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1.
J Nanosci Nanotechnol ; 19(8): 4623-4631, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30913758

RESUMO

Synthesis of 4,4'-((phenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) derivatives was successively carried out using Cu doped ZnO nanomaterials. The nanocrystalline Cu-ZnO was obtained by decomposing as-synthesized copper-zinc oxalate intermediate at 520 °C. The prepared Cu-ZnO nanostructured catalyst was characterized with FTIR, X-ray diffraction, field emission scanning electron microscope and electron diffraction techniques. XRD analysis indicates the formation of highly crystalline hexagonal phase of ZnO along with the presence of monoclinic CuO. FESEM photographs shows the existence of plate like structures made up of small spherical shaped particles having size in the range of 30-50 nm. As-synthesized Cu-ZnO was used as heterogeneous catalyst for one pot synthesis of 4,4'-((phenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) derivatives using phenyl hydrazine, ethyl acetoacetate and aromatic aldehydes. The 3-methyl-1-phenyl-1H-pyrazol-5-ol was obtained as in-situ precursor to the series of bis-pyrazolone derivatives. The progress of reaction was monitored by thin layer chromatography. The obtained organic product was further characterized and confirmed by FT-IR, 1H-NMR, 13C-NMR and HRMS spectroscopic techniques. The Cu-ZnO catalyst confers upto 96% yield of pyrazolone derivatives in ethanol solvent at refluxing condition. The Cu-ZnO catalyst was used successfully up to 5 cycles without much loss of catalytic activity. Overall, the use of environmental friendly Cu-ZnO nano-structures as a heterogeneous catalyst shows higher yield and lower reaction time towards the synthesis of bispyrazolone derivatives by Tandem Knoevenagel/Michael reaction.

2.
J Nanosci Nanotechnol ; 19(6): 3479-3486, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30744775

RESUMO

We report tunable-morphology oriented facile yet scalable route to synthesize 1D (nanorod) and 2D (nanobelt) MoO3 nanostructures at gram scale using conventional as well as sonochemistry assisted sol-gel technique. The structural, morphological and optical properties of the samples can be befittingly altered by varying the synthesis protocol. The resultant orthorhombic MoO3 nanomorphs demonstrated efficient and expeditious photocatalytic degradation of the pollutant dye, Methylene Blue (MB). We have observed that appreciable photocatalytic MB dye-degradation can be accomplished within 30 minutes with high rate constants of 0.0786 min-1 and 0.233 min-1 for rod and belt-like MoO3-nanostructures, respectively. The pilot results indicate that the resultant MoO3 nanomorphs can be potentially used as solar light driven industrial photocatalyst material with their intrinsic photostability.

3.
J Nanosci Nanotechnol ; 18(5): 3441-3447, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29442850

RESUMO

SnS nanostructured materials have attracted enormous interest due to their important properties and potential application in low cost solar energy conversion systems and optical devices. From the perspective of SnS based device fabrication, we offer single-stroke in-situ technique for the generation of Sn based sulphide and oxide nanostructures inside the polymer network via polymer-inorganic solid state reaction route. In this method, polyphenylene sulphide (PPS)-an engineering thermoplastic-acts as chalcogen source as well as stabilizing matrix for the resultant nano products. Typical solid state reaction was accomplished by simply heating the physical admixtures of the tin salts (viz. tin acetate/tin chloride) with PPS at the crystalline melting temperature (285 °C) of PPS in inert atmosphere. The synthesized products were characterized by using various physicochemical characterization techniques. The prima facie observations suggest the concurrent formation of nanocrystalline SnS with extraneous oxide phase. The TEM analysis revealed formation of nanosized particles of assorted morphological features with polydispersity confined to 5 to 50 nm. However, agglomerated particles of nano to submicron size were also observed. The humidity sensing characterization of these nanocomposites was also performed. The resistivity response with the level of humidity (20 to 85% RH) was compared for these nanocomposites. The linear response was obtained for both the products. Nevertheless, the nanocomposite product obtained from acetate precursor showed higher sensitivity towards the humidity than that of one prepared from chloride precursor.

