Sol-gel Research Articles

Reset-Voltage Controlled Resistance-State and Applications of Forming-Free Fe-Doped SrTiO3 Thin-Film Memristor.

In this study, we prepared a strontium ferrite titanate (STF) thin film using a sol-gel process to insulate resistive random-access memory (RRAM) applications. Compared to the typical strontium titanate (STO) RRAM, the improvement in the resistive switching characteristics in STF RRAM is obvious. The Al/STO/ITO/Glass RRAM set/reset voltages of -1.4 V/+3.3 V and the Al/STF/ITO/Glass RRAM set/reset voltages of -0.45 V/+1.55 V presented a memory window larger than 103, a low operating voltage and device stability of more than 104 s. In this study, the influence of Fe on the conducting paths and the bipolar resistive switching properties of Al/STF/ITO/Glass RRAM devices is investigated.

Origin of magnetism via cation vacancy defects in non-stoichiometric NiCo2O4 nanoparticles: A synchrotron-based x-ray absorption and x-ray magnetic circular dichroism spectroscopic study

The present study probes the effect of cation distributions in the structural, optical, electronic, and magnetic properties of mixed-valent inverse-spinel NiCo2O4 (NCO) nanoparticles (NPs). NCO NPs were prepared using the sol–gel combustion method and the grain size was obtained in the magnetic exchange length range assumed to be from single-ion anisotropy. The Raman and photoluminescence spectroscopies confirm the presence of an inverse-spinel structure with different oxidation states, and vibrating sample magnetometry clarifies the existence of ferromagnetism with the presence of magnetic anisotropy among the cations. These NPs annealed at a higher grain-growth temperature accumulate ferrimagnetic properties and produce magneto-crystalline anisotropy making NCO an assuring material for spintronic applications. A detailed x-ray absorption spectroscopy and x-ray magnetic circular dichroism studies reveal an indestructible correlation between the distribution of the present cations and the element-specific origin of ferrimagnetic behavior. Ni is found to be accountable for the magnetic moment and electronic conduction, whereas Co is associated mainly with the generation of the magnetic anisotropy even in the polycrystalline NP form. This describes the anti-ferromagnetic coupling between Co and Ni ions that is pivotal in demonstrating the exchange interaction between these cations. The above result signifies the site-dependent cation valence states for the magnetic properties, and the extent of growing conditions are related to such cation-site dysfunction. This depicts further tunability in NCO as a functional oxide material.

Structural, optical, and magnetic properties study of Dy-Cr co-doped bismuth ferrite (BFO) nanoparticles

Dysprosium-Chromium co-doped bismuth ferrite (Bi0.9Dy0.1Fe1-xCrxO3, x = 0, 0.05, and 0.1) nanoparticles were prepared by the sol–gel technique. The formed gel, held in an evaporating dish, was burned in a hot oven at 210 °C to form fluffy ash. The ground-burnt ash was sintered in a temperature-programmed electric furnace for 5 h at 820°C. The XRD results confirmed that all the prepared samples were in a rhombohedra structure with space group R3c. The XRD analysis revealed that the crystallite size decreased from 19.75 nm to 17.97 nm as the co-dopants increased. The energy dispersive x-ray (EDX) spectroscopy confirmed the presence of the ions as per the stoichiometry ratio. The VSM magnetic measurements revealed that the magnetic parameters, saturation magnetization (Ms), and remnant magnetization (Mr) relatively increased from 1.34 emu/g to 1.63 emu/g, and 0.262 to 0.412, respectively, with increasing the co-dopants, but the coercive field decreased. The UV–Vis measurement showed that the energy band gap (Eg) increased from 1.93 eV to 2.15 eV as the concentration of the co-dopants increased from x = 0 to x = 0.10.

The Sol-Gel Process, a Green Method Used to Obtain Hybrid Materials Containing Phosphorus and Zirconium.

