Bioactive magnetic nanoparticles of Fe–Ga synthesized by sol–gel for their potential use in hyperthermia treatment

Hyperthermia is one of the most recents therapies for cancer treatment using particles with nanometric size and appropriate magnetic properties for destroying cancer cells. Magnetic nanoparticles (MNP’s) of Fe–Ga and synthesized using a polycondensation reaction by sol–gel method were obtained. MNP’s of Fe_1.4Ga_1.6O₄ that posses an inverse spinel structure were identified by X-Ray Diffraction, Transmission Electron Microscopy, Scanning Electron Microscopy and Energy Dispersive Spectroscopy. The results showed that the MNP’s are composed only by Fe, Ga and O and their size is between 15 and 20 nm. The magnetic properties measured by Vibration Sample Magnetometry demonstrated a saturation magnetization value of 37.5 emu/g. To induce the MNP’s bioactivity, a biomimetic method was used which consisted in the immersion of MNP’s in a Simulated Body Fluid (SBF) for different periods of time (7, 14 and 21d) along with a wollastonite disk. The formation of a bioactive layer, which closely resembles that formed on the existing bioactive systems and with a Ca/P atomic ratio within a range of 1.37–1.73 was observed on the MNP’s. Cytotoxicity of MNP’s was evaluated by in vitro hemolysis testing using human red blood cells at concentrations between 0.25 and 6.0 mg/mL. It was found that the MNP’s were not cytotoxic at none of the concentrations used. The results indicate that Fe–Ga MNP’s are potential materials for cancer treatment of both hard and soft tissue by hyperthermia and drug carriers, among other applications.     

Opto-electronic and antibacterial activity investigations of mono-dispersed nanostructure copper oxide prepared by a novel method: reduction of reactive oxygen species (ROS)

A novel approach for synthesis of copper oxide nanoparticles is reported by separation of nucleation and growth. The nano-material was characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and UV–Vis diffuse reflectance spectroscopy, transmission electron microscopy, atomic force microscopy, and Brunauer–Emmett–Teller analyses. Optical analysis of mono-dispersed nanostructure copper oxide by UV–Vis diffused reflectance spectroscopy showed the band gap value of 1.47 eV with a blue-shift in the optical band gap due to quantum confinement effect. The dynamic light scattering and zeta potential results showed fairly narrow size distribution and colloidal stability. The results showed that nano-particles were mono-dispersed spheres of 8 nm with no aggregation. Cell viability of treated murine fibroblast cell line (L-929) treated by different concentrations of nanoparticles showed significant viability up to 96% at concentrations 15 and 30 μg ml^?1. The nanoparticles exhibited outstanding and stable antibacterial activity against Staphylococcus aureus ATCC 6538 at 30 µg ml^?1. The viability and reactive oxygen species (ROS) generation in the L-929 cell line indicated that the nanoparticles were not toxic at the concentrations which were effective on bacteria. ROS analysis using DCFH-DA probe on L-929 were exposed to 7.5–60 μg ml^?1 of copper oxide nanoparticles in 6 h revealed ROS generation was decreased dramatically compare to the untreated cells and positive control.     

Controlled-release formulation of perindopril erbumine loaded PEG-coated magnetite nanoparticles for biomedical applications

Iron oxide nanoparticles (FNPs) were synthesized due to low toxicity and their ability to immobilize biological materials on their surfaces by the coprecipitation of iron salts in ammonia hydroxide followed by coating it with polyethylene glycol (PEG) to minimize the aggregation of iron oxide nanoparticles and enhance the effect of nanoparticles for biological applications. Then, the FNPs–PEG was loaded with perindopril erbumine (PE), an antihypertensive compound to form a new nanocomposite (FPEGPE). Transmission electron microscopy results showed that there are no significant differences between the sizes of FNPs and FPEGPE nanocomposite. The existence of PEG–PE was supported by the FTIR and TGA analyses. The PE loading (10.3 %) and the release profiles from FPEGPE nanocomposite were estimated using ultraviolet–visible spectroscopy which showed that up to 60.8 and 83.1 % of the adsorbed drug was released in 4223 and 1231 min at pH 7.4 and 4.8, respectively. However, the release of PE was completed very fast from a physical mixture (FNPs–PEG–PE) after 5 and 7 min at pH 4.8 and 7.4, respectively, which reveals that the release of PE from the physical mixture is not in the sustained-release manner. Cytotoxicity study showed that free PE presented slightly higher toxicity than the FNPs and FPEGPE nanocomposite. Therefore, the decrease toxicity against mouse normal fibroblast (3T3) cell lines prospective of this nanocomposite together with controlled-release behavior provided evidence of the possible beneficial biological activities of this new nanocomposite for nanopharmaceutical applications for both oral and non-oral routes.     

