Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 27
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Langmuir ; 39(51): 18846-18865, 2023 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-38095629

RESUMO

Retrieving the spent photocatalysts from the reaction system is always a challenging task. Therefore, the present work is focused on immobilizing sulfur-doped-Bi2O3/MnO2 (S-BOMO) heterojunction photocatalysts over different support matrices and evaluating their performance for the removal of sulfamethoxazole (SMX) in water under visible light. Our findings revealed S-BOMO coated clay beads (S-BOMO CCB) achieving more than 86% (240 min) SMX degradation ∼3, ∼1.3, and ∼2 times higher compared to S-BOMO coated on the different substrates, including glass beads, floating stones, and polymer material substrates, respectively. Mott-Schottky measurements confirmed the construction of the Z-scheme heterojunction involving MnO2 and 2S-Bi2O3. This Z-scheme mechanism, along with its narrow band gap of 1.58 eV, resulted in a rapid spatial transfer of the photogenerated charge carriers between the semiconductors and is believed to enhance the overall photocatalytic activity of the nanocomposite. Radical trapping and electron paramagnetic resonance results clearly established the active role of hydroxyl radicals and hydrogen peroxide in the degradation of SMX. Further, the 2S-BOMO CCB demonstrated excellent stability and photocatalytic activity over multiple runs. According to the sensitivity analysis and the results of anion effect experiments, phosphate and sulfate ions exhibit a significant impact on sulfamethoxazole degradation. Toxicity analysis revealed that 2S-BOMO CCB and sulfamethoxazole degradation byproducts were apparently innocuous. Additionally, the practical applicability of 2S-BOMO CCB was examined in various real water matrices, with the degradation efficiency followed the order: tap water < groundwater < surface water < hospital wastewater < municipal wastewater < pharmaceutical industry wastewater. The economic assessment revealed the reduction in the overall cost of the immobilized 2S-BOMO following the recovery process. Overall, the findings of this work provided critical insights into the synthesis and performance of incredibly effective and stable immobilized photocatalysts for the degradation of pharmaceutical pollutants.

2.
Langmuir ; 37(6): 2213-2226, 2021 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-33541084

RESUMO

The present work reports on the fabrication of a lightweight microwave absorber comprising MnCo2O4 prepared from the urea complex of manganese (Mn)/cobalt (Co) and nitrogen-doped reduced graphite oxide (NRGO) by facile hydrothermal method followed by annealing process and characterized. The phase analysis, compositional, morphological, magnetic, and conductivity measurements indicated dispersion of paramagnetic MnCo2O4 spherical particles on the surface of NRGO. Our findings also showed that Mn, Co-urea complex, and GO in the weight ratio of 1:4 (NGMC3) exhibited maximum shielding efficiency in the range of 55-38 dB with absorption as an overall dominant shielding mechanism. The reflection loss of NGMC3 was found to be in the range of -90 to -77 dB with minima at -103 dB (at 2.9 GHz). Such outstanding electromagnetic wave absorption performance of NRGO/MnCo2O4 nanocomposite compared to several other metal cobaltates could be attributed to the formation of percolated network assisted electronic polarization, interfacial polarization and associated relaxation losses, conductance loss, dipole polarization and corresponding relaxation loss, impedance matching, and magnetic resonance to some extent.

3.
Langmuir ; 37(45): 13409-13419, 2021 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-34736324

RESUMO

The present study is focused on room-temperature synthesis carried out by reduction of an aqueous silver nitrate (AgNO3) and AgNO3/graphene oxide (GO) dispersion using a low-cost commercial Fehling B solution in one step to form silver quantum dots (Ag QDs) and their Ag/reduced graphene oxide (Ag/RGO) nanocomposites and their characterization. The crystallinity, surface chemistry, structural, and morphological studies indicated the formation of crystalline small-sized quasispherical-functionalized Ag particles distributed uniformly on the surface of RGO. The conductivity measurements further showed an improvement in the conductivity of Ag/RGO nanocomposites as compared to neat Ag QDs. Our findings showed that Ag/RGO nanocomposites prepared by using 0.055 wt % of GO exhibited a total enhanced electromagnetic interference (EMI)-shielding efficiency (SET) of ∼39.2-42.3 dB (2-8 GHz) with a maximum value of ∼43.8 dB at 7. 5 GHz due to conduction loss, an interconnected conducting network, and a synergistic effect, and it followed an absorption mechanism. Furthermore, this superior absorption-dominated shielding conferred reflection loss (RL) in the range of -79 to -82.5 dB with a RL minima of -88 dB at 7.5 GHz, considering an effective absorption bandwidth of ∼6 GHz with 99.9% absorptivity. It is anticipated that Ag/RGO nanocomposites prepared in one step at room temperature could find potential EMI-shielding applications.