The sol-gel process is a green method used in the last few decades to synthesize new organic-inorganic phosphorus-containing hybrid materials. The sol-gel synthesis is a green method because it takes place in mild conditions, mostly by using water or alcohol as solvents, at room temperature. Therefore, the sol-gel method is, among others, a promising route for obtaining metal-phosphonate networks. In addition to phosphorus, the obtained hybrid materials could also contain titanium, zirconium, boron, and other elements, which influence their properties. The sol-gel process has two steps: first, the sol formation, and second, the transition to the gel phase. In other words, the sol-gel process converts the precursors into a colloidal solution (sol), followed by obtaining a network (gel). By using the sol-gel method, different organic moieties could be introduced into an inorganic matrix, resulting in organic-inorganic hybrid structures (sometimes they are also referred as organic-inorganic copolymers).

Unraveling the structural and magnetic characteristics of Mg doped CoCr2O4

In this paper, we explore the structural and magnetic properties of Mg doped CoCr2O4nanopowder (typical size of 10 nm) synthesized via the sol–gel auto-combustion method. X-ray diffraction, XPS, and FTIR spectraconfirm spinel structure (space group Fd-3 m) with Mg2+ doped at Cr3+. Interestingly, temperature-dependent magnetizations show various magnetic transitions between 5–300 K. While they show ferrimagnetic ordering below Curie temperature of 100 K (CoCr2O4) to 80 K (CoCr1.8Mg0.2O4) samples, the irreversibility betweenFC and ZFC curves at blocking temperature attribute to spin blocking nature of nanoparticles. Finally, at very low temperatures (13–26 K), magnetizations again rise indicating spin-spiral transition of CoCr1.8Mg0.2O4.Furthermore, the effect of these transitions onM−H loopcan be evidentin terms of coercivity, saturation magnetization, andnon-saturation behaviorat high magnetic fields.

Porous polyimide composite films containing mesoporous hollow silica nanospheres with ultralow dielectric constant and dissipation loss

Porous polyimide hybrid films with ultralow dielectric constant and dissipation loss were synthesized during chemical imidization and rapid evaporation of polymer solutions. Polyimide (PI) of bis(4-aminophenyl)-1,4-diisopropylbenzene (BISP) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) were synthesized in N-methylpyrrolidinone (NMP) to yield the corresponding poly(amic acid)s (PAA)s, which were then chemically imidized. To reduce the dielectric properties of the porous PI films, amine-functionalized, surface-modified hollow silica nanoparticles (AHNS) with various sizes from 100 nm to 1 μm, prepared via sol-gel process, were added with PAA at 3, 5, or 10 % weight content, followed by chemical imidization to produce the porous PI/AHNS films. To avoid the high-volume shrinkage of wet gels and maintain the high porosity of the PI with low polarizability, AHNS nanoparticles were added to the porous structure of the PI xerogels as a physical crosslinker. The polyimide hybrid film with 10 nm AHNS nanoparticles at 10 % weight content showed a dielectric constant of 1.151 and a dissipation rate of 0.001 at a frequency of 10 GHz.

ROS/Thermo dual-sensitive hydrogel loaded with a nanoemulsion of patchouli essential oil for ulcerative colitis

Patchouli essential oil (PEO) is acknowledged as a potent contender for the management of ulcerative colitis (UC). However, the limited ability of PEO to be absorbed by the body and its low stability substantially limit its potential uses. Furthermore, UC lesions are mainly concentrated in the rectal and colonic mucosa, with excessive production of reactive oxygen species (ROS). Herein, a nanoemulsion of PEO (PEONE) was developed to enhance the stability and bioavailability of a drug. Subsequently, we developed a novel platform for the rectal administration of a ROS/thermo dual-sensitive Bletilla striata polysaccharide-based hydrogel (RTH) co-loaded with PEONE to efficiently treat UC. As expected, the sol–gel transition of PEONE@RTH, after its intrarectal administration, resulted in its extended presence in the colon and facilitated its attachment to the inflammation site. Moreover, PEONE@RTH alleviated dextran sulfate sodium-induced UC symptoms by suppressing inflammation and oxidative stress, repairing the damage to the intestinal epithelial barrier (claudin-1 and occludin), increasing short-chain fatty acid content and inhibiting the MAPK signalling pathway. Additionally, PEONE@RTH exhibits exceptional safety and biocompatibility. Thus, PEONE@RTH has the potential to provide a novel approach for treating UC and other intestinal disorders characterised by similar clinical conditions.

