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Development of a Hybrid Chitosan- and Niacinamide-Coupled ZnO Nanoparticle Composite for Sun Protection Application
摘要： Zinc oxide nanoparticles (ZnO) have long been utilized as UV-protective sunscreen components due to their high durability and lower skin irritation while maintaining capability for blocking UV rays. However, the dispersal and transparency properties of ZnO need to be enhanced in order to improve the capacity for creating effective sunscreen through control of the physiochemical properties of ZnO. In this study, chitosan or niacinamide, which are suitable functional cosmetic compounds and effective skin lightening agents, are combined with ZnO for the development of better UV-protective products. Each biocompatible coating material is individually attached on its surface after the synthesis of ZnO. The size is 70 nm using the sol-gel method. Their morphology and chemical structure are characterized by FT-IR, XRD, SEM, TEM, TGA, and zeta potential. The results indicate that approximately 50% of chitosan and 5% niacinamide were coated on the ZnO. To confirm the capacity of each surface-coated ZnO with chitosan and niacinamide as a sunscreen, we measured their transmission, reflectance, and sun protection factor (SPF) using a UV spectrophotometer and SPF. As a result, the niacinamide-coated ZnO shows remarkably lower transmission and high reflectance against UV rays than that of bare ZnO and chitosan-coated ZnO. Furthermore, niacinamide-coated ZnO exhibits great lightening effects. Consequently, these results demonstrate that niacinamide coating is highly effective for the production of sunscreen emulsions.
关键词： Zinc oxide nanoparticles,TEM,FT-IR,SEM,XRD,UV-protective sunscreen,TGA,chitosan,SPF,sol-gel method,zeta potential,niacinamide,sun protection factor
更新于2025-09-12 10:27:22
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Study on the thermal, dielectric, dynamic, mechanical analysis of graphene decorated with Graphene Quantum Dots (GDGQD) reinforced epoxy nanocomposite
摘要： The thermal conductivity, dielectric properties and Dynamic Mechanical Analysis (DMA) were studied for Graphene Decorated with Graphene Quantum Dots (GDGQD)-epoxy nanocomposite. A maximum thermal conductivity enhancement of 19 % registered for 0.75 wt. % GDGQD sample where a low acoustic impedance mismatch between the interface of GDGQD fillers and the epoxy matrix occur and a dielectric constant increase of 6 % due to the better charge accumulation at the conductive filler/ insulating polymer interface of the composite. Further DMA is performed using the cantilever mode. The loss modulus peak obtained for 0.75 wt. % GDGQD-epoxy sample given a maximum value due to the interface interaction and the corresponding storage modulus shown a maximum increment of 21%, due to the molecular dynamics and cross-linking density of the epoxy matrix with GDGQD. The thermal stability of the samples evaluated using Thermal Gravimetric Analysis (TGA) shown an improvement in glass transition temperature (Tg) of nanocomposite for 0.75 wt. % GDGQD by 11°C where a greater dispersion of the fillers and efficient functional groups interaction are responsible factors.
关键词： Dynamic Mechanical Analysis (DMA),Graphene Oxide (GO),Thermal gravimetric analysis (TGA),GDGQD
更新于2025-09-11 14:15:04
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Synthesis and electro-optic properties of novel Y-type polyimide containing nitrothiazolylazodioxyphenyl group
摘要： New Y-type polyimide (5) containing nitrothiazolylazodioxyphenyl groups as nonlinear optical (NLO) chromophores, which are components of the polymer backbone, was prepared and characterized. Polyimide 5 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. Polyimide 5 shows a thermal stability up to 300 °C in thermogravimetric analysis with glass-transition temperature (Tg) obtained from differential scanning calorimetry near 130 °C. The second harmonic generation (SHG) coefficient (d33) of poled polymer film at the 1064 nm fundamental wavelength is around 2.32 pm/V. The dipole alignment of polymer 5 exhibits a thermal stability even at 5 °C higher than Tg, and there is no SHG decay below 135 °C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.
