Anna Modrzejewska-Sikorska

Deposition of silver nanoparticles on organically-modified silica in the presence of lignosulfonate

It is shown that the chemical reduction of silver ions by lignosulfonate (LS) in a mixed aqueous–organic solvent produces silver nanoparticles (AgNPs). If, additionally, spherical silica (SiO2) (surface-functionalized with various organic groups) is introduced to the reaction mixture, the LS-stabilized Ag-NPs are deposited on the surface of the silica spheres, forming a SiO2–LS–AgNPs hybrid material. The efficiency of the process is found to depend significantly on both the polarity of the organic solvent and the hydrophobicity of the SiO2-grafted functionalities. The most effective synthesis was in a mixed dimethylformamide–water solvent with octadecylsilane-functionalized SiO2. It is concluded that hydrophobic forces are essential for the successful coupling of LS–AgNPs with the surface of the modified silica. The formation of LS–AgNPs was monitored by UV-Vis spectroscopy, and the properties of the final hybrid materials were determined by EDS, elemental analysis, NIBS, TGA colorimetric analysis and HRTEM techniques. The resulting SiO2–LS–AgNPs hybrids were also used as SERS substrates with Rhodamine 6G as a test molecule.

Functionalization of organically modified silica with gold nanoparticles in the presence of lignosulfonate.

It is shown that lignosulfonate (LS) can be used as an effective reducing agent for gold ions and simultaneously as a stabilizing agent for gold nanoparticles (AuNPs). When organically modified silica is introduced to the reaction mixture, most of the AuNPs grow on the surface of the silica due to hydrophobic interactions between LS and organic layers covering the solid particles. It was also found that the structure of the organic layer is crucial for the effective deposition of gold nanoparticles onto silica spheres in terms of particle size and gold content in the final SiO2-LS-AuNPs composites. Due to the hydrophobicity of the modified silica it was necessary to carry out the modification in mixed organic/aqueous solvent. The polarity of the organic co-solvent was found to have an effect on the size of the deposited Au-NPs and their quantity. The physical appearance of the obtained hybrids was analyzed by colorimetry, and their structure and composition were evaluated using transmission electron microscopy (TEM). Additionally dispersive and thermal properties were examined by dynamic light scattering (DLS) and thermogravimetry (TG), respectively. The obtained multifunctional hybrid materials exhibits remarkable catalytic activity for the reduction of C.I. Basic Blue 9 (Methylene Blue) by borohydride.

Synthesis and characterisation of precipitated CuO · SiO2 oxide composites

Purpose – The purpose of this paper is to propose a new method of synthesis of CuO · SiO2 oxide composite based on the reaction of precipitation from water solutions of sodium silicate and copper nitrate.Design/methodology/approach – Solutions of sodium silicate and copper nitrate were used as substrates. The effects of direction of substrate supply, concentration, excess of reagents and temperature of precipitation on the physicochemical properties of the products were analysed.Findings – A new method of synthesis of CuO · SiO2 oxide composite based on a precipitation reaction is proposed.Research limitations/implications – Only sodium silicate and copper nitrate solutions were used.Practical implications – The CuO · SiO2 oxide composite obtained can be used as blue pigment or polymer filler.Originality/value – The paper determines optimum conditions of CuO · SiO2 oxide composite precipitation to obtain products with desired physicochemical, dispersive and structural properties.

Lignosulfonate-stabilized selenium nanoparticles and their deposition on spherical silica

We report a novel room-temperature synthesis of selenium nanoparticles, which for the first time uses lignosulfonate as a stabilizer. Various lignosulfonates obtained both from hardwood and softwood were tested. Selenium oxide was used as the precursor of zero-valent selenium. Three different reducers were tested - sodium borohydride, hydrazine and ascorbic acid - and the latter proved most effective in terms of the particle size and stability of the final colloid. The lignosulfonate-stabilized selenium nanoparticles had a negative zeta potential, dependent on pH, which for some lignosulfonates reached -50mV, indicating the excellent stability of the colloid. When spherical silica particles were introduced to the synthesis mixture, selenium nanoparticles were deposited on their surface. Additionally, star-like structures consisting of sharp selenium needles with silica cores were observed. After drying, the selenium-functionalized silica had a grey metallic hue. The method reported here is simple and cost-effective, and can be used for the preparation of large quantities of selenium colloids or the surface modification of other materials with selenium.

Synthesis of dextrin-stabilized colloidal silver nanoparticles and their application as modifiers of cement mortar

Various commercial dextrins were used as reducing and stabilizing agents for a novel one-step synthesis of silver nanoparticles from ammonia complexes of silver ions. As a result, stable colloids of silver were formed during the reaction with the particle size being the function of the dextrin type. The obtained colloids were characterized by UV-vis spectrophotometry, size distribution (using Non-Invasive Backscatter optics) and transmission electron microscopy (TEM). The achieved results clearly indicate the possibility of low-cost production of large quantities of colloidal silver nanoparticles using materials derived from renewable sources. The resulting silver colloids can be used for different purposes, e.g. as bactericidal agents. Combination of the aforementioned properties of nanosilver particles with plasticizing properties of dextrin enables to obtain cement mortars with increased workability and enhanced compressive strength. Moreover, the obtained material is also characterized by increased immunity to adverse impact of microorganisms.

Bakteriobójcza aktywność koloidów srebra stabilizowanych hydrolizatami skrobiowymi oraz ich wpływ na wytrzymałość zapraw cementowych

The article analyzes silver colloids stabilized with starch hydrolysates for their bactericidal properties as well as determining the size and shape of investigated colloids. The strength properties of cement mortars with the admixtures of the analyzed starch hydrolysates, sodium lignosulfonates and their combination with nanosilver were also investigated. To determine the presence of silver nanostructures, colloidal silver were analyzed