Klaus Afflerbach; Sandra Afflerbach; Reinhard Trettin; Wolfgang Krumm
Abstract
One major scientific challenge is a shift of the energy generation and utilization towards sustainability and efficiency. Therefore, thermochemical heat storage concepts offer a promising contribution as for example by integration in Concentrated Solar Power (CSP) applications. The reaction system Ca(OH)2/CaO ...
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One major scientific challenge is a shift of the energy generation and utilization towards sustainability and efficiency. Therefore, thermochemical heat storage concepts offer a promising contribution as for example by integration in Concentrated Solar Power (CSP) applications. The reaction system Ca(OH)2/CaO is seen as a superior candidate but its poor powder properties yet hinder a technical implementation. The authors have recently proven, that these obstacles can be overcome by a persistent particle size stabilization of the pre-granulated storage material. Within the present study, the mechanical capsule material properties are improved by admixing of additives to the powdery precursor. By thermochemical conversion in a laboratory reactor, the cyclability and the suitability for moved reaction beds of the storage material is proven. The investigations are complemented by attrition tests on the most promising sample material and an encapsulated reference material. It is shown that the chemically enhanced encapsulation is a suitable approach to retain good flow properties and reduce attrition significantly. An encapsulated sample with an enhanced shell material composition containing 5%(w/w) of diatomaceous earth and 1%(w/w) of flux agent is found to be of superior stability over ten thermochemical cycles. A comparative macroscopic evaluation of the sample material after tenfold thermochemical cycling emphasizes the potential of this approach.
Sreenu Bhanoth; Anuraj Kshirsagar; Pawan K Khanna; Aakriti Tyagi; Ankita Leekha; Vijay Kumar; Anita Verma
Abstract
Present article describes one-pot, two-stage, in-situ controlled atmosphere method for synthesis of core-shell quantum dots (QDs) comprising of ZnSe, CdS and CdSe combinations e.g. CdS/CdSe, ZnSe/CdS and ZnSe/CdSe. The present method emphasizes on creating an effective surface passivation of core as ...
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Present article describes one-pot, two-stage, in-situ controlled atmosphere method for synthesis of core-shell quantum dots (QDs) comprising of ZnSe, CdS and CdSe combinations e.g. CdS/CdSe, ZnSe/CdS and ZnSe/CdSe. The present method emphasizes on creating an effective surface passivation of core as well as formation of passivated shell via utilization of cyclo-octeno-1, 2, 3-selenadiazole as a precursor for selenium. Synthesis of ZnSe/CdS was compared by using two different selenium precursors viz cyclo-octeno-1, 2, 3-selenadiazole (C8-SDZ) and cyclo-hexeno-1, 2, 3-selenadiazole (C6-SDZ). Optical properties (UV-Visible and PL spectroscopy) indicate narrow peak width with band gap ranging in between 2.30 eV to 2.56 eV. The XRD analysis revealed the formation of respective core-shell QDs with zinc blende crystal structure. TEM analysis showed formation of spherical shaped core-shell QDs with lattice spacing of 0.35 nm due to presence of (111) crystal plane. By virtue of the excellent optical properties of ZnSe/CdS core shell QDs, this was subjected to bio-evaluation in terms of cytotoxicity and therapeutic efficacy. Approximately, 65% bio-toxicity was observed in MCF-7 with negligible haemolysis by ZnSe/CdS QDs. About, 34% tumour regression was shown by ZnSe/CdS QDs, as against 93% observed by Mitomycin C (Positive control) with respect to placebo (PBS).
Vaishali Shukla; Bhargav Raval; Man Singh
Abstract
An intermolecular charge and electron transfer processes in photoluminescent ZnS- L-Cysteine: core-shell Nanoparticles (NPs) extend highly sensitive and variable valence at the core (ZnS)-shell (L-Cysteine) interface primarily due to an extensive mixing of materials frontier orbital (i.e. covalency). ...
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An intermolecular charge and electron transfer processes in photoluminescent ZnS- L-Cysteine: core-shell Nanoparticles (NPs) extend highly sensitive and variable valence at the core (ZnS)-shell (L-Cysteine) interface primarily due to an extensive mixing of materials frontier orbital (i.e. covalency). Water soluble, ZnS- L-Cysteine: core-shell photo luminescent NPs achieved by straight forward micellar route that is thrust area of research in nanoscience for the control particle size and remarkable properties through chemical co-precipitation method. In the paper we studied, the synthesis of CTAB capped ZnS NPs as well ZnS- L Cysteine: core-shell NPs and examined by their composition, particle size and optical and luminescent properties. The NPs stabilized with CTAB and demonstrated the regular ZnS blue emission on recombination over ZnS band-crevice from shallow electron traps at 490 nm. The onset of the absorption was 80 nm blue shifts moved from 345 nm (bulk) to 265 nm, showing a quantum size impact. Quantum mechanical effect of light applied especially in semiconducting NPs through optoelectronic orbital model, which detect and control the light through electronic devices.
