Host (nanodimensional pores of mesoporous material)–guest (semiconductor nanoparticles) nanocomposite materials

An aluminosilicate with the MCM-41 structure (AlMCM-41) was used as a host for the synthesis of cobalt sulfide nanoparticles. Cobalt sulfide nanoparticles were introduced in host by ion exchange and hydrothermal methods. Products (CoSAlMCM-41) were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), EDX, IR, BET and UV–vis spectroscopy. The results show that CoS nanoparticles encapsulated into channels of AlMCM-41 material by hydrothermal synthesis and they grow outside the mesopore AlMCM-41 matrix by ion-exchange methods. Absorption peaks at higher energy than the fundamental absorption edge of bulk CoS indicate quantum confinement effect in nanoparticles as a consequence of their small size. The absorption spectra show that the optical band gap for CoS nanoparticles by hydrothermal and ion-exchange methods are 3.73 and 4.89, respectively.     

Preparation of high nickel-containing MCM-41-type mesoporous silica via a modified direct synthesis method

A method with modifying tetraethyl orthosilicate (TEOS) with nickel species has been developed for the synthesis of mesoporous silica with high nickel content (11.8 wt.% of Ni or even higher). With the method, MCM-41-type materials were obtained with high BET surface area reaching 868 m²/g and pore volume up to 0.73 cm³/g. The materials were characterized by means of X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, N₂ adsorption, Fourier transform infrared and X-ray photoelectron spectroscopy. Nickel species were incorporated into the silica frameworks. The mesostructures still remain after activation using H₂ at 773 K.     

Photocatalytic degradation of basic blue 9 by CoS nanoparticles supported on AlMCM-41 material as a catalyst

In this investigation photocatalytic degradation of basic blue 9 or methylene blue (MB) as color pollutants was studied. Cobalt sulfide was supported on AlMCM-41 material using ion-exchange method. The results show that CoS/AlMCM-41 is an active photocatalyst. The catalyst is characterized by X-ray diffraction (XRD) UV–vis diffused reflectance spectra (UV–vis DRS) and scanning electron microscopy (SEM) techniques. The maximum effect of photodegradation was observed at 7 wt% CoS/AlMCM-41. Pseudo-first order reaction with k = 0.032 was observed for the photocatalytic degradation reaction. The effect of some parameters such as pH, amount of photocatalyst and initial concentration of dye were also examined. The effect of dosage of photocatalyst was studied in the range 0.04–1.2 g/L. It was seen that 0.8 g/L of photocatalyst is an optimum value for the dosage of photocatalyst. In the best conditions, the degradation efficiency was obtained 0.32 ppm for MB dye.     

Plasmachemical synthesis of maghemite nanoparticles in atmospheric pressure microwave torch

The powder of γ − Fe₂O₃ nanoparticles was synthesized in microwave torch at atmospheric pressure from 0.05 sccm of Fe(CO)₅ vapors in 670 sccm of argon. The optimization of the torch reactor design and deposition conditions allowed continual synthesis of γ − Fe₂O₃ nanoparticles at low power consumption. The synthesized powder was collected at the reactor walls and analyzed by TEM, X-ray diffraction and Raman spectroscopy without any further purification or treatment. The mean diameter of NPs, as observed by TEM, was 12 nm with a 90% confidence interval 5.5-22 nm.     

Acylisoxazolone-impregnated Si-MCM-41 mesoporous materials as promising liquid-solid extractants of metals

The solid-liquid extraction of Cu(II) from 0.33 M (Na⁺, H⁺)SO₄²⁻ sulphate medium at 25 °C by calcined mesoporous materials type Si-MCM-41, impregnated by the acidic extractant 3-phenyl-4-benzoyl-isoxazol-5-one (HPBI), has been tested. The Si-MCM-41 material was impregnated by HPBI using the dry impregnation method. It was characterized by physico-chemical methods: N₂-sorption, XRD, SEM and determination of the amount of HPBI in the solid. The extraction rate was determined as a function of pH and extractant concentration in the material. The extraction of Cu(II) into impregnated mesoporous material can reach 99%.     

