SiO2 Nanostructures Research Articles

Elucidation on Abnormal Capacity Increase in SiO2@C Core-Shell Nanospheres Anode for Lithium-Ion Battery.

An abnormal capacity increase stage has been observed in nanostructured SiO2 after the initial capacity drop stage. To investigate the Li+ storage kinetic mechanism for each stage, SiO2@C core-shell nanospheres with a total diameter of ∼108 to 170 nm but an adjustable C shell thickness of ∼4 to 31 nm have been fabricated. First, the existence form and specific content of SiO2 nanoparticles with a size of ∼6-10 nm, which are embedded in the outer C shell of SiO2@C core-shell nanospheres, were confirmed by SEM, TEM, BET, and TGA, respectively. It was found that the initial stage for capacity drop happens at 15-43 cycles and is followed by an enhancement stage, which presents an increase of ∼120 to 180% in capacity relative to the lowest capacity value during cycling. Among them, the sample of P-1 with a diameter of 109 nm for the SiO2 core and thickness of 31 nm for the C shell delivers the highest specific capacity of 1060 mAh/g at 100 mA/g and a capacity increase rate of ∼180% through 300 cycles. XPS analysis for the delithiation process indicates that the capacity drop and increase stage involves the partial oxidation of Li silicate, which is correlated to the formation of Li2Si2O5. Our study can be used to explain the mechanism of the abnormal capacity increase phenomenon for the SiO2 anode and provide a high-capacity anode material for LIB application.

Tuning the Immune Cell Response through Surface Nanotopography Engineering

Dendritic cells (DCs) are central regulators of the immune response by detecting inflammatory signals, aberrant cells, or pathogens. DC‐mediated immune surveillance requires morphology changes to adapt to the physical and biochemical cues of the external environment. These changes are assisted by a dynamic actin cytoskeleton–membrane interface connected to surface receptors that will trigger signaling cascades. In recent years, the development of synthetic immune environments has allowed to investigate the impact of the external environment in the immune cell response. In this direction, the bioengineering of functional topographical features should make it possible to establish how membrane morphology modulates specific cellular functions in DCs. Herein, the engineering of one‐dimensional nanostructured SiO2 surfaces by soft‐nanoimprint lithography to manipulate the membrane morphology of ex vivo human DCs is reported. Super‐resolution microscopy and live‐cell imaging studies show that vertical pillar topographies promote the patterning and stabilization of adhesive actin‐enriched structures in DCs. Furthermore, vertical topographies stimulate the spatial organization of innate immune receptors and regulate the Syk‐ and ERK‐mediated signaling pathways across the cell membrane. In conclusion, engineered SiO2 surface topographies can modulate the cellular response of ex vivo human immune cells by imposing local plasma membrane nano‐deformations.

Volcanic Eruption in the Nanoworld: Efficient Oxygen Exchange at the Si/SnO2 Interface.

Here, a phenomenon of efficient oxygen exchange between a silicon surface and a thin layer of tin dioxide during chemical vapor deposition is presented, which leads to a unique Sn:SiO2 layer. Under thermodynamic conditions in the temperature range of 725-735°C, the formation of nanostructures with volcano-like shapes in "active" and "dormant" states are observed. Extensive characterization techniques, such as electron microscopy, X-ray diffraction, synchrotron radiation-based X-ray photoelectron, and X-ray absorption near-edge structure spectroscopy, are applied to study the formation. The mechanism is related to the oxygen retraction between tin(IV) oxide and silicon surface, leading to the thermodynamically unstable tin(II)oxide, which is immediately disproportionate to metallic Sn and SnO2 localized in the SiO2 matrix. The diffusion of metallic tin in the amorphous silicon oxide matrix leads to larger agglomerates of nanoparticles, which is similar to the formation of a magma chamber during the natural volcanic processes followed by magma eruption, which here is associated with the formation of depressions on the surface filled with metallic tin particles. This new effect contributes a new approach to the formation of functional composites but also inspires the development of unique Sn:SiO2 nanostructures for diverse application scenarios, such as thermal energy storage.

