Formation Of Silica Nanoparticles Research Articles

Solidification of a Silica-Based Solid Composite Electrolyte for Lithium-Ion Batteries Induced By UV Irradiation

The use of solid electrolytes in lithium-ion batteries (LIBs) instead of their liquid counterparts may significantly increase their energy density. Of particular interest are solid composite electrolytes (SCEs) which can be synthesized by incorporating ionic liquids (ILs, salts with a melting point lower than 100 °C) into a solid matrix. This class of SCE can have a wide electrochemical stability window and is typically non-flammable.Chen et al.1 developed an SCE with excellent ionic conductivity, consisting of a mesoporous silica monolith which encloses an IL electrolyte (solid nanocomposite electrolyte or nano-SCE). It is formed from a precursor solution which does not contain acids such as formic acid or HCl, meaning that it can be impregnated into porous electrodes without causing damage to the latter. However, its gelation process is long and variable (5-9 days), and is considerably affected by its presence within the electrode. As such, the nano-SCE has poor manufacturability and is not compatible with the continuous roll-to-roll processing typically used for LIB manufacturing. The manufacturability of the nano-SCE can be significantly improved by making its solidification process instantaneous upon subjection to an external trigger.As such, organic modification was used to produce silica-based precursor solutions capable of triggered solidification, for instance by irradiation with UV light. This solidification process takes a few minutes to complete and does not depend on pH, rendering it particularly versatile. The aging of the precursor solutions was studied with 29Si, 1H, and 13C NMR spectroscopy, which revealed that the alkoxysilane precursor molecules condensed into larger soluble structures over the course of five weeks. The aged precursor solutions remained stable over an indefinite period of time. When a photo-initiator is added to these solutions and they are irradiated with UV light, the soluble structures are linked together, resulting in the formation of silica nanoparticles which subsequently aggregate into a porous matrix which encapsulates the ionic liquid electrolyte (ILE).The adaptation does not compromise the functional properties such as ionic conductivity or electrochemical stability. As determined with Raman spectroscopy, the extent of organic modification and amount of ILE can be optimized to decrease the interaction of lithium ions with the other ions as compared to the neat ILE. The increased Li+ mobility means that the SCE can reach higher ionic conductivity (2.7 mS cm-1 at 20 °C) values than the neat ILE (2.5 mS cm-1). Anodic and cathodic linear sweep voltammetry in three-electrode cells was performed to determine that the SCEs can have an electrochemical stability window exceeding 5 V (i.e. lithium plating < 0 vs Li+/Li and electrolyte oxidation > 5.0 V vs Li+/Li). Electrochemical impedance spectroscopy further confirmed the SCE’s compatibility with lithium metal. As no acids are added to the precursor solution, a good electrode compatibility is expected. As such, the precursor solutions were impregnated into NMC622-based electrodes, solidified, and incorporated in half cells. These cells had an initial discharge capacity of 162 mAh g-1 at 0.1 C, retaining 86.8% of this capacity after 100 cycles.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Solidify project under grant agreement No. 875557.(1) Chen, X.; Put, B.; Sagara, A.; Gandrud, K.; Murata, M.; Steele, J. A.; Yabe, H.; Hantschel, T.; Roeffaers, M.; Tomiyama, M.; et al. Silica Gel Solid Nanocomposite Electrolytes with Interfacial Conductivity Promotion Exceeding the Bulk Li-Ion Conductivity of the Ionic Liquid Electrolyte Filler. Sci. Adv. 2020, 6 (2). https://doi.org/10.1126/sciadv.aav3400.

Polymeric nanocomposite hydrogel scaffold for jawbone regeneration: The role of rosuvastatin calcium-loaded silica nanoparticles

Bones are subject to different types of damages ranging from simple fatigue to profound defects. In serious cases, the endogenous healing mechanism is not capable of healing the damage or restoring the normal structure and function of the bony tissue. The aim of this research was to achieve a sustained delivery of rosuvastatin and assess its efficacy in healing bone tissue damage. Rosuvastatin was entrapped into silica nanoparticles and the system was loaded into an alginate hydrogel to be implanted in the damaged tissue. Silica nanoparticles were formulated based on a modified Stöber technique and alginate hydrogel was prepared via sprinkling alginate onto silica nanoparticle dispersion followed by addition of CaCl2 to promote crosslinking and hydrogel rigidification. The selected nanoparticle formulation possessed high % drug content (100.22±0.67%), the smallest particle size (221.00±7.30 nm) and a sustained drug release up to 4 weeks (98.72±0.52%). The fabricated hydrogel exhibited a further delay in drug release (81.52±4.81% after 4 weeks). FT-IR indicated the silica nanoparticle formation and hydrogel crosslinking. SEM visualized the porous and dense surface of hydrogel. In-vivo testing on induced bone defects in New Zealand rabbits revealed the enhanced rate of new bone tissue formation, its homogeneity in color as well as similarity in structure to the original tissue.

