Sol-gel Parameters Research Articles

Revolutionizing scandium detection in real samples: Unleashing the power of sol-gel-based optical sensor.

The development of a highly selective and ultra-sensitive optical sensor for detecting scandium (Sc3+) ions involves incorporating the reagent 2,3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) into a silica sol-gel thin film on a glass substrate. This innovative approach utilizes tetraethoxy-silane (TEOS) as the precursor, maintaining a sol-gel pH level of 4.5, a water-to-alkoxide ratio of 5:1, and a DCHNAQ concentration of 5.0 × 10-4M. A detailed exploration of the impact of sol-gel parameters on the sensing capabilities of the developed sensor has been meticulously undertaken. This innovative sensor demonstrates remarkable selectivity in evaluating Sc3+ ions over a dynamic range of 7.5-170ng/mL, with limits of quantification and detection recorded at 7.3 and 2.20ng/mL, respectively. Consistent results are achieved with a minimal RSD of 1.47 and 0.94% for Sc3+ ions at 50 and 100ng/mL, respectively, coupled with a swift response time of three min. Assessments of interference demonstrate a noteworthy preference for Sc3+ions, accomplished by enclosing DCHNAQ within the sol-gel framework and making optimal structural modifications to the doped sol-gel. The sensor offers straightforward regeneration using a 0.25M EDTA solution, exhibiting complete reversibility. Comparative analysis with other methodologies underscores the efficacy in determining Sc3+ions in various reference materials, including plant leaves, fish, water, alloys, ores, and monazite samples.

Optimization and evaluation of ultra-trace amounts of lead in real samples using sol–gel based optical sensor coupled with colorimetry

The entrapment of the sensitive reagent 5-(2′-bromophenylazo)-6‑hydroxy-pyrimidine-2,4‑dione (BPAHPD) in a silica sol-gel thin film coated on a glass substrate has been investigated for the development of a highly sensitive and selective optode for the determination of lead ions. The fabrication of thin films requires tetraethoxysilane as a precursor, a sol-gel pH of 2.75, a water: alkoxide ratio of 5:1, and a BPAHPD concentration of 4.0 × 10–4 M. The effect of sol-gel parameters on the optode's sensing performance was investigated. The fabricated optode is utilized for lead ion detection over a dynamic range of 4.00–144 ng mL–1 with detection and quantification limits of 1.20 and 3.95 ng mL–1, respectively. It gave repeatable results with relative standard deviation (RSD) values of 1.90% and 1.15% for lead concentrations of 40.0 and 80.0 ng mL–1, respectively, and a response time of two minutes. Through capturing BPAHPD in a sol-gel matrix and appropriately modifying the structure of doped sol-gel, interference studies have determined that lead exhibits a high degree of selectivity. To ascertain total lead, Pb4+ was reduced to Pb2+ using a few drops of 6.00 M hydrochloric acid and a freshly prepared sodium azide solution of 2.50 % (w/v). The optode can be easily regenerated with 0.15 M of nitric acid solution. The optode has complete reversibility. Optode detection of lead in diverse vegetable, food, biological, water, and soil samples yielded favorable results when compared to other techniques.

Influence of the alcoholic solvent and gelation temperature on the structural and water vapor adsorption properties of silica adsorbents synthesized by sol-gel method without catalyst

Silica adsorbents with controlled porosity were produced by sol-gel technique without using catalyst. Mesoporosity and water vapor adsorption properties were evaluated for the synthesized silica materials. This study was supported by several characterizations, including FTIR, SEM and Nitrogen sorption. It has been shown that the mesoporous structure and the water adsorption performance of the silica are entirely dependent of the solvent type used and gelation temperature. The present study shows that for the adsorption parameters used in this work, the control of the sol-gel parameters can give rise to silica adsorbents with greater adsorption capacity than the commonly used commercial silica. The highest adsorption capacities were measured for silica structures synthesized with tert-butanol and gelled at 90 °C, which absorbs up to 65% more than its mass due to both high mesopore volume and big pore size. The silica materials were synthesized in this work by a simple sol-gel synthesis, which represents an important advantage in terms of safety and environmental sustainability, besides reinforcing the simplicity and novelty of the processing route employed herein to obtain silica adsorbents with a controlled porous structure.