Application of High-Surface Tension and Hygroscopic Ionic Liquid-Infused Nanostructured SiO2 Surfaces for Reversible/Repeatable Anti-Fogging Treatment

Anti-fogging coatings/surfaces have attracted much attention lately because of their practical applications in a wide variety of engineering fields. In this study, we successfully developed transparent anti-fogging surfaces using a non-volatile and hygroscopic ionic liquid (IL), bis(hydroxyethyl)dimethylammonium methanesulfonate ([BHEDMA][MeSO3]), with a high surface tension (HST, 66.4 mN/m). To prepare these surfaces, a layer of highly transparent, superhydrophilic silica (SiO2) nano-frameworks (SNFs) was first prepared on a glass slide using candle soot particles and the subsequent chemisorption of tetraethoxysilane (TEOS). This particulate layer of SNFs was then used as the support for the preparation of the [BHEDMA][MeSO3] layer. The resulting IL-infused SNF-covered glass slide was highly transparent, superhydrophilic, hygroscopic, and had self-healing and reasonable reversible/repeatable anti-fogging/frosting properties. This IL-infused sample surface kept its excellent anti-fogging performance in air for more than 8 weeks due to the IL’s non-volatile, HST, and hygroscopic nature. In addition, even if the water absorption limit of [BHEDMA][MeSO3] was reached, the anti-fogging properties could be fully restored reversibly/repeatably by simply leaving the samples in air for several tens of minutes or heating them at 100 °C for a few minutes to remove the absorbed water. Our IL-based anti-fogging surfaces showed substantial improvement in their abilities to prevent fogging when compared to other dry/wet (super)hydrophobic/(super)hydrophilic surfaces having different surface geometries and chemistries.

Multi-scale study on strength development, hydration behavior and phase evolution of recycled powder multi component cementitious materials

Recycled powder (RP) is considered to be a successful low-carbon alternative to ordinary Portland cement (OPC). However, the microstructure and synergistic mechanism of RP multi-component cementitious materials (RP-MCCM) after physical activation are still unclear. The purpose of this study is to study the strength development, hydration and phase structure evolution of MCCM by constructing RP-MCCM. When the content of RP after grinding activation is 30% (C70RG30), its 28 days compressive strength is increased by 7.6% on the basis of non-activation. Compared with the ternary system of RP and FA mixed with 15% (C70RG15F15), its 28 days compressive strength increased by 8.08%. After RP incorporation, the Al-OH is enhanced, the C-O and CO32- bonds peaks become narrower, and the S is evenly distributed, which is beneficial to the increase of the AFt and the CaCO3 content, but weakens the C-S-H and C-A-H phases. In the C70RG15F15 ternary system, CaCO3, Ca(OH)2, and SiO2 nanostructures are tightly bonded together without obvious faults, which improves the structural compactness and strength. RP grinding activation is mainly manifested in surface improvement, internal C-S-H activation and increase of active sites.

Cu-O-Si-C interface-induced high-adhesion and anticorrosion of the DLC coatings on inner wall of copper tube prepared by PECVD

Deposition of well-adherent diamond-like‑carbon (DLC) films on copper is relatively difficult due to weak bonds between copper and carbon. The Cu-O-Si-C nanostructure was proposed to improve the adhesion and the corrosion-resistance of multilayer Si-DLC/DLC film on an inner surface of copper tube prepared by PECVD. First, the copper alloy was pretreated by oxygen. Then mixture gas of tetramethylhexylsilane (TMS) and oxygen was used to deposit interlayer, and finally multilayer Si-DLC/DLC film was deposited using the gas C2H2 and argon. Transmission Electron Microscope (TEM) demonstrated that there existed CuSiO3, CuO, SiC, SiO2 nanostructures in the interlayer. And X-ray Photoelectron Spectroscopy (XPS) proved that there were actually CuO, SiC and SiO bonds at the interface. These bonds and compounds enhanced the adhesion between multilayer Si-DLC/DLC film and copper substrate. The polarization potential was significantly improved to −0.07 V, achieved through the process of oxygen pre-implantation and the combined deposition of oxygen and TMS. Furthermore, the adhesion of the film was estimated by the Rockwell test and reached HF1-HF2. The Cu-O-Si-C microstructure plays a crucial role in enhancing the adhesion and corrosion resistance of multilayer Si-DLC/DLC film.