SrWO4:Tb3+ nanoparticles: synthesis,characterization, and luminescence

Nanoparticles of SrWO₄ doped with Tb³⁺ were synthesized in ethylene glycol, Dimethyl sulfoxide, and water. X-ray powder diffractions show that the nanoparticles synthesized in all these solvents have a pure tetragonal scheelite structure without the presence of deleterious phases. Scanning electron microscopy images show that nanoparticles are in the range of 15–25 nm with an inhomogeneous nature. The emission spectra of SrWO₄:xTb³⁺ nanoparticles show the characteristic green emission (545 nm) of Tb³⁺ ions corresponding to ⁵D₄ → ⁷F₅ transition due to efficient charge transfer from WO₄ ^2? to Tb³⁺ ions, when they are excited at 254 nm. Other emissions can be observed due to ⁵D₄ → ⁷F_{6, 4, 3} transitions. The optimum concentration of Tb³⁺ ions for the highest luminescence was found to be 10 mol%. The luminescence intensity of the samples prepared in ethylene glycol is higher than that in Dimethyl sulfoxide and water. The excellent luminescence properties of SrWO₄:Tb³⁺ phosphor makes it as a potential green phosphor.     

Optical properties of Er3+–Ag co-doped ZnO nanocrystals prepared by combustions method

The Er³⁺–Ag co-doped ZnO nanocrystals have been synthesized by citric acid-assisted combustions method. The effect of different concentration of silver nanoparticles (NPs) on Er³⁺ doped ZnO nanocrystals and the optical behaviors are explored. The nanocrystals were characterized by X-ray diffractions, scanning electron microscopy, UV–Vis–NIR absorption spectra, X-ray photoelectron spectroscopy, and photoluminescence, respectively. The luminous intensity of Er³⁺ doped ZnO nanocrystals was significantly influenced by the concentration of silver NPs. A large enhancement in up-conversion intensity has been observed when the concentration of silver NPs was 0.10 mol%. The effect of localized surface plasmon resonance of silver NPs and the energy transfer between the silver NPs and Er³⁺ ions (²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2) are discussed as the sources of enhancement or quenching.     

Low temperature sintering and characteristics of K2O–B2O3–SiO2–Al2O3 glass/ceramic composites for LTCC applications

The K₂O–B₂O₃–SiO₂, K₂O–B₂O₃–SiO₂–2 %Al₂O₃, K₂O–B₂O₃–SiO₂–4 %Al₂O₃ glasses with different Al₂O₃ content were prepared. Different proportions (50, 55, 60, 65, 70 %) of the three glasses were respectively mixed with alumina ceramic-filler, then the mechanical and dielectric properties were investigated. The results showed K₂O–B₂O₃–SiO₂–2 %Al₂O₃ glass/alumina filler (glass:alumina = 60:40) had the excellent comprehensive properties, so further study was continued with part of alumina ceramic-filler replaced by the silica ceramic-filler on this composite. Then the X-ray diffraction analysis revealed that the alumina and silica fillers existed as the crystal phase, and the densification was seriously damaged when the silica content reached to three quarters of the fillers. With the increase of the silica-filler, the composites’ density and dielectric constant exhibited uniform decrease, but thermal expansion coefficient (TEC) uniformly increased. When the glass:alumina:silica was equal to 60:30:10, a best composite property was presented as a bulk density of 2.582 (g cm^?1), a dielectric constant of 6.1 and a dielectric loss of 2 × 10^?3 at 1 MHz, a flexural strength of 168 MPa, and a TEC of 8.62 × 10^?6 °C^?1.     

Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

A new kind of asymmetric organic–inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO₂ hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m^?2 h^?1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology.     