Richard Dvorsky
Abstract
A new preparation method of lamellar core-shell ZnO-(Si)-ZnO nanostructures with high specific surface area and high photocatalytic efficiency is presented in this article. This novel method is based on the application of controlled vacuum sublimation of the frozen liquid dispersion of silicon nanoparticles ...
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A new preparation method of lamellar core-shell ZnO-(Si)-ZnO nanostructures with high specific surface area and high photocatalytic efficiency is presented in this article. This novel method is based on the application of controlled vacuum sublimation of the frozen liquid dispersion of silicon nanoparticles which were prepared by using the "top-down" process in cavitation Water Jet Mill disintegrator. The particle size of thus disintegrated silicon nanoparticles was measured by dynamic light scattering (DLS). Final product ZnO-(Si)-ZnO was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and amount of ZnO and Si was measured by energy dispersive x-ray spectroscopy (EDAX). Specific surface area was obtained from Brunauer-Emmett-Teller analysis (BET). The photocatalytic activity of ZnO-(Si)-ZnO nanostructure was verified by the decomposition of methylene blue (MB) solution. The Final nanomaterial shows a relatively high specific surface area of 134 m2/g and significantly higher photocatalytic activity compared to standard TiO2 (Degussa P25). Such procedure based on the controlled vacuum sublimation of frozen liquid of suitable metal salts could be a promising method for obtaining photocatalytic nanomaterials with higher specific surface area.
Utkarsh Jain; Jagriti Narang;Nidhi Chauhan
Abstract
Xanthine oxidase (XOD) was extracted from bovine milk. Immobilization of extracted XOD was performed by covalently N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry on core–shell magnetic nanoparticles (MNPs)/carboxylated multiwalled carbon nanotube ...
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Xanthine oxidase (XOD) was extracted from bovine milk. Immobilization of extracted XOD was performed by covalently N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry on core–shell magnetic nanoparticles (MNPs)/carboxylated multiwalled carbon nanotube (c-MWCNT) composite film. The film was electrodeposited on glass plate electrode (usually the surface of fluorine doped tin oxide (FTO). In order to characterize nanocomposite modified FTO electrode, various methods including scanning electron microscopy (SEM), cyclic voltammetry (CV), Fourier transform infrared (FTIR), and electrochemical impedance spectroscopy (EIS) were performed. These methods were evaluated prior and following XOD immobilization. The working optimal conditions for instance 30 °C, +0.2 V vs. Ag/AgCl, sodium phosphate buffer at pH 7.0 were attributed for developing this biosensor. The linearity of the response upto 150 μM xanthine concentration, 0.05 μM (S/N = 3) detection limit and a response time within 3 s were obtained. The biosensor was stored at 4 °C and used above 100 times for a long period of 120 days. The loss of 50 % of activity was noticed. This fabricated biosensor was then employed determining xanthine in fish meat sample.
Suraksha Rasal; Sunita Jadhav;Pawan K. Khanna; Priyesh V. More; Chaitanya Hiragond
Abstract
ZnO/CdS core-shell hetero nanostructures with different shell thickness have been successfully developed by a solution chemistry method employing rapid homogenization concept. The obtained core/shell nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy ...
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ZnO/CdS core-shell hetero nanostructures with different shell thickness have been successfully developed by a solution chemistry method employing rapid homogenization concept. The obtained core/shell nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), FTIR, Raman, photoluminescence (PL), and UV-visible spectroscopy. All analytical and spectroscopic tools supported the formation of CdS shell over ZnO core. ZnO/CdS core-shell nanostructures were evaluated for their photocatalytic activity against methylene blue (MB), a common industrial water pollutant. It was observed that the ZnO/CdS core-shell nanostructures can effectively function as a photocatalyst under both UV and sunlight for degradation of MB. It was also observed that the degradation of MB was higher from core/shell nanostructures than the physical mixture of ZnO-CdS which was prepared separately.
Jagriti Narang; Utkarsh Jain; Nitesh Malhotra; Sandeep Singh; Nidhi Chauhan
Abstract
An amperometric lysine biosensor was fabricated by immobilizing lysine oxidase onto core shell magnetic nanoparticles (Core–shell MNPs)/multiwalled carbon nanotube (MWCNT) layer deposited on Au electrode via carbodiimide linkage. Transmission electron microscopy (TEM) for core–shell MNPs, ...
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An amperometric lysine biosensor was fabricated by immobilizing lysine oxidase onto core shell magnetic nanoparticles (Core–shell MNPs)/multiwalled carbon nanotube (MWCNT) layer deposited on Au electrode via carbodiimide linkage. Transmission electron microscopy (TEM) for core–shell MNPs, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and Fourier transform impedance spectroscopy (FTIR) studies were used to characterize the modified electrode. Sensor showed optimal response within 2s at 30ºC in 0.05 M sodium phosphate buffer pH 6.0 when polarized at +0.2 V vs. Ag/AgCl. Linear working range of the biosensor was determined by 0.05 -700 μM with a detection limit of 0.05 μM. A good correlation (r = 0.98) was obtained between serum lysine levels measured by the standard HPLC method (y) and the present method (x). A number of serum substances had practically no interference. The sensor was used in 150 assays and had a storage life of 180 days at 4 o C. This nanohybrid biosensor will be useful for detection of lysine in food and pharmaceutical industries.