Silica Nanoparticle Formation from Supercritical Geothermal Sources

Silica precipitation from high-enthalpy, depressurized supercritical fluids is investigated to determine the best method for accessing the scaling potential as a function of time, position and fluid composition. The most relevant knowledge application is for geothermal sources where the wells are drilled closed to magma and the temperature gradients in the rock are very high. The power potential per well for such a system is large compared to conventional geothermal power production, but several knowledge gaps, among them mineral precipitation from produced fluids, limit commercial use. For the high-enthalpy supercritical well fluid used as a base case in this review, conventional methods for reducing the silica content before it enters a turbine limit the power output. Knowledge of the particle-number density, size and time scales of growth in different depressurization scenarios, along with the silica solubility, kinetics and morphology, is essential to handle deposits and avoid scaling in inconvenient parts of the power plant. Experimental data on the precipitation of silica from highly supersaturated superheated steam are scarce, and it is known that the kinetics of precipitation in steam differ from those of liquid water. We argue that to quantify the number of solids in the depressurized supercritical fluid and superheated steam, dividing the process into three separate but dependable mathematical steps is a reliable approach: (1) the nucleation of nanocolloids, (2) growth by agglomeration, and (3) deposition onto a surface.

High Adsorption Capacity of Ammonia Gas Pollutant Using Adsorbents of Carbon Composites

Air pollution is one of the most environmentally harmful to the human health and the climate change. The present study is aimed to investigate the effectiveness and capability of novel composite adsorbents prepared from modification of activated carbons (ACs) in the removal of air pollutants. The effect of both triethoxysilane propylamine (TEPSA) and carbon nanotube (CNT) on the adsorption properties of AC (TEPSA/CNT/AC); in addition, silica gel prepared from TEPSA to form silica nanoparticles (SiNP) along with CNT and AC (SiNP/CNT/AC), was studied. Ammonia gas (NH3) was used in this study as a typical emerging gas air pollutant. The physicochemical characteristics of the prepared ACs samples were analyzed using BET surface area, SEM, EDX, TEM and FTIR. Their results proved considerable changes in the porosity and surface functional groups after modifying AC surface with TEPSA or SiNP and CNT instantly. The adsorption findings showed that the NH3 removal efficiency using the prepared AC samples reached almost 97, 86 and 75% during 90 min at 25 °C for each sample of SiNP/CNT/AC, TESPA/CNT/AC and AC, respectively. Adsorption of NH3 relied mainly on the presence of silica particles and mesopore distributions in CNT rather than large total surface area in AC alone. Thus, the combination of SiNP as silanol and siloxane groups with CNT on AC surface raised significantly the adsorption capacity of NH3 from 194 to 300 mg/g. Conclusively, the SiNP/CNT/AC sample exhibited the best performance among all prepared samples used for the adsorption of NH3 gas from the indoor air. Also, Langmuir and Freundlich models were applied, and the results revealed that Freundlich model fits well the equilibrium adsorption data.

Multicomponent Cu-Mn-Fe silica supported catalysts to stimulate photo-Fenton-like water treatment under sunlight