The use of mesoporous silica in the removal of Cu(I) from the cyanidation process

This research proposed the use of a mesoporous silica material (SiO₂) as a Cu(I) adsorbent in a pre-treatment of cyanide effluents employed in gold and silver extraction. Two copper sources were employed: a [Cu(CN) _X ]^?(X+1) standard solution, and a cyanide solution obtained from an ore of Peña de Bernal, Chihuahua, México, which was named Cu(I)–CN–PB. Mesoporous silica removes around 90 % of the Cu(I)–CN at 30 min in Cu(I)–CN solutions with 50 ppm of the metals; while, in a solution with a high concentration of copper (311 ppm), around 52 % was removed. The adsorption dates were adjusted following the Langmuir model; obtained a maximum adsorption capacity (Q ₀) of 8.01 mg g^?1 and a separation factor (R _L) lower than one, which indicates a favorable thermodynamic adsorption process of Cu(I)–CN by SiO₂. However, a similar copper removal capability and low selectivity was observed when Cu(I)–CN–PB was employed as the copper source. Therefore, a modification on the silica’s surface with phenyl groups was performed, in order to enhance the metallic ion selectivity. IR spectroscopy and TGA/DTA analysis confirmed the coupling of organic groups; on the other hand, nitrogen adsorption indicated a decrease on the BET surface area of the silica at 76 %, a modification of the silica structure was observed with the formation of two pore diameter (3.6 and 5.37 nm); ¹³C CP-MAS NMR indicated two different chemical shifts that corresponded to the phenyl groups on the two different pores observed. Phenyl groups enhance the selectivity for copper in the cyanide effluent, increasing the removal to 99 %.     

Enhancing the antifouling property of poly(vinylidene fluoride)/SiO2 hybrid membrane through TIPS method

PVDF/SiO₂ hybrid membranes with outstanding antifouling property were prepared from PVDF/glycerol triacetate system via thermally induced phase separation method, and characterized by scanning electron microscope, energy dispersive X-ray spectrometer analyses, differential scanning calorimeter, and wide angle X-ray diffraction. Their properties such as permeability, porosity, pore size distribution, and mechanical performance were also determined. The results show that SiO₂ nanoparticles modified by 3-aminopropyltriethoxysilane can be uniformly dispersed in membranes due to improved compatibility between PVDF solution and nanoparticles. The addition of SiO₂ particles to PVDF/glycerol triacetate mixture has a strong effect on crystallinity of the resulting hybrid membrane, which does not affect the type of PVDF crystal structure. Water flux recovery ratio is significantly increased from 11.7 % for pure PVDF membrane to 93.8 % for PVDF/SiO₂ hybrid membrane with addition of 8 wt% modified SiO₂. This remarkable promotion is related to the implantation of SiO₂ nanoparticles into the inner surface of membrane, which effectively restrains the adsorption of bovine serum albumin on the pore walls and improves antifouling property of the final membranes. Additionally, pure water flux of the hybrid membrane is increased by 276 %, i.e., from 85 to 320 L m^?2 h^?1, tensile strength is increased by 26.5 %, and elongation at break is increased by 85.4 % compared with that of pure membrane.     

Toward p-type conduction in Cs-doped ZnO: an eco-friendly synthesis method

An alcohol-free, eco-friendly technique was adapted for the synthesis of undoped ZnO and Cs-(cesium) doped ZnO nanoparticles (NPs). The effect of annealing and dopant concentration on its structural and optical properties was investigated. X-ray diffraction results confirmed the formation of polycrystalline hexagonal wurtzite structure and enhanced crystallinity was observed for 1 mol%: Cs-doped ZnO NPs. Scanning electron microscopy results revealed triangular-shaped NPs and increase in the crystallite size is noticed with increase in dopant concentration. UV–visible results showed shift in the band edge toward higher wave length side with increasing Cs concentration. Reduction in bandgap was observed for Cs-doped ZnO NPs, due to quantum confinement effect. Transmittance value increased to 86 % with the inclusion of Cs in ZnO lattice. Room temperature photoluminescence analysis of Cs-doped ZnO NPs reveals bandedge emission along with 450 nm emission due to Zn vacancy and Zn interstitial defects. Electrical measurements confirmed the realization of p-type conductivity in Cs-doped ZnO NPs with a carrier concentration of 1.3 × 10¹⁸/cm³.     