Dipali Nagaonkar; Mahendra Rai
Abstract
Bimetallic nanoparticles have emerged up as advanced nanomaterials due to the synergism between two metallic nanoparticles in core-shell or alloy arrangement. Moreover, bioinspired synthesis of nanoparticles is an evergreen approach of nanobiosciences. In this experiment, we have fabricated silver, gold ...
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Bimetallic nanoparticles have emerged up as advanced nanomaterials due to the synergism between two metallic nanoparticles in core-shell or alloy arrangement. Moreover, bioinspired synthesis of nanoparticles is an evergreen approach of nanobiosciences. In this experiment, we have fabricated silver, gold and silver (core) - gold (shell) bimetallic nanoparticles using leaf extract of Catharanthus roseus Linn. by sequential reduction technique. The sequentially reduced silver-gold nanoparticles in core-shell arrangement were detected by shift in the surface plasmon resonance of nanoparticles from 423 nm to 526 nm with the aid of UV-Visible spectrophotometer. Nanoparticle tracking analysis confirmed the mean particle size for all the nanoparticles within the range 11 to 65 nm. X-Ray diffraction analysis revealed Bragg’s reflections denoting face cubic centered crystalline nature of all the synthesized nanoparticles. Transmission electron microscopy showed that silver and silver-gold nanoparticles are quite polydispersed and spherical in shape while anisotropic Au nanoparticles were also observed. These phytofabricated Ag-Au nanoparticles have been evaluated with enhanced antibacterial and anticandidal potential over their monometallic counterparts with particular reference to some pathogenic bacteria and Candida sp. The maximum lethality of bimetallic nanoparticles was observed for Escherichia coli followed by Pseudomonas aeruginosa, while Candida parapsilosis was found to be the least susceptible organism for the silver-gold nanoparticles.
Faruq Mohammad; Tanvir Arfin
Abstract
In continuation to our previous work, the superparamagnetic Fe3O4@Au core-shell type nanoparticles (NPs) were further characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), electrical conductivity, impedance and cyclic voltammetry measurements. From the analysis of ...
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In continuation to our previous work, the superparamagnetic Fe3O4@Au core-shell type nanoparticles (NPs) were further characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), electrical conductivity, impedance and cyclic voltammetry measurements. From the analysis of DSC and TGA results with our Fe3O4@Au NPs of about 6.25 ± 0.6 nm size, we observed a clear endothermic peak at 310°C due to the decomposition of the oleic acid/oleylamine surface ligands and the particles found to contain more than 80% of the metallic content from the mixed compositions of gold and iron oxide were observed. Because of the conduction through the Fe3O4@Au grain, the impedance profile of the pellet exhibited a well-resolved semi-circle and an inclined spike in a far low-frequency region. The electrical conductivity of the Fe3O4@Au material found to be increased with an increase of temperature. The standard Gibbs free energy (ΔG) of the reaction provided a criterion for spontaneous changes in the equilibrium of the material. From the analysis of the results of ΔG, it appears that at 25°C temperature, ΔS found to be negative. The calculated enthalpy, ΔH = -0.635 kJ/mol, at the corresponding entropy of ΔS = -0.132 kJ/mol. Finally, the activation energy in temperature range of 25-200°C for the Fe3O4@Au core-shell material was calculated using Line fitting and the surface characterization by using cyclic voltammetry. The electrochemical redox property of the Fe3O4@Au shows quasi-reversible wave corresponding to Au 3+ /Au 2+ .In addition, the electrochemical parameters for Fe3O4@Au NPs of E c p < /sub>, E a p < /sub>, E o 1/2 and were also obtained. Since the Fe3O4@Au material has low activation energy at low temperature range which makes it a good candidate as an ion conductor and even has the potential uses in many solid state devices and also in the future prospects of electrochemistry applications.
Ajay Shankar; Sandeep Kumar; Sanjeeve Thakur; Rajni Porwal; R. P. Pant
Abstract
Nanocrystalline NixCo1-xFe2O4 were synthesized and studied for their structural and magnetic properties. The effect of doping ion concentration on lattice parameter, crystallite size and the lattice strain pertaining to the ionic radii has been investigated. Electron microscopy supports the parameters ...
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Nanocrystalline NixCo1-xFe2O4 were synthesized and studied for their structural and magnetic properties. The effect of doping ion concentration on lattice parameter, crystallite size and the lattice strain pertaining to the ionic radii has been investigated. Electron microscopy supports the parameters and gives morphological view of the system. The magnetic measurement reveals the information on the effect of stoichiometry variation in existing superparamagnetism. Further, the spin dynamics and their role on dipolar interactions, extent of superexchange and spin-spin relaxation among nanoparticles have been investigated. Also, an attempt has been made to understand the UV irradiation effect on photosensitive Co 2+ ion on Ni ferrite by in-situ electron spin resonance measurements.
