Study on crystallinity and morphology controlling of titania using acrylamide gel method and their photocatalytic properties

In this study, polyacrylamide gel method was used for preparation of pure and mixed phase TiO₂ nanoparticles. The influence of synthesis conditions on the physicochemical properties of products was investigated. It was found that the type of acid, which was used for acidifying the precursor solution together with calcination temperature can affect the phase structure, crystalline size, morphology and thereby photocatalytic activity of obtained TiO₂ nanoparticles. Different trends were observed during the phase transformation, particle growth, shift in energy of band gap with the change in tensile strain to compressive strain of the prepared TiO₂ nanomaterial. X-ray diffraction (XRD) showed that prepared nanocrystals, which were calcined at 450 °C have pure anatase and anatase–rutile mixed structures. The prepared samples having crystallite size between 5 nm and 60 nm were observed at different calcination temperatures. In addition, the photocatalytic activities of the prepared samples were evaluated by monitoring the degradation of Cresol Red (CR). The results show that the photocatalyst (TEC_I), exhibits the highest photocatalytic efficiency where 94.7% of CR can be decomposed after UV exposure for 75 min.     

Improved efficiency of sol–gel synthesized mesoporous anatase nanopowders in photocatalytic degradation of metoprolol

The structural and morphological properties of mesoporous anatase nanopowders, synthesized by sol–gel method, have been modified by varying the duration of calcination, in order to obtain more efficient photocatalyst than Degussa P25 in the degradation of relatively large pollutant molecules (>1 nm in size). According to X-ray diffraction analysis, the crystallite size was increased from 13 to 17.5 nm with the increase of calcination time from 1 to 7 h. The analysis of nitrogen sorption experimental data revealed that all samples were mesoporous, with a mean pore diameters in the range of ∼5–9 nm. The corrugated pore structure model was employed to evaluate pore structure tortuosity. Nanopowder properties have been related to the photocatalytic activity, tested in the degradation of metoprolol tartrate salt, selective β₁-blocker used in a variety of cardiovascular diseases, with molecular size of 0.610 nm × 1.347 nm. The study has demonstrated that samples calcined for 4 and 5 h have displayed higher photocatalytic performance than Degussa P25, whereas the sample calcined for 3 h has shown comparable activity.     

Photocatalytic properties of SrTiO3 nanoparticles prepared by a polyacrylamide gel route

A polyacrylamide gel method has been used to prepare SrTiO₃ nanoparticles. It is found that the choice of chelating agent has a great influence on the SrTiO₃ synthesis. The use of citric acid as the chelating agent leads to the synthesis of pure SrTiO₃ at a calcination temperature of 550 °C. By using the chelating agent acetic acid, however, a much higher calcination temperature at 800 °C is required to produce a single sample. The citric acid- and acetic acid-resulted samples exhibit both sphere- particle morphology, and have an average particle size of ~ 55 nm and ~ 100 nm, respectively. The photocatalytic properties of the as-prepared SrTiO₃ nanoparticles have been investigated by the degradation of Congo Red, RhB, MO, and MB under ultraviolet irradiation. The citric acid-resulted sample is found to exhibit a photocatalytic activity higher than the acetic acid-resulted sample, expectedly due to its relatively smaller particle size. In addition, different degradation efficiencies are found between the dyes, and the highest degradation efficiency is observed for Congo Red.     

Surface plasmon induced photoluminescence enhancement in the Au–ZnS nanocomposite

In this study, we prepared a novel Au–ZnS nanocomposite by simple homogeneous precipitation at room temperature. It is found that the defect emission (around 490 nm) from ZnS is dramatically tailored by the presence of Au nanoparticles. Specifically, the photoluminescent performance of this structure is strongly influenced by the size and concentration of Au cores and the surfactant. When the Au core is 12 nm and the mass fraction of Au is 0.050%, an enhancement of up to 38.5% in the photoluminescent intensity was observed. This enhancement is attributed to energy transfer from ZnS to Au followed by a large local electromagnetic field on or near the surface of the Au nanoparticles.     