Fabrication and optical properties of ZnS:Mn2+ quantum dots/SiO2 nanocomposites

ZnS:Mn²⁺ quantum dots (QDs)/SiO₂ nanocomposites were successfully synthesized by stöber method. The results showed that the Mn²⁺ ions were substitutionally incorporated into the ZnS host and the average size of the ZnS:Mn²⁺ (5 %) QDs was about 5.5 nm. The yellow–orange emission from the Mn^{2+ 4}T₁–⁶A₁ transition was observed in the photoluminescence spectra, the peak intensity increased as the Mn²⁺ doped ratio increased, and showed a maximum when the concentration of the Mn²⁺ ions kept at 3 %. As the hydrolysis time of tetraethyl orthosilicate increased, the intensity of the yellow–orange emission reached the highest value when t = 4 h for the ZnS:Mn²⁺ (5 %) QDs/SiO₂ nanocomposites.     

Enhanced fermentative production of Cephalosporin C by magnetite nanoparticles in culture of Acremonium chrysogenum

Magnetite (Fe₃ O₄) nanoparticles (MNPs) have many applications in bioprocesses. This study investigated bioprocess production of Cephalosporin C (CPC) by Acremonium chrysogenum. The effect of MNPs was tested for enhancing the fermentation process. MNPs were synthetised by a straightforward method of co‐precipitation. Various concentrations of MNP (0, 0.0025, 0.005, 0.01, 0.02 and 0.04 g/l) were added to fermentation media of the strain. During fermentation, evaluations were taken for titer of CPC, biomass, pH value and morphology of the strain. Comparison was made between CPC produced in the control medium and that in the nanoparticle enriched media from several consecutive batches; it was determined that MNP addition had a positive effect on the bioprocess and enhanced titer production. The titer of CPC in MNP‐containing medium (0.04 g/l) increased by 60% compared with MNP‐free medium. These results show that MNPs present good potential for improving bioprocesses and enhancing productivity of CPC fermentation by A. chrysogenum.Inspec keywords: fermentation, nanoparticles, iron compounds, precipitation (physical chemistry), bioenergy conversion, pH, productivity, biotechnologyOther keywords: fermentative production, Cephalosporin C, magnetite nanoparticles, Achremoneum chrysogenum, bioprocess production, MNP effect, coprecipitation, MNP concentrations, biomass, pH value, strain morphology, enhanced titer production, MNP‐containing medium, MNP‐free medium, CPC fermentation productivity, A. chrysogenum, Fe₂ O₄      

Quantitative determination of raw and functionalized carbon nanotubes for the antibacterial studies

The UV–visible spectrophotometric method has been described the study of raw carbon nanotubes (R-MWCNTs) and functionalized multiwall carbon nanotubes (F-MWCNTs) for the control of bacterial growth by using validated analytical techniques. The absorption spectra of functionalized carbon nanotubes (F-MWCNTs) and raw carbon nanotubes (R-MWCNTs) show maximum absorbance at λ _max 600 nm. The linear relationship was found between absorbance and concentration of R-MWCNTs and F-MWCNTs in the range of 0.25–2.0 μg mL^?1. The linear regression equation was evaluated by statistical treatment of calibration data and gives the value of correlation coefficient for F-MWCNTs (0.9999) and R-MWCNTs (0.9993), which indicate excellent linearity. The Optical and regression characteristics of the proposed method were found apparent molar absorptivity, limits of detection (LOD), and limit of quantitation (LOQ) for R-MWCNTs and F-MWCNTs (5.75 × 10²: 8.25 × 10² L mol^?1 cm^?1), (0.052: 0.018 μg mL^?1), and (0.055: 0.158 μg mL^?1), respectively. The validity of the proposed method was checked by precision, accuracy, linearity, limits of detection (LOD), and limit of quantitation (LOQ). The RSD (%) and quantitative recoveries (%) were obtained (0.026–0.0086) and (100.34 and 100.71) for R-MWCNTs: for F-MWCNTs by UV–visible spectrophotometric, respectively.     

