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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Fiber Probe for the Selective Plasmonic Sensing of Catechol Utilizing ZnO Decorated MWCNTs
摘要： The widespread use of dihydroxybenzenes in various industries like photography, pesticides, dyes, antioxidants and medicines has lead their inadvertent disposal in soil and water. Catechol is an isomer of dihydroxybenzene whose disposal in ground and river water has necessitated requirement of its highly sensitive sensor due to its toxic effects. Being of polar nature it is easily uptaken by cells but not released properly leading to its accumulation in cells. It is regarded as human group 2B carcinogen by IARC with severe effect on central nervous system. Due to its toxicity, co-carcinogenic activity and low biodegradability it is declared as serious threat for ecology by USEPA and Europian Union [1, 2]. Therefore, we report, here, a selective and sensitive surface plasmon resonance (SPR) based catechol sensor utilising zinc oxide decorated multi-walled carbon nanotubes (MWCNTs) functionalised with CTAB (cetyl trimethyl ammonium bromide) as a sensing layer on an optical fiber probe. Surface plasmon technique makes the sensor highly sensitive, whereas use of an optical fiber provides the advantage of miniaturised probe with facility of continuous online monitoring. The sensor fabrication broadly consists of three steps. The first step involves the chemical route for the preparation of nanocomposite. Firstly, ZnO nanoparticles were prepared through the reduction of zinc acetate by NaOH. Then the nanoparticles were decorated on sidewall functionalised MWCNTs followed by functionalization with CTAB [3]. The TEM image of ZnO decorated MWCNTs is shown in fig.1(a). The second step involves the thermal deposition of silver on 1 cm uncladded region of the fiber probe. Finally, the nanocomposite was coated on the fiber probe by dip coating method. All the steps of probe fabrication are schematically depicted in fig.1(b). To characterize, the probe was fixed in a flow cell having the facility of inlet and outlet for the samples. Polychromatic light was launched from one end of the probe and the SPR spectrum of the catechol sample of a given concentration in the flow cell was recorded by the spectrometer at the other end.
关键词： surface plasmon resonance,optical fiber probe,CTAB,catechol,ZnO decorated MWCNTs
更新于2025-09-16 10:30:52
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Rapid Room-Temperature Synthesis of Mesoporous TiO2 Sub-Microspheres and Their Enhanced Light Harvesting in Dye-Sensitized Solar Cells
摘要： Submicron sized mesoporous spheres of TiO2 have been a potential alternative to overcome the light scattering limitations of TiO2 nanoparticles in dye‐sensitized solar cells (DSSCs). Currently available methods for the growth of mesoporous TiO2 sub‐microspheres involve long and relatively high temperature multi‐stage protocols. In this work, TiO2 mesoporous sub‐microspheres composed of ~5 nm anatase nanocrystallites were successfully synthesized using a rapid one‐pot room‐temperature CTAB‐based solvothermal synthesis. X‐Ray Diffraction (XRD) showed that the grown structures have pure anatase phase. Transmission electron microscopy (TEM) revealed that by reducing the surfactant/precursor concentration ratio, the morphology could be tuned from monodispersed nanoparticles into sub‐micron sized mesoporous beads with controllable sizes (50–200 nm) and with good monodispersity as well. The growth mechanism is explained in terms of the competition between homogeneous nucleation/growth events versus surface energy induced agglomeration in a non‐micelle CTAB‐based soft templating environment. Further, dye‐sensitized solar cells (DSSCs) were fabricated using the synthesized samples and characterized for their current‐voltage characteristics. Interestingly, the DSSC prepared with 200 nm TiO2 sub‐microspheres, with reduced surface area, has shown close efficiency (5.65%) to that of DSSC based on monodispersed 20 nm nanoparticles (5.79%). The results show that light scattering caused by the agglomerated sub‐micron spheres could compensate for the larger surface areas provided by monodispersed nanoparticles.
关键词： CTAB,light scattering,surfactant,titanium dioxide,dye‐sensitized solar cells,anatase
更新于2025-09-16 10:30:52
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Growth mechanism of gold nanorods: the effect of tip-surface curvature as revealed by molecular dynamics simulations
摘要： To understand the anisotropic growth mechanism of gold nanorods (AuNRs) during colloidal synthesis is critical for controlling the nanocrystal size and shape and thus has implications in tuning the properties for applications in a wide range of research and technology fields. In order to investigate the role of the cetyltrimethylammonium bromide (CTAB) coating in the anisotropic growth mechanism of AuNRs, we used molecular dynamics (MD) simulations and built a computational model that considered explicitly the effect of the curvature of the gold surface on CTAB adsorption and therefore differentiated the CTAB arrangements on flat and curved surfaces, representing the lateral and tip facets of growing AuNRs, respectively. We verified that on a curved surface, a lower CTAB coverage density and larger intermicellar channels are generated compared to those on a flat surface. Using umbrella sampling simulations, we measured the free energy profile and verified that the environment around a curved surface corresponds to an easier migration from the solution to the gold surface for the [AuBr2]? species than does a flat surface. Long unbiased molecular dynamics simulations also corroborated the umbrella sampling results. Therefore, the [AuBr2]? diffusion through the environment of the tips is much more favorable than in the case of lateral facets. This shows that the surface curvature is an essential component of the anisotropic growth mechanism.