Deposition of high-quality, nanoscale SiO2 films and 3D structures

Silicon dioxide (SiO2) is ubiquitous in biomedical diagnostics and other applications as a capture medium for nucleic acids and proteins. Diagnostic devices have seen rapid miniaturisation in recent years, due to the increased demand for portable point-of-care diagnostics. However, there are increasing challenges with incorporating SiO2 nanostructures into diagnostic devices, due to the complexity of nanostructured SiO2 synthesis, often involving etching and chemical vapour deposition under high vacuum conditions.We report a novel and straightforward method for deposition of high-quality, nanoscale SiO2 films and 3D SiO2 structures using thermal decomposition of polydimethylsiloxane (PDMS), in a furnace at atmospheric pressure at 500 °C. This method allows individual nanometre controllability of conformal pinhole-free layers on a variety of materials and morphologies. The temperature ramp rate is a key factor in determining the SiO2 deposit morphology, with slower ramp rates leading to highly conformal 2D films and faster ones yielding 3D nanodentrite structures. For the 2D films, the film thickness, as determined by spectroscopic ellipsometry and confirmed by SEM data, is shown to correlate excellently with initial PDMS source material mass in the thickness range 0.8–18 nm. Fits to ellipsometry models confirm that the refractive index of the deposited film matches the expected value for SiO2, while electrical breakdown measurements confirm that the breakdown strength of the films is comparable to that of high-quality thermal oxides. Depositions on high aspect ratio ZnO nanostructures are shown to be highly conformal, leading to core-shell ZnO-SiO2 nanostructures whose shell thickness is in excellent agreement with the expected values from deposition on planar substrates. At faster ramp rates an abrupt morphological transition is seen to a deposit which displays a 3D nanodentrite morphology. The possibilities for applications of both morphologies (and core-shell combinations with other nanostructured materials) in biosensing and related areas are briefly discussed, and the DNA capture capabilities of each nanostructure are measured. The high aspect ratio nanodendrite structures allow for significant DNA capture within microfluidic devices in the presence of low DNA concentrations, with a maximum average capture efficiency of 43.4 % achieved in the presence of 10 ng/mL of DNA, which is an improvement by a factor of ∼ 3 over planar Si surfaces. Improvements by factors of >10 over planar surfaces were achieved at higher DNA concentrations of 100 and 1000 ng/mL.

Formation of intraneuronal iron deposits following local release from nanostructured silica injected into rat brain parenchyma

Nanostructured materials with controllable properties have been used to cage and release various types of compounds. In the present study, iron-loaded nanostructured sol-gel SiO2–Fe materials were prepared and injected into the rat brain to develop a method for gradual iron delivery into the neurons with the aims to avoid acute iron toxicity and develop an animal model of gradual, metal-induced neurodegeneration. Nanoparticles were prepared by the traditional method of hydrolysis and condensation reactions of tetraethyl orthosilicate at room temperature and subsequent heat treatment at 200 °C. FeSO4 was added in situ during the silica preparation. The resulting materials were characterized by UV-VIS and infrared spectroscopies, X-ray diffraction, and N2 adsorption-desorption. An in vitro ferrous sulfate release test was carried out in artificial cerebrospinal fluid as the release medium showing successful ferrous sulfate loading on nanostructured silica and sustained iron release during the test time of 10 h. Male Wistar rats administered with SiO2–Fe nanoparticles in the substantia nigra pars compacta (SNpc) showed significant intraneuronal increase of iron, in contrast to the animals administered with FeSO4 that showed severe neuronal loss, 72 h post-treatment. Both treatments induced lipid fluorescent product formation in the ventral midbrain, in contrast to iron-free SiO2 and PBS-only injection controls. Circling behavior was evaluated six days after the intranigral microinjection, considered as a behavioral end-point of brain damage. The apomorphine-induced ipsilateral turns in the treated animals presented significant differences in relation to the control groups, with FeSO4 administration leading to a dramatic phenotype, compared to a milder impact in SiO2–Fe administrated animals. Thus, the use of SiO2–Fe nanoparticles represents a slow iron release system useful to model the gradual iron-accumulation process observed in the SNpc of patients with idiopathic Parkinson's disease.