Removal of contaminants of emerging concern (CEC) from water is a serious problem. Using sunlight to assist in this process is one of the most sustainable methods for water treatment. In this study, we demonstrate that tailoring the morphology and optimizing the metal concentration in the multicomponent catalysts through an appropriate synthetic strategy leads to Fenton-like and photo-Fenton-like systems capable of effectively degrading bisphenol A and coumarin as model endocrine disruptors and coumarin as a probe for •OH detection. Multicomponent Cu-Mn-Fe silica supported catalysts were prepared via direct synthesis by incorporating magnetic Fe3O4 nanoparticles, Mn and Cu during the formation of silica nanoparticles with interparticle mesoporosity. Comprehensive characterization by advanced microscopic and spectroscopic techniques revealed qualitatively and quantitatively the presence of magnetic Fe oxides covered with the silica support, isolated Mn cations/oxo species into silica framework and CuO particles attached to the silica framework. The Fenton-like activities of the catalysts are due to the catalytic disproportionation of H2O2 by Cu2+ species and isolated Mn species in the silica support. The investigated catalysts are efficient concerning the homolytic cleavage of H2O2 to hydroxyl radicals, with a further positive effect of hydroxyl radical formation observed under visible-light illumination thus acting as photo-Fenton-like catalysts. Fe oxides with magnetic properties are used for easy separation of the catalyst/photocatalyst after the reaction and do not contribute to the catalytic/photocatalytic performance.

In Situ Formation of Silica Nanoparticles Decorated with Well-Defined Homopolymers and Block Copolymers

In Situ Formation of Silica Nanoparticles Decorated with Well-Defined Homopolymers and Block Copolymers

Tandem photo-crosslinking/sol–gel reaction for the green synthesis of morphology-alterable, redox-responsive silica particles

Silica-based nanoparticles have been employed in versatile biomedical applications during the past decades and one of the important research focuses has been the synthesis of biothiol-degradable redox responsive silica to resolve the toxicity concerns of bioaccumulation. In the conventional sol-gel approach, the use of acidic or basic catalyst was always necessary. Solvent, heating, and templates were often applied. Besides, multi-step synthetic procedures were also frequently required to obtain the desired silane with disulfide-linkage for the following synthesis. We developed a facile and green photo-crosslinking coupled sol–gel reaction to produce disulfide-linked redox-responsive silica particles in water at room temperature. The reaction was template-free and initiated by visible light irradiation of photosensitizer (rose bengal). The particle size was tunable by adjusting the concentration of silica precursors, photosensitizer, and irradiation time of LED. The morphologies of the silica nanoparticles can be dramatically altered by simply changing the thiolated silica precursors. The kinetics of the silica precursors during the hydrolysis and photocrosslinking reactions played a critical role. Rose bengal served as a photosensitizer for silica nanoparticle formation and a photodynamic drug. The encapsulated rose bengal remained effective to generate singlet oxygen with superior performance than that of free ones. The disulfide bonds created in the silica matrix responded to reducing reagents, resulting in controllable self-disassembly. Additionally, we found that the presence of magnesium salts affected the rate of the photocrosslinking reaction, forming rod-shaped particles. The current results provide insights for future stimuli-responsive silica-based material development.

Influence of chemical and bio-surfactants on physiochemical properties in mesoporous silica nanoparticles synthesis

The present study pointedly investigates the synthesis of mesoporous silica nanoparticles (sol–gel method) using four different surfactants (biosurfactants, CTAB, SDS and tween-80) under mild condition, was characterized by XRD (Low and wide angle), FTIR, FESEM, HRTEM, UV-VIS-NIR and XPS. The amorphous character of mesoporous silica (22.77O and 21.69O; XRD), hexagonal array with long-range ordered mesopores (SAXS), highest percentage of purity (47.9 and 56.09%; HRTEM-EDXS), perfect spherical shape with particle size (162 and 286 nm; FESEM), significant linkage of Si–O–Si (XPS) and absorption wavelength (271 and 262 nm; UV-VIS-NIR) affirmed with interesting outcomes in case of tween-80 and biosurfactant respectively, as compare to CTAB and SDS-mediated silica nanoparticles. In addition, the band gap of biosurfactant (5.29eV) and Tween-80 (3.78eV) mediated nanoparticles was also remarked lower as compare to other two surfactants as-synthesized nanoparticles. The promising formed silica nanoparticles could be greatly recommended to execute in heavy metals treatment, dye removal, anticancer activity, antioxidant activity, drug delivery, energy storage, etc.