4.
Langmuir ; 37(24): 7430-7441, 2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34115512

RESUMO

The evolution of high electromagnetic absorption materials is essential in the fast growing electronic industry in overcoming electromagnetic pollution. In view of this, a series of Ni nanoparticle-decorated functionalized graphene sheets (FG/Ni) are synthesized by a solvothermal method using different ratios of FG/Ni precursors. Subsequently, FG/Ni is subjected to in situ polymerization of aniline to form FG/Ni/PANI ternary composites and characterized. The total electromagnetic interference shielding efficiency (SET) measurements on FG/Ni/PANI with an optimized FG/Ni ratio (50 mg:600 mg NiCl2·6H2O) exhibit enhanced performance, i.e., ∼47-65 dB (2-3.8 GHz) and ∼65-45 dB (3.8-8 GHz), following absorption as the dominant mechanism due to the matching of dielectric loss and magnetic loss. It is anticipated that such excellent performance of robust FG/Ni/PANI ternary composites at a very low thickness (0.5 mm) has great potential in the application of microwave-absorbing materials.

5.
Langmuir ; 36(16): 4519-4531, 2020 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-32237716

RESUMO

Fe3O4@SiO2@PPy core-shell nanocomposites were fabricated by the coating of SiO2 on Fe3O4 through base catalyzed hydrolysis of tetraethyl orthosilicate followed by encapsulation of polypyrrole (PPy). Subsequently, these trilaminar composites have been characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller, superconducting quantum interference devices, and measurement of the total shielding efficiency in the frequency range of 2-8 GHz. Our findings showed the highest total shielding efficiency (∼32 dB) of Fe3O4@SiO2@PPy (Fe3O4@SiO2/pyrrole wt/wt = 1:9) and followed reflection as the dominant shielding mechanism. Such performance was attributed to poor impedance matching between the PPy (conducting)/SiO2 (insulating) and high electrical conductivity of Fe3O4@SiO2@PPy. Alternatively, electromagnetic (EM) waves incident on the SiO2@PPy interface could also account for enhancing the total shielding efficiency of Fe3O4@SiO2@PPy because of multireflection/refraction. Our earlier work also showed excellent total shielding efficiency of Fe3O4@C@PANI nanocomposites, through absorption as the dominant shielding mechanism. These findings clearly suggest that EM interference shielding in Fe3O4@SiO2@PPy and Fe3O4@C@PANI trilaminar core@shell nanocomposites is controlled by tuning of the shells through switching of the mechanism.

6.
J Nanosci Nanotechnol ; 19(6): 3367-3375, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30744764

RESUMO

ZrO2/MWCNT nanocomposites have been prepared by simple refluxing method and characterized by X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FTIR), and Raman analysis suggests chemical interactions present between zirconia and Multiwalled carbon nanotube (MWCNT) in the as prepared nanocomposites. Electromagnetic inteference shielding efficiencies (EMI SE) for the nanocomposites were found to increase with increasing amount of MWCNT loading. Highest EMI SE value of 29.1-30.5 dB was obtained for nanocomposite containing 15 wt% loading of MWCNT in the microwave frequency range of 2-8 GHz. This optimum performance is due to several factors like highest percentage of intermolecular H-bonding, highly defective, interconnected network structure, high conductivity and dielectric permittivities of the nanocomposites.