Silica materials recovered from photonic industrial waste powder: its extraction, modification, characterization and application

This study explored the possibility of recovering waste powder from photonic industry into two useful resources, sodium fluoride (NaF) and the silica precursor solution. An alkali fusion process was utilized to effectively separate silicate supernatant and the sediment. The obtained sediment contains purified NaF (>90%), which provides further reuse possibility since NaF is widely applied in chemical industry. The supernatant is a valuable silicate source for synthesizing mesoporous silica material such as MCM-41. The MCM-41 produced from the photonic waste powder (PWP), namely MCM-41(PWP), possessed high specific surface areas (1082 m²/g), narrow pore size distributions (2.95 nm) and large pore volumes (0.99 cm³/g). The amine-modified MCM-41(PWP) was further applied as an adsorbent for the capture of CO₂ greenhouse gas. Breakthrough experiments demonstrated that the tetraethylenepentamine (TEPA) functionalized MCM-41(PWP) exhibited an adsorption capacity (82 mg CO₂/g adsorbent) of only slightly less than that of the TEPA/MCM-41 manufactured from pure chemical (97 mg CO₂/g adsorbent), and its capacity is higher than that of TEPA/ZSM-5 zeolite (43 mg CO₂/g adsorbent). The results revealed both the high potential of resource recovery from the photonic solid waste and the cost-effective application of waste-derived mesoporous adsorbent for environmental protection.     

Metal nanocrystal memory with sol-gel derived HfO2 high-κ tunnel oxide

An all-solution processed metal-oxide-semiconductor (MOS) capacitor structure containing gold (Au) nanoparticles (NPs) within HfO₂ high-κ oxide was fabricated. The ultra-thin (~ 10 nm) HfO₂ high-κ tunnel oxide layer was prepared by sol-gel process and showed good electrical properties, which were critical to superior memory property of the MOS structure. Au NPs with particle size of about 3.3 nm were synthesized by chemical reduction method and then self-assembled onto HfO₂ tunnel oxide. Finally, a Si/HfO₂/Au NPs/HfO₂ memory structure was constructed after the substrate had been covered with a sol-gel-derived HfO₂ control oxide layer (~ 13 nm). By utilizing high-quality HfO₂ as tunnel oxide, the MOS structure containing Au NPs showed memory effect even at a low voltage of ± 3 V. Although its memory window was only 0.8 V by a swapping voltage between ± 5 V, the MOS showed desirable retention characteristics. Therefore, we have fabricated nanocrystal memory device with sol-gel derived HfO₂ high-k tunnel oxide which are attractive for low operation voltage non-volatile memory applications.     

Physicochemical characterization of Fe3O4/SiO2/Au multilayer nanostructure

The purpose of this research was to synthesize and characterize gold-coated Fe₃O₄/SiO₂ nanoshells for biomedical applications. Magnetite nanoparticles (NPs) were prepared using co-precipitation method. Smaller particles were synthesized by decreasing the NaOH concentration, which in our case this corresponded to 35 nm using 0.9 M of NaOH at 750 rpm with a specific surface area of 41 m² g⁻¹. For uncoated Fe₃O₄ NPs, the results showed an octahedral geometry with saturation magnetization range of 80–100 emu g⁻¹ and coercivity of 80–120 Oe for particles between 35 and 96 nm, respectively. The magnetic NPs were modified with a thin layer of silica using Stober method. Small gold colloids (1–3 nm) were synthesized using Duff method and covered the amino functionalized particle surface. Magnetic and optical properties of gold nanoshells were assessed using Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM), UV–Vis spectrophotometer, atomic and magnetic force microscope (AFM, MFM), and transmission electron microscope (TEM). Based on the X-ray diffraction (XRD) results, three main peaks of Au (1 1 1), (2 0 0) and (2 2 0) were identified. The formation of each layer of a nanoshell is also demonstrated by Fourier transform infrared (FTIR) results. The Fe₃O₄/SiO₂/Au nanostructures, with 85 nm as particle size, exhibited an absorption peak at ∼550 nm with a magnetization value of 1.3 emu g⁻¹ with a specific surface area of 71 m² g⁻¹.     