Nanohybrid Pebax/PEGDA-GPTMS membrane with semi-interpenetrating network structure for enhanced CO2 separations

Polymeric membranes containing polyethylene oxide (PEO) groups are promising CO2 separation materials, but suffer from the trade-off between separation performance and mechanical strength. To overcome this challenge, we combine the merits of semi-interpenetrating polymer network and nanohybrid to maintain a high PEO loading and robust membrane structure. The membranes were prepared by introducing in-situ formed PEO networks with silica nodes into Pebax1657 to produce a semi-interpenetrating network structure. The introduced network and in situ formed silica nanoparticles reduce the chain packing efficiency of Pebax matrix to enhance the CO2 diffusivity, while the increased PEO content enhances CO2 solubility. Under feed gas pressure of 25 bar, nanohybrid membranes containing 40 wt% polymer network display excellent gas separation performance with CO2 permeability of 272.8 Barrer and CO2/N2 selectivity of 79.6 under mixed gas separation tests, surpassing 2008 Robeson upper bound. Moreover, the hybrid membranes showed high mechanical strength, the Young's modulus increases by 1.95 times. This strategy provides a simple route for the design of nanohybrid membranes with high separation performance as well as excellent durability.

Porous Silicon Nano-Quill Anodes for Lithium-Ion Batteries

The growing population and increasing demands for energy are overwhelming our supply of fossil fuels and limiting the availability for future generations. Technologies for energy storage devices are emerging to replace conventional fuel-based technologies to meet emissions goals set by world governments and the rapid electrification of the transportation sector. Lithium-ion batteries (LIBs) are widely used for energy storage in devices across many commercial applications. LIB electrodes are continuously evolving due to demands for higher energy density and long cycling life. Among the recent developments in anode electrode materials, silicon (Si) is regarded as the most promising replacement for graphite due to its high theoretical specific capacity (~4200 mAh g-1), which is over 10 times greater than that of conventional graphite anodes (~372 mAh g-1). Despite the advancements, persisting challenges hinder the commercialization of Si for LIB anodes. Si-based electrodes are susceptible to rapid degradation due to the large volume change (approx. 400%) of Si particles during lithium insertion and extraction. The repeated volume change leads to the pulverization of the Si material, ultimately leading to decreased cycling stability from the loss of contact with the current collector. To overcome this obstacle, 3-dimensional porous and hollow nanostructures have been employed to provide sufficient void space to accommodate the volume change during electrochemical cycling. However, with the demands for material cost-reduction from industry, Si structures' strategic engineering must be cost-effective for commercial viability.Our team has developed a patent-pending cost-effective, scalable, and green methodology to use bio-renewable templates to synthesize a 3-dimensional Si architecture, called Si nano-quills (SiNQs). We innovated a two-step, cost-effective process that yields SiNQs with a porous morphology and hollow interior structure. First, in a scalable sol-gel process, silica gel particles were prepared using commonly available low-cost chemicals. The unique mesoporous SiNQ morphology was engineered using surfactant-modified cellulose nanocrystals as a bio-renewable sacrificial template. The templates were removed via thermal treatment to form silica nanoparticles. These particles, called silica nano-quills (SilicaNQs), possess a 3-dimensional bulk structure comprised of hollow quill-like arms and a high degree of porosity. In the second step, we employed a low-temperature magnesiothermic reduction method to convert SilicaNQs into SiNQs with a relatively large surface area. Anode electrodes were fabricated using SiNQs as the active material for electrochemical testing. The slurry was prepared using the active material, carbon black, and PVDF with a mass ratio of 60:20:20 coated onto an ion-permeable Bucky Paper (BP, a flexible and conductive paper made of carbon nanotubes). The 2032-type coin cells were assembled for battery testing using SiNQ electrodes (with an active mass loading of 1 mg cm-2) and a lithium metal chip as the counter electrode. The coin cells were cycled at a current rate of 0.1C (420 mA g-1) over the potential range of 0.01 – 1.0 V at room temperature. The SiNQ anode offered superior battery capacity retention of 73% of the initial reversible capacity of 963 mAh g-1 after 220 cycles. In comparison, batteries fabricated from the Mg reduction of commercially available mesoporous silica, SBA-15, offer capacity retention of only 52.6% after 100 cycles. The SiNQ precursor is engineered to possess porous walls with a superior BET surface area (1265 m2 g-1) compared to SBA-15 (550 m2 g-1). After Mg reduction, the SiNQs retain a BET surface area of 232 m2 g-1, whereas the surface area of reduced SBA-15 is 74 m2 g-1. The superior performance of SiNQs is due to their unique morphology that offers high surface area and porosity for effective diffusion of lithium ions and more sites for interactions with lithium ions, leading to a higher reversible capacity. Moreover, the porous architecture of SiNQs can effectively mitigate the volume change issue during lithiation and delithiation processes, thus providing a good cycling performance.

