Uniform α-Fe2O3 nanotubes fabricated for adsorption and photocatalytic oxidation of naphthalene

Uniform α-Fe₂O₃ nanotubes with small aspect ratio were successfully fabricated by a hydrothermal method. In situ Fourier-transform infrared spectroscopy was used to study the mechanistic details of adsorption and photocatalytic oxidation of naphthalene over theα-Fe₂O₃ nanotubes. A possible degradation mechanism of naphthalene was proposed.     

One-step approach to prepare magnetic iron oxide/reduced graphene oxide nanohybrid for efficient organic and inorganic pollutants removal

An environmentally friendly effective technique was demonstrated to prepare iron oxide/reduced graphene oxide nanohybrid (IO/RGO) at room temperature by using banana peel ash aqueous extract as the base source and Colocasia esculenta leaves aqueous extract as the reducing agent. The nanohybrid was characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, transmission electron microscopy, vibrating sample magnetometry, Raman spectroscopy and thermal studies. The results indicated the decoration of superparamagnetic IO nanoparticles on the surface of the RGO. Both organic and inorganic pollutants were effectively removed from the contaminated water (for Pb²⁺ and Cd²⁺ within 10 min, whereas for tetrabromobisphenol A within 30 min) by IO/RGO. The study revealed that adsorption followed pseudo-second order kinetics and isotherms were well described by the Langmuir model in all the cases. The thermodynamics parameters (ΔG°, ΔS° and ΔH°) were calculated from the temperature dependent isotherms and indicated that the adsorptions were endothermic and spontaneous.     

Synthesis of carbon nitride powder by selective etching of TiC0.3N0.7 in chlorine-containing atmosphere at moderate temperature

We reported the synthesis of carbon nitride powder by extracting titanium from single inorganic precursor TiC_0.3N_0.7 in chlorine-containing atmosphere at ambient pressure and temperature not exceeding 500 °C. The TiC_0.3N_0.7 crystalline structure acted as a template, supplying active carbon and nitrogen atoms for carbon nitride when it was destroyed in chlorination. X-ray diffraction data showed that the obtained carbon nitride powders were amorphous, which was in good agreement with transmission electron microscope analysis. The composition and structure of carbon nitride powders were analyzed by employing Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Results indicated that disorder structure was most likely for the carbon nitride powders and the N content depended greatly on the chlorination temperature. Thermal analysis in flowing N₂ indicated that the mass loss started from 300 °C and the complete decomposition occurred at around 650 °C, confirming the low thermal stability of the carbon nitride material.     

The effect of the presence of Ag nanoparticles on the photocatalytic degradation of oxalic acid adsorbed on TiO2 nanoparticles monitored by ATR-FTIR

Photocatalytic degradation of oxalic acid adsorbed on the Ag/P25 TiO₂ composite nanoparticle films were investigated using ATR-FTIR technique under UV irradiation. Ag/P25 TiO₂ composite nanoparticle films with various Ag content were tested. Topography and chemical structure/composition of the composite nanoparticle films were analyzed by AFM and XPS respectively. It was found that in the degradation reaction of the oxalic acid, the presence of only 2% Ag nanoparticles leads to six times more oxalic acid degradation compared to that degraded in the presence of pure P25 TiO₂ nanoparticles. The degradation rate of the oxalic acid is three times higher in the case of Ag/TiO₂ composite nanoparticle film than in the case of pure TiO₂ nanoparticles. It was observed that both the rate of oxalic acid degradation and the degraded amount of the oxalic acid were significantly affected by Ag incorporation.     

Optical properties change in amorphous (As2S3)0.87Sb0.13 thin films by photo and thermal induced process

Exposure with above band gap light and thermal annealing at a temperature near to glass transition temperature, of thermally evaporated amorphous (As₂S₃)_0.87Sb_0.13 thin films of 1 μm thickness, were found to be accompanied by structural effects, which in turn, lead to changes in the optical properties. The optical properties of thin films induced by illumination and annealing were studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Photo darkening or photo bleaching was observed in the film depending upon the conditions of the light exposure or annealing. These changes of the optical properties are assigned to the change of homopolar bond densities.     