Synthesis and characterization of lithium alumina silicate (LiAl(SiO3)2) from naturally sourced silica: a comparative study

This study investigates the synthesis and characterization of lithium aluminosilicate (LiAl(SiO3)2) using naturally sourced silica (NSS) from the Djamâa region in Algeria and compares it with laboratory-sourced silica (LSS). The synthesis was conducted using the sol–gel method and solid-state reactions with lithium carbonate, aluminum oxide, and SiO2. Characterization techniques included X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRD analysis confirmed the crystalline structure of the synthesized lithium aluminosilicate, revealing distinct crystal phases: the NSS material exhibited a tetragonal spodumene-II phase. In contrast, the LSS material showed a hexagonal spodumene-III phase. The crystallite sizes were 21.96 μm for NSS and 22.14 μm for LSS, with crystallinity percentages of 60.77% and 57.55%, respectively. FTIR spectroscopy verified the successful incorporation of lithium and aluminum into the silica framework. SEM analysis provided detailed insights into surface morphology and particle size distribution, highlighting the uniformity of the materials. Specifically, the LSS material exhibited cylindrical spaces between particles, whereas the NSS material displayed spherical spaces.

ZIF-8 Modified Ce–Sol–gel Film on Rebar for Enhancing Corrosion Resistance

ZIF-8 Modified Ce–Sol–gel Film on Rebar for Enhancing Corrosion Resistance

In-situ carbon integration on atomically dispersed platinum metal oxide nanocomposites for hydrogen evolution reaction

In this study, a novel in-situ carbon growth technique by a modified sol gel synthesis method is presented. The carbon support developed on a transition metal oxide composite transforms the electronic conductivity and is engineered for hydrogen evolution reaction by a dispersion of unit atomic concentration of platinum. Through two different synthesis techniques, platinum dispersion is implemented on the metal oxide-carbon system, one by direct sol-gel technique and another by chemical reduction technique, whereby a homogeneous dispersion of the noble metal on the composite is achieved. Carbon-based cerium oxide and titanium oxide composites are used as the base material, and one atomic percentage of platinum metal is ensured while synthesizing each of the carbon composites. The functionality of these catalysts towards hydrogen evolution reaction in a 0.5 M H2SO4 acidic media revealed the synthesis technique's uniqueness and the effect of metal support interaction that plays a vital role in the electrocatalytic activity. The intrinsic activity of the titania system, along with enhanced metal support interaction due to highly enriched platinum availability on the surface of the substrate, provides for strong electrochemical activity. The titanium oxide carbon composite with platinum dispersed by hydrazine reduction exhibited the finest activity with an overpotential of just 44 mV at j = 10 mA/cm2 and a tafel slope of 118 mV/dec. The gas chromatographic analysis on platinum supported titania catalyst showcased better performance by a margin of four times than the commercial three weight percentage platinum supported carbon.

Zinc oxide-based sensor prepared by modified sol–gel route for detection of low concentrations of ethanol, methanol, acetone, and formaldehyde

Abstract We4 4 We received the acceptance date as 26 September 2024. Could you please update it to reflect this exact date for our project, instead of 1 October 2024? This is very important for our project funding. successfully synthesized zinc oxide (ZnO) nanoparticles using the sol–gel method, followed by their application onto alumina substrates for sensor testing. Comprehensive characterization of the nanomaterials was carried out utilizing XRD, SEM, TEM, UV–VIS-IR, and Photoluminescence (PL) techniques. The nanoparticles displayed a hexagonal wurtzite crystal structure, typical of ZnO. UV–Vis-IR spectroscopy revealed significant absorption in the UV region, with the band gap energy calculated to be 3.22 eV. PL spectra indicated the presence of various defects, such as oxygen vacancies and zinc interstitials, within the ZnO structure. SEM analysis of the deposited film surface showed spherical agglomerates, confirming the nanoscale dimensions, while energy-dispersive x-ray spectroscopy spectra affirmed the high purity of the ZnO films, rich in Zn and O elements. Sensor tests demonstrated the ZnO sensor’s high sensitivity to low concentrations of volatile organic compounds such as ethanol, formaldehyde, methanol, and acetone. Notably, at an operational temperature of 300 °C, the sensor exhibited a remarkable response to 5 ppm of each gas, with the following response and response/recovery times: for methanol, 11.47 and 36 s/57 s; for acetone, 11.54 and 25 s/52 s; for formaldehyde, 0.79 and 53 s/58 s; and for ethanol, 3.88 and 9 s/59 s.

Enhancing Thermochemical Energy Storage Performance of Perovskite with Sodium Ion Incorporation

Perovskite materials are promising for thermochemical energy storage due to their ability to undergo redox cycling over a wide temperature range. Although BaCoO3 exhibits excellent air cycling properties, its heat storage capacity in air remains suboptimal. This study introduces Na into the lattice structure to enhance oxygen vacancy formation and mobility. DFT+U simulations of the surface structure of Na-doped BaCoO3−δ indicate that incorporating Na improves surface stability and facilitates the formation of surface oxygen vacancies. NaxBa1−xCoO3−δ compounds were synthesized using a modified sol–gel method, and their properties were investigated. The experimental results demonstrate that Na doping significantly enhances the redox activity of the material. The heat storage capacity increased by above 50%, with the Na0.0625Ba0.9375CoO3−δ solid solution achieving a heat storage density of up to 341.7 kJ/kg. XPS analysis reveals that Na doping increases the concentration of surface defect oxygen, leading to more active oxygen release sites at high temperatures. This enhancement in redox activity aligns with DFT predictions. During high-temperature cycling, the distribution of Na within the material becomes more uniform, and no performance degradation is observed after 300 cycles. Even after 450 cycles, Na0.0625Ba0.9375CoO3−δ retains over 96% of its initial redox activity, significantly outperforming fresh BaCoO3−δ. These findings elucidate the mechanism by which Na doping enhances the thermochemical heat storage performance of BaCoO3−δ and provide new insights for the design of perovskite-based materials.

Highly sensitive and selective rGO-LaFeO3 nanocomposite based formaldehyde sensors towards air quality monitoring

Formaldehyde (HCHO), a ubiquitous volatile organic compound and recognized human carcinogen, is extensively used in industrial applications such as resin and adhesive production. Even minimal exposure to HCHO can induce serious health effects, including respiratory distress and dermal irritation. Thus, the advancement of highly sensitive and selective sensors for HCHO detection is imperative for safeguarding environmental and indoor air quality. Herein, we report the development of a very sensitive, highly selective, and stable HCHO sensor based on reduced graphene oxide (rGO) and lanthanum ferrite (LaFeO3). LaFeO3 and rGO-LaFeO3 nanocomposites with different compositions were synthesized through an affordable and straightforward sol-gel process. Among them, the LFGO(50:1) sensor demonstrated the highest response and selectivity towards HCHO, with a detection limit (theoretically) as low as 19 ppb (1.5 fold). Notably, it exhibited approximately 15-fold p-type response to 1 ppm of HCHO, while operating at 260°C. The sensor also showed quick response and recovery times of around 1.5 seconds and 36 seconds, respectively while having negligible response to other VOCs, including ethanol, methanol, and NH3. A synergistic effect of rGO and LaFeO3 is attributed to this improved sensing behavior. rGO offers a large surface area that facilitates the adsorption of HCHO molecules, while LaFeO3 acts as a catalyst for the oxidation of HCHO. The sensor also showed good selectivity, stability, and reproducibility, making the material a promising candidate for practical applications towards environment monitoring, indoor air quality control, and industrial safety.

Photocatalytic degradation of propranolol hydrochloride in aqueous medium employing bentonite-TiO2 nanocomposites

Propranolol hydrochloride, a widely used medication, contaminates water bodies as it’s not fully metabolized by humans. Conventional water treatment methods are ineffective against it, necessitating more advanced approaches like heterogeneous photocatalysis. TiO2, often used as a photocatalyst, is typically combined with other materials to form nanocomposites, enhancing its activity. This study evaluated TiO2 synthesized via sol–gel method with organophilized bentonite for propranolol removal. Composites were prepared through solvothermal treatment, and an experimental design assessed the TiO2/bentonite ratio, time, and temperature of the solvothermal treatment effects on photocatalytic activity. Increasing these parameters led to a nanocomposite capable of removing over 99 % of propranolol in water after 60 min of adsorption followed by 150 min of photocatalysis. The nanocomposite remained active after four treatment cycles. Characterization revealed TiO2 (anatase) nanoparticles with a size range of 6–13 nm dispersed in bentonite’s fine tubular structures. This research underscores the potential of TiO2-based nanocomposites in addressing pharmaceutical contamination in water bodies efficiently.

Repurposing Industrial and Agricultural Wastes as Sustainable Alternatives in Photovoltaic Cells and Dye Degradation

AbstractCombustion of coal at thermal power plants generates enormous amounts of coal fly ash (CFA). Proper disposal of CFA is an important issue today because environmental problems are considered a burning issue worldwide. On the other hand, groundnut shells (GNS), regarded as agricultural waste in general, litter landfills everywhere and create soil degradation. Since both CFA and GNS contain abundant silica, this work focuses on extracting amorphous silica from these materials through a total dissolution–precipitation process. The silica was extracted from it and used to prepare titanium oxide (TiO₂) hybrids. The GNSS were extracted from GNS, and the CFAS was extracted from the CFA. The methods used were based on sol–gel. These hybrids were further tested for the performance of their solar cells in dissolving dyes. The overall results of the obtained physical properties of CFAS and GNSS are similar to those of conventional silica. More importantly, TiO₂/GNSS and TiO₂/CFAS hybrids showed enhanced photocatalytic efficiency compared to the pure TiO₂. Therefore, it is evidence of repurposing CFA and GNS, which have high potential for use as sustainable applications in renewable energy and environmental remediation.

Up-conversion materials for solid-state lighting

AbstractConventional phosphor-converted white LEDs (WLEDs), using (Stokes) down-conversion light emission, suffer from a red deficiency that increases the Color Temperature towards “cool white light” above 5000 K. The present work describes a phosphor-Up-converted WLED approach that wishes to overcome this issue by achieving white light generation (WLG) through Up-conversion photoluminescence (UCPL), without energy losses due to Stokes shift and excited by a 980 nm LED instead of the more expensive blue LEDs. The UC materials include thin films of lanthanide (Ln)-doped aluminosilicate glass multilayers, alternating (Ln)-doped aluminosilicate and titania films in the form of 1-D photonic crystals and Ln ion-implanted materials. Sol-gel (SG) processing has been used as a low-cost high purity processing method to prepare titania, as well as aluminosilicate films containing Er3+, Tm3+ and Yb3+, for WLG and possible application as WLED materials. The total Ln content varied from a high of 22 mol% to as low as 5.8 mol%. The materials prepared have been characterized by UV-Vis-NIR (using a variable angle specular reflection accessory), plus FTIR and UCPL spectroscopies. The UC light emission was analyzed with the help of CIE chromaticity diagrams. Graphical abstract

Algorithm development and metal oxide nanoparticle analysis in magnetic resonance imaging: Advancing neurodegenerative disease diagnostics

Magnetic resonance imaging (MRI) is critical in the diagnosis of neurodegenerative diseases, enabling the detection of brain lesions. Recent research has examined metallic nanoparticles (NPs) as MRI contrast agents (CAs) that can enhance lesion visibility by altering relaxation times. This study investigates the effects of metal oxide NPs on MRI relaxation times and brain lesion signals and proposes an algorithm for automated relaxation time determination using these NPs. The utilized NPs were synthesized using the sol‒gel method and characterized using Fourier-transform infrared spectroscopy and X-ray diffraction. MRI scans were performed on a phantom infused with varying concentrations of each metal oxide NP to assess changes in pixel signal intensities and relaxation rates. Our analysis involved segmenting the MRI images to focus on regions with different NP concentrations. The algorithm computed the longitudinal relaxation time for each region, revealing that Fe2O3 NPs exhibited the most substantial effect on signal intensity and relaxation time. The results indicated a high correlation (r = 0.9977), demonstrating strong agreement and confirming the reliability of our method. Our findings suggest that metallic oxide NPs, particularly Fe2O3, can considerably alter magnetization and act as effective negative CAs in MRI. These capabilities can improve the monitoring and treatment efficacy of neurodegenerative diseases. Our method for quantifying longitudinal relaxation times can potentially enhance routine clinical MRI assessments, offering a promising tool for future clinical applications.