Biosynthesis of Silica Nanoparticles Using the Leaf Extract of Punica granatum and Assessment of Its Antibacterial Activities Against Human Pathogens

Plant-mediated nanoparticle synthesis is a revolutionary technique with numerous applications in fields, such as agriculture, food processing, and medicine. This study reports that Punica granatum leaf extract is capable of the green and eco-friendly synthesis of silica nanoparticles that provides a simple, cost-effective, and efficient methodology. P. granatum leaf extract was employed as a capping and stabilizing agent for the formation of silica nanoparticles, which were synthesized by a biological method using tetra ethyl ortho silicate. Biosynthesized silica nanoparticles are characterized by X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. All the analyses and characterization determined that the particles were spherical in shape and amorphous in nature with an average size of 12nm. P. granatum-assisted silica nanoparticles were tested for antibacterial activity by a well-diffusion method against two-gram negative bacterial pathogens (E. coli and Salmonella sp.). The antibacterial studies prove that P. granatum-assisted silica nanoparticles have good antibacterial properties. These studies will help us find a new nano-drug or medicine against multidrug-resistant bacteria.

Medium controlled aggregative growth as a key step in mesoporous silica nanoparticle formation

Near monodisperse mesoporous silica nanoparticles (MSN) represent a promising and rapidly developing type of mesoporous silica materials; however, the vast data on their synthesis remains unorganized and ill-understood. We systematically studied the formation of MSN under basic and neutral conditions using various temperatures, CTAB concentrations, hydrolyzing agents (triethanolamine, ammonia, phosphate buffers), and media with different colloidal stabilization properties (with ethanol as a cosolvent and monovalent salts). In the typical conditions for the preparation of stable MSN colloids, the particle size was controlled by colloidal stabilization by the medium (solvent type, ionic strength, and surfactant concentration) in agreement with the “aggregative growth” mechanism, rather than by solely the hydrolysis and condensation rates conventionally used for data interpretation in the classical nucleation theory. Medium properties (pH, ion types and concentration, polarity) also defined the efficiency of silica-surfactant cooperative self-assembly, which directly affected the porosity, mesopore size and pore wall thickness. Interestingly, this traditional silica-surfactant route showed a limited effect on the particle size, emphasizing the dominating role of colloidal stabilization in the studied reaction conditions. In situ pH measurements showed that every reaction medium has unique pH evolution profiles depending on the buffer capacity, hydrolysis and condensation rates. Reaction systems that fail to maintain the working pH can lead to non-porous products or undesired particle morphology and size distribution. The established particle formation mechanism allowed us to formulate comprehensive guidelines for preparing relatively concentrated colloids of near monodisperse (PDI 5–15%) mesoporous 30–700 nm silica spheres with variable porosity and mesopore size. These findings will be particularly useful in designing new mesoporous silica-containing materials for biomedical applications.

Silica Nanoparticles from Coir Pith Synthesized by Acidic Sol-Gel Method Improve Germination Economics.

Lignin is a natural biopolymer. A vibrant and rapid process in the synthesis of silica nanoparticles by consuming the lignin as a soft template was carefully studied. The extracted biopolymer from coir pith was employed as capping and stabilizing agents to fabricate the silica nanoparticles (nSi). The synthesized silica nanoparticles (nSi) were characterized by ultraviolet–visible (UV–Vis) spectrophotometry, X-ray diffraction analysis (XRD), Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Analysis (EDAX), Dynamic Light Scattering (DLS) and Fourier-Transform Infrared Spectroscopy (FTIR). All the results obtained jointly and independently verified the formation of silica nanoparticles. In addition, EDAX analysis confirmed the high purity of the nSi composed only of Si and O, with no other impurities. XRD spectroscopy showed the characteristic diffraction peaks for nSi and confirmed the formation of an amorphous nature. The average size of nSi obtained is 18 nm. The surface charge and stability of nSi were analyzed by using the dynamic light scattering (DLS) and thus revealed that the nSi samples have a negative charge (−20.3 mV). In addition, the seed germination and the shoot and root formation on Vigna unguiculata were investigated by using the nSi. The results revealed that the application of nSi enhanced the germination in V. unguiculata. However, further research studies must be performed in order to determine the toxic effect of biogenic nSi before mass production and use of agricultural applications.