A single flexible nanofiber to obtain simultaneous tunable color-electricity bifunctionality

For the purpose of developing new-typed multifunctional composite nanofibers, novel composite nanofibers with tunable color-electricity bifunctionality have been successfully fabricated via facile one-pot electrospinning technology. The obtained bifunctional composite nanofibers are composed of polyvinyl pyrrolidone (PVP) as the matrix, Tb(BA)₃phen and Eu(BA)₃phen (BA = benzoic acid, phen = phenanthroline) as luminescence materials and polyaniline (PANI) as conductive material. Scanning electron microscopy, energy dispersive spectrometry, fluorescence spectroscopy and Hall effect measurement system are used to characterize the morphology structure and properties of the [Tb(BA)₃phen + Eu(BA)₃phen]/PANI/PVP composite nanofibers. The results indicate that the bifunctional composite nanofibers possess excellent photo luminescence and electrical conduction. The emitting color of the luminescent composite nanofibers can be tuned by adjusting the mass ratios of Tb(BA)₃phen, Eu(BA)₃phen and PANI in a wide color range of red-yellow-green under the excitation of 297-nm single-wavelength ultraviolet light. The electrical conductivity reaches up to the order of 10^?4 S/cm. The luminescent intensity and electrical conductivity of the composite nanofibers can be tunable by adding various amounts of Tb(BA)₃phen, Eu(BA)₃phen and PANI. The bifunctional composite nanofibers are expected to possess many potential applications in areas such as color display, electromagnetic shielding, molecular electronics and biomedicine.     

Passivation and antireflection AZO:H layer in AZO:H/p-Si heterojunction solar cells

In this work, aluminum-doped zinc oxide (AZO)/p-Si heterojunction solar cells were prepared by sputtering of ~120 nm AZO thin films in Ar or Ar–H₂ atmosphere on textured p-Si wafers, and the effects of hydrogen incorporation on the solar cell performance were investigated. Results showed that the performance of AZO/p-Si heterojunction solar cells was improved with the increase of hydrogen volume concentration from 0 to 23 %. The AZO:H/p-Si heterojunction solar cells prepared in Ar–23 % H₂ exhibited a short-circuit current density of 29 mA/cm² and a conversion efficiency of 2.84 %. The reflectance measurement indicated that the reflectance of p-Si surface in the range of 400–1,100 nm decreased from 13 to 4 % after AZO:H films coating; and the capacitance–voltage measurement indicated that the density of defect states at AZO/p-Si interface was decreased after hydrogen incorporation. Passivation and antireflection functions can be realized in AZO:H films deposited in Ar–H₂, which opens a novel route to prepare cost-effective AZO/p-Si heterojunction solar cells.     

Nanoparticles of deoxycholic acid,polyethylene glycol and folic acid-modified chitosan for targeted delivery of doxorubicin

Chitosan (CS) was first modified hydrophobically with deoxycholic acid (DCA) and then with polyethylene glycol (PEG) to obtain a novel amphiphilic polymer (CS–DCA–PEG). This was covalently bound to folic acid (FA) to develop nanoparticles (CS–DCA–PEG–FA) with tumor cell targeting property. The structure of the conjugates was characterised using Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopy and X-ray diffraction. Based on self-aggregation, the conjugates formed nanoparticles with a low critical aggregation concentration of 0.035 mg/ml. The anti-cancer drug doxorubicin (DOX) was encapsulated into the nanoparticles with a drug-loading capacity of 30.2 wt%. The mean diameter of the DOX-loaded nanoparticles was about 200 nm, with a narrow size distribution. Transmission electron microscopy images showed that the DOX-loaded nanoparticles were spherical. The drug release was studied under different conditions. Furthermore, the cytotoxic activities of DOX in CS–DCA–PEG–FA nanoparticles against folate receptor (FR)-positive HeLa cells and FR-negative fibroblast 3T3 cells were evaluated. These results suggested that the CS–DCA–PEG–FA nanoparticles may be a promising vehicle for the targeting anticancer drug to tumor cells.     

Influence of Al2O3/SiO2 ratio on the microstructure and properties of low temperature co-fired CaO–Al2O3–SiO2 based ceramics

In this work, in order to obtain the materials for low temperature co-fired ceramics applications, CaO–Al₂O₃–SiO₂ (CAS) based ceramics were synthesized at a low sintering temperature of 900 °C. The influences of Al₂O₃/SiO₂ ratio on the microstructure, mechanical, electrical and thermal properties were studied. According to the X-ray diffractomer and scanning electron microscopy results, the addition of the Al₂O₃ is advantageous for the formation of the desired materials. Anorthite(CaAl₂Si₂O₈) is the major crystal phase of the ceramics, and the SiO₂ phase is identified as the secondary crystal phase. No new crystal phase appears in the ceramics with the increasing Al₂O₃ content. More or less Al₂O₃ addition would all worsen the sintering, mechanical and dielectric properties of CAS based ceramics. The ceramic specimen (Al₂O₃/SiO₂ = 20/18.5) sintered at 900 °C shows good properties: high bending strength = 145 MPa, low dielectric constant = 5.8, low dielectric loss = 1.3 × 10^?3 and low coefficient of thermal expansion value = 5.3 × 10^?6 K^?1. The results indicate that the prepared CAS based ceramic is one of the candidates for low temperature co-fired ceramic applications.     