关键词： thermogravimetric analysis (TGA),NLO,dipole alignment,SHG coefficient,differential scanning calorimetry (DSC),polyimide
更新于2025-09-11 14:15:04
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Structural diversity, topology and luminescent properties of a two-dimensional Cd(II) coordination polymer incorporating 4,4′-dipyridyl and 4,4′-sulfonyldibenzoic acid
摘要： A new Cd(II) derivative, [Cd2(H2O)4(bipy)(sdba)2]·10H2O (1), is synthesized hydro(solvo)thermally by the combination of divalent cadmium nitrate tetrahydrate as metal salt, an N-donor ancillary ligand 4,4'-bipyridine (bipy), and the flexible aromatic carboxylate, 4,4￠-sulfonyldibenzoic acid (sdba), as organic linker. Single crystal X-ray diffraction analysis reveals that the Cd(II) atoms show a distorted trigonal bipyramidal environment. In the asymmetric unit, both the carboxylate and the N-donor connectors bridge pairs of cadmium ions; this ultimately leads to the formation of a set of undulated sheets formed by fused rings comprising six cadmium centers, two bipy and four sdba ligands. Considering the cadmium ions as nodes and the ligands as connectors, the structure can be described as a stack of 3-c uninodal nets of the type hcb, with point symbol {44.62} and vertex symbol [6.6.6]. The encapsulation of the Cd(II) derivative displays a moderate luminescent property.
关键词： Photoluminescence,TGA,Topology,Cd(II),2-D polymer
更新于2025-09-11 14:15:04
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A quantitative XPS examination of UV induced surface modification of TiO2 sorbents for the increased saturation capacity of sulfur heterocycles
摘要： UV pretreatment has proven effective in enhancing the sulfur heterocycle specificity and saturation capacity of TiO2 adsorbents. Previous efforts in our laboratory have shown this effect to persist for over two weeks and were attributed to increased densities of surface hydroxyl groups as assessed by XPS and FTIR evaluations. This paper presents further evidence of the previous assertion by tracking the UV-induced conversion of adsorbed water and lattice oxygen into surface hydroxyls as monitored by XPS. Two different commercial TiO2 adsorbents (@ 163 and 70 m2/g) were investigated at various hydration levels as determined by TGA. Deconvolution of the XPS spectra demonstrated both the qualitative nature and quantitative conversion of adsorbed water and lattice oxygen according to the following stoichiometry, where one lattice oxygen is converted into two surface hydroxyls. Eight different reaction cases were examined using the 163 and 70 m2/g supports at four different hydration levels each. The measured stoichiometry for the above-noted conversion varied from 1.83 to 2.15 with an average value of 1.98 and a standard deviation of 0.10. Samples removed from the XPS chamber and stored in laboratory conditions showed that photo-generated surface hydroxyls could persist for over two weeks with or without handling.
关键词： XPS,TGA,Hydroxyl group,Titanium dioxide,UV,Photo-assisted adsorptive desulfurization
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Synthesis and characterization of TiO2 co-polymeric hydrogel
摘要： In this study, TiO2 doped acrylic acid-co-vinyl pyrrolidone (AA-co-VP) composite co-polymeric hydrogel was synthesized by free radical polymerization technique. Titanium dioxide (TiO2) were chosen because of its superior properties such as high activity, chemical stability, low cost, non-toxicity, and stability during irradiation. TiO2 doping were carried out by varying mass ratios as 0.05%, 0.5% and 1%. Conversion, cross-linking and swelling values of each hydrogel were calculated. According to swelling behavior, while TiO2 dope ratio increase, swelling value was also increased. Chemical, morphological and thermal properties of hydrogels were specified by using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDX), mapping and thermogravimetric analysis (TGA-DSC) techniques. TiO2 doping provides superior properties to co-polymeric hydrogel. Hydrogels have also characteristic properties of both acrylic acid and vinyl pyrrolidone.
关键词： SEM-EDX,hydrogel,TGA-DSC,free radical polymerization,acrylic acid-co-vinyl pyrrolidone,FTIR,TiO2,swelling behavior
更新于2025-09-09 09:28:46
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Growth and characterization of third-order nonlinear optical lithium hydrogen maleate dihydrate single-crystal
摘要： A third-order nonlinear optical crystal of lithium hydrogen maleate dihydrate (LHMD) is grown by the process of slow evaporation at room-temperature. The LHMD crystal system is orthorhombic and is a member of P space group. Using FTIR spectral investigation, the presence of main functional groups in LHMD crystal is identified. The optical behavior of the crystal is determined by UV-Visible spectroscopy. The bandgap energy of the LHMD crystal is calculated to be 3.4 eV. By Vickers microhardness measurements, the mechanical behavior has been assessed. The melting point of LHMD is determined by TG-DTA analysis. The defects present in the LHMD crystal are studied by dielectric loss and dielectric constant. SHG studies are performed for the LHMD crystal by Kurtz and Perry method. The third-order nonlinear characteristics of the LHMD crystal are analyzed by Z-scan technique. The laser damage threshold (LDT) study is carried out to verify the suitability of the crystal for laser applications.
关键词： LHMD,optical studies,TGA,third-order nonlinear studies,hardness
更新于2025-09-09 09:28:46