4.
RSC Adv ; 13(35): 24767-24776, 2023 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-37601590

RESUMO

AlCl3-loaded ZnO nanoparticles have been explored as an efficient catalyst for 1,4-dihydropyridine synthesis under ambient temperature and solvent-free conditions. For this purpose, ZnO nanoparticles were synthesized by a simple solution-based precipitation technique using a stoichiometric amount of zinc sulfate and oxalic acid. The AlCl3@ZnO nanocrystalline catalyst was prepared by loading 20% AlCl3 on ZnO nanoparticles by a simple wet-impregnation technique. This catalyst efficiently performed Hantzsch pyridine reactions with various aromatic aldehydes, ethyl acetoacetate and ammonium acetate. The nanostructured AlCl3-loaded ZnO catalyst was characterized by UV-DRS, XRD, FESEM, EDS, FETEM-STEM-EDS and XPS techniques. The comprehensive characterization reveals the formation of AlCl3-loaded ZnO catalysts with an average particle size of 70-80 nm. The loading of AlCl3 on the ZnO surface was confirmed by minor shifts in the XPS and XRD peaks. FETEM-STEM-EDS also indicates reasonable AlCl3 loading on ZnO nanoparticles. The 20% AlCl3-loaded ZnO nanocatalyst (AlCl3@ZnO) confers 92% yield for the synthesis of 1,4-dihydropyridine under solvent-free and ambient temperature conditions. The synthesized 1,4-dihydropyridines were characterized by 1H-NMR, 13C-NMR, HRMS and FT-IR spectroscopic techniques. The reported catalyst is highly efficient, environmentally friendly and could become an alternative to homogenous and heterogenous catalytic reactions.

6.
J Nanosci Nanotechnol ; 12(2): 887-93, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22629869

RESUMO

We, herein, report the antimicrobial properties of uncapped silver nanoparticles for a Gram positive model organism, Bacillus subtilis. Uncapped silver nanoparticles have been prepared using less-explored DC arc thermal plasma technique by considering its large scale generation capability. It is observed that the resultant nanoparticles show size as well as optical property dependent antimicrobial effect.


Assuntos
Antibacterianos/química , Nanopartículas Metálicas , Prata/química , Antibacterianos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Transmissão , Prata/farmacologia
7.
Antioxidants (Basel) ; 11(5)2022 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-35624869

RESUMO

Rubia cordifolia L. (Rubiaceae) is an important plant in Indian and Chinese medical systems. Extracts prepared from the root, stem and leaf have been used traditionally for the management of various diseases. Some of the known effects are anti-inflammation, neuroprotection, anti-proliferation, immunomodulation and anti-tumor. A comparative account of the extracts derived from different organs that lead to the identification of the most suitable solvent is lacking. We explored the presence of phytochemicals, antioxidant activity and anti-proliferative properties of a variety of solvent-based extracts of root, and methanol extracts of stem and leaf of R. cordifolia L. The antioxidant potential was determined by DPPH, hydrogen peroxide, nitric oxide and total antioxidant assays. The anti-proliferative nature was evaluated by MTT assay on HeLa, ME-180 and HepG2 cells. The composition of the extracts was determined by UPLC-UV-MS. We found that the root extracts had the presence of higher amounts of antioxidants over the stem and leaf extracts. The root extracts prepared in methanol exhibited the highest cytotoxicity in HepG2 cells. The main compounds identified through UPLC-UV-MS of the methanol extract give credibility to the previous results. Our comprehensive study corroborates the preference given to the root over the stem and leaf for extract preparation. In conclusion, we identified the methanol extract of the root to be the most suited to have bioactivity with anti-cancer potential.

8.
Small ; 7(7): 957-64, 2011 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-21387556

RESUMO

The simple, template-free, low-temperature, large-scale synthesis of nanostructured CdS with the hexagonal wurtzite phase from bulk cadmium oxide under solid-phase conditions is demonstrated for the first time. The novel approach involves the homogenization of cadmium oxide (CdO) and thiourea in various stoichiometric ratios at moderate temperature. Among the different molar ratios of CdO and thiourea studied, the CdO/NH(2) CSNH(2) molar ratio of 1:2 is found to be the best to obtain highly pure CdS. The obtained CdS nanostructures exhibit excellent cubic morphology and high specific surface area with a particle size in the range of 5-7 nm. The bandgap of the nanostructured CdS is in the range of 2.42 to 2.46 eV due to its nanocrystalline nature. In photoluminescence studies, emission is observed at 520.34 and 536.42 nm, which is characteristic of the greenish-yellow region of the visible spectrum. Considering the bandgap of the CdS is within the visible region, the photocatalytic activity for H(2) generation and organic dye degradation are performed under visible-light irradiation. The maximum H(2) evolution of 2945 µmol h(-1) is obtained using nanostructured CdS prepared in the 1:2 ratio, which is three times higher than that of bulk CdS (1010 µmol h(-1) ). CdS synthesized using the 1:2 molar ratio shows maximum methylene blue degradation (87.5%) over a period of 60 min, which is approximately four times higher than that of bulk CdS (22%). This amazing performance of the material is due to its nanocrystalline nature and the high surface area of the CdS. The proposed simple methodology is believed to be a significant breakthrough in the field of nanotechnology, and the method can be further generalized as a rational preparation scheme for the large-scale synthesis of various other nanostructured metal sulfides.