Investigating the corrosion performance of Ti-6Al-4V biomaterial alloy with hydroxyapatite coating by artificial neural network

As a result of its excellent mechanical characteristics and bio-compatibility, the Ti-6Al-4V alloy offers a wide-ranging applications in the medical industry. However, long-term application of these alloys may lead to a decline in corrosion resistance as well as other serious problems in these alloys. To resolve these problems, it is possible to modify the implant surface to enhance the corrosion and bio-compatibility properties. On the Ti-6Al-4V substrate surface, the TiN coating was applied by the Plasma-Assisted Chemical Vapour Deposition (PACVD) method together with the hydroxyapatite coating (HA) using the sol–gel method. Furthermore, the corrosion performance of bio-active hydroxyapatite layer coating on Ti-6Al-4V implant surface was evaluated through the application of the Artificial Neural Network (ANN) and Gene Expression Programming (GEP) models. The generated models were analysed and compared to a response surface methodology (RSM). The hydroxyapatite sol–gel parameters on Ti-6Al-4V implant materials were used as independent variables (input variables). The Ecorr values computed from potentiodynamic polarization measurements were used as a dependent variable (output variable) in the models. The results of the ANN technique (sigmoid activation function, LM training algorithm and 9 neurons in hidden layer) were in good consistent with the experimental Ecorr values, indicating this model is slightly better than the GEP and RSM models. Finally, the findings demonstrated that the ANN technique is an appropriate and robust tool for quantitative modeling of corrosion resistance, and that it can be applied to a variety of surface engineering applications.

Studies on Improvement of Mechanical Stability of Silica Coatings

AbstractSuperficial defects are the prominent drawbacks of the most usual real‐world surfaces. The response of the coatings to the external deforming scratches is an issue of an importance when industrial applications are concerned. It is very well known that, the network of silica not only in the aerogels but also in coatings is weaker. In this study, the role of polymethylmethacrylate blended with the silica particles is studies. Also, the sol–gel parameters to obtain hydrophobic and scratch resistance silica coatings on glass are modified. The mechanical strength of the coating from 6 B to B is enhanced. The hydrophobicity of coatings is quantified by water drop contact angle. The measured contact angle values are 149° and sliding angle 4°. Scanning electron microscopy reveals dual assembly of micro and nanoparticles of the order of 100–500 nm. These coatings are examined through Fourier transform infrared spectroscopy, scanning electron microscopy, surface roughness, etc.

Nanoscale tailoring on thin bimetallic organo-oxide membranes for H2/CO2 separation

The design of tailored novel membrane networks with excellent hydrothermal stability allowing gas sieving is highly desired to take them a step closer to large scale commercialization for energy efficient separation. Bistriethoxysilylmethane (BTESM) containing SiCSi bonds was used as a precursor for the fabrication of Ti-incorporated BTESM organosilica membranes on a macroporous ceramic support with a mesoporous intermediate layer. The precise engineering on the sol-gel parameters allowed the formation of bimetallic clusters with 2–4 nm size range in the clear organo-oxide sols. XPS analyses indicated the development of SiOTi connections in the organo-oxide membrane network. A high H2 permeance of 6.3 × 10−7 mol/m2sPa and attractive ideal selectivities of 10, 10, 119 and 222 for H2/N2, H2/CH4, H2/C3H6 and H2/C3H8, respectively are attained from an exceptionally thin BTESM membrane. H2/CO2 ideal selectivity increases from 4 to 8 upon incorporation of 15 mol% Ti into membrane network while selectivities increase to 32 for H2/N2, 44 for H2/CH4, and 246 for H2/C3H8 with 1.25-fold increase in H2 permeance. H2/CO2 ideal selectivity of 24 was achieved with moderate H2 permeance of 1.7 × 10−7 mol/m2sPa after hydrothermal treatment for 45 h for BTESM15 membrane as thin as 65 nm. This is the one of the thinnest ceramic supported organosilica membrane reported having acceptable H2 permeance after hydrothermal treatment.