Electrical memory features of ferromagnetic CoFeAlSi nano-particles embedded in metal-oxide-semiconductor matrix

Half-metallic Heusler material Co₂FeAl_0.5Si_0.5 (CFAS) nano-particles (NPs) embedded in metal-oxide-semiconductor (MOS) structures with thin HfO₂ tunneling and MgO control oxides were investigated. The CFAS NPs were prepared by rapid thermal annealing. The formation of well-controlled CFAS NPs on thin HfO₂ tunneling oxide was confirmed by atomic force microscopy (AFM). Memory characteristics of CFAS NPs in MOS devices exhibited a large memory window of 4.65 V, as well as good retention and endurance times of 10⁵ cycles and 10⁹ s, respectively, demonstrating the potential of CFAS NPs as promising candidates for use in charge storage.     

Size and morphology controlled synthesis of gold nanoparticles in green solvent: Effect of reducing agents

The effect of reducing agents on the synthesis of Au(0) metallic nanoparticles (Au NPs) prepared in green solvent medium of β-d-glucose-water dispersions has been reported first. The different equivalent amounts of NaBH₄ and pH values adjusted by NaOH were tested for the reduction of Au salt (HAuCl₄·3H₂O (hydrogen tetrachloroaurate (III) trihydrate) to obtain Au NPs. The type and the amount of reducing agent and the pH of the solution affected the size and morphology of the NPs. Addition of 4 equivalents of NaBH₄ produced homogeneously dispersed 5.3 nm (σ = 0.7) diameter particles. Excess addition of NaBH₄ caused the NPs to settle down as the precipitate forming mesh or wire structure. When salt was reduced by the addition of NaOH (pH = 8.0) the particles were larger (14.2 nm) and less homogeneous (σ = 2.8). At pH = 12.2 the NPs settled at the bottom of the vial when preparation was left overnight. The wire and mesh like structures were obtained at higher pH = 12.2.     

Ar assisted carbidization of TiO2 (1 1 0) supported Mo nanoparticles by decomposition of C2H4

Ar⁺ assisted carbidization of Mo nanoparticles supported on TiO₂ (1 1 0) is studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In order to activate the diffusion of carbon into the bulk of Mo nanoparticles we applied Ar ions (1 keV) during the exposure of C₂H₄. XPS exhibited that the decomposition of C₂H₄ at 850 K accompanied by ion bombardment results in an almost complete carbidization of nanocrystalline Mo while this treatment performed without ion bombardment results only in the carbidization of the particle surface. The modification of the crystallinity of the Mo-carbide particles was deduced from STM measurements.     

Synthesis and characterization of novel magnetically separable NiFe2O4@AlMCM-41-Cu2O core-shell and its performance in removal of dye

The synthesis of magnetic NiFe₂O₄@AlMCM-41-Cu₂O core-shell as a new class of visible light driven photocatalyst was suggested. The magnetic NiFe₂O₄ core was prepared by solvothermal method. The intermediate AlMCM-41 shell was prepared by the method of liquid crystal templating mechanism and subsequently cuprous oxide (Cu₂O) nanoparticles (NPs) were synthesized in NiFe₂O₄@AlMCM-41core-shell via colloidal chemistry approach. The properties of prepared magnetic core-shell were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption–desorption measurement and vibration sample magnetometer (VSM). Based on EDX results, the weight percentage (wt%) of NiFe₂O₄ core, MCM-41 shell and Cu₂O NPs were calculated to be 68.89, 30.55 and 0.56%, respectively. It consisted of mesoporous structure with a surface area of 687.00 m² g^?1, an average pore size of 2.95 nm and possessed excellent magnetic properties of 4.74 emu g^?1. The TEM results indicated that the NiFe₂O₄ as core were regular spheres with diameter of 68 nm, and the average thickness of AlMCM-41 shells was ～35 nm. The particles size of Cu₂O incorporated in core-shell was less than 5 nm. The photocatalytic activity was evaluated under visible light irradiation using the removal of methylene blue (MB) dye as a model reaction. The removal rate of MB achieved up to 90% after 60 min under visible light irradiation, and the NiFe₂O₄@AlMCM-41-Cu₂O can be recycled and reused.     

