Relationship between size of cadmium sulfide nanoparticles and water pool diameter in reverse micelles

Preparation of CdS nanoparticles in water-sodium bis(2-ethylhexyl) sulfosuccinate-isooctane reverse micelles with various water contents is studied. A direct correlation between the water pool diameter in the reverse micelles and the mean size of CdS nanoparticles is found.     

Preparation of cadmium sulfide nanoparticles in self-reproducing reversed micelles

Octyl octanoate (O-OL) underwent hydrolysis in sodium octanoate (NaOA) reversed micelles in 85:15 = isooctane:octanol (OL) (v/v), containing w = [H2O]/[NaOA] = 40. The products of the hydrolysis, octanoic acid (OA) and octanol (OL), lead to the formation of additional (albeit smaller) reversed micelles; hence the process is considered to be self-reproducing. Self-reproduction was found to be catalyzed by lithium hydroxide, solubilized in the water pools, as well as by hydrogen sulfide, added to the solution of the reversed micelles. Addition of hydrogen sulfide to cadmium perchlorate containing self-reproducing reversed micelles resulted in the formation of cadmium sulfide (CdS) nanoparticles. Diameters of the CdS containing nanoparticles could be altered from 5.4 to 1.8 nm by changing the [Cd2+]/[H2S] ratios from 0.25 to 10. The CdS nanoparticles formed were capped by mercaptopropionic acid, isolated as solids, and could be repeatedly redispersed in water without changing their sizes. Additional CdS nanoparticles were generated in the supernatants removed from the precipitated capped CdS nanoparticles.     

Spectroluminescent properties of cadmium selenide nanoparticles synthesized in AOT reverse micelles

Cadmium selenide nanoparticles have been synthesized in solutions of AOT/water/n-heptane reverse micelles with average micelle water pool diameters of 25, 30, and 47 Å using cadmium sulfate (CdSO₄) and sodium selenosulfate (Na₂SeSO₃) as precursors. Absorption and fluorescence spectra of the obtained nanoparticles were recorded. The picosecond dynamics of fluorescence decay over the entire range of their emission band have been investigated by time-resolved fluorescence spectroscopy. A procedure for the stabilization of nanoparticles by dodecanethiol was developed for electron microscopy analysis.     

Photochemical synthesis of cadmium sulfide nanoparticles

The formation of cadmium sulfide nanoparticles upon UV irradiation of aqueous solutions of cadmium thiosulfates was established on the basis of spectroscopic and macroscopic data. The yield and size of the cadmium sulfide nanoparticles depend on the ratio of cadmium to thiosulfate ions in solution, the concentration of the solution, and the irradiation duration. The cadmium sulfide nanoparticles with a diameter of 4 nm were obtained by the photolysis of solutions with a concentration of 10⁻³ mol L⁻¹ at the ratio S₂O₃ ²⁻: Cd²⁺ = 2: 1.     

Specifics of the preparation of anisotropically shaped gold nanoparticles in triton X-100 reverse micelles

The influence of the form of micelles and reactant concentrations on the formation and growth of gold nanoparticles in reverse micelles based on Triton X-100 (polyoxyethylene octyl phenyl ether) was studied. It was shown that spherical nanoparticles of 3–4 nm in size are formed in the presence of sodium sulfite and ascorbic acid and particles of an extended shape are formed in the presence of ascorbic acid alone. It was found that the ultimate shape and size of the nanoparticles depend not only upon the form of micelles but also on the acid concentration, since the products of its oxidation can be selectively sorbed on the surface of the particles and act as additional shape modifiers.     

Tuning the properties of CdSe nanoparticles in reverse micelles

A new and simple approach of synthesizing size-quantized CdSe colloids in reverse micellar suspension is described. The room temperature reaction between Cd²⁺ and selenosulfate is carried out within the water pool of di-octyl sulphosuccinate (Aerosol-OT) reverse micelles. The size dependent absorption and emission properties of these small CdSe particles (3—5 nm) are described. The Q-sized CdSe nanoparticles exhibit an emission yield of 0.13. Up to a factor of two enhancement in the emission efficiency can be achieved following the surface functionalization of CdSe colloids with triethyl amine.     