Assuntos
Compostos de Cádmio/química , Nanoestruturas/química , Sulfetos/química , Catálise , Microscopia Eletrônica de Transmissão , Nanotecnologia/métodos , Óxidos/química , Fotoquímica/métodos
9.
J Nanosci Nanotechnol ; 11(6): 5098-101, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21770149

RESUMO

Herein we report an extremely simple one-pot synthesis of lead sulphide nanorods inside the engineering thermoplastic (i.e. polyphenylene sulphide) which plays a dual role of stabilizing matrix as well as a chalcogen source. The effect of molar ratios of the reactants on the morphology of the samples was studied. The prima facie observations suggest the effective formation of 1-D PbS nanorods along with cubic lead as an impurity phase. The average aspect ratio is found to be approximately 4 to 42 depending upon the reactant molar ratio.

10.
J Nanosci Nanotechnol ; 11(8): 6815-22, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22103085

RESUMO

We herein report the feasibility of novel polymer-inorganic solid state reaction route for simultaneous in situ generation of Cu2S and Cu nanostructures in polymer network. Polyphenylene Sulphide (PPS) which is engineering thermoplastic acts as chalcogen source as well as stabilizing matrix for the resultant nano products. Typical solid state reaction was accomplished by simply heating the physical admixtures of the two reactants i.e., copper acetate and PPS by varying molar ratios mainly 1:1, 1:5, 1:10, 1:15, 1:20 at the crystalline melting temperature (285 degrees C) of PPS. The synthesized products were characterized using various physicochemical characterization techniques like X-ray Diffractometry, Field emission Scanning Electron Microscopy, Transmission Electron Microscopy, UV-Visible spectroscopy and X-ray photoelectron spectroscopy. The prima facie observations suggest occurrence of nanocrystalline Cu2S in case of product obtained with equimolar ratio, whereas remaining samples show mixture of Cu and Cu2O. The TEM analysis reveals nanoscale polydispersity (5-60 nm) and prevalence of mainly spherical morphological features in all the cases with occasional indications of plate like and cubical morphological features depending upon the molar ratio of the reactants. The humidity sensing characterization of these nanocomposites was also performed. The resistivity response with the level of humidity (20 to 70% RH) was compared for these nanocomposites. The linear response is obtained for all the samples. The sensitivity of 1:1 molar ratio sample was found to be maximum among all the samples.

11.
J Nanosci Nanotechnol ; 21(10): 5337-5343, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33875127

RESUMO

In our current endeavor, 3-dimensional (3D) tungsten oxide (WO3) nanostructures (nanocubes, nanobars and nanobricks) have been swiftly generated via hydrothermal route at 160 °C for 24 h. Physico-chemical characterization of the resultant powder revealed formation of WO3 nanostructures with predominantly faceted cube, brick and rectangular bar-like morphology. The present study was also aimed at exploring the antimicrobial and anticancer potential of WO3 nanostructures. Antimicrobial activity was tested against different micro-organisms viz., Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli and Aspergillus fumigatus. The antibacterial and antifungal activity was ascertained against these micro-organisms by measuring the diameter of inhibition zone in agar well diffusion test which revealed that the resultant WO3 nanostructures acted as excellent antibacterial agents against both bacteria and fungi but were more effective against the fungus, A. fumigatus. To examine the growth curves of bacterial cells, time kill assay was monitored for E. coli, against which significant antibacterial action of WO3 nanostructures was noted. The anti-cancer activity of WO3 nanostructures was found to be concentration-dependent against KB cell line by viable cell count method. In our pilot study, WO3 nanostructures suspension with concentration in the range of 10-1 to 10-5 mg/ml was found to kill KB cells effectively.


Assuntos
Anti-Infecciosos , Escherichia coli , Antibacterianos/farmacologia , Anti-Infecciosos/farmacologia , Antifúngicos/farmacologia , Humanos , Testes de Sensibilidade Microbiana , Projetos Piloto , Tungstênio/farmacologia
12.
Sci Rep ; 11(1): 13068, 2021 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-34158586

RESUMO

Over the past few years, biogenic methods for designing silver nanocomposites are in limelight due to their ability to generate semi-healthcare and para-pharmaceutical consumer goods. The present study reports the eco-friendly synthesis of silver nanoparticles from the hitherto unexplored mucus of territorial snail Achatina fulica by the facile, clean and easily scalable method. The detailed characterization of the resultant samples by UV-Visible Spectroscopy, FESEM-EDS, XRD and FTIR Spectroscopy techniques corroborated the formation of silver nanoparticles in snail mucus matrix. The resultant samples were tested against a broad range of Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and a fungal strain Aspergillus fumigatus by well diffusion method. The results indicate that silver nanoparticles in mucus matrix exhibit strong antibacterial as well as antifungal activity. The pertinent experiments were also performed to determine the inhibitory concentration against both bacterial and fungal strains. Anticancer activity was executed by in vitro method using cervical cancer cell lines. Curiously, our biogenically synthesized Ag nanoparticles in biocompatible mucus revealed anticancer activity and demonstrated more than 15% inhibition of Hela cells. We suggest an interesting possibility of formulating antimicrobial and possibly anticancer creams/gels for topical applications in skin ailments.


Assuntos
Anti-Infecciosos/farmacologia , Antineoplásicos/farmacologia , Química Verde , Nanopartículas Metálicas/química , Muco/química , Prata/farmacologia , Caramujos/química , Animais , DNA/análise , Células HeLa , Humanos , Concentração Inibidora 50 , Nanopartículas Metálicas/ultraestrutura , Testes de Sensibilidade Microbiana , Proteínas/análise , RNA/análise , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Staphylococcus aureus/efeitos dos fármacos , Difração de Raios X
13.
Nanoscale ; 12(15): 8502-8510, 2020 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-32242550

RESUMO

Unique N doped Sn3O4 nanosheets have been demonstrated successfully using a facile hydrothermal method. Investigations of the triclinic phase and the impurities were performed using powder X-ray diffraction analysis (XRD) and Raman spectroscopy. The morphological analysis demonstrated a rectangular intra- and inter-connected nanosheet-like structure. The length of the nanosheets was observed to be in the range of 200-300 nm and the thickness of the nanosheets was less than 10 nm. The optical study reveals an extended absorption edge into the visible region, owing to the incorporation of nitrogen into the lattice of Sn3O4, which was further confirmed using X-ray photoelectron spectroscopy (XPS). Considering the band structure in the visible region, the photocatalytic activities of pristine and N doped Sn3O4 nanosheets for hydrogen evolution from water under natural sunlight were investigated. 4% N-Sn3O4 showed a higher photocatalytic activity (654.33 µmol-1 h-1 0.1 g-1) for hydrogen production that was eight times that of pristine Sn3O4. The enhanced photocatalytic activity is attributed to the inhibition of charge carrier separation owing to the N doping, morphology and crystallinity of the N-Sn3O4 nanostructures. A stable efficiency was observed for three cycles, which clearly shows the stability of N-Sn3O4.

14.
J Nanosci Nanotechnol ; 20(4): 2122-2129, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31492220

RESUMO

Innovative colorimetric biosensing platform has been realized by in-situ synthesis of silver nanoparticles in silk-fibroin matrix derived from domesticated silkworm species Bombyx mori. As-synthesized nano-biocomposite dispersion was characterized by UV-Vis spectroscopy and transmission electron microscopy. In a pilot attempt to develop hassle free on-site screening protocol, such green hybrid systems were explored for colorimetric detection of broad range of metal ion targets, viz. toxic heavy metals such as mercury and chromium (which adversely affect hydrosphere, lithosphere, anthroposphere and biosphere) as well as relatively less-toxic metals like copper and iron in a solution. Quite interestingly, our simple biointerfacial-sensing approach reveals highly selective colorimetric sensor response down to ppb level for mercury ions analyte.


