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Mechanistic Study on Facet-Dependent Deposition of Metal Nanoparticles on Decahedral-Shaped Anatase Titania Photocatalyst Particles
摘要： Facet-selective gold or platinum-nanoparticle deposition on decahedral-shaped anatase titania particles (DAPs) exposing {001} and {101} facets via photodeposition (PD) from metal-complex sources was reexamined using DAPs prepared with gas-phase reaction of titanium (IV) chloride and oxygen by quantitatively evaluating the area deposition density on {001} and {101} and comparing with the results of deposition from colloidal metal particles in the dark (CDD) or under photoirradiation (CDL). The observed facet selectivity, more or less {101} preferable, depended mainly on pH of the reaction suspensions and was almost non-selective at low pH regardless of the deposition method, PD or CDL, and the metal-source materials. Based on the results, the present authors propose that facet selectivity is attributable to surface charges (zeta potential) depending on the kind of facets, {001} and {101}, and pH of the reaction mixture and that this concept can explain the observed facet selectivity and possibly the reported facet selectivity without taking into account facet-selective reaction of photoexcited electrons and positive holes on {101} and {001} facets, respectively.
关键词： zeta potential,pH dependence,facet-selective reaction,facet-selective metal photodeposition,{001} and {101} facets,decahedral-shaped anatase titania particles
更新于2025-09-23 15:22:29
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Optical properties and zeta potential of carbon quantum dots (CQDs) dispersed nematic liquid crystal 4a?2- heptyl-4-biphenylcarbonitrile (7CB)
摘要： In this work, carbon quantum dots (CQDS) of three concentrations 0.1, 0.2 and 0.5 wt% have been dispersed in nematic liquid crystal 4-Heptyl-4-biphenylcarbonitrile (7CB). The results on the optical properties and zeta potential of pure and CQDs dispersed nematic 7CB have been reported. It has been observed that the dispersion of CQDs in host nematic matrix induces quenching of photoluminescence and reduces the Ultra-Violet-Visible (UV–Vis) absorbance of pure nematic at a lower wavelength. From the result of fluorescence decay profile, the fluorescence life time of pristine and dispersed nematic systems have been obtained. No remarkable changes in nematic lifetime in the presence of CQDs have been observed, which confirm that no energy is transferred from nematic to CQDs. Further, it has been found that due to dispersion of CQDs the numerical values of zeta potential are increased for the dispersed systems with 0.1 and 0.2 wt% concentrations of CQDs as compared to pure 7 CB. This result demonstrates that the study of zeta potential provides useful information on the stability and aggregation of the CQDs dispersed nematic systems.
关键词： Carbon quantum dots,UV–Vis absorbance,Zeta potential,Nematic liquid crystal,Time resolved fluorescence
更新于2025-09-23 15:19:57
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Electrostatic Repulsion Controls Efficiency of Cu‐free Click‐Reaction with Azide‐Modified Semiconductor Quantum Dots
摘要： Determination of factors influencing the efficiency of conjugation of various molecules with colloidal semiconductor quantum dots (QDs) is an important step toward their biomedical application. We have utilized controlled strain promoted [3+2] azid-alkyne cycloaddition (SPAAC) as an instrument for studying the influence of charge interaction between QDs and molecules on the efficiency of their conjugation. Azide-modified polymer-encapsulated core-shell CdSe/ZnS QDs, bicyclononyne(BCN)-modified JOE dye and BCN-BHQ1(Black Hole Quencher 1)-modified oligonucleotide duplex were used as model objects for conjugation. Strong surface negative charge of carboxylic QDs was shown to suppress efficient conjugation with negatively charged dsDNA or JOE dye (2',7'-dimethoxy-4',5'-dichloro-fluorescein) molecules. Utilization of zwitter-ionic QDs with reduced surface charge allows significantly enhance the efficiency of QDs conjugation with dsDNA.
关键词： bioconjugation,QDs,click-chemistry,zeta potential,SPAAC
更新于2025-09-12 10:27:22
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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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Performance Enhancement of Chitosan Filled Silver Vanadate Nano-rods
摘要： Silver vanadate nanorods synthesized via chemical precipitation route at room temperature were characterized using UV/Vis. optical electronic spectra, fourier transform infrared (FTIR) spectroscopy, transmission and scanning electron microscopy (TEM, SEM), Zeta potential and X-ray diffraction (XRD). XRD indicates the presence of both β and α phases of silver vanadate. Chitosan samples filled with pre-calculated amounts of synthesized silver vanadate nano-rods were prepared via ordinary casting route. XRD of the prepared polymeric samples reveals amorphous nature and indicating a homogenous distribution of inorganic filler within the matrix without any tendency for crystallization. FTIR shows maintenance of chitosan characteristic bands in all samples. Optical energy gap for both direct and indirect transitions generally indicates a gradual decrease with increasing inorganic filler content. The biological activity against two-gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis), two gram-negative bacteria (Escherichia coli, Pseudomonas aeuroginosa) in addition to one fungus (Candida albicans) were also studied and correlated with both optical energy gap and nanoparticle dopant concentration.
关键词： UV/Vis.,Zeta Potential,Silver vanadate,FTIR,Chitosan,XRD
更新于2025-09-11 14:15:04
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Effect of the reaction medium on the characteristics of silanized titanium dioxide particles: Differences obtained in the Zeta potential data and infrared spectra
摘要： In this document we present the differences in the Zeta potential and in the Infrared spectra data obtained from the characterization of silanized titanium dioxide particles, using two different solvents as reaction media: ethanol and toluene. Also, we provide micrographs of transmission electron microscopy in order to show morphological differences between the analyzed samples.
关键词： Zeta Potential Figure,Fourier Transformed Infrared Figure,Colloid and Surface Chemistry,Chemical Engineering,Transmission Electron Microscope images
更新于2025-09-10 09:29:36
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Mesoporous silica modified luminescent Gd2O3:Eu nanoparticles: physicochemical and luminescence properties
摘要： Highly colloidal Gd2O3:Eu nanoparticles (core-NPs) were synthesized by thermal decomposition via weak base at low temperature. The sol–gel chemical process was employed for silica layer surface coating to increase solubility, colloidal stability, biocompatibility, and non-toxicity at the ambient conditions. XRD results indicate the highly puri?ed, crystalline, single phase, and cubic phase Gd2O3 nanocrystals. TEM image shows that the mesoporous thick silica layer was effectively coated on the core nanocrystals, which have irregular size with nearly spherical shape and grain size about 10–30 nm. An absorption spectra and zeta potential results in aqueous media revealed that solubility, colloidal stability, and biocompatibility character were enhanced from core to core–shell structure because of silica layer surface encapsulation. The samples, demonstrated excellent photoluminescence properties (dominant emission 5D0 → 7F2 transition in the red region at 610 nm), indicated to be used in optical bio-detection, bio-labeling, etc. The photoluminescence intensity of the silica shell modi?ed core/shell NPs was suppressed relatively core-NPs; it indicates the multi-photon relaxation pathways arising from the surface coated high vibrational energy molecules of the silanol groups. The core/nSiO2/mSiO2 nanocrystals display strong emission (5D0 → 7F2) transition along with excellent solubility and biocompatibility, which may ?nd promising applications in the photonic based biomedical ?eld.
关键词： silica,Gadolinium oxide,Biocompatible,Luminescence properties,Zeta potential,Mesoporous
更新于2025-09-09 09:28:46