Hydrolysis and Condensation of Tetraethyl Orthosilicate at the Air–Aqueous Interface: Implications for Silica Nanoparticle Formation

The silica (SiO2) nanoparticles of a well-known silica precursor tetraethyl orthosilicate (TEOS) are generally synthesized via a promising solution-gelation inorganic polymerization process. The monodisperse silica nanoparticles have potential applications ranging from the formation of dental nanocomposites to antireflective coatings. In the present study, we have systematically investigated the in situ interfacial molecular structure of TEOS and its impact on the interfacial water structure during the processes of hydrolysis and condensation at the air–aqueous interface using sum-frequency generation (SFG) vibrational spectroscopy. With the presence of water, a gradual decrease in the SFG intensity in the CH-stretch region for each concentration of TEOS with time reflects the elimination of ethoxy groups, which is a signature of the hydrolysis process. Further, the impact of the hydrolysis process is revealed from the significant enhancement in the SFG signal in the OH-stretch region. The hydrolysis of TEOS is then followed by condensation in which the ≡Si─O– charged species are replaced by forming the ≡Si─O─Si≡ bridging network. The signature of the condensation process is reflected with the gradual decrease in the observed enhanced SFG signal in the OH-stretch region. The formation of monodispersed silica nanoparticles as an end product of size variation from 1.75 to 4.67 nm with the increase in TEOS concentration is confirmed with the DLS measurements. We have also probed the pH-dependent SFG studies at three different pH values (2.0, 5.8, and 9.0). The dominant pH-dependent hydrolysis process is revealed from the observed molecular structure of TEOS at the air–aqueous interface.

Kinetics of the complex formation of silica nanoparticles with collagen

Time-resolved small-angle X-ray scattering measurements were made for a mixed solution of negatively charged silica nanoparticles (SiNPs) and positively charged atelocollagen (AC) in buffers at pH = 3 and 4 at 25 °C, in which the scattering intensity from the AC molecules was very weak in the investigated q (magnitude of the scattering vector) range. The scattering intensity from the SiNPs at the low q end and middle q range gradually increased and decreased, respectively, and reached asymptotic values approximately 5–20 min after rapid mixing of the two solutions of SiNPs and AC. This clearly shows that the structural formation of the SiNP–AC complex is on the time scale of minutes. Furthermore, the structure factor at 30 min after mixing is consistent with the previously investigated data for SiNPs and triple helical AC at 15 °C. The obtained time scale to form the complex can be important information to control the aggregating structure of SiNPs with the aid of collagen molecules.

Increased Stability of Polysaccharide/Silica Hybrid Sub‐Millicarriers for Retarded Release of Hydrophilic Substances

AbstractThis work reports an in situ strategy for the synthesis of hybrid sub‐millispheres as carriers for encapsulating and controlling the release of hydrophilic pharmaceutical compounds in both neutral and acidic media. An organic–inorganic hydrogel is prepared by ionotropic gelation, and its efficiency for entrapping hydrophilic molecules is investigated. Two biopolymers, namely chitosan or alginate, are used to generate a scaffold network, in which the formation of silica nanoparticles takes place in situ by a sol–gel process. Model hydrophilic molecules (erioglaucine disodium salt and ephedrine hydrochloride) are encapsulated within polymer matrix, and the subsequent release is controlled by tailoring the hybrid network structure. Kinetic studies demonstrate that the release of the active substance is slower in the presence of silica, which increases as well the structural stability of the carrier in both neutral and acidic media. As a result, by incorporating nanostructured silica into the polymer matrix, the presented system overcomes the limitations of the ionotropic method for entrapping hydrophilic substances.

Fabrication of superhydrophillic and graded index antireflective double layer coating for solar photovoltaics module using aerosol impact deposition assembly

In the study presented, a double layer graded refractive indices silicon dioxide nano-porous coating was deposited on glass substrates to reduce the optical losses in solar photovoltaics using the technique referred as Aerosol Impact Deposition Assembly (AIDA). The proposed system consists of the gaseous precursors namely Silane, Oxygen and Helium that ionize in the plasma reaction chamber of AIDA to form silica nanoparticles. The nanoparticles size and shape can be controlled by the flow rates of each precursor gas, pressure difference in reaction and deposition chamber, and the proportion of helium gas. The assembly accelerates the silica nanoparticles towards deposition chamber with high impact speed using a small slit nozzle where they are coated on a glass/silicon substrate placed on a moving stage. Using this technique, thin film silica nanoparticle double layer was coated and characterized using Transmission electron microscope (TEM), Scanning Electron Microscope and Atomic Force Microscope to determine the particle shape, size, and morphology respectively. The average nanoparticle size determined from TEM image was 12.5 nm while the porosity of the top and bottom thin films was 60% and 42%, respectively. The UV-Spectroscopy results showed that reflection losses were decreased from 9% to 2% in a broad range of solar spectrum i.e., wavelength 300-1200 nm. In addition, due to high porosity and sufficient roughness, the coated thin film showed excellent self-cleaning and antifogging properties with water contact angle less than 5o. Moreover, short current density of the cell was increased by 1.4 mA/cm2, from 39.1 mA/cm2 to 40.5 mA/cm2, which shows enhancement in the electrical performance of the solar cell.

Photocatalytic degradation of dyes using one-step synthesized silica nanoparticles

Schematic route diagram of one step synthesis of Silica nanoparticles. • Synthesis of silicon oxide based employing sol–gel method. • Degradation of dye methylene blue and methyl orange. Silica nanoparticles are synthesized by one step simple, rapid and cost effective sol–gel method using methyltrimethoxysilane (MTMS) as precursor. Synthesized silica nanoparticles are characterized by UV–Visible spectroscopic techniques, XRD and FE-SEM. From UV curve the maximum absorbance observed was at the wavelength 297 nm which indicates formation of silica nanoparticles. The FE-SEM analysis showed the larger size of nanoparticles is due to agglomeration of silica nanoparticles. The X-ray diffraction pattern indicate the structure of the silica nanoparticles. FT-IR spectra of silica nanoparticles are indicative of the stretching vibration of Si-O-Si bonds and Si-OH vibration respectively. TGA indicates the final degradation temperature of silica nanoparticles are near about 515 °C temperature. Photo degradation process is carried out by employing different dyes along with UV irradiating at pH-7. Photodegradation of both (10 ppm) methylene blue and methyl orange with 1.5 g/dm 3 SiO 2 photocatalyst dose accomplished around 98 and 95% degradation in 90 min at 25 °C with pH-7. Finally, it can be concluded that silica nanoparticles support to the photo degradation of methylene blue and methyl orange. Hence nanoparticles synthesized using sol–gel method can be used for degradation of various industrial pollutants dyes.

Complex Formation of Silica Nanoparticles with Collagen: Effects of the Conformation of Collagen.

Negatively charged Ludox silica nanoparticles (SiNPs) form a complex with atelocollagen (AC) in acidic buffers (pH = 4 or 3). AC is a low-immunogenic derivative of collagen obtained by the removal of N- and C-terminal telopeptide components. Mixed solutions of negatively charged SiNPs and AC were turbid, while positively charged SiNPs (Ludox CL) did not form a complex with AC in pH 4 buffer, indicating that electrostatic attraction is the dominant force to form the complex. Small-angle X-ray scattering (SAXS) and circular dichroism (CD) measurements were made for AC and Ludox LS (or CL) solutions in acetate buffer (pH 4.0) and citrate buffer (pH 3.0). The CD data showed that the stability of the triple helical structure of AC in the buffers is not affected by the complexation. The resulting complex consisting of triple helical AC and SiNPs did not influence the SAXS profile except for the lowest q region investigated. On the contrary, different scattering profiles were observed for the single chain AC and SiNP mixture indicating densely packed SiNPs in the complex. This scattering behavior was fairly explained in terms of the sticky hard sphere model (SHSM). This AC conformation-dependent complexation may be because of the hydrogen bonding interaction between the single chain AC and SiNPs. The temperature-induced change of the complex formation can be applied for thermoresponsive hybrid materials.

Surface modification of blended fabrics by silica nanoparticles to improve their printability

The sol-gel technique offers an effective way of modifying fabrics, and has many advantages. In this paper, silica nano particles in the solid form were prepared from TEOS precursor; further application of these silica nanoparticles to polyester wool, and polyester cotton blends as well as polyester and cotton fabrics is carried out. Improved fabrics printability, as well as acquiring antibacterial properties were achieved. The basic idea for using sol-gel technology to modify fabric blend surfaces in order to solve their coloration problems and to attain solid shades using a single set of dyes.