An assembly strategy of polylactic acid (PLA)-SiO2 nanocomposites embedded in polypropylene (PP) matrix

The aim of this work is to evaluate the effect of adding different amounts of SiO 2 nanoparticles (NPs) during the synthesis of polylactic acid (PLA) and polypropylene (PP) blends on the proccesability. The analysis was carried out in terms of the morphological, rheological and mechanical properties as well as their potential applications for packaging. To reach this goal, it was initially realized an optimization of sol–gel parameters to produce of SiO 2 NPs with a particle size <20 nm. Thereafter, different quantities of SiO 2 NPs (1, 2, 3, 5 wt.%) were incorporated into PLA matrix through melt mixing process to achieve pellets and finally, it was realized the polymer blend to produce PP 100-x (PLA-SiO 2 ) x nanocomposites (x = 5, 10 and 20 wt.%, of PLA-SiO 2 pellets). It was found that the addition of SiO 2 into PLA matrix improves the crystallinity percentage, from 10 to 77 %, depending on the SiO 2 quantity; however, it also restricts the movement of PLA chains favoring a viscous behavior. A high dispersion of PLA-SiO 2 systems into PP matrix was obtained in composites containing 1 wt.% of SiO 2 . The presence of inorganic nanostructures modified the dipole–dipole interaction between organic components affecting the microstructure and thermal stability (lower T d ). The observed interaction and high dispersion with low amounts of SiO 2 NPs (1 wt.%), led to improve the interfacial miscibility, which in turn enhanced the mechanical properties in the PP 90 (PLA-SiO 2 ) 10 nanocomposites, compared to PP and PLA. The results indicate that at the end of product shelf-life, this composition can promote a faster degradation in contrast with pure PP and PP-PLA composites.

Synthesis of La0.8Zn0.2MnO3 nanocatalysts for decomposition of VOCs in a DBD plasma reactor; Influence of sol-gel parameters

In this study, La0.8Zn0.2MnO3 nanocatalysts were synthesized using sol-gel method at different citric acid to metal nitrate (C/N) ratios and different calcination temperatures. The synthesized catalysts were used for oxidation of benzene, toluene, and xylene (BTX) in a catalytic-plasma hybrid reactor at different input voltages of 5, 7.5, 10, 12.5, and 15 kV. The synthesized catalysts were analyzed by XRD, FESEM, EDX, FTIR, BET, and TEM. XRD analysis confirmed the effect of calcination temperature on crystalline degree of LnMnO3 phase in perovskite La0.8Zn0.2MnO3 catalyst. TEM analysis also confirmed production of particles in nanometer range. Moreover, FTIR and BET analyses indicated that C/N ratio has a direct effect on the amount of metal oxide functional groups and surface area of the resultant catalyst, respectively. The reactor tests showed that the use of C/N= 0.5 and calcination temperature of 700°C in catalyst preparation resulted in the best performance in BTX oxidation. Increasing the voltage up to 15 kV had a good effect on the oxidation ability of the catalyst as well. In these conditions, the highest oxidation percentages of benzene, toluene and xylene were equal to 90.00, 89.86, and 88.64 %, respectively.

Sol-Gel Derived Hydroxyapatite Coatings for Titanium Implants: A Review.

With the growing demands for bone implant therapy, titanium (Ti) and its alloys are considered as appropriate choices for the load-bearing bone implant substitutes. However, the interaction of bare Ti-based implants with the tissues is critical to the success of the implants for long-term stability. Thus, surface modifications of Ti implants with biocompatible hydroxyapatite (HAp) coatings before implantation is important and gained interest. Sol-gel is a potential technique for deposition the biocompatible HAp and has many advantages over other methods. Therefore, this review strives to provide widespread overview on the recent development of sol-gel HAp deposition on Ti. This study shows that sol-gel technique was able to produce uniform and homogenous HAp coatings and identified the role of surface pretreatment of Ti substrate, optimizing the sol-gel parameters, substitution, and reinforcement of HAp on improving the coating properties. Critical factors that influence on the characteristics of the deposited sol-gel HAp films as corrosion resistance, adhesion to substrate, bioactivity, morphological, and structural properties are discussed. The review also highlights the critical issues, the most significant challenges, and the areas requiring further research.