Structural control of nanoporous frameworks consisting of minimally stacked graphene walls

This mini-review provides an in-depth analysis of the formation and post-processing of nanoporous graphene materials via methane chemical vapor deposition (CH4-CVD) using nanostructured metal oxide templates, including Al2O3, MgO, and SiO2. Initially, the formation of graphene sheets is discussed in terms of the role of CH4-CVD, the influence of templates, and the underlying mechanism for tailoring the structures of the graphene-based materials. Following this, the discussion extends to the post-graphene formation process. We focus on key steps, including template removal and graphene repair via zipping reactions at high temperatures. Additionally, we evaluate the conditions to prevent undesired structural transformations. The correlation between the structural features and transformations occurring during post-processing is also examined. The materials fabricated through these methods exhibit impressive properties of high porosity, minimal edge sites, superior oxidation resistance, and elasticity, positioning them as promising materials in various applications.

Microwave-assisted sol-gel synthesis of mesoporous NiO-decorated silica nanostructures utilizing biogenic silica source for supercapacitor applications

Developing efficient and sustainable energy storage materials is essential for supercapacitor technology. This study presents a microwave-assisted sol-gel synthesis of nickel oxide-decorated SiO2 nanostructures employing rice husk as a silica source for supercapacitor application. Rice husk, an abundant agricultural waste, was utilized as a cost-effective and environmentally friendly precursor for silica synthesis. Sol-gel synthesis assisted by microwaves allowed rapid and controlled formation of the silica nanostructure via alkaline extraction with NaOH, acidification with acetic acid, and capping with PEG. Likewise, nickel precursor with an appropriate concentration was introduced during the formation of silica nanostructures, leading to NiO-decorated silica nanostructures. XRD, FTIR, BET, FESEM, EDS, and HRTEM analysis demonstrated that NiO was decorated on the silica nanostructure distinctly depending on the concentration of nickel precursor. The electrochemical studies using 2 M KOH electrolyte revealed that the maximum specific capacitance of RH-SiO2, NiO@RH-SiO2-1, and NiO@RH-SiO2-2 was found to be 102 F/g, 405 F/g, and 506 F/g at a current density of 0.5 A/g with superior energy density and power density. It is also found that the electrode exhibits high-capacitance retention and good cycle stability after 5000 cycles. The obtained result revealed that when the nickel precursor concentration was increased, the specific capacitance was also increased because high nickel precursor concentration leads to the formation of NiO species which can serve as reactive surfaces for carrier transport. Moreover, the asymmetric supercapacitor (ASC) was fabricated using NiO@RH-SiO2-2 and it provides an excellent energy density of 31.25 Wh kg−1 at a power density of 745 W kg−1 with long-term cyclic stability (96.4% specific capacitance retention after 10,000 cycles). Based on these results, NiO-decorated silica nanostructures can be a promising electrode material for supercapacitor applications.