7.
J Nanosci Nanotechnol ; 18(6): 4057-4064, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29442743

RESUMO

MWCNTs/hectorite 3D hybrid filler was prepared from the 1:1 combination by weight of constituent MWCNTs (1D) and hectorite (2D) through simple dry grinding method. The resulting hybrid filler was subsequently utilized for the preparation of Ethylene-co-vinyl acetate (EVA)/MWCNTs/hectorite nanocomposites by solution intercalation method. Transmission electron microscopy and X-ray diffraction studies of the nanocomposites confirm homogeneous dispersion of the fillers in the polymer matrix. Mechanical, thermal and dielectric properties of neat EVA are significantly enhanced with increase in filler content. The improvement in tensile properties observed at 4 wt.% filler content are: 243% in tensile strength (1.78 MPa to 6.11 MPa), 105% in elongation at break (366% to 750%) and 426% in toughness (3.36 MPa to 17.67 MPa) without significant change (1.12 MPa to 1.31 MPa) in Young's modulus. Differential scanning calorimetry confirms significant increase in crystallinity, crystallisation temperature (Tc) and crystallite melting temperature (Tm) of the nanocomposites vis-a-vis neat EVA. Observed shift in Tc by more than 10 °C (~87 to ~98 °C) and Tm by more than 30 °C (~118 to ~151 °C) are really significant confirming the improved thermal stability of the nanocomposites. Maximum improvements in dielectric constant and AC conductivity observed at 5 wt.% hybrid filler content are ~25% and ~50% respectively. Superior mechanical properties of the nanocomposites combined with enhanced thermal stability and dielectric properties make it a prospective material for flexible dielectric applications. Properties attained can be attributed to improved polymer-filler interaction on account of homogeneous dispersion.

8.
J Nanosci Nanotechnol ; 18(4): 2569-2575, 2018 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-29442928

RESUMO

Tin oxide thin films were uniformly deposited by successive ionic layer adsorption reaction (SILAR) method on glass substrates using ethylene diamine as a complexing agent. The proper annealing treatment in air converts as-deposited amorphous films into crystalline and removes defects, reducing strain in the crystal lattice. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR) spectroscopy. The film shows good optical transparency in the range of 200-1000 nm wavelength and electrical resistivity decreases upon annealing.

9.
J Nanosci Nanotechnol ; 15(3): 1984-2000, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26413611

RESUMO

Graphite oxide, also referred as graphitic oxide or graphitic acid, is an oxidized bulk product of graphite with a variable composition. However, it did not receive immense attention until it was identified as an important and easily obtainable precursor for the preparation of graphene. This inspired many researchers to explore facts related to graphite oxide in exploiting its fascinating features. The present article culminates up-dated review on different preparative methods, morphology and characterization of physical/chemical properties of graphite oxide by XRD, XPS, FTIR, Raman, NMR, UV-visible, and DRIFT analyses. Finally, recent developments on intercalation and applications of GO in multifaceted areas of catalysis, sensor, supercapacitors, water purification, hydrogen storage and magnetic shielding etc. has also been reviewed.


Assuntos
Grafite/química , Óxidos/química , Estabilidade de Medicamentos , Temperatura
10.
J Nanosci Nanotechnol ; 15(5): 3733-42, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-26504999

RESUMO

The present work describes the dual role of graphene as an initiator and filler for polymerization of N-vinylcarbazole and formation of poly(N-vinylcarbazole)/graphene (PVK/Gr) nanocomposites. Fourier transformation infrared (FTIR) and X-ray diffraction (XRD) studies confirmed the formation of PVK as well its graphene nanocomposites. Scanning electron micrograph (SEM) and transmission electron microscopy (TEM) revealed the graphene platelets are dispersed in the matrix of spherical PVK. X-ray photoelectron spectroscopy (XPS) also revealed formation of PVK and presence of interaction between PVK and graphene. Thermograivmetric analysis (TGA) have shown that the thermal stability of PVK/graphene (0.5 wt%) is maximum improved by -76 degrees C compared to neat PVK, when 20 wt% weight loss is taken as a point of comparison. Ultraviolet (UV) and photoluminescence (PL) studies established the charge transfer from polymer chains to the graphene platelets. Dielectric measurements have shown the maximum improvement (87%) in dielectric constant (ε) with 1 wt% graphene loading. The variation of ac conductivity (σ) with frequency (ψ) confirmed the insulating behavior of PVK/graphene nanocomposites possessing high dielectric constant.


