT (AOT). Small-angle neutron scattering (SANS) data show that mixed AOT/PRS RMs have a spherical structure and size similar to that of pure AOT micelles. Excitation of the ligand-to-metal charge transfer (LMCT) band in the PRSs promotes electron transfer from PRS to associated metal counterions, leading to the generation of metal and metal-oxide nanoparticles inside the RMs. This work presents proof of concept for employing PRSs as precursors to obtain nearly monodisperse inorganic nanoparticles: here both Co(3)O(4) and Bi nanoparticles have been synthesized at high metal concentration (10(-2) M) by simply irradiating the RMs. These results point toward a new approach of photoreactive self-assembly, which represents a clean and straightforward route to the generation of nanomaterials.     

A simple urea-based route to ternary metal oxynitride nanoparticles

Ternary metal oxynitrides are generally prepared by heating the corresponding metal oxides with ammonia for long durations at high temperatures. In order to find a simple route that avoids use of gaseous ammonia, we have employed urea as the nitriding agent. In this method, ternary metal oxynitrides are obtained by heating the corresponding metal carbonates and transition metal oxides with excess urea. By this route, ternary metal oxynitrides of the formulae MTaO₂N (M=Ca, Sr or Ba), MNbO₂N (M=Sr or Ba), LaTiO₂N and SrMoO_3−xN_x have been prepared successfully. The oxynitrides so obtained were generally in the form of nanoparticles, and were characterized by various physical techniques.     

Dissolution of cellulose in ionic liquids as a way to obtain test materials for metal-ion detection

Cellulose films containing entrapped analytical reagents suitable for metal-ion detection are produced by joint dissolution of cellulose and the reagents in ionic liquids then precipitation with water. The conditions of preparation of these test materials have been optimized and their properties have been studied. The film obtained by use of the ionic liquid 1-butyl-3-methylimidazolium chloride and 1-(2-pyridylazo)-2-naphthol has been used for colorimetric determination of divalent zinc, manganese, and nickel with detection limits at the 10⁻⁶ mol L⁻¹ level.     

A novel approach to thermal Analysis of Thin films

A novel instrument is described called the Thin film Analyser (TFA) which quantitatively measures changes in mechanical and rheological properties of drying films in-situ on a test panel. It is based around a simple force-sensing device, capable of carrying various probes, which can be positioned in anX-Y plane over the panel. Temperature control is achieved by means of a heating block under the sample. By imposing a thermal gradient along the block, measurements can be obtained at a series of temperatures in a single experiment. Several applications of the TFA to the drying of curable and latex-based coatings are discussed, as well as some more specialized uses. The TFA concept represents a novel approach to the thermal analysis of thin films.The authors gratefully acknowledge the design, engineering and software development work of the Instrument Group at ICI Paints, in particular John Hayton, Neil Burrows, Tony Evans and Ian Francis, who have now built three versions of the TFA.     

Emission properties and applications of nanostructured luminescent oxide nanoparticles

Rare earth doped oxide materials are well known for their numerous applications in light emitting devices. An interesting issue is to study the emission properties of nanoparticles, with the aim to understand the influence of small size and surface effects on the emission processes. These particles could furthermore be used in new applications such as the elaboration of transparent emitting devices or new biological labels. The work presented here concerns highly luminescent rare earth doped yttrium vanadates (YVO₄:Eu) and lanthanum phosphate LaPO₄:Ce,Tb·xH₂O nanoparticles. Simple aqueous colloidal syntheses are used for the elaboration of concentrated colloids based on the progressive decomposition of polymeric precursors at moderate temperature (60–90 °C). Both types of particles exhibit strong emission (quantum yields of 25% and 45% for vanadates and phosphates, respectively), but significantly lower than that for the equivalent bulk materials. The alteration of the emission processes is discussed in terms of surface quenching effects. Improvements are obtained through the elaboration of core/shell nanostructures. Surface derivatization has been achieved through the controlled growth of an organically modified silica shell using a functionalized silane precursor. Two examples are given concerning the applications of those particles. The first one is the elaboration of transparent and highly luminescent thin films, obtained by the dispersion of the functionalized particles in a sol–gel silica matrix. The other one is the use of guanidine functionalized particles as biological labels for the single particle detection of sodium channels in cardiac cells.     