Space Charge Characteristics and Breakdown Properties of Nanostructured SiO2/PP Composites

Polypropylene (PP) has gained attention in the industry as an environmentally friendly material. However, its electrical properties are compromised due to space charge accumulation during operation, limiting its application in high-voltage DC cable insulation. This study investigates the effect and mechanism of SiO2 with a DDS surface hydrophobic treatment on space charge suppression and the electrical properties of PP composites. The PP matrix was doped with SiO2 nanostructures, both with a DDS surface hydrophobic treatment and untreated as a control group. The functional group structure and dispersion of nanostructured SiO2 in the matrix were characterized. The findings reveal that the incorporation of SiO2 nanostructures effectively mitigates charge accumulation in PP composites. However, a high concentration of unsurfaced nanostructures tends to agglomerate, resulting in inadequate space charge suppression and a diminished DC breakdown field strength. Nonetheless, surface treatment improves the dispersion of SiO2 within the matrix. Notably, the composite containing 1.0 wt% of surface hydrophobic SiO2 exhibits the least space charge accumulation. Compared to the base material PP, the average charge density is reduced by 83.9% after the 1800 s short-circuit discharges. Moreover, its DC breakdown field strength reaches 3.45 × 108 V/m, surpassing pure PP by 19.4% and untreated SiO2/PP composites of the same proportion by 24.0%.

Unveiling the SO2 Resistance Mechanism of a Nanostructured SiO2(x)@Mn Catalyst for Low-Temperature NH3-SCR of NO.

Low N2 selectivity and SO2 resistance of Mn-based catalysts for removal of NOx at low temperatures by NH3-SCR (selective catalytic reduction) technology are the two main intractable problems. Herein, a novel core-shell-structured SiO2@Mn catalyst with greatly improved N2 selectivity and SO2 resistance was synthesized by using manganese carbonate tailings as raw materials. The specific surface area of the SiO2@Mn catalyst increased from 30.7 to 428.2 m2/g, resulting in a significant enhancement in NH3 adsorption capacity due to the interaction between Mn and Si. Moreover, the N2O formation mechanism, the anti-SO2 poisoning mechanism, and the SCR reaction mechanism were proposed. N2O originated from the reaction of NH3 with O2 and the SCR reaction, as well as from the reaction of NH3 with the chemical oxygen of the catalyst. Regarding improving the SO2 resistance, DFT calculations showed that SO2 was observed to preferentially adsorb onto the surface of SiO2, thus preventing the erosion of active sites. Adding amorphous SiO2 can transform the reaction mechanism from Langmuir-Hinshelwood (L-H) to Eley-Rideal (E-R) by adjusting the formation of nitrate species to produce gaseous NO2. This strategy is expected to assist in designing an effective Mn-based catalyst for low-temperature NH3-SCR of NO.

Rational Design of a Biocatalyst Based on Immobilized CALB onto Nanostructured SiO2

The adsorption of the lipase B from Candida antarctica (CALB) over nanostructured SiO2 (Ns SiO2 from now on) with and without the addition of polyols (sorbitol and glycerol) was investigated. The isotherms of adsorption made it possible to establish that the maximum dispersion limit was 0.029 µmol of protein per surface area unit of Ns SiO2 (29.4 mg per 100 mg of support), which was reached in 30 min of exposure. The studies through SDS-PAGE of the immobilization solutions and infrared spectroscopy of the prepared solids determined that CALB (from a commercial extract) is selectively adsorbed, and its secondary structure distribution is thus modified. Its biocatalytic activity was corroborated through the kinetic resolution of rac-ibuprofen. Conversions of up to 70% and 52% enantiomeric excess toward S-ibuprofen in 24 h of reaction at 45 °C were achieved. The biocatalytic performance increased with the increase in protein loading until it leveled off at 0.021 µmol.m−2, reaching 0.6 µmol.min−1. The biocatalyst containing the lipase at the maximum dispersion limit and co-adsorbed polyols presented the best catalytic performance in the kinetic resolution of rac-ibuprofen, an improved thermal resistance (up to 70 °C), and stability under long-term storage (more than 2 years).

Elastic properties of SiO2 nanostructure in high-pressure conditions

In this study, the elastic properties of two high-pressure polymorphs SiO2 nanostructure, stishovite and CaCl2-type, are obtained using Density Functional Theory in 0-80 GPa high pressure domain at zero temperature, based on reducing an interacting many-electron problem to a single-electron problem. It is shown that below 40 GPa, the stishovite phase is more stable; superior to this limit, the CaCl2-type phase becomes more stable, using Gibbs free energy method. Furthermore, the pressure dependence of the density, volume, bulk, and shear moduli were defined in the selected pressure domain.