Dynamic light scattering and UV–vis spectroscopy of gold nanoparticles solution

Gold nanoparticles solution prepared in water by laser ablation at 1064 nm of a gold metal plate was characterized by dynamic light scattering and UV–vis spectroscopy. Polarized dynamic scattering allows the measurement of translational diffusivity of Au nanoparticles, while depolarized scattering yields simultaneously the characterization of translational and rotational diffusivities. From these measurements the size and shape of Au nanoparticles are determined. Dynamic light scattering yields an average radius of 32 nm for the spherical nanoparticles in as prepared solution. The same measurements performed in an aged solution reveal the formation of ellipsoidal nanoparticles with minor and major semi-axis of 36 nm and 69 nm, respectively. The measured values allow to fit the UV–vis spectra with the Mie-Gans model and to measure the concentration of Au nanoparticles obtaining a complete characterization of their nanostructure. Dynamic light scattering results a powerful technique to characterize the size and shape of gold nanoparticles.     

Synthesis of mesoporous Zn–Al spinel oxide nanorods with membrane like morphology

A well-aligned ZnAl₂O₄ spinel oxide nanorods with hierarchical pore structure was synthesized by a simple route using polycarbonate membrane as the sacrificial template. Spinel formation and the template removal occurred in one-step by calcination at 550 °C. SEM analysis of the calcined sample showed a membrane morphology made up of aligned rods with micron sized pores in between them. TEM analysis revealed that individual rods are 130 ± 30 nm in diameter and are nanoporous in nature. These rods are made up of nanoparticles of the sizes ranging from 5 to 12 nm. HRTEM analysis further showed that these nanoparticles are crystalline with the lattice spacing in commensurate with the ZnAl₂O₄ spinel oxide. Adsorption–desorption study shows Type IV isotherm with the pore size around 3.4 nm and high specific surface area of about 140 m²/g.     

Sensitive detection of mercury (II) ion using water-soluble captopril-stabilized fluorescent gold nanoparticles

In our work, a simple, facile, and green method was developed for the synthesis of water-soluble and well-dispersed fluorescent gold nanoparticles (Au NPs) within 5 min, using captopril as a capping agent. The as-prepared Au NPs showed strong emission at 414 nm, with a quantum yield of 5.5%. The fluorescence of the Au NPs can be strongly quenched by mercury (II) ion (Hg^2 +) due to the stronger interactions between thiolates (RS^?) and Hg^2 +. It was applied to the detection of Hg^2 + in water samples in the linear ranges of 0.033–0.133 μM and 0.167–2.500 μM, with a detection limit of 0.017 μM. Therefore, the as-prepared Au NPs can meet the requirement for monitoring Hg^2 + in environmental samples.     

Synthesis of sulfated zirconia nanopowders via polyacrylamide gel method

In the present study, polyacrylamide gel method was applied for synthesis nanosized sulfated zirconia powders, first time. An assessment of the influence of calcination temperature and sulfate ion loading on the properties of synthesized powders was performed and the samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and thermal analysis. The results revealed that tetragonal phase was obtained on calcination at 500 °C and was stable towards higher temperatures (650 °C). The increase of crystallite size with increasing calcination temperature was observed. Calcination for long duration time led to evolution of some sulfur species, furthermore results in higher particle size (∼100–200 nm) as compared to calcination for short duration time resulting in lower particle size (<50 nm). The presence of sulfate had no significant effect on thermal stability of polyacrylamide gel network whereas structure and the nature of the sulfur species bound with the zirconia surface are affected by the sulfur content.     

Size effect of Au seeds on structure of Au–Pt bimetallic nanoparticles

Au–Pt bimetallic nanoparticles (NPs) were synthesized by a seeded growth method. Au NPs with different sizes were obtained by reducing HAuCl₄ with butyllithium, and AuPt bimetallic NPs were synthesized by reducing H₂PtCl₆ with oleylamine using the pre-synthesized Au NPs as seeds. The size of Au seeds was found to be a key factor on the structure of Au–Pt bimetallic NPs. Using big Au NP seeds (8 nm or 12 nm) resulted in the formation of Au–Pt dendritic structures. While relatively small Au NPs (3 nm) were used as seeds, the fast atomic diffusion inside relatively small bimetallic NPs will result in an Au–Pt alloy formation.     

Structural and magnetic properties of pristine and Fe-doped NiO nanoparticles synthesized by the co-precipitation method

Ni_1?xFe_xO (x = 0 and 0.03) nanoparticles are synthesized by a chemical route. XRD and TEM measurements confirm phase purity and crystallinity of the nanoparticles. Fe substitution in NiO reduces considerably the average particle size of the nanoparticles. The pristine NiO sample with size 14 nm and Fe-substituted sample having size 7 nm show room temperature ferromagnetism. The pristine NiO having 31 nm size and Fe-substituted sample with size 25 nm are found to be antiferromagnetic. The M–H and M–T behavior of the pristine and Fe-doped samples are explained with a core–shell model with an antiferromagnetic core and a ferromagnetic shell. The disordered spins at the shell give rise to a spin-glass like frozen state below 10 K. The obtained room temperature ferromagnetism in the pristine and Fe-doped NiO has been attributed to particle size effect.     