Assuntos
Grafite/química , Nanocompostos/química , Polivinil/química , Nanotecnologia , Espectrofotometria Ultravioleta , Termogravimetria
11.
Environ Res ; 135: 95-104, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25262081

RESUMO

The present work is focused on the preparation of Fe nanorods by the chemical reduction of FeCl3 (aq) using NaBH4 in the presence of glycerol as template followed by annealing of the product at 500°C in the presence of H2 gas flow. Subsequently, its surface has been modified by silica followed by silver nanoparticles to form silica coated Fe (Fe@SiO2) and Ag encapsulated Fe@SiO2 nanostructure employing the Stöber method and silver mirror reaction respectively. XRD pattern of the products confirmed the formation of bcc phase of iron and fcc phase of silver, though silica remained amorphous. FESEM images established the growth of iron nanorods from the annealed product and also formation of silica and silver coating on its surface. The appearance of the characteristics bands in FTIR confirmed the presence of SiO2 on the Fe surface. Magnetic measurements at room temperature indicated the ferromagnetic behavior of as prepared iron nanorods, Fe@SiO2 and silver encapsulated Fe@SiO2 nanostructures. All the samples exhibited strong microwave absorption property in the high frequency range (10GHz), though it is superior for Ag encapsulated Fe@SiO2 (-14.7dB) compared with Fe@SiO2 (-9.7dB) nanostructures of the same thickness. The synthesized Ag encapsulated Fe@SiO2 nanostructure also exhibited the SERS phenomena, which is useful in the detection of the carcinogenic dye crystal violet (CV) upto the concentration of 10(-10)M. All these findings clearly demonstrate that the Ag encapsulated Fe@SiO2 nanostructure could efficiently be used in the environmental remediation.


Assuntos
Recuperação e Remediação Ambiental/métodos , Violeta Genciana/isolamento & purificação , Ferro/química , Nanotubos/química , Dióxido de Silício/química , Prata/química , Análise Espectral Raman , Absorção Fisico-Química , Boroidretos , Recuperação e Remediação Ambiental/instrumentação , Glicerol , Temperatura Alta , Hidrogênio , Microscopia Eletrônica de Varredura , Micro-Ondas , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
12.
J Nanosci Nanotechnol ; 14(5): 3758-64, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24734629

RESUMO

The present work is focused on the preparation of tungsten disulfide-multiwalled carbon nanotube (WS2-MWCNT) hybrids by simple dry grinding of WS2 and MWCNT in different proportion by weight (1:3, 1:1, 3:1). The as prepared hybrids have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Raman analyses. XRD results indicated complete exfoliation of MWCNT among WS2 particles in WS2-MWCNT (3:1) and (1:1) hybrids. FESEM images showed the formation of a 3-D network in WS2-MWCNT (1:1) hybrid with uniform dispersion of MWCNT being evident from HRTEM images. Raman analysis also suggested significant interaction between WS2 and MWCNT. WS2-MWCNT (1:1) hybrid, when used as anode material in lithium ion battery, exhibited a high initial charge capacity (483 mA h g(-1)) and an improved cycling stability with over 80% retention of the first cycle capacity after 20 cycles compared to only 40% capacity retention in pristine WS2. Such enhanced electrochemical performance of WS2-MWCNT (1:1) hybrid has been attributed to synergistic effect of WS2 and MWCNT.

13.
J Nanosci Nanotechnol ; 12(12): 8975-84, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23447947

RESUMO

The present work deals with the preparation and characterization of silane grafted MMT (S-MMT), organomodified MMT (O-MMT) and silane grafted organomodified montmorillonite (OS-MMT) reinforced silicone rubber (SR) nanocomposites. XRD of SR filled with O-MMT (1-8 wt%), OS-MMT (1-8 wt%) and S-MMT (1-5 wt%) suggested the formation exfoliated morphology, which has also been supported by the corresponding TEM images of 3 wt% filled SR nanocomposites. TGA and DSC studies of SR/OS-MMT (3 wt%) nanocomposites have shown that the thermal stability, glass transition temperature and crystallization temperature are maximum improved with respect to neat SR by 50, 14 and 10 degrees C respectively. This is attributed to the synergistic effect of organo-modification followed by amino silane grafting of MMT on thermal properties of SR. The tensile strength of SR/S-MMT (5 wt%), SR/O-MMT (3 wt%) and SR/OS-MMT (3 wt%) relatively improved by 134, 312, and 259% respectively suggesting that the synergistic effect of OS-MMT is not effective in reinforcing the mechanical properties of SR. In all probability, the curing of SR through hydrosilylation is inhibited by the lone pair on nitrogen in NH2 group of OS-MMT.