Development of a transparent hydrorepellent modified SiO2 coatings for glazed sanitarywares

The formulation of innovative transparent hydrorepellent coatings is strongly motivated in order to satisfy the market request and necessity to improve the cleanability of the sanitarywares. A lot of attention is devoted to the use of cheap precursors, low temperature synthesis process and industrial scalability potentiality. In this framework, in the present paper the set-up of the deposition of modified SiO₂ coatings on glazed ceramic supports by spraying technique was reported. Several solutions were formulated using as precursor tetraethylorthosilicate (TEOS) and co-precursor methyltriethoxysilane (MTES) in different molar ratios (i.e. 50:50, 25:75, 75:25), in suitable solvents and mixture of solvents (i.e. H₂O, ethanol). The influence of the process parameters (i.e. precursors ratio, solvents, catalyser, annealing temperature) on the properties of the produced coatings was deeply investigated by means of scanning electron microscopy (SEM), simultaneous thermogravimetric and differential analyses (TG–DTA), infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and Vickers microhardness. Their hydrophobic behaviour was tested by the measurements of the static water contact angles and the chemical and stain resistance by the conformity to some tests of the standard UNI 4543. The obtained coatings were amorphous, homogeneous, uniform, thin (average thickness 300 nm), crack-free, leading to an improved hardness value of the glazed ceramic support (4.47 GPa vs 3.68 GPa for the coated and uncoated substrates, respectively), and allowed to improve both the hydrophobic behaviour and the chemical and stains resistance of the glazed sanitaryware supports, on the basis of the standard UNI 4543. The best hydrophobic performances were revealed in the case of coatings prepared starting from acidic catalysis derived precursor solutions. Moreover, the highest water contact angle values were detected for lower temperatures annealing, due to the methyl groups preservation, in agreement with the FT-IR and TG–DTA findings.     

Synthesis and characterizations of Nd doped SrFe12O19 nanoparticles

This is the first report ever on Nd³⁺ doped M-type hexaferrite nanoparticles: SrNd_xFe_12−xO₁₉ (0 ≤ x ≤ 1) prepared by citrate precursor using the sol–gel technique followed by gel to crystallization. The influence of the Nd³⁺ substitution, Fe³⁺/Sr²⁺ molar ratio and the calcination temperature on the crystallization of ferrite phase have been examined using powder X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), inductance capacitance resistance meter bridge (LCR) and vibrating sample magnetometer (VSM). The structural analysis reveals that the Nd³⁺ ions rearrange themselves in the host lattice without disturbing the parent lattice and Fe³⁺/Sr²⁺ molar ratio less than 12 is more favorable to achieve single phase hexaferrite at calcination temperature 900 °C for 4 h. Mid-IR analysis confirms that Nd³⁺ occupies the octahedral site. Detailed studies of electrical properties of prepared materials have been investigated in the frequency range 100–1000 Hz at room temperature by LCR meter and two probe technique. The result shows that the electrical properties strongly depend upon the frequency of applied field and dopant concentration. The magnetic measurements showing a considerable improvement in coercivity with the substitution of Nd³⁺ on iron sites, while the unsubstituted hexaferrites have highest value of specific saturation magnetization.     

Hydrothermal synthesis of nanocrystalline VO2 from poly(diallyldimethylammonium) chloride and V2O5

Novel vanadium dioxide nanorods were fabricated from V₂O₅ in the presence of a reducing agent, the poly(diallyldimethylammonium chloride) (PDDA) via a hydrothermal method at 180 °C for 48 h. The samples produced were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), nitrogen adsorption (BET) and thermogravimetry (TG/DTG). The nanorods obtained are approximately 50 nm wide and from 300 to 500 nm long and presents high surface area (42 m² g⁻¹). The nanocrystalline B phase VO₂ is not produced by hydrothermal treatment in the absence of the PDDA polyelectrolyte.     

Sol–gel synthesis and characterization of Li2O–As2O5–SiO2 glassy system

The ternary 10% Li₂O + 90% (xAs₂O₅ + (1 − x) SiO₂) (x = 0.025, 0.05, 0.075 and 0.1) (LAS) glassy system with different compositions were prepared using sol–gel technique. All the prepared samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry techniques. The observed peak-free XRD patterns confirm the amorphous phase of the prepared LAS compounds. Structural coordination of LAS glassy samples was confirmed by Fourier transform infrared spectroscopy. Thermal behavior of the glassy samples was characterized by differential scanning calorimetry. Bulk conductivity of all the LAS glassy samples was calculated by analyzing the impedance data measured at different temperatures. Activation energy (E_a) is evaluated from the log σT vs. 1000/T plot and it is found to be 0.837 eV.     