Assuntos
Fibroínas , Mercúrio , Nanopartículas Metálicas , Nanocompostos , Colorimetria , Íons , Prata
15.
Sci Rep ; 10(1): 4198, 2020 03 06.
Artigo em Inglês | MEDLINE | ID: mdl-32144298

RESUMO

Herein, the preparation of gold nanoparticles-silk fibroin (SF-AuNPs) dispersion and its label-free colorimetric detection of the organophosphate pesticide, namely chlorpyrifos, at ppb level are reported. The silk fibroin solution was extracted from B. mori silk after performing degumming, dissolving and dialysis steps. This fibroin solution was used for synthesis of gold nanoparticles in-situ without using any external reducing and capping agent. X-ray Diffractometry (XRD), Field Emission Transmission Electron Microscopy (FETEM) along with Surface Plasmon Resonance based optical evaluation confirmed generation of gold nanoparticles within SF matrix. The resultant SF-AuNPs dispersion exhibited rapid and excellent colorimetric pesticide sensing response even at 10 ppb concentration. Effect of additional parameters viz. pH, ionic concentration and interference from other pesticide samples was also studied. Notably, SF-AuNPs dispersion exhibited selective colorimetric pesticide sensing response which can be calibrated. Furthermore, this method was extended to various simulated real life samples such as tap water, soil and agricultural products including plant residues to successfully detect the presence of chlorpyrifos pesticide. The proposed colorimetric sensor system is facile yet effective and can be employed by novice rural population and expert researchers alike. It can be exploited as preliminary tool for label-free colorimetric chlorpyrifos pesticide sensing in water and agricultural products.


Assuntos
Clorpirifos/química , Colorimetria/métodos , Fibroínas/química , Ouro/química , Nanopartículas Metálicas/química , Nanocompostos/química , Praguicidas/química , Fibroínas/ultraestrutura , Hidrodinâmica , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Difração de Raios X
16.
RSC Adv ; 9(18): 10289-10296, 2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-35520940

RESUMO

Herein, a facile hydrothermally-assisted sonochemical approach for the synthesis of a ZnO decorated Sn3O4 nano-heterostructure is reported. The phase purity of the nano-heterostructure was confirmed by X-ray diffraction and Raman spectroscopy. The morphological analysis demonstrated a nanosheet-like structure of Sn3O4 with a thickness of 20 nm, decorated with ZnO. The optical band gap was found to be 2.60 eV for the ZnO@Sn3O4 nano-heterostructure. Photoluminescence studies revealed the suppression of electron-hole recombination in the ZnO@Sn3O4 nano-heterostructure. The potential efficiency of ZnO@Sn3O4 was further evaluated towards photocatalytic hydrogen production via H2O splitting and degradation of methylene blue (MB) dye. Interestingly, it showed significantly superior photocatalytic activity compared to ZnO and Sn3O4. The complete degradation of MB dye solution was achieved within 40 min. The nano-heterostructure also exhibited enhanced photocatalytic activity towards hydrogen evolution (98.2 µmol h-1/0.1 g) via water splitting under natural sunlight. The superior photocatalytic activity of ZnO@Sn3O4 was attributed to vacancy defects created due to its nano-heterostructure.

17.
RSC Adv ; 9(56): 32735-32743, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-35529759

RESUMO

One-pot green synthesis of propargylamines using ZnCl2 loaded TiO2 nanomaterial under solvent-free conditions has been effectively accomplished. The aromatic aldehydes, amines, and phenylacetylene were reacted at 100 °C in the presence of the resultant catalyst to form propargylamines. The nanocrystalline TiO2 was initially synthesized by a sol-gel method from titanium(iv) isopropoxide (TTIP) and further subjected to ZnCl2 loading by a wet impregnation method. X-ray diffraction (XRD) patterns revealed the formation of crystalline anatase phase TiO2. Field emission scanning electron microscopy (FESEM) showed the formation of agglomerated spheroid shaped particles having a size in the range of 25-45 nm. Transmission electron microscopy (TEM) validates cubical faceted and nanospheroid-like morphological features with clear faceted edges for the pure TiO2 sample. Surface loading of ZnCl2 on spheroid TiO2 nanoparticles is evident in the case of the ZnCl2 loaded TiO2 sample. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti4+ and Zn2+ species in the ZnCl2 loaded TiO2 catalyst. Energy-dispersive X-ray (EDS) spectroscopy also confirmed the existence of Ti, O, Zn and Cl elements in the nanostructured catalyst. 15% ZnCl2 loaded TiO2 afforded the highest 97% yield for 3-(1-morpholino-3-phenylprop-2-ynyl)phenol, 2-(1-morpholino-3-phenylprop-2-ynyl)phenol and 4-(1,3-diphenylprop-2-ynyl)morpholine under solvent-free and aerobic conditions. The proposed nanostructure-based heterogeneous catalytic reaction protocol is sustainable, environment-friendly and offers economic viability in terms of recyclability of the catalyst.