A novel route to in‐situ incorporation of silver nanoparticles into supramolecular hydrogel networks

A novel strategy was developed for the in situ incorporation of silver nanoparticles into the supramolecular hydrogel networks, in which colloidally stable silver hydrosols were firstly prepared in the presence of an amphiphilic block copolymer of poly(oxyethylene)‐poly(oxypropylene)‐poly(oxyethylene) and then mixed with aqueous solution of α‐cyclodextrin. The analyses from rheology, X‐ray diffraction, and scanning electron microscopy confirmed the formation of the supramolecular‐structured hydrogels hybridized with silver nanoparticles. In particular, the colloidal stability of the resultant silver hydrosol and its gelation kinetics in the presence of α‐cyclodextrin as well as the viscoelastic properties of the resultant hybrid hydrogel were investigated under various concentrations of the used block copolymer. It was found that the used block copolymer could act not only as the effective reducing and stabilizing agents for the preparation of the silver hydrosol but also as the effective guest molecule for the supramolecular self‐assembly with α‐cyclodextrin. In addition, the effects of silver nanoparticles on the gelation process and the hydrogel strength were also studied. Such a hybrid hydrogel material could show a good catalytic activity for the reduction of methylene blue dye by sodium borohydride. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 740–749, 2009     

A facile route to synthesize silver nanoparticles in polyelectrolyte capsules

We are reporting a novel green approach to incorporate silver nanoparticles (NPs) selectively in the polyelectrolyte capsule shell for remote opening of polyelectrolyte capsules. This approach involves in situ reduction of silver nitrate to silver NPs using PEG as a reducing agent (polyol reduction method). These nanostructured capsules were prepared via layer by layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and dextran sulfate (DS) on silica template followed by the synthesis of silver NPs and subsequently the dissolution of the silica core. The size of silver nanoparticles synthesized was 60±20 nm which increased to 100±20 nm when the concentration of AgNO(3) increased from 25 mM to 50 mM. The incorporated silver NPs induced rupture and deformation of the capsules under laser irradiation. This method has advantages over other conventional methods involving chemical agents that are associated with cytotoxicity in biological applications such as drug delivery and catalysis.     

Preparation and characterization novel dioctyl terephthalate blended polyvinyl alcohol-composite films incorporated with the graphene oxide and silver nanoparticles

Dioctyl terephthalate is of great interest as a replacement for the phthalate plasticizers such as dioctyl phthalate and diisononyl phthalate due to its orthophthalate-free and non-carcinogenic properties. This study focused on the production, characterization and optimization of the quality characteristics of its film properties, such as the mechanical, hydrophilic and thermal properties of dioctyl terephthalate-blended polyvinyl alcohol composites modified with graphene oxide and silver nanoparticles using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) based Taguchi Method. Dioctyl terephthalate has brought remarkable features, such as high elastic modulus, and hydrophilic and thermal stability to the polyvinyl alcohol matrix. The optimum Dioctyl terephthalate -blended polyvinyl alcohol films have a 2.26 times lower contact angle and a 13.41 times higher elastic modulus than the reference polyvinyl alcohol film. Dioctyl terephthalate should be preferentially used to manufacture more durable and hydrophilic composite films such as fibers, disposable underpad or industrial swab, instead of toxic phthalate plasticizers.     

In2O3-based multicomponent metal oxide films and their prospects for thermoelectric applications

Thermoelectric properties of In₂O₃–SnO₂-based multi-component metal oxide films formed by spray pyrolysis method are studied. It is shown that the introduction of additional components such as gallium and zinc can control the parameters of the deposited layers. At that, the doping with gallium is more effective for optimization of the efficiency of the thermoelectric conversion. The explanation of the observed changes in the electro-physical and thermoelectric properties of the films at the composition change is given. It is found that the main changes in the properties of multicomponent metal oxide films take place at concentrations of dopants which correspond to their limit solubility in the dominant oxide.     

Efficient immobilization of silver nanoparticles on metal substrates through various thiol molecules to utilize a gap mode in surface enhanced Raman scattering

To utilize a gap mode in surface enhanced Raman scattering, we elucidated the interaction between adsorbed species and Ag nanoparticles (AgNPs). Various thiol molecules such as normal alkanethiols, thiols with a phenyl, cyclohexane or naphthalene ring on Ag films immobilized AgNPs through van der Waals force, and electrostatic interaction. Immobilized AgNPs provided enormous Raman enhancement by a factor of 10⁷–10¹⁰ for thiol molecules at a nanogap, in consistent with that anticipated by finite difference time domain calculations. Only alkanethiols with a tert-methyl group and those with a carboxylic group did not immobilize any AgNPs probably owing to steric hindrance. A gap mode is relevant for a variety of metals even with large damping like Pt and Fe, indicating a crucial role of electric multipoles in AgNPs generated by a localized surface plasmon and induced mirror images in metal substrates for markedly enhanced electric field at a nanogap.     