Influence of Various Sol–Gel Parameters on the Physico‐Chemical Properties of Sulfuric Acid Chelated Zirconia Aerogels Dried at Ambient Pressure

AbstractThis work represents the influence of various sol–gel parameters on the physico‐chemical properties of sulfuric acid chelated zirconia aerogels dried at ambient pressure. The sol–gel parameters such as concentrations of precursor, chelating agent and catalyst are found to be the dominant factors which influence the physical, chemical and textural properties of the aerogels. Therefore, the influence of concentration of Zr precursor, ZrPr:H2SO4 molar ratio and ZrPr:H2O molar ratio on these properties of zirconia aerogels is studied. Zirconia lacogels are formed by the hydrolysis and condensation of zirconium n‐propoxide in n‐propanol chelated with sulfuric acid (18.4 M) and catalyzed with deionized water. Aerogels are obtained by subsequent solvent exchange, silylation, washing and ambient pressure drying. The physico‐chemical properties of as synthesized zirconia aerogels are carried out using FESEM, EDS, BET analysis and FTIR spectroscopy. The good quality zirconia aerogels are obtained using the molar ratio of ZrPr:PrOH:H2SO4:H2O:HMDZ::1:2.93:1.18:1.77:0.59. They possess the density of 0.54 g cm‐3, BET surface area of 328 m2 g‐1 and micropore volume of 0.028 cm3 g‐1. These aerogels can be applied as heterogeneous catalysts in many fields.

Influence of the synthesis parameters on the mesoporous structure and adsorption behavior of silica xerogels fabricated by sol–gel technique

Silicon dioxide xerogels with controlled mesoporosity were produced by sol–gel technique. The mesoporosity and adsorption behavior of methylene blue (MB) were evaluated for the fabricated silica materials. This study is supported by several characterizations, including FTIR, TEM, SEM, and N2 sorption. The adsorption kinetics of MB on the prepared samples was evaluated at room temperature over time. It was demonstrated that the pore structure and adsorption performance of silica are closely dependent on the pH of the sol–gel solution, H2O:TEOS molar ratio, the addition of F127 template, and heat treatment performed. The present study shows that for the adsorption parameters used in this work, the control of sol–gel parameters can give rise to silica xerogels with higher adsorption capacities than SBA-16 silica molecular sieve used as the reference and already recognized as an efficient dye adsorbent. The highest adsorption capacities were measured for silica structures obtained without the use of acidic catalyst, heat treatment or F127 template. As the pore volume of the studied materials is much larger than the amount of MB captured in the adsorption tests, such results seem to be related to the specific surface area and pore size obtained in the sol–gel synthesis. Therefore, it appears that large surface areas and pore sizes accelerate the adsorption kinetic and increase the amount of MB able to stay in equilibrium in the pore structure of silica. As a matter of fact, the work developed here underlines the advantages regarding the simplicity, safety, environmental preservation and cost saving of the synthesis methodology developed herein when compared with the other methodologies commonly used to fabricate silica adsorbents.

Effects of Reynolds and Froude dimensionless numbers on geometry of silica powders: simultaneous optimization using overall evaluation criteria technique

Specific surface area, mean pore diameter, and pore volume are among the most important geometrical properties, which can be controlled by the sol-gel mixing parameters during the silica synthesis. In this paper, these geometrical parameters were simultaneously optimized by overall evaluation criteria (OEC) technique in the Taguchi method. The optimum conditions were obtained at Reynolds dimensionless number (Re) of 250,000, Froude dimensionless number (Fr) of 0.034, acid dripping time (θ) of 60 min and acid normality (N) of 8, which resulted in BET specific surface area, BJH pore diameter and pore volume of 473.12 m2g−1, 5.21 nm, and 0.861 m3g−1, respectively. Analysis of variance demonstrated that only Re had a significant effect on the OEC values with 76.3% of contribution. The samples were characterized by SEM, BET–BJH analyses. Morphological observations confirmed the considerable effects of N, Re, and Fr on geometrical properties such as particle shapes, N2 adsorption–desorption isotherms and pore size distribution.