Preparation of flexible,hydrophobic, and oleophilic silica aerogels based on a methyltriethoxysilane precursor

We report the synthesis of flexible, hydrophobic, and oleophilic silica aerogels through a two-step acid–base sol–gel reaction followed by supercritical drying, in which methyltriethoxysilane (MTES) is used as a precursor, ethanol (EtOH) as a solvent, and hydrochloric acid (HCl) and ammonia (NH₃·H₂O) as catalysts. At the optimal molar ratio of MTES:EtOH:H₂O:HCl:NH₃·H₂O is 1:18:3.5:1.44 × 10^?4:1.2, MTES-based silica aerogels show the minimum density of 0.046 g/cm³ and the maximum compression ratio of 80 % with 15.09 kPa stress. They are superhydrophobic with a water contact angle of 157° and thermally stable up to 350 °C. We also find that they show the excellent adsorption for ethanol with a ratio of 1400 %.     

Surface passivation of multicrystalline silicon wafers by porous silicon combined with an ultrathin nanoparticles aluminum coating film

In this paper, we demonstrate that we may efficiently improve surface passivation of multi-crystalline silicon (mc-Si) while combining formation of porous silicon (PS) and deposition of ultrathin aluminum (Al) film. Aluminum Nanoparticles were deposited by thermal evaporation onto PS formed on mc-Si wafers. Optoelectronic properties of Al/PS/mc-Si and Al/mc-Si treated samples were investigated before and after annealing in the 400–700 °C temperature range. The surface passivation effectiveness was pointed out based on minority carrier lifetime and photoluminescence measurements. It was found that, at a minority carrier density Δn = 10¹⁵ cm^?3, the effective minority carrier lifetime increases from 1.5 μs (for the bare mc-Si wafer) to about 6 and 14 μs before and after thermal annealing, respectively. FTIR analyses show strong correlation between the minority carrier lifetime values and hydrogen and Al passivation. Major beneficial effect of the co-presence of Al and Al–O on the optoelectronic properties is also demonstrated. The reflectivity of Al/PS treated mc-Si decrease significantly at 500 nm as compared to untreated mc-Si (from 31 % for untreated mc-Si wafers to 8 % for Al/PS treated ones), which is due to the roughly ordered structure and to the Al nanoparticles.     

Thermal blooming and photoluminescence characterizations of sol–gel CdO–SiO<Subscript>2</Subscript> with different nanocomposite

The CdO NPs was synthesized using the sol–gel method and the nanoparticles were characterized using an UV–Vis spectrophotometer, with shape and size were examined by SEM and XRD. The XRD analysis respects the Bragg’s law and confirmed the crystalline nature of CdO nanoparticles. From the XRD, the average size of CdO NPs was found to be around 41 nm. The photoluminescence spectra of the CdO NPs, as recorded at room temperature, were excited at 300 nm wavelength. The broad emission peaks were between 600 and 650 nm (orange emission). The optical limiting performance of the nanocomposite was described in the sol–gel state. Also, this study has observed and studied the diffraction rings generated in CdO NPs using the same CW laser. The number of rings increases almost exponentially with an increasing volume fraction of SiO₂ in the nanocomposites. The refractive index change, Δn, and effective nonlinear refractive index, n ₂, were found to be 10^?4 and 10^?8 cm²/W, respectively. The effective nonlinear refractive index, n ₂, was determined based on the observed number of rings. The threshold values of the CdO, CdO–2SiO₂ and CdO–5SiO₂ nanocomposites are 7.1, 6.55 and 6.34 mW, respectively. This large nonlinearity is attributed to the thermal effect. The present studies suggest that the nanocomposite is a potential candidate for optical device applications such as the optical limiters. The thermal blooming technique was applied to evaluate the thermo-optic coefficient and thermal diffusivity of the CdO NPs. In the thermal blooming experimental setup a transistor–transistor logic modulated CW laser of wavelength 532 nm was used as the excitation source.