A facile route to sonochemical synthesis of magnetic iron oxide (Fe3O4) nanoparticles

A facile sonochemical approach was applied for the large scale synthesis of iron oxide magnetic nanoparticles (NPs) using inexpensive and non-toxic metal salts as reactants. The as-prepared magnetic iron oxide NPs has been characterized by XRD, TEM, EDS, and VSM. X-ray diffraction (XRD) and EDS analysis revealed that Fe₃O₄ NPs have been successfully synthesized in a single reaction by this simple method. Transmission electron microscopy (TEM) data demonstrated that the particles were narrow range in size distribution with 11 nm average particle size. Moreover, TEM measurements also show that the synthesized nanoparticles are almost spherical in shape. The magnetization curve from vibrating sample magnetometer (VSM) measurement shows that as-synthesized NPs were nearly superparamagnetic in magnetic properties with very low coercivity, and magnetization values were 80 emu/g, which is very near to the bulk value of iron oxide. The estimated value of mass susceptibility of as-synthesized nanoparticles is Xg = 5.71 × 10^− 4 m³/kg.     

Low-temperature and ambient-pressure synthesis of TiO2(B)

Nanocrystalline TiO₂(B) powder was obtained by the hydrolysis of an ionic liquid like titania precursor (the triethylammonium salt of hexafluorotitanate) induced by the addition of boric acid in the presence of dopamine. The entire synthetic procedure was carried out at ambient pressure and low temperature (85 °C). X-ray diffraction, high resolution transmission electron microscopy and selected area electron diffraction characterization techniques confirmed the formation of the TiO₂(B) phase. Moreover, Raman spectroscopy indicated that TiO₂(B) was the major component, although it also revealed the presence of anatase as a minor component (< 10%). The as-prepared material has a mesoporous architecture with high specific surface area (235 m² g^− 1).     

Formation of metallic vanadium nanoparticles in SiO2 by ion implantation and of vanadium oxide nanoparticles by additional thermal oxidation

Metallic V nanoparticles (NPs) were formed in silica glass by implantation with V⁺ ions of 60 keV to a fluence of 1.0 × 10¹⁷ ions/cm². Annealing in oxygen gas at 800 °C transformed the metallic NPs to oxide NPs. While the mean diameter of the metal V NPs was 8.4 nm in the as-implanted state, the diameters steeply increased during oxidation, with some exceeding 100 nm. Since at least 15 different composition phases, such as V₂O₃, V₃O₇, V₆O₁₃, V₉O₁₇, etc., are known for vanadium oxides, identification of the oxide phase of the NPs was not easy. X-ray diffraction (XRD) was not a powerful tool for phase identification of the NPs, because the diffraction peaks were broad due to the nanometric sizes of the particles and readily shift due to stress effects. The temperature dependence of the optical absorption spectrum was measured. The observed spectra were almost unchanged between 3.3 and 370 K. Combining the spectral result and the XRD results, the candidates were narrowed down to three phases, V₂O₅, V₄O₉, and V₇O₁₃, from the 15 candidates. Among the three, the V₂O₅ phase is the most probable because the absorption spectrum and the oxygen partial pressure for its formation were both consistent.     

Void formation in silica glass induced by thermal oxidation after Zn ion implantation

Thermal annealing effects on Zn⁺ ion-implanted silica glass (a-SiO₂) have been studied in order to control void formation. Void formation in a-SiO₂ with Zn⁺ ion implantation and subsequent oxidation has been observed using transmission electron microscopy (TEM). Zn⁺ ions of 60 keV were implanted into a-SiO₂ to a fluence of 1.0 × 10¹⁷ ions/cm². After the implantation, thermal annealing at 600 or 700 °C for 1 h in oxygen gas was conducted. In as-implanted state, metal Zn nanoparticles (NPs) of 10-15 nm in diameter are formed in the depth region around the projected range. The size of the Zn nanoparticles increases after the annealing at 600 °C in oxygen gas. Annealing in oxygen gas at 700 °C for 1 h caused two processes: (1) the migration of Zn atoms which formed Zn NPs in as-implanted state to the surface of the a-SiO₂ substrate and (2) the transformation to the oxide phase on the substrate. The transportation of Zn NPs to the surface leaves voids of 10-25 nm in diameter inside the a-SiO₂. These results indicate that the oxidation at 700 °C for 1 h causes the migration of Zn atoms to the surface without diffusion and recombination of vacancies which form the voids.     