Fabrication of superconducting YBCO agglomerated particles (ANPs) by electrospinning

Superconducting YBa2Cu3O7-δ (YBCO) agglomerated nanoparticle (ANPs) was fabricated by electrospinning technique and sol-gel of a homogeneous precursor of Y-Ba-Cu acetate and Poly (vinyl pyrrolidone) (PVP). The sol-gel solution of YBCO is conducted by adding 4.0 g of (Y-Ba-Cu) metal acetate according to a stoichiometric ratio of 1:2:3 molar mass and 5.0 g of PVP powder in 25.0 ml solution contains propionic acid 10 ml, acetic acid 5 ml and methanol 10 ml. By optimizing electrospinning process, sol-gel parameters and heat treatment, YBCO ANPs were obtained with a transition temperature of Tc ~90 K using the AC susceptibility. YBCO ANPs was found with high surface area 6.8310 m2/g, and not affected by high calcination temperature at 950 oC in comparison with bulk YBCO sample. XRD Characterization of YBCO was demonstrated YBCO has orthorhombic phase, FESEM images of the electrospun YBCO sample showed ANPs of size in the 200 – 400 nm range. A closer examination revealed that agglomerates contain finer particles of size ~50 nm. Electrospinning is an effective technique can produce various morphologies of YBCO superconductor at the nanoscale with unique properties for practical applications.

Role of water in the sol-gel synthesis of yttrium monosilicate

Yttrium monosilicate (YMS) is a candidate environmental barrier coating material. It is a line compound, and its synthesis requires strict stoichiometric control of the starting materials. In this work, YMS was synthesised by the sol-gel method. Yttrium oxide and tetraethyl orthosilicate (TEOS) were used as precursors. The ratio of water to ethanol was varied to study the role of water in the formation of phase-pure YMS. The formation of secondary phases during synthesis was attributed to the complex interaction of TEOS with water in the presence of ethanol. It was seen that water and ethanol play a significant role in aqueous sol-gel processes involving silica than merely being present as solvents. The results are helpful in identifying the suitable sol-gel parameters for the synthesis of phase-pure yttrium monosilicate.

Influence of fish collagen on viscoelastic properties and sol-gel phase transition of chitosan solutions

The thermosensitive hydrogels are widely used in tissue engineering due to their non-invasive application. Special interest of researchers, due to the specific characteristics of both materials, is aimed at composites of natural origin obtained from chitosan hydrogels combined with collagen. The mechanical properties of the thermosensitive chitosan-fish collagen hydrogels and the sol-gel phase transition parameters were determined by the rotational rheometry measurement techniques. Based on comparison of the obtained storage modulus G' curves, it was found that the addition of collagen negatively affects the mechanical properties of composite scaffolds. The addition of this protein substance decreases their elasticity. Only the smallest concentration (0.25g collagen/1 g chitosan) of collagen improves the mechanical properties of composite hydrogels, from 56 kPa to 61 kPa. Conducted non-isothermal studies allowed to conclude that the addition of collagen causes an increasing temperature of sol-gel phase transition. However, the observed changes are not a monotone function of the biopolymer concentration.

Engineering of Mesoporous Silica Coated Carbon‐Based Materials Optimized for an Ultrahigh Doxorubicin Payload and a Drug Release Activated by pH, T, and NIR‐light

AbstractAmong the challenges in nanomedicine, engineering nanomaterials able to combine imaging and multitherapies is hugely needed to address issues of a personalized treatment. In that context, a novel class of drug releasing and remotely activated nanocomposites based on carbon‐based materials coated with mesoporous silica (MS) and loaded with an outstanding level of the antitumoral drug doxorubicin (DOX) is designed. First, carbon nanotubes (CNTs) and graphene sheets (called “few‐layer graphene” FLG) are processed to afford a distribution size that is more suitable for nanomedicine applications. Then, the controlled coating of MS shells having a thickness tailored with the sol–gel parameters (amount of precursor, sol–gel time) around the sliced CNTs and exfoliated FLGs is reported. Furthermore, the drug loading in such mesoporous nanocomposites is investigated and the surface modification with an aminopropyltriethoxysilane (APTS) coating leading to a controlled polysiloxane layer provides an ultrahigh payload of DOX (up to several folds the mass of the initial composites). Such new CNT‐based nanocomposites are demonstrated to release DOX at low acidic pH, high temperature (T), and remotely when they are excited by near infrared (NIR) light. Such nanoconstructs may find applications as components of innovative biomedical scaffolds for phototherapy combined with drug delivery.