Synthesis, structure, I–V characteristics, and optical properties of chromium oxide thin films for optoelectronic applications

Abstract Improving coating technology and thin film formation by optimizing the experimental parameters has become essential for various industrial and technological fields. This work aims to study the influence of the precursor materials on the physical and electro-optical properties of Cr2O3 thin films. The solutions were prepared using the sol–gel route and deposited on glass slides using the spin coating technique. The structure and morphology of the films were studied using XRD, FT-infrared (IR), and field-emission scan-electron microscope. The results indicated the formation of a high-purity Cr2O3 (Eskolaite) phase in the form of spherical nanoparticles with sizes of 17–25 nm. Three bands appear at 490, 765, and 889 cm − 1 {{\rm{cm}}}^{-1} in the FTIR spectra, which are attributed to Cr – O {\rm{Cr}}{\rm{\mbox{--}}}{\rm{O}} / Cr ═ O {\rm{Cr}}{\rm{═}}{\rm{O}} vibrations. The I–V curves showed linear behavior and good ohmic features. Ultraviolet-visible-near infrared spectra showed that the films are highly transparent, with band gaps in the range of 2.60–2.90 eV, and refractive indices in the range of 1.92–2.25. The sheet resistances, the new figure of merit, the real and fictional dielectric constants, and the optical conductivity were discussed. The Cr2O3 thin films are the best candidates for various utilizations, including solar cells, sensors in the IR region, and energy storage.

Photocatalytic remediation of fluoranthene contaminated soil by eco-friendly GQDs/TiO2/α-FeOOH composite photocatalyst: Efficiency, influence factors, mechanism, and toxicity analysis

Polycyclic aromatic hydrocarbons (PAHs), as a persistent organic pollutant, have adverse effects on soil environment and human health. In this study, a new type of iron-based material graphene quantum dots (GQDs)/TiO2/α-FeOOH was used to construct a photocatalytic system to achieve effective degradation of fluoranthene in soil. The hydrothermal method and sol–gel method were used to synthesize GQDs/TiO2/α-FeOOH composite photocatalyst, which exhibited enhanced photocatalytic activity by promoting charge transfer, increasing specific surface area, and broadening light absorption range. The degradation ratio of fluoranthene in soil suspension by GQDs/TiO2/α-FeOOH was 67.37 % under the condition of 24 h of simulated sunlight irradiation, water/soil ratio of 10:1, and catalyst dosage of 50 mg/g. •O2– and h+ played the major roles in degradation process, and the catalytic mechanism was proposed. The degradation products and degradation pathway of fluoranthene were analyzed by GC–MS detection and DFT calculation, and the toxicity of degradation products was predicted by simulation calculation. The effect of remedial soil on seed germination was investigated through germination test of tomato seeds, and results showed that the productivity of fluoranthene contaminated soil was recovered in a certain extent.

Hybrid Activity of P–Si–N Moieties for Improved Fire Retardancy of Cotton Fabric Coated Using Sol-Gel Process

A sol-gel matrix was generated from S– and P-based acids to prepare a fire-retardant solution system for coating natural cotton fibers. The physical properties, surface morphology, and elemental composition of the coated samples were assessed using optical scanning electron microscopy. The thermal behavior of the coated samples was documented using TGA and VFT tests, which confirmed higher thermal stability of the phosphate-based coatings. High char residue formation (~44.5%) and self-extinguishing properties were observed for the phosphate-based coating under non-curing conditions. The superior properties of phosphate-based coatings P5-4h could be ascribed to the collaborative effect of P–Si–N—i.e., the combined activity during the combustion process and pyrolysis of the coated sample.