18.
R Soc Open Sci ; 5(6): 171986, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30110479

RESUMO

We herein report a simple chemical route to prepare Au-Ag and Ag-Au core-shell bimetallic nanostructures by reduction of two kinds of noble metal ions in the presence of a water-soluble polymer such as poly(vinyl alcohol) (PVA). PVA was intentionally chosen as it can play a dual role of a supporting matrix as well as stabilizer. The simultaneous reduction of metal ions leads to an alloy type of structure. Ag(c)-Au(s) core-shell structures display tendency to form prismatic nanostructures in conjunction with nanocubes while Au(c)-Ag(s) core-shell structures show formation of merely nanocubes. Although UV-visible spectroscopy and X-ray photoelectron spectroscopy analyses of the samples typically suggest the formation of both Ag(c)-Au(s) and Au(c)-Ag(s) bimetallic nanostructures, the definitive evidence comes from high-resolution transmission electron microscopy-high-angle annular dark field elemental mapping in the case of Au(c)-Ag(s) nanomorphs only. The resultant nanocomposite materials are used to fabricate resistors on ceramic rods having two electrodes by drop casting technique. These resistors are examined for their relative humidity (RH) response in the range (2-93% RH) and both the bimetallic nanocomposite materials offer optimized sensitivity of about 20 Kohm/% RH and 300 ohm/% RH at low and higher humidity conditions, respectively, which is better than that of individual nanoparticles.

19.
J Nanosci Nanotechnol ; 7(3): 952-9, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17450858

RESUMO

In an endeavor to synthesize tetragonal nanocrystallites of BaTiO3 at much reduced reaction time, we explored the possibility of performing microwave assisted semi-solvothermal reaction by using Ba(OH)2 . 8H2O and amorphous titanium hydrous gel as precursors and 1,4-butanediol and water as solvent. Typically, such a microwave assisted reaction was accomplished within 2 hrs at 220 degrees C as against 12 hrs required in conventional approach. The crystallized BaTiO3 powders (microwave assisted as well as conventionally processed for reference) were characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. We have detected metastable cubic phase by XRD while locally symmetric tetragonal phase by Raman spectroscopy in case of conventional semi-solvothermal processing. On the contrary, we could detect co-existence of tetragonal and cubic phases by XRD and only tetragonal phase by Raman spectroscopy in case of microwave assisted semi-solvothermal processing. The TEM analysis indicates typical particle size distribution in the range of approximately 20 to 80 nm for conventionally processed powder while that in the range of approximately 20 to 50 nm for microwave processed powder. HRTEM images evince the distortion from an ideal cubic structure in case of microwave processed powder which can be correlated with anisotropic lattice contraction during the microwave induced heating. AFM analysis exhibited relatively less aggregation of nanoparticles for microwave assisted process.


Assuntos
Compostos de Bário/química , Nanopartículas Metálicas/química , Titânio/química , Cristalografia por Raios X , Nanopartículas Metálicas/ultraestrutura , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Micro-Ondas , Nanotecnologia , Solventes , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
20.
J Nanosci Nanotechnol ; 7(12): 4412-20, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18283821

RESUMO

For the swift generation of hierarchical nanostructures of CdS, we propose herein a docile microwave-induced semi-solvothermal reaction (i.e., involving simultaneous usage of nonaqueous and aqueous solvents) between cadmium acetate and thiourea in binary solution of diethylenetriamine and deionized water. Typically, such microwave-assisted reaction was accomplished within 5 minutes as against 12 h required in conventional approach. The resultant products were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis by X-rays, laser Raman spectroscopy and photoluminescence spectroscopy. X-ray diffraction data indicates occurrence of hexagonal CdS with strong (002) preferred orientation. SEM images reveal formation of solvent-ratio dependent complex morphological (i.e., hierarchical) features both at the microscale and nanoscale. Fine-scale microstructure examination by TEM discloses formation of entangled nanorods, nano(potato)sticks, nanoflowers etc. Elemental analysis facility (equipped with TEM) suggests presence of Cd rich product. Raman spectroscopy shows the fundamental and overtone bands pertaining to hexagonal CdS with remarkable enhancement in relative intensities of such bands in case of sample corresponding to diethylenetriamine(DETA)/deionized water(DI) volume ratio of 6:1. Room temperature photoluminescence spectra mainly reveal broad asymmetric emission background composed of classical band edge and trap-induced emission in CdS.

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