Biomass-derived carbon coated SiO2 nanotubes as superior anode for lithium-ion batteries

Silica (SiO2) is regarded as a promising anode for lithium-ion batteries due to the high specific capacity, abundant resources and low cost. However, the inherently poor electrical conductivity and the huge volume variation during charge/discharge process significantly hinder the application of SiO2. Designing nanostructured SiO2 and coating with high conductivity materials are effective methods to solve the above challenges. In this work, advanced SiO2 anodes were prepared by coating hollow SiO2 nanotubes (SNTs) with lignin or phenolated and depolymerized lignin furfural resin (PDLF)-derived carbon. The novel structure of the obtained SNTs greatly promotes the rapid transport for both Li+ and electron, increases the exposed active sites for Li+ insertion and accommodates the volume change of SNTs. Especially, PDLF possesses abundant functional groups, high carbon content and thermosetting property, which are beneficial to the dispersion of SNTs and formation of a cross-linked 3D conductive network. Thereby, SNTs@C-PDLF presents higher specific capacity of 661 mAh g−1 at 100 mA g−1, superior rate capability (262 mAh g−1 at 3000 mA g−1) and better cycling stability (549 mAh g−1 at 1000 mA g−1 after 800 cycles) compared with SNTs@C-lignin and pristine SNTs.

Environmentally friendly mesoporous SiO2 with mixed fiber/particle morphology and large surface area for enhanced dye adsorption

Rice straw is made up of hemicelluloses (19–27%), celluloses (32–47%), lignin (5–24%), and ash (13–20%), which are all agricultural waste. Rice straw ash is considered a green/eco-friendly source of silicon dioxide (SiO2). This study focuses on the synthesis and characterization of different mesoporous SiO2 nanostructures derived from rice straw waste material through controlling the pH of the extraction process for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR), diffuse reflectance spectroscopy (DRS), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscope (HRTEM), zeta potential, and surface area analyzer were used to examine the produced materials. Amorphous silica nanostructures, S3 and S7, were produced at pH values of 3 and 7, respectively, according to XRD measurement, whereas higher pH causes the production of crystalline silica (S9). The pH of the extraction has a major effect on the morphology of the resultant nanosilica, as S3 has an irregular shape, S7 is made of distorted spherical particles, and S9 is composed of mixed fiber and spherical particle structures. For pollutant removal, greenly produced SiO2 nanostructures were used. The optimal mesoporous nanosilica (S9) demonstrated the highest surface roughness, the largest surface area (262.1 m2/g), the most negative zeta potential (− 20.2 mV), and the best dye adsorption capacity (71.4 mg/g).

Templated Synthesis of SiO2 Nanotubes for Lithium-Ion Battery Applications: An In Situ (Scanning) Transmission Electron Microscopy Study.

One of the weaknesses of silicon-based batteries is the rapid deterioration of the charge-storage capacity with increasing cycle numbers. Pure silicon anodes tend to suffer from poor cycling ability due to the pulverization of the crystal structure after repeated charge and discharge cycles. In this work, we present the synthesis of a hollow nanostructured SiO2 material for lithium-ion anode applications to counter this drawback. To improve the understanding of the synthesis route, the crucial synthesis step of removing the ZnO template core is shown using an in situ closed gas-cell sample holder for transmission electron microscopy. A direct visual observation of the removal of the ZnO template from the SiO2 shell is yet to be reported in the literature and is a critical step in understanding the mechanism by which these hollow nanostructures form from their core-shell precursors for future electrode material design. Using this unique technique, observation of dynamic phenomena at the individual particle scale is possible with simultaneous heating in a reactive gas environment. The electrochemical benefits of the hollow morphology are demonstrated with exceptional cycling performance, with capacity increasing with subsequent charge-discharge cycles. This demonstrates the criticality of nanostructured battery materials for the development of next-generation Li+-ion batteries.