传感器用镓掺杂氧化锌纳米盘/纳米花状结构催化剂的制备及表面表征

采用简便的旋涂过程和一步水热法在压电基片上制备了Ga掺杂的ZnO纳米薄膜(GZO)。在水热处理过程中,通过添加不同的聚合物可形成纳米盘和纳米花状形貌的薄膜。采用场发射扫描电镜(Fe-SEM)、X射线衍射(XRD)和Raman光谱表征了样品的形貌、微结构和组成。 XRD和FE-SEM结果证明,在AlN/Si压电基片上形成的纳米盘、纳米棒和纳米花状GZO均为纤维锌矿相。采用浸渍法进一步在所制GZO样品上固定了绿色的荧光蛋白质(GFP)。运用原子力显微镜和荧光光谱分析了GFP与GZO表面结合的性质,考察了其用于传感器和生物成像技术的可行性。痕量GFP的固定使该材料产生荧光响应,表明其用于紫外光传感器时具有较好活性。     

A general nonaqueous route to binary metal oxide nanocrystals involving a C-C bond cleavage

A widely applicable solvothermal route to nanocrystalline iron, indium, gallium, and zinc oxide based on the reaction between the corresponding metal acetylacetonate as metal oxide precursor and benzylamine as solvent and reactant is presented. Detailed XRD, TEM, and Raman studies prove that, with the exception of the iron oxide system, where a mixture of the two phases magnetite and maghemite is formed, only phase pure materials are obtained, gamma-Ga(2)O(3), zincite ZnO, and cubic In(2)O(3). The particle sizes lie in the range of 15-20 nm for the iron, 10-15 nm for the indium, 2.5-3.5 nm for gallium, and around 20 nm for zinc oxide. GC-MS analysis of the final reaction solution after removal of the nanoparticles showed that the composition is rather complex consisting of more than eight different organic compounds. Based on the fact that N-isopropylidenebenzylamine, 4-benzylamino-3-penten-2-one, and N-benzylacetamide were the main species found, we propose a detailed formation mechanism encompassing solvolysis of the acetylacetonate ligand, involving C-C bond cleavage, as well as ketimine and aldol-like condensation steps.     

Zinc oxide nanoparticles incorporated in ultrathin layer silicate films and their photocatalytic properties

This study has been conducted to determine whether the nanosized semiconductor crystals qualify as photocatalysts also in that case when they are self-assembled to form ultrathin films in the thickness range of 10–500 nm. For this purpose, multilayer films of Zn(OH)₂ and ZnO nanoparticles were prepared by the layer-by-layer self-assembly method on glass surface. A transparent layer silicate, synthetic hectorite was used as sticking material. The quality of multilayer formation has been investigated in detail by absorption spectrophotometry, XRD and atomic force microscopy (AFM). Evidence was found for the uniform deposition of the different components. The increment of nanofilm thickness was constant and independent from the number of layers deposited previously. Photocatalytic measurements were made with model organic materials β-naphtol and industrial kerosene in a home-made loop-type batch reactor. Decomposition has been continously monitored by UV spectrometry. Significant photodegradation of the organic molecules were only found in the presence of the nanofilms.     

Self-organization of dipeptide-grafted polymeric nanoparticles film: A novel method for surface modification

Novel dipeptide-grafted polymeric nanoparticles were prepared by grafting the dipeptide (Gly-Gly) to a block copolymer backbone, comprised of styrene-alt-(maleic anhydride) and styrene. In aqueous solution PSt₁₃₀-b-P(St-alt-MAn)₅₈-g-GlyGly₂₆ formed stable dispersed spherical aggregates of ca. 75 nm. The critical micelle concentration for the dipeptide-grafted block copolymer self-aggregates was 6.3 × 10⁻³ mg mL⁻¹. The zeta-potential of the aggregates was estimated experimentally. The dispersed polymer nanoparticles effectively self-organized to form stable nanoparticle thin films on hydrophobic solid surfaces, such as octadecyltrichlorosilane modified glass (OTS-G). As the ionic strength and temperature of the polymer suspension increased the surface coverage of the nanoparticle film increased and its hydrophobicity (water contact angle) decreased. Significantly less bovine serum albumin (BSA) adsorbed to nanoparticles modified surfaces with compared OTS-G surfaces. Diglycine grafted polymer nanoparticles have the potential to be used as a novel platform to study protein-protein interactions and to control fouling.