Synthesis and characterization of CuInSe2 nanoparticles via a solution method

Pure CuInSe₂ nanoparticles have been successfully synthesized via a solution method in the solvent of oleylamine. Anhydrous InCl₃, CuCl, and Se powder were used as the starting materials. The CuInSe₂ samples were characterized by XRD, TEM, and XPS techniques. It was found that tetragonal chalcopyrite structured CuInSe₂ nanoparticles were obtained with temperature above 230 °C. Sample prepared at 200 °C possesses triangular morphology and a minute amount of In₂Se₃ coexists as intermediate. CuInSe₂ nanoparticles with size of 20.2 ± 0.4 nm were prepared at 230 °C and the narrow size distribution was ascribed to the employment of hot injection, which was better for homogeneous nucleation. Stable “ink” can be formed when the as-synthesized CuInSe₂ nanoparticles were dispersed in organic solvents such as hexane and tolune, and such “ink” might have a practical application in CuInSe₂-based solar cells.     

Highly stable,protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics

A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8 ± 1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected‐area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics.     

Magnetic chitosan nanoparticles for removal of Cr(VI) from aqueous solution

A simple method was introduced to prepare magnetic chitosan nanoparticles by co-precipitation via epichlorohydrin cross-linking reaction. The average size of magnetic chitosan nanoparticles is estimated at ca. 30 nm. It was found that the adsorption of Cr(VI) was highly pH-dependent and its kinetics follows the pseudo-second-order model. Maximum adsorption capacity (at pH 3, room temperature) was calculated as 55.80 mg·g^? 1, according to Langmuir isotherm model. The nanoparticles were thoroughly characterized before and after Cr(VI) adsorption. From this result, it can be suggested that magnetic chitosan nanoparticles could serve as a promising adsorbent for Cr(VI) in wastewater treatment technology.     

A new and clean method on synthesis of gold nanoparticles from bulk gold substrates

In this work, we report a new pathway to prepare clean gold nanoparticles in neutral solutions with aid of natural chitosan. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1N NaCl and 1 g L^?1 chitosan from ?0.28 to +1.22 V vs. Ag/AgCl at 500 mV s^?1 for 200 scans. The durations at the cathodic and anodic vertices are 10 and 5 s, respectively. After this process, positively charged Au- and chitosan-containing complexes were produced in the solution. Then the solution was heated from room temperature to boiling at a heating rate of 6 °C min^?1 to prepare Au nanoparticles. The particle sizes of prepared Au (1 1 1) nanoparticles are ca. 10 nm. Moreover, the prepared Au nanoparticles in solutions are capable for anti-oxidation and stable in an ambient atmosphere for at least three months.     

Synthesis of TbMnO3 nanoparticles via a polyacrylamide gel route

We report here the synthesis of TbMnO₃ nanoparticles via an acrylamide gel route. XRD, TG analysis, DSC analysis, and FTIR spectroscopy are combinatively used to investigate the thermal decomposition process of precursor xerogels and the formation of TbMnO₃ phase. It is demonstrated that high-phase-purity TbMnO₃ nanoparticles can be prepared by using different chelating agents at a sintering temperature of 800 °C. SEM observation and XRD analysis reveal that the particle size and morphology of the products have a dependence on the chelating agent. The particles prepared using citric acid as the chelating agent appear to be regularly spherical in shape and highly uniform in size with a diameter of ～67 nm, while the sample prepared by using the chelating agent EDTA mainly consists of sphere-, ellipsoid-, and rod-like particles and exhibits a relatively broad particle size distribution with an average particle size centered around 115 nm. The use of a combination of citric acid and EDTA generally results in sphere- and ellipsoid-like particles with an average particle size between those of the samples prepared separately by using the two chelating agents.     