The influence of pressure on the structure and the self-cleaning properties of sputter deposited TiO2 layers

TiO₂-layers for self-cleaning applications were deposited on glass and silicon wafer by reactive dc-sputtering at various oxygen and argon pressures in the range from 0.18 Pa to 3.0 Pa. With an increasing sputtering pressure the microstructure of the resulting films is significantly modified. The deposited crystal phases change from rutile to anatase and the density and the refractive index decrease by a factor of about 1.3. The microstructure of the layers is strongly influenced by the sputtering pressure. An improvement of the hydrophilicity as well as of the photocatalytic activity can be observed, due to the changes in the structure of the layers.     

Controllable synthesis of hierarchical nanostructures of CaWO4 and SrWO4 via a facile low-temperature route

CaWO₄ and SrWO₄ nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of the fundamental experimental parameters including the concentration of reactants, the reaction time and the temperature, the products with different morphologies of dumbbell, coral, rod and dendrite have been obtained, respectively. The possible formation mechanism of these unique morphologies has been proposed based on surfactant self-assembly under different experimental conditions. The as-synthesized CaWO₄ samples with various morphologies exhibit different photoluminescence properties. X-ray powder diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and luminescence spectroscopy were used to characterize these products.     

Polyol mediated synthesis of nanocrystalline M3SbS3 (M=Ag, Cu)

A simple and convenient polyol-mediated route has been developed to produce nanocrystalline Ag₃SbS₃ and Cu₃SbS₃ from AgNO₃ and Cu(NO₃)₂ and SbCl₃ with thiourea at 197 °C. The products were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Analysis shows that glycol agitated state and injection rate have a great effect on the purity of the final products.     

One simple synthesis route to whisker-like nanocrystalline boron nitride by the reaction of NaBH4 and NaN3

Nanocrystalline boron nitride (BN) was synthesized via a simple route by the reaction of sodium borohydride with sodium azide in an autoclave at 600 °C. X-ray powder diffraction pattern indicated that the product was hexagonal BN, and the cell constant was a = 2.495 Å, c = 6.687 Å. Transmission electron microscopy image showed that it consisted of whisker-like particles with an average size of 200 nm × 20 nm. The product was also studied by FT-IR, XPS and TGA. It has good thermal stability and oxidation resistance in high temperature.     

The formation of a SiOx interfacial layer on low-k SiOCH materials fabricated in ULSI application

The characterizations of SiOCH films using oxygen plasma treatment depends linearly on the O₂/CO flow rate ratio. According to the results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses, it was found that the carbon composition decreases with increasing O₂/CO flow rate ratio, because more carbon in the Si–O–C and Si–CH₃ bonds on the film surface would be converted by oxygen radicals. It was believed that the oxygen plasma could oxidize the SiOCH films and form a SiO_x interfacial capping layer without much porosity. Moreover, the result of FTIR analysis revealed that there was no water absorbed on the film. A SiO₂-like capping layer formed at the SiOCH film by the O₂/CO flow rate ratio of 0.75 had nearly the same dielectric properties from the result of capacitance–voltage (C–V) measurement in our research.     

Electron beam induced structural evolution in Fe3O4SiO2 particles: A new route to obtain movable core structures

SiO₂ hollow spheres with movable Fe₃O₄ core were obtained by exposing the pre-synthesized Fe₃O₄SiO₂ particles (with an adsorption interlayer of ethylene glycol) under the irradiation of electron beam inside transmission electron micrograph (TEM). In the formation process, the evaporation of adsorbed ethylene glycol and the evolution of amorphous SiO₂ layer played important roles, and that should be attributed to the high temperature and trapped charges induced by the irradiation of electron beam. This work provided a new route to obtain particles with movable core structure and extended the applications of electron beam.     