Structural and magnetic properties of Mn nanoparticles prepared by arc-discharge

Mn nanoparticles are prepared by arc discharge technique. MnO, α-Mn, β-Mn, and γ-Mn are detected by X-ray diffraction, while the presence of Mn₃O₄ and MnO₂ is revealed by X-ray photoelectron spectroscopy. Transmission electron microscopy observations show that most of the Mn nanoparticles have irregular shapes, rough surfaces and a shell/core structure, with sizes ranging from several nanometers to 80 nm. The magnetic properties of the Mn nanoparticles are investigated between 2 and 350 K at magnetic fields up to 5 T. A magnetic transition occurring near 43 K is attributed to the formation of the ferrimagnetic Mn₃O₄. The coercivity of the Mn nanoparticles, arising mainly from Mn₃O₄, decreases linearly with increasing temperature below 40 K. Below the blocking temperature T_B ≈ 34 K, the hysteresis loops exhibit large coercivity (up to 500 kA/m), owing to finite size effects, and irreversibility in the loops is found up to 4 T, and magnetization is not saturated up to 5 T. The relationship between structure and the magnetic properties are discussed.     

Ag nanoparticle incorporation in mesoporous silica synthesized by solution plasma and their catalysis for oleic acid hydrogenation

The incorporation of Ag nanoparticles on mesoporous silica as the supporting material and their catalysis for oleic acid hydrogenation were described in this study. The template removal and Ag nanoparticle incorporation were concurrently taken place in the novel glow discharge in a solution, namely solution plasma process under controlled conditions. With only 15 min of discharge time, Ag nanoparticles were incorporated on the mesoporous silica matrix confirmed by the evidences of XRD and TEM and the template inside mesopores was mostly removed confirmed by FTIR spectra. The hydrogenation catalysis of oleic acid was preliminarily tested using UV-VIS spectroscopy after oxidation using permanganate ions (MnO₄⁻). It was found that the conversion was observed to be 12.83% in the butanol system and reached to 90.56% in ethanol.     

Chemiluminescence immunoassay based on dual signal amplification strategy of Au/mesoporous silica and multienzyme functionalized mesoporous silica

A chemiluminescent dual signal amplification strategy for the determination of α-fetoprotein (AFP) was proposed based on a sandwich immunoassay format. Monoclonal antibody of AFP immobilized on the gold nanoparticles doped mesoporous SiO₂ (Au/SiO₂) were prepared and used as a primary antibody. Horseradish peroxidase (HRP) and HRP-labeled secondary antibody (Ab₂) co-immobilized into the mesoporous SiO₂ nanoparticles (HRP-Ab₂/SiO₂) were used as the labeled immunological probe. Due to the high ratio surface areas and pore volumes of the mesoporous SiO₂, not only the amount of AFP monoclonal antibody but also the amount of the modified HRP and Ab₂ in HRP-Ab₂/SiO₂ were largely increased. Thus the chemiluminescent signal was amplified by using the system of luminol and H₂O₂ under the catalysis of HRP. Under the optimal conditions, two linear ranges for AFP were obtained from 0.01 to 0.5 ng mL⁻¹ and 0.5 to 100 ng mL⁻¹ with a detection limit of 0.005 ng mL⁻¹ (3σ). The fabricated signal amplification strategy showed an excellent promise for sensitive detection of AFP and other tumor markers.     

Formation of CdS nanoparticles by gas-diffusion method in sol–gel derived ureasilicate matrix

CdS nanoparticles (NPs) were prepared by exposing a hybrid ureasilicate gel containing cadmium (II) ions to H₂S gas at room temperature. Additional component (tetraethoxysilane) was introduced during the synthesis in order to improve the mechanical properties of the host matrix. The obtained material was subsequently subjected to an annealing treatment under an argon atmosphere at temperatures that varied from 43 to 102 °C. The size of the embedded NPs increased with thermal annealing. The optical absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM) measurements confirmed the formation of CdS nanoparticles (NPs) exhibiting quantum confinement effect.