Sol-gel derived flexible silica aerogel as selective adsorbent for water decontamination from crude oil

Oil spills are the most important threat to the sea ecosystem. The present study is an attempt to investigate the effects of sol-gel parameters on seawater decontamination from crude oil by use of flexible silica aerogel. To this goal, methyltrimethoxysilane (MTMS) based silica aerogels were prepared by two-step acid-base catalyzed sol-gel process, involving ambient pressure drying (APD) method. To investigate the effects of sol-gel parameters, the aerogels were prepared under two different acidic and basic pH values (i.e. 4 and 8) and varied ethanol/MTMS molar ratios from 5 to 15. The adsorption capacity of the prepared aerogels was evaluated for two heavy and light commercial crude oils under multiple adsorption-desorption cycles. To reduce process time, desorption cycles were carried out by using roll milling for the first time. At optimum condition, silica aerogels are able to uptake heavy and light crude oils with the order of 16.7 and 13.7, respectively.

Silica aerogel paper honeycomb composites for thermal insulations

Applicability of super-insulating silica aerogel materials for thermal insulation is still restricted by limited mechanical strength. We report on a systematic improvement of silica aerogels in respect to shrinkage, density and thermal conductivity by varying sol-gel parameters as the molar ratios of TEOS:EtOH:H2O or the hydrolysis time. The received silica aerogels can be combined with paper-based honeycomb structures to improve the mechanical strength. We successfully manufactured such silica aerogel paper honeycomb composites. The challenges in the preparation are the must to prevent shrinkage of the silica aerogels during synthesis, to avoid cracks by supercritical drying, and to get a perfect bonding at the paper–silica interface. The composite materials are characterized with respect to their compression modulus, thermal conductivity, and flammability.

Exploiting the effects of catalyst geometric properties to boost the formation of light olefins in Fischer-Tropsch synthesis: Statistical approach for simultaneous optimization

A statistical study was carried out to investigate simultaneous effects of different geometrical properties of the catalyst on the extent of light olefins in Fischer-Tropsch synthesis. Applying Taguchi design of experiment, a total of nine impregnated CoMnCe/SiO2 catalysts were prepared and tested in a fixed-bed reactor under the following operating conditions: T = 533.15 K, 558.15 K and 583.15 K, P = 2 bar, H2/CO = 2 and GHSV = 4500 hr−1. Specific surface area, pore diameter, pore volume, and pore structure (pore size distribution) were considered as the main geometrical factors which were controlled by tuning such sol-gel parameters in silica synthesis as Reynolds (Re) and Froude (Fr) dimensionless numbers as well as acid dripping time (Ө), and acid normality (N). Analysis of variance demonstrated that, both of specific surface area and pore volume imposed significant effects on the production of lower olefins. Statistical analysis indicated that, the mesoporous catalyst with a wide pore size distribution and large specific surface area and pore volume favored (i.e. maximized) the production of light olefins. These optimum geometries were achieved by setting the silica synthesis parameters to Re = 250,000, Fr = 0.213, Ө = 30 min, and N = 6.

A close correlation between nucleation sites, growth and final properties of ZnO nanorod arrays: Sol-gel assisted chemical bath deposition process

Different ZnO seed layers are synthesized by changing sol-gel parameters, including precursor concentration, type of solvent, and type of additive in order to systematically investigate the importance of seed layer properties on the nucleation, growth, and final properties of zinc oxide (ZnO) nanorod (NR) arrays. The X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) show the importance of the seed layer on ZnO NRs properties. Results verify that the relative intensity (RI factor) of (002) polar planes in the XRD patterns of ZnO nanoparticles (NPs) together with the aspect ratio, density, and alignment of ZnO NRs control the structural characteristics of those arrays. For instance, the RI factor of ZnO NPs and NRs follow the same trend when changing precursor concentration in sol preparation step. However, the importance of other parameters, including aspect ratio, density, and alignment of NRs is confirmed by changing solvent and additive. In addition, FESEM images show that the density of ZnO NRs is proportional to NPs density and inversely proportional to the size of ZnO NPs in the seed layers. Besides, the significant role of wrinkled inter-layer on NRs properties, together with the formation mechanism of that inter-layer are profoundly investigated.