Low-temperature synthesis,structural and magnetic properties of self-dopant LaMnO3+δ nanoparticles from a metal-organic polymeric precursor

Self-dopant LaMnO_3+δ nanoparticles have been successfully synthesized by metal citrate complex method based on Pechini-type reaction route, at low temperature (773 K). Powder X-ray diffraction and transmission electron microscope revealed pure and nanostructured phase of LaMnO_3+δ (δ = 0.125) with an average grain size of ∼72 nm (773 K) and ∼80 nm (1173 K). DC-magnetization measurements under an applied magnetic field of H = ±60 kOe showed an increase in the magnetization with the increase of calcination temperature. Ferromagnetic nature shown by non-stoichiometric LaMnO_3+δ was verified by well-defined hysteresis loop with large remanent magnetization (M_r) and coercive field (H_c). Surface areas of LaMnO_3+δ nanoparticles were found to be 157.4 and 153 m² g⁻¹ for the samples annealed at 773 K and 1173 K, respectively.     

Sonication–hydrothermal combination technique for the synthesis of titanate nanotubes from commercially available precursors

Titanate nanotubes with inner diameters of 2–6 nm, outer diameters of 5–10 nm and lengths up to 600 nm were fabricated by directly using commercial TiO₂ powders as the precursors via sonication–hydrothermal combination approach. The formation processes during sonication treatment under different sonication powers and times and hydrothermal treatment were studied by scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization. The chemical composition of the titanate nanotubes was determined in terms of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. The influence of the particle size of the precursors on the formation processes was also examined. The tubular structure of the titanate nanotubes can be remained at the calcination temperature ≤450 °C, but was completely destroyed at high calcination temperature 600 °C.     

Magnetite nanoparticles with high heating efficiencies for application in the hyperthermia of cancer

Magnetic hyperthermia is a safe method for cancer therapy. A gap-type alternating current magnetic field (100 kHz, 100–300 Oe) is expected to be clinically applicable for magnetic hyperthermia. In this study, magnetite nanoparticles (MNPs) varying in size from 8 to 413 nm were synthesized using a chemical coprecipitation and an oxidation precipitation method to find the optimum particle size that shows a high heating efficiency in an applied magnetic field. The particles' in vitro heating efficiency in an agar phantom at an MNP concentration of 58 mg Fe/ml was measured in an applied magnetic field. In a magnetic field of 120 Oe, the temperature increase (ΔT) of the agar phantom within 30 s was 9.3 °C for MNPs with a size of 8 nm, but was less for the other samples, while in a magnetic field of 300 Oe, ΔT = 55 °C for MNPs with a size of 24 nm, and ΔT = 25 °C for MNPs with a size of 8 nm. The excellent heating efficiency of MNPs with a size of 24 nm in a magnetic field of 300 Oe may be due to a combination of the effects of both relaxation and hysteresis losses of the magnetic particles. It is believed that MNPs with a size of 8–24 nm will be useful for the in situ hyperthermia treatment of cancer.     

The morphology and size of nanostructured Au in Au/SBA-15 affected by preparation conditions

Template-free mesoporous silica SBA-15 was reacted with TPTAC to generate positively charged functional groups PTA⁺ on the pore surface. Through ion exchange, a uniform distribution of anionic metal complexes on the intrachannel surface of host silica was achieved. In this study, ethanol and water were used as solvent for HAuCl₄ precursor solutions impregnated on SBA-15 mesoporous silica. The solvent used can affect the size and location of the resulting nanoparticles. Large Au nanoparticles (15–43 nm) were found on the as-prepared Au/SBA-15 as observed by PXRD, XAS, UV–vis and TEM. This may have originated through Si–OH reduction of chloroaurate complexes generated in the aqueous solution of HAuCl₄, and such particles were not present when ethanolic solution was used. After NaBH₄ and H₂ reduction, the average size of Au nanoparticles, which was incorporated into the channels of SBA-15, was found to be limited to ≤  7 nm.     

Synthesis and sintering of tin-doped indium oxide nanoparticles with uniform size

The urea-based hydrothermal (UBH) method can synthesize indium tin oxide (ITO) nanopowders with good monodispersity and size uniformity. However, the resulting formation of high pressure CO₂ gas by the hydrolysis of urea during the hydrothermal process is unsafe. The pressure generated by the UBH method can be lowered by connecting the hydrothermal reactor to a vessel containing sodium hydroxide solution to quickly absorb CO₂ gas. ITO nanoparticles with particle sizes of 90 ± 3 nm and 40 ± 3 nm can be produced. The size of the as-prepared nanoparticles is readily controlled by adjusting the precursor concentration. Using properly mixed nanoparticles with a volume ratio of V_40 nm:V_90 nm = 30:70 as the raw materials, ITO can be sintered to a high and consistent density of 99.3–99.5% of the theoretical density.