Effect of dioctyl sulfide on the kinetics of oxidative dissolution of gold nanoparticles in triton N-42 reverse micelles

The effect of additions of hydrophobic dioctyl sulfide (L) on the kinetics of dissolution of gold nanoparticles in the interaction with a dispersed aqueous hydrochloric solution of H₂O₂ in Triton N-42 reverse micelles (decane was the dispersion medium) was studied spectrophotometrically. The process consists of a two-stage oxidation Au⁰ → AuCl₂⁻ → AuCl₄⁻ at the surface of gold particles; the first stage occurs in two ways: a spontaneous reaction and an autocatalytic reaction involving AuCl₄⁻ ions. With small additions of L (c _L < c _Au), only spontaneous oxidation of Au(0) to Au(I) takes place because Au(I) is completely bound in an inert complex AuLCl. When unbound L is exhausted, the newly formed AuLCl is accumulated in micellar shells, changes the properties of the medium inside the micelles, and affects the rate constant of the autocatalytic reaction, which increases with increasing c _L. At high concentrations of L, the coagulation of particles occurs instead of their dissolution, because of the deterioration of the protective properties of micellar shells as a result of the ingression and accumulation of dioctyl sulfide molecules on account of selective adsorption on gold particles. The rate constants of all stages of dissolution and coagulation are determined.     

Properties and biocompatibility of colloid cadmium sulfide nanoparticles

The properties and cytotoxicity of aqueous colloidal solutions of cadmium sulfide CdS nanoparticles obtained by chemical condensation were explored. Dynamic light scattering and optical spectroscopy were used to study the hydrodynamic diameter, size distribution, zeta-potential and optical properties of the CdS nanoparticles in solution. The cytotoxicity of colloidal CdS nanoparticles at different concentrations was assessed on cultures of human dermal fibroblasts and the cancer HeLa line.     

Biochemical synthesis of gold and zinc nanoparticles in reverse micelles

Gold and zinc nanoparticles were obtained in AOT reverse micelles in isooctane by reduction of the corresponding metal ions by the natural pigment quercetin (the biochemical synthesis technique). Gold and zinc ions were introduced into the micellar solution of quercetin in the form of aqueous solutions, HAuCl₄ and [Zn(NH₃)₄]SO₄, to the water to AOT molar ratios 1–3 and 3–4, respectively. The process of nanoparticle formation was investigated by spectrophotometry. Nanoparticle size and shape were determined by transmission electron microscopy. The data obtained allow to conclude that there are two steps in metal ion-quercetin interaction: (1) complex formation, and (2) complex dissociation with subsequent formation of nanoparticles and a second product, presumably oxidized quercetin. Gold nanoparticles were found to be of various shapes (spheres, hexahedrons, triangles, and cylinders) and sizes, mainly in the 10–20 nm range; zinc nanoparticles are chiefly spherical and ～5 nm in size. In both cases, the nanoparticles are stable in the air in micellar solution over long periods of time (from a several months to a several years).     

Formation dynamics of reverse micelles and nanosized effects that accompany chemical reduction of silver nanoparticles in them

Dynamic light scattering has been employed to study the time evolution of a sodium bis(2-ethylhexyl) sulfosuccinate/isooctane/water/quercetin/AgNO₃ system during the formation of reverse micelles (RMs), as well as water solubilization and formation of Ag nanoparticles (NPs) in them. It has been shown that physicochemical processes occurring in the reverse micellar system lead to the formation of light-scattering elements with average sizes of 0.67?2 nm (individual molecules of the surfactant and reductant), 2.5?4.5 nm (“dry” RMs) and 16?20 nm (RMs containing Ag NPs). The synthesis is accompanied by the formation of silver NPs with other sizes in an amount of less than 5%.     

AHOT/异辛烷反胶束体系制备铁酸钴纳米粒子

分别以阴离子表面活性剂二(2-乙基己基)丁二酸酯磺酸钠(AOT)和新型表面活性剂二(2-乙基己基)羟基丁二酸酯磺酸钠(AHOT)与异辛烷/水构建的反胶束体系为微反应器,合成了CoFe2O4纳米粒子;利用TGA,XRD,TEM等手段对产物进行了表征;讨论了两种表面活性剂构建的反胶束体系对产物合成过程及纳米粒子形貌和尺寸的影响.     

The preparation of gold nanoparticles in triton N-42 reverse micelles after preliminary concentration from acid sulfate-chloride solutions

The distribution of Au(III) between an acid (3 mol/l HCl) aqueous phase and a micellar Triton N-42 solution in n-decane was studied as a function of the concentration of Na₂SO₄ (0–3.55 mol/l). The high distribution coefficients (200–500) allow 50-fold absolute concentration to be performed at a 90% extraction. Au⁰ nanoparticles were obtained by the injection solubilization of a reducing agent (hydrazine) into micellar extracts. At low solubilization capacities (≤1 vol %) and high reducing agent concentrations (≥0.2 mol/l) in Triton N-42 micelles, stable systems of Au⁰ nanoparticles suitable for the spectrophotometric determination of gold were obtained. At high solubilization capacities and low hydrazine concentrations, reduction was accompanied by coagulation and sedimentation processes. These processes were studied by spectrophotometry and the static and dynamic light scattering methods.     