Synthesis of naturally cross-linked polycrystalline ZrO2 hollow nanowires using butterfly as templates

Butterfly wing skeleton is a widely used hard-template in recent years for fabricating photonic crystal structures. However, the smallest construction units for the most species of butterflies are commonly larger than ∼50 nm, which greatly hinders their applications in designing much smaller functional parts down to real “nano scale”. This work indicates, however, that hollow ZrO₂ nanowires with ∼2.4 μm in length, ∼35 nm in diameter and ∼12 nm in wall thickness can be synthesized via the selection of suitable butterfly bio-templates followed by heat processing. Especially, the successful fabrication of these naturally cross-linked ZrO₂ nanotubes suggests a new optional approach in fabricating assembled nano systems.     

Synthesis and characterization of In2O3 nanocube via a solvothermal-calcination route

In₂O₃ nanocubes have been generated by a two-step process, a simple solvothermal technique for In(OH)₃ nanocubes and subsequent reaction with O₂ to form the In₂O₃ nanocubes, which exhibit morphologies identical to the original In(OH)₃ nanocube. The In(OH)₃ nanocubes and the In₂O₃ nanocubes are well-crystallized single-crystal nanostructure. Under optimal conversion conditions, the final geometry features of In₂O₃ are predetermined by the size and morphology of the In(OH)₃ nanocubes. The size of In(OH)₃ nanocubes is effected by pH value of solution.     

Ultrasonic spray pyrolysis of surface modified TiO2 nanoparticles with dopamine

Spherical, submicronic TiO₂ powder particles were prepared in the low temperature process of ultrasonic spray pyrolysis (150 °C) by using as a precursor aqueous colloidal solutions consisting of surface modified 45 Å TiO₂ nanoparticles with dopamine. Detailed structural and morphological characterization of colored submicronic TiO₂ spheres was performed by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser particle size analysis and FTIR techniques. Also, optical characterization of both dopamine-modified TiO₂ precursor nanoparticles and submicronic TiO₂ powder particles was performed using absorption and diffuse reflectance spectroscopy, respectively. A significant decrease of the effective band gap (1.9 eV) in dopamine-modified TiO₂ nanoparticles compared to the band gap of bulk material (3.2 eV) was preserved after formation of submicronic TiO₂ powder particles in the process of ultrasonic spray pyrolysis under mild experimental conditions. Due to the nanostructured nature, surface-modified assemblage of TiO₂ nanoparticles preserved unique ability to absorb light through charge transfer complex by photoexcitation of the ligand-to-TiO₂ band, conventionally associated with extremely small TiO₂ nanoparticles (d < 20 nm) whose surface Ti atoms, owing to the large curvature, have penta-coordinate geometry.     

Combustion synthesis of nanocrystalline ZrO2 powder: XRD, Raman spectroscopy and TEM studies

ZrO₂ powder was prepared by the gel combustion technique using citric acid as a fuel and nitrate as an oxidant. Calcination at 600 °C of the dried powder, obtained after sluggish combustion of the citrate–nitrate gel, produced nanocrystalline ZrO₂ powder. The Rietveld refinement of the powder XRD data clearly suggested the presence of predominantly tetragonal phase of zirconia. TEM studies showed the agglomerated powder composed of nearly spherical nanocrystals of about 10 nm. The absence of cubic phase of zirconia was conclusively inferred by Raman spectroscopy.     

Studies of interaction of amines with TOPO/TOP capped CdSe quantum dots: Role of crystallite size and oxidation potential

This work reports the interaction of aliphatic (triethyl amine, butyl amine) and aromatic amines (PPD, aniline) with CdSe quantum dots of varied sizes. The emission properties and lifetime values of CdSe quantum dots were found to be dependent on the oxidation potential of amines and crystallite sizes. Smaller CdSe quantum dots (size 5 nm) ensure better surface coverage of amines and hence higher quenching efficiency of amines could be realized as compared to larger CdSe quantum dots (size 14 nm). Heterogeneous quenching of amines due to the presence of accessible and inaccessible set of CdSe fluorophores is indicated. PPD owing to its lowest oxidation potential (0.26 V) has been found to have higher quenching efficiency as compared to other amines TEA and aniline having oxidation potentials 0.66 and >1.0 V, respectively. Butyl amine on the other hand, plays a dual role: its post-addition acts as a quencher for smaller and enhances emission for larger CdSe quantum dots, respectively. The beneficial effect of butyl amine in enhancing emission intensity could be attributed to enhance capping effect and better passivation of surface-traps.