Green route synthesis and characterization of β-Bi2O3/SiO2 and β-Bi2O3/Bi2O2.75/SiO2 using Juglans regia L. shell aqueous extract and photocatalytic properties for the degradation of RB-5

BackgroundPhotocatalyst oxides added with silicon improve their photocatalytic properties. In this research, nanostructured β-Bi2O3/SiO2 and β-Bi2O3/Bi2O2.75/SiO2 were obtained by means of a green method mediated by the using the aqueous extract of J. regia shell as the source of reducing biomolecules and as a natural source of plant silicon.MethodThe β-Bi2O3/SiO2 and β-Bi2O3/Bi2O2.75/SiO2 nanostructures were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and photoluminescence spectroscopy. The photocatalytic activity was measured by the degradation of Reactive Black 5 dye (RB-5).ResultsFT-IR and XPS demonstrated the presence of plant silicon in the bismuth oxide photocatalysts. HR-TEM showed that the crystal size of the as-synthesized materials is ~ 25 nm and revealed that the β-Bi2O3 synthesized with ground shell extract and heat-treated at 300 °C contains the Bi2O2.75 phase. Good photocatalytic activity was found in all the studied materials; particularly, the heat-treated nanostructures showed excellent properties resulting in 92% degradation of RB-5 under UV–Vis light after 15 min of exposure, and 98% after 180 min.ConclusionsThe findings of this research suggest that the metabolites coating the Bi2O3, which generate a large amount of hydroxyl radicals, the plant silicon content, and the crystalline defects conferred by the synthesis medium, all contribute to the improved degradation of the azo dye, providing the nanostructures with better photocatalytic activity.

SPR based refractive index modulation of nanostructured SiO2 films grown using GLAD assisted RF sputtering technique

Low refractive index materials have always gained attention for avoiding optical losses in numerous devices like Light emitting diodes (LEDs), Distributed Bragg Reflectors (DBRs) etc. Glancing angle deposition (GLAD) has proven to be an effective method for depositing porous nanostructures with low refractive index. SiO2 has the lowest refractive index in comparison to most of the materials present in nature and is therefore utilized extensively in the fabrication of optical devices with minimum optical losses. The present work focuses on the SiO2 nanostructured thin films grown using glancing angle (GLAD) configuration in RF Sputtering technique under varying deposition conditions (glancing angle and pressure) at fixed thickness. The deposited porous SiO2 nanostructured layers have well-defined nanorods of feature size smaller than 100 nm. The refractive index corresponding to all the deposited SiO2 nanostructured films came out to be smaller than the corresponding value (1.49) mentioned in the literature for bulk SiO2. The refractive index has been observed to vary in a wide range (1.05 to 1.40). Characterization of the deposited SiO2 nanostructured films was carried out using Fourier Transform Infrared (FTIR) spectroscopy, Energy Dispersive X-Ray (EDS) analysis, and Atomic Force Microscopy (AFM) to assess the qualitative properties of the deposited nanostructured SiO2 films. Surface Plasmon Resonance (SPR) and Ellipsometry studies are performed to determine the refractive index value of the deposited nanostructured SiO2 thin films. A refractive index value as low as ∼ 1.05 at a wavelength of 633 nm is achieved for SiO2 nanostructured thin film deposited at 30 mTorr deposition pressure and 80° glancing angle.

Improvement of the optical transmittance of a SiO2 surface by a femtosecond-laser-induced homogeneous nanostructure formation

It has been reported that periodic nanostructures with a period size of 200–330 nm can be formed on silicon suboxide (SiO x , x ≈ 1) with 800-nm, 100-fs laser pulses at a fluence much smaller than that needed for nanostructuring on glasses such as fused silica and borosilicate glass. We demonstrated that a homogeneous SiO2 nanostructure with a period of ∼240 nm can be produced using a two-step ablation process and heat treatment in air at 1000°C for 144 hours. Optical microscopic images of the nanostructured surface illuminated by non-polarized visible light show that the transmittance increases as the reflectivity decreases.