14.
J Nanosci Nanotechnol ; 12(4): 3048-58, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22849064

RESUMO

A simple one pot synthesis method for the silver catalyzed growth of pure hexagonal close packed cobalt by the reduction of cobalt salt using hydrazine hydrate in the presence of triethanolamine (TEA), diethanolamine (DEA) and ethylene glycol (EG) as capping agents at 90 degrees C within 10 min has been reported. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the product prepared in the presence of capping agents show the formation of the well defined porous flowery architecture originating from the interlinked 2D wavy nanoflakes. When the same reaction is performed in the absence of any capping agent, the agglomeration of the flakes of cobalt with irregular spherical morphology is observed. The effect of the reaction conditions on the size and the shape of the products have also been studied. Vibration sample magnetometer (VSM) shows, that the products are ferromagnetic in nature irrespective of the capping agents used and possess high value of coercivity, when prepared in the absence of any capping agent. These cobalt microflowers have also been proved as an alternative to the other available expensive catalysts (Au, Ag, Pt) in the room temperature production of p-aminophenol for its applications in pharmaceutical, photographic and plastic industries.

15.
J Nanosci Nanotechnol ; 11(3): 2506-13, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21449414

RESUMO

W-Ag (80.2W-19.8Ag, 70.4W-29.6Ag and 60.5W-39.5Ag) and W-Cu (79.7W-20.3Cu, 70.5W-29.5Cu and 59.8W-40.2Cu) nanocomposites in the size range of 24-30 nm have been synthesized by thermal decomposition of W(CO)6/CH3COOAg and W(CO)6/Cu(acac)2 in diphenyl ether as solvent at 220 degrees C in presence of oleic acid and hexadecyl amine and characterized. FTIR spectra have been used to explain the role of oleic acid and hexadecyl amine in the synthesis of W-Ag and W-Cu composite powders. XRD studies show that the tungsten phase is amorphous, whereas both Ag and Cu crystallize in fcc for as-synthesized W-Ag and W-Cu nanocomposites. These composite powders when annealed at 700 degrees C results in the formation of bcc tungsten and peaks corresponding to fcc silver and copper still persists. The particle size, shape and distribution of these nanocomposites of various compositions have been studied by SAXS, ESEM and TEM and found to be nearly spherical with the average diameters below 30 nm.


Assuntos
Cobre/química , Cristalização/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Prata/química , Tungstênio/química , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Nanotecnologia/métodos , Tamanho da Partícula , Propriedades de Superfície , Temperatura
16.
ACS Omega ; 6(13): 9164-9175, 2021 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-33842785

RESUMO

The present work is focused on fabrication of reduced graphene oxide/iron(II/III) oxide/polyaniline (RGO/Fe3O4/PANI) ternary composite by a hydrothermal method, its characterization, and application in the development of a high microwave absorbing shielding material. The RGO/Fe3O4/PANI composite showed dramatic enhancement of dielectric loss and magnetic loss compared to Fe3O4/PANI and RGO/Fe3O4 binary composites. This is ascribed to the embedment of more heterostructure phases. As a result, RGO/Fe3O4/PANI showed remarkably high SET (∼28 dB) through the absorption dominant mechanism. Our findings also showed maximum R L of Fe3O4/PANI, RGO/Fe3O4, and RGO/Fe3O4/PANI in the range of 2-8 GHz corresponding to -25 to -35, -40 to -46, and approximately -64 dB, respectively. This is in all probability due to the good impedance matching between permittivity/permeability and dielectric/magnetic losses.

17.
ACS Omega ; 6(7): 4582-4596, 2021 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-33644566

RESUMO

This study is focused on the preparation of the CuS/RGO nanocomposite via the hydrothermal method using GO and Cu-DTO complex as precursors. X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopy study revealed the formation of the CuS/RGO nanocomposite with improved crystallinity, defective nanostructure, and the presence of the residual functional group in the RGO sheet. The morphological study displayed the transformation of CuS from nanowire to quantum dots with the incorporation of RGO. The galvanostatic charge/discharge curve showed that the CuS/RGO nanocomposite (12 wt % Cu-DTO complex) has tremendous and outperforming specific capacitance of 3058 F g-1 at 1 A g-1 current density with moderate cycling stability (∼60.3% after 1000 cycles at 10 A g-1). The as-prepared nanocomposite revealed excellent improvement in specific capacitance, cycling stability, Warburg impedance, and interfacial charge transfer resistance compared to neat CuS. The fabricated nanocomposites were also investigated for their bulk DC electrical conductivity and EMI shielding ability. It was observed that the CuS/RGO nanocomposite (9 wt % Cu-DTO) exhibited a total electromagnetic shielding efficiency of 64 dB at 2.3 GHz following absorption as a dominant shielding mechanism. Such a performance is ascribed to the presence of interconnected networks and synergistic effects.