Luminescence of polymer composite materials with cadmium sulfide nanoparticles

The structure and optical characteristics of CdS nanoparticles synthesized in low-density polyethylene were studied. The particles have a hexagonal structure of the greenockite type; the presence of the cubic phase is also possible. The position of the absorption edge slightly depends on the average size of particles because of their polydispersity. It has been shown that the luminescence spectra of nanoparticles are strongly distorted by scattering and self-adsorption in the samples. To correct the spectra, a program for Monte-Carlo simulation of luminescence propagation in the samples was developed. It was shown that the luminescence band at 500–550 nm in the experimental spectra might be spurious because of luminescence absorption in the edge region.     

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.     

Thermochemicstry of the oxidative dissolution of silver nanoparticles in AOT reverse micelles

A procedure has been developed for thermochemical studies of two types of silver nanoparticles: coagulated nanoparticles in isolated nanopowders and unbound nanoparticles enclosed in micelles. The first type of nanoparticle was obtained and studied after destroying micelles. The heats and rates of dissolution of unbound nanoparticles (i.e., nanoparticles enclosed in micelles and involved in Brownian motion together with the latter) were determined by reacting them with nitric acid solubilized in micelle systems of the same composition. The heats of solution of Ag⁰ in HNO₃ found for isolated nanopowders were ?10 × (1 ± 0.3) kJ/mol; they were close to the results obtained for bulk samples under the same conditions. The heats of solution of nanoparticles in micelles were estimated at ?(17–25) kJ/mol. The dissolution rates of silver nanoparticles in micelles as functions of micelle composition were two to three times the dissolution rates of isolated nanopowders.     

Synthesis of TiO2 nanoparticles utilizing hydrated reverse micelles in CO2

Titanium dioxide nanoparticles were produced by the controlled hydrolysis of titanium tetraisopropoxide (TTIP) in the presence of reverse micelles formed in CO2 with the surfactants ammonium carboxylate perfluoropolyether (PFPECOO-+NH4) (Mw = 587) and poly(dimethyl amino ethyl methacrylate-block-1H,1H,2H,2H-perfluorooctyl methacrylate) (PDMAEMA-b-PFOMA). Based on dynamic light scattering measurements, the amorphous TiO2 particles formed by injection of TTIP are larger than the reverse micelles, indicating surfactant reorganization. The size of the particles and the stability of dispersions in CO2 were affected by the molar ratio of water to surfactant headgroup (w(o)), precursor concentration, and injection rate. The amorphous particle size did not change upon depressurization and redispersion in CO2. PDMAEMA-b-PFOMA provided greater stability against particle aggregation at higher reactant concentration compared with PFPECOO-+NH4. The crystallite size after calcination, which was examined by X-ray diffraction and transmission electron microscopy, increased with w(o).     

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.     

Preparation of mesoporous cadmium sulfide nanoparticles with moderate pore size

The preparation of cadmium sulfide nanoparticles that have a moderate pore size is reported. This preparation method involves a hydrothermal process that produces a precursor mixture and a following acid treatment of the precursor to get the porous material. The majority of the particles have a pore size close to 20 nm, which complements and fills in the gap between the existing cadmium sulfide materials, which usually have a pore size either less than 10 nm or are well above 100 nm.     

Functionalization of (CdSe)ZnS nanoparticles in reverse micelles of Aerosol OT

A method is optimized for in situ functionalization and activation of (CdSe)ZnS nanoparticles in reverse micelles of Aerosol OT, as well as their conjugation with antibodies. The efficiency of particle functionalization depends on the method of micellar solution formation. Fluorescence remains practically unchanged, provided that NH₂ groups of polymers bonded to the nanoparticles are activated by glutaric aldehyde. All operations of antibody conjugation should be carried out in reverse micelles for the maximum preservation of the fluorescence properties of the particles. Nanoparticles are isolated from reverse micelles using a mixture of acetone with a solution composed of 50 mM NaHCO₃ and 200 mM NaCl. The optimum medium for dissolving the precipitate of the particles consists of NaHCO₃ (50 mM), bovine serum albumin (0.1%), and Twin 85 (0.05%). The modified particles were subjected to photoactivation in an aqueous medium at room temperature and daylight.