关键词： molecular dynamics,growth mechanism,CTAB,umbrella sampling,surface curvature,gold nanorod synthesis
更新于2025-09-12 10:27:22
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Dumbbell–Like Silica Coated Gold Nanorods and their Plasmonic Properties
摘要： Silica coated gold nanorods with dumbbell-like morphology allowing dual functionalization in an individual nanostructure have attracted great attention for applications such as sensing and biological imaging. We report a detailed study on the feasibility of controlling the morphology of silica coating on gold nanorods. The morphology of the silica shell can be either cylindrical or dumbbell shaped. The morphology of the silica shell can be either cylindrical or dumbbell shaped. With constant GNR concentration, the ratio of CTAB and TEOS concentration is the key to determine the amount of available TEOS for silica deposition on GNR since the TEOS will diffuse towards the surface of GNRs. The effect of morphologies on surface-enhanced Raman scattering (SERS) performance was also investigated and we found that the dumbbell morphology of silica coated gold nanorods has the most significant SERS enhancement. Our study is significant in terms of the capability to control the dumbbell morphology of silica coated gold nanorods, which can eventually broaden the application of these plasmonic nanomaterials.
关键词： SERS,TEOS,plasmonic properties,dumbbell-like morphology,CTAB,Silica coated gold nanorods
更新于2025-09-12 10:27:22
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Effects of shape-controlling cationic and anionic surfactants on the morphology and surface resonance plasmon intensity of silver@copper bimetallic nanoparticles
摘要： Cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were used as a soft template to determine the morphology of silver@copper bimetallic nanoparticles. The subsequent addition of ascorbic acid to the Ag+, Cu2+ and surfactants solutions, leads to the formation of prefect transparent pale yellow color with in 5 min at ca. 409 nm. The visual observations and UV-visible spectra reveal that the color (pale yellow, dark brown, and wine red), surface resonance plasmon (SRP) intensity and shape of the spectra depends on the Ag+/Cu2+ molar ratio, [CTAB], and reaction time. Sub-, post- and dilution micellar effects are accountable to the fast and slow nucleation and growth processes. The morphology and SRP and rate constants for the formation of silver@copper decreases with increasing [CTAB]. The typical optical properties were dominated by the silver metal. The absence of SRP peaks at ca. 425 nm, 590 nm and 800 nm ruled out the possibility to the formation of AgNPs, CuNPs and CuO, respectively. Transmission electron microscopy (TEM) also confirms the formation of silver@copper nanoparticles. The pseudo-first order rate constants, activation energy, enthalpy of activation and entropy of activation were calculated and discussed for the degradation of methyl orange. The mole fraction of XAg = 0.50 and XCu = 0.499 were calculated in silver@copper.
关键词： silver@copper,Nanoparticles,Mole fraction,SDS,CTAB
更新于2025-09-10 09:29:36
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CTAB-assisted synthesis of dissilient hollow spherical MoS2 for efficient hydrogen evolution
摘要： Dissilient hollow spherical MoS2 was prepared by one-step hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The structure and morphology of the prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The addition of CTAB plays an important role in controlling the morphology of MoS2. As the amount of CTAB was increased, the morphology of MoS2 changed from flake to hollow sphere and finally broked up. Compared with MoS2 without CTAB and closed hollow spherical MoS2, the dissilient hollow spherical MoS2 showed better electrochemical performance in the hydrogen evolution reaction (HER) and good stability after 1000 cycles. We attribute this improvement to large specific surface area and many catalytic active sites of the dissilient hollow spheres. In general, the optimized catalyst exhibited an onset overpotential of 159 mV, a low Tafel slope of 65 mV dec-1, and relatively good stability.
关键词： HER,Dissilient,MoS2,CTAB,Hollow sphere
更新于2025-09-09 09:28:46
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Selective recognition of Cr (VI) ion as Cr <sub/>2</sub> O <sub/>7</sub><sup>2?</sup> in aqueous medium using CTAB‐capped anthracene‐based nanosensor: Application to real water sample analysis
摘要： Surfactant‐capped nanoparticles of 9, 10‐diphenyl anthracene prepared by reprecipitation method found highly fluorescent due to aggregation‐induced enhanced emission (AIEE). Cetyltrimethyl ammonium bromide (CTAB) surfactant not only generated positive zeta potential on the surface of nanoparticles to attract anions of interest but also stabilized nanoparticles into brick‐shape morphology. The fluorescence of nanoparticles is quenched by Cr2O7 ion very significantly in comparison with other diverse ions, namely, MnO4, S2O8 showed increase in the fluorescence of nanoparticles, the interference found is negligible in the Cr (VI) analysis. The selectivity and sensitivity of nanoparticles for recognition of Cr2O7 were explored by systematic fluorescence titration. The fluorescence quenching data fits into the usual Stern‐Volmer equation. A calibration curve constructed by plotting quenching of fluorescence (ΔF) against concentration of Cr (VI) exhibiting a linear fit in the equation, ΔF = 3070x, is used for the estimation of chromium concentration (x). The correlation coefficient value R2 = 0.998 obtained from curve is nearly equal to 1 indicates linear fit between quenching data and concentration of Cr (VI). The estimated values of limit of detection (LOD) in the method 0.01392 μg.mL?1 is far below the permissible value of Cr (VI) 0.05 μg.mL?1 in drinking water approved by world health organization (WHO) and United State Environmental Protection Agency (USEPA). The proposed method of Cr (VI) detection is applied for real sample collected from hard chrome deposition industry from nearby region. The amount of Cr (VI) estimated by present method is comparable with AAS determination for the same samples.
关键词： Diphenylanthracene nanoparticles,Cr (VI) ion,CTAB,aggregation induced enhanced emission,electrostatic interaction
更新于2025-09-04 15:30:14