18.
ACS Appl Mater Interfaces ; 13(45): 54324-54338, 2021 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-34727690

RESUMO

Dyes are considered as recalcitrant compounds and are not easily removed through conventional water treatment processes. The present study demonstrated the fabrication of polyaniline hollow microsphere (PNHM)/MnO2/Fe3O4 composites by in situ deposition of MnO2 and Fe3O4 nanoparticles on the surface of PNHM. The physicochemical characteristics and adsorption behavior of the prepared PNHM/MnO2/Fe3O4 composites towards the removal of toxic methyl green (MG) and Congo red (CR) dyes have been investigated. The characterization study revealed the successful synthesis of the prepared PNHM/MnO2/Fe3O4 adsorbent with a high Brunauer-Emmett-Teller (BET) surface area of 191.79 m2/g. The batch adsorption study showed about 88 and 98% adsorption efficiencies for MG and CR dyes, respectively, at an optimum dose of 1 g/L of PNHM/MnO2/Fe3O4 at pH ∼6.75 at room temperature (303 ± 3 K). The adsorption phenomena of MG and CR dyes were well described by the Elovich and pseudo-second-order kinetics, respectively, and Freundlich isotherm model. The thermodynamics study shows that the adsorption reactions were endothermic and spontaneous in nature. The maximum adsorption capacity (Qmax) for MG and CR dyes was observed as 1142.13 and 599.49 mg/g, respectively. The responsible adsorption mechanisms involved in dye removal were electrostatic interaction, ion exchange, and the formation of the covalent bonds. The coexisting ion study revealed that the presence of phosphate co-ion considerably reduced the CR dye removal efficiency. However, the desorption-regeneration study demonstrated the successful reuse of the spent PNHM/MnO2/Fe3O4 material for the adsorption of MG and CR dyes for several cycles. Given the aforementioned findings, the PNHM/MnO2/Fe3O4 nanocomposites could be considered as a promising adsorbent for the remediation of dye-contaminated water.

19.
J Nanosci Nanotechnol ; 10(1): 555-60, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20352891

RESUMO

In this paper, we present the formation of high quality trigonal phase selenium (t-Se) scrolled nanotubes and nanowires at 100 degrees C by a simple wet chemical method using of Na2S as new reducing agent and poly(vinylpyrolidone) (PVP) as the stabilizing agent. The Na2S used in this method is not only cheaper and easily available but also easy to handle as compared to many earlier reported inorganic reducing agents e.g., hydrazine hydrate, hydroxyl amine hydrochloride, sodium borohydride, H2O2 etc. The phase purity of the as obtained product is confirmed by X-ray diffraction (XRD), Raman spectroscopy. We have also proposed a possible growth mechanism for the formation of scroll-type nanotubes on the basis of a series of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies of the product obtained at different reaction durations.

20.
Dalton Trans ; 49(46): 16993-17004, 2020 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-33191423

RESUMO

The present work is focused on the synthesis of bismuth sulfide (Bi2S3) nanorod/reduced graphene oxide (RGO) composites via a one-step hydrothermal method using GO and bismuth nitrate in 5 : 1, 3 : 1 and 2 : 1 weight ratios and their characterization. The morphological studies revealed the formation of homogeneously dispersed Bi2S3 nanorods on RGO sheets along with occasional wrapping in the Bi2S3 nanorod/RGO (3 : 1) composite. XRD, FTIR, Raman and XPS studies suggested the incorporation of Bi2S3 in RGO sheets. The galvanostatic charge-discharge measurements showed that the Bi2S3 nanorod/RGO (3 : 1) composite exhibited the highest specific capacitance (1932 F g-1) at 1 A g-1 in the presence of 2 M aqueous KOH in a three-electrode cell. This is ascribed to the enhanced contact area between metal sulfide nanoparticles and RGO, increased conductivity and synergistic effect of Bi2S3 and RGO. The optimized Bi2S3 nanorod/RGO (3 : 1) composite also maintained an excellent cycling stability with ∼100% capacitance retention after 700 cycles. It is noted that the supercapacitor performance of the Bi2S3 nanorod/RGO (3 : 1) composite was better than group V and VI metal chalcogenides and their nanocomposites reported in several previous studies.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA