RESUMO
Hydrogen heralded as a promising renewable and environmentally friendly energy carrier, carries inherent risks owing to its highly flammable nature. A mere 4 % concentration of hydrogen in the air can trigger an explosion. To counteract this peril, a composite material comprising PbOX -ZnO (2 : 1) was synthesized, characterized, and subsequently employed to fabricate a hydrogen sensing device. Various analytical tools were used to characterize as-deposited materials, including X-ray diffraction, Scanning electron microscopy /Energy Dispersive X-ray Spectroscopy, Transmission electron microscopy UV-Vis Reflectance Spectroscopy and Fourier-transform infrared spectroscopy. The device exhibited favorable properties, such as good selectivity, stability, and a low detection limit for hydrogen. At ambient room temperature, the device demonstrated a sensing signal reaching 468.7, with a response time (T90) of 155 seconds and a recovery time (Tr90) of 69 seconds when exposed to a hydrogen concentration of 5â ppm. This performance underscores the device's rapid and effective response to hydrogen exposure. Moreover, the PbOX-ZnO (2 : 1) composite-based device exhibited a detection limit of 2.4â ppm, functioning accurately within a linear range spanning from 5â ppm to 50â ppm. This capability confirms its precision in accurately detecting hydrogen concentrations within this designated range.
RESUMO
Photoactive polymer and quantum dots (QDs)/nanocrystals (NCs)-based bulk heterojunction (BHJ) solar cells have the combined positivity of organic semiconductors and inorganic components, which can enable a high carrier mobility and absorption coefficient. Additionally, the NCs also provide the opportunity to tune the band gap to obtain enhanced absorption in a broad solar spectrum. Among the semiconductors, lead chalcogenide NCs are of particular interest due to their good photosensitivity in the near-infrared (NIR) region of the solar spectrum. These NCs have large exciton Bohr radii (18, 46, and 150 nm for PbS, PbSe, and PbTe, respectively) and tunable sizes depending on the optical bandgaps between 0.3 and 1.5 eV. Independently, lead chalcogenide NCs have been studied extensively for different applications; however, uses in polymer-NC-based bulk heterojunction solar cells are limited. This Review has been structured on the lead chalcogenide NCs incorporated in polymer composite-based bulk heterojunction solar cells covering the material, properties, and solar cell performance to find the issues and explore future opportunities.
RESUMO
Truly alloyed PbS(x)Se(1-x) (x = 0-1) nanocrystals (â¼5 nm in size) have been prepared, and their resulting optical properties are red-shifted systematically as the sulfur content of the materials increases. Their optical properties are discussed using a modified Vegard's approach and the bowing parameter for these nanoalloys is reported for the first time. The alloyed structure of the nanocrystals is supported by the energy-filtered transmission electron microscope images of the samples, which show a homogeneous distribution of sulfur and selenium within the nanocrystals. X-ray photoelectron spectroscopy studies on ligand-exchanged nanocrystals confirmed the expected stoichiometry and various oxidized species.
RESUMO
Aerosol-assisted chemical vapor deposition of Cd[(SP(i)Pr(2))(2)N](2) leads to the growth of cadmium sulfide and/or phosphide thin films on glass. Decomposition of the precursor has been studied by pyrolysis-gas chromatography/mass spectrometry and modeled by density functional theory.
Assuntos
Compostos de Cádmio/química , Membranas Artificiais , Compostos Organometálicos/química , Fosfinas/química , Sulfetos/química , Vidro/química , Tamanho da Partícula , Teoria Quântica , Propriedades de SuperfícieRESUMO
Formation of unusual CdTe rods on Si/SiO(2) and gold coated Si/SiO(2) surfaces is reported from chemical vapor deposition of Cd[(TeP(i)Pr(2))(2)N](2).
Assuntos
Compostos de Cádmio/química , Ouro/química , Nanotubos/química , Dióxido de Silício/química , Telúrio/químicaRESUMO
We report a transient absorption and luminescence study addressing the charge separation, recombination, and regeneration reactions at nanostructured metal oxide/PbS quantum dot/organic hole conductor heterojunctions. We show that yields of charge separation are significantly higher at PbS/SnO(2) interfaces relative to PbS/TiO(2) interfaces, and conclude that this behavior is a result of the ca. 300-500 meV lower conduction band edge in SnO(2) as compared to TiO(2). We also report a correlation between the PbS particle size and the yield of charge separation at PbS/SnO(2) interfaces, with a smaller PbS particle radius resulting a higher yield of charge separation. Finally we investigated the regeneration of the photooxidized PbS by an organic hole transporting material, namely, spiro-OMeTAD. The overall spiro-OMeTAD(+) yield is found to be 27% at a SnO(2)/PbS (approximately 3 nm diameter)/spiro-OMeTAD heterojunction. The addition of a lithium salt was found to raise the overall spiro-OMeTAD(+) yield from its initial value of 27% (where no Li(+) is present) to 50%. We believe this to be a result of an increase in the primary charge injection yield to near unity as the SnO(2) conduction band is lowered (with increasing [Li(+)]), increasing the driving force for electron injection. The present findings are discussed with relevance to the design of PbS-sensitized metal oxide layers for DSSCs.
RESUMO
Group 14 metal complexes of heavy chalcogen-centered anions, M[(TeP(i)Pr(2))(2)N](2) (5, M = Sn; 6, M = Pb) and M(TeP(i)Pr(2)NP(i)Pr(2)Se)(2) (7, M = Sn; 8, M = Pb), were synthesized in 64-89% yields by metathesis of alkali-metal salts of the ligands with group 14 metal dihalides. Crystallographic characterization of the complexes revealed that 5, 6, and 8 engage in metal...chalcogen secondary bonds to generate dimers, whereas 7 is monomeric in the solid state. Multinuclear ((1)H, (31)P, (77)Se, and (125)Te) solution NMR data for these homoleptic complexes evinced dynamic behavior leading to the equivalence of the two ligand environments. The Pb(II) complex 6 was utilized as a single-source precursor to micrometer-scale lead telluride particles via two divergent techniques: aerosol-assisted chemical vapor deposition of the complex in THF/CH(2)Cl(2) solution onto glass substrates yielded rectangular prisms, while solution injection of 6 in tri-n-octylphosphine onto Si/SiO(2)(100) substrates heated to 200-220 degrees C resulted in the formation of wires. PXRD and EDX analysis of the products confirmed the phase purity of the PbTe materials.
Assuntos
Chumbo/química , Compostos Organometálicos/química , Compostos Organometálicos/síntese química , Ácidos Fosfínicos/química , Telúrio/química , Estanho/química , Ligantes , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
ZnO hexagonal single-crystal slices with predominant (0001) and (0001) facets have been fabricated by poly(ethylene glycol)-assisted chemical bath deposition.
RESUMO
The title compound, {(C(6)H(16)NO)[Cu(2)(CH(3)COO)(5)]·CH(2)Cl(2)}(n), consists of acetate-bridged Cu(2)(CH(3)COO)(4) units that are connected via another acetate anion at each terminus to form infinite anionic [{Cu(2)(CH(3)COO)(4)}(CH(3)COO)](n) chains along [100]. The connecting acetate is hydrogen bonded to the dieth-yl(2-hydroxy-ethyl)ammonium cation, and the dichloro-methane solvent mol-ecule fills the remaining voids in the structure. The O-Cu-Cu angles along the polymeric chain are nearly linear [175.49â (5)°], but individual O-Cu-Cu-O units along the chain are bent and rotated against each other at the bridging acetate ion. Translation of each Cu(2)(CH(3)COO)(4) unit along the chain, represented by the least-squares plane of the two copper ions along with four of the acetate O atoms, rotated these units by 35.16â (3)°.
RESUMO
Aerosol-assisted chemical vapour deposition (AACVD) of Cd[(SPiPr2)(SePiPr2)N]2 yields hexagonal cadmium selenide and monoclinic cadmium phosphide films on glass substrates between 475 and 525 °C at different argon flow rates. The films were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). All the results of XRD, EDAX and XPS are in agreement with our previous investigations on Cd[(SePiPr2)2N]2. A breakdown mechanism is proposed based on mass spectra and density functional theory calculations. A large peak at m/z 207 in the mass spectra, previously assigned by us as a new aromatic species, is also observed for this complex.
RESUMO
The enhanced magneto-optical properties of nanoscaled lanthanide chalogenide semiconductors which have a wide energy gap were observed at around 500 nm for the first time. The nanoscaled semiconductors, Eu(1-x)Se nanoparticles 1 (cubic shapes) and 2 (spherical shapes), were synthesized by the thermal reduction of Eu(III) ion with organic ligands containing Se atoms. The resulting Eu(1-x)Se nanoparticles were characterized by X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, superconducting quantum interference devices magnetometer, and microwave induced plasma atomic emission spectroscopy measurements. The particle grain sizes of 1 and 2 were estimated to be 11 and 20 nm, respectively. The concentration-normalized Veldet constants (the magnitude of the Faraday effect) of Eu(1-x)Se nanoparticles were much larger than those of corresponding bulk EuSe and EuS nanoparticles.
RESUMO
There is a need for a method to facilitate the development of novel, reproducible colloidal surface-enhanced Raman scattering (SERS) substrates to encourage the use of SERS in applied studies. In this study we show for the first time that by using suitably designed SERS experiments in conjunction with multivariate analysis of variance (MANOVA), an objective assessment of colloidal SERS reproducibility can be made. This is demonstrated with the analyte cresyl violet, but could be extended to any analyte of interest for which reproducible SERS data are needed.
Assuntos
Interpretação Estatística de Dados , Ouro , Nanopartículas Metálicas , Análise Espectral Raman/métodos , Absorção , Benzoxazinas , Coloides , Ácido Edético , Oxazinas , Prata , Propriedades de SuperfícieRESUMO
Facile and reproducible methods for the syntheses of bis(di-iso-propylselenophosphinyl)selenide ((i)Pr2PSe)2Se (1), bis(di-iso-propylselenophosphinyl)diselenide ((i)Pr2PSe)2Se2 (2) and bis(di-phenylselenophosphinyl)selenide (Ph2PSe)2Se (3) is reported.
RESUMO
The reactions of bis(dialkylselenophosphinyl)selenide with a series of metals have been investigated: synthesis of several metal selenophosphinate complexes and their structures are reported.
RESUMO
Aerosol-assisted chemical vapour deposition (AACVD) of Cd[(SePiPr2)2N]2 is shown to deposit cadmium selenide and/or cadmium phosphide on glass substrates, depending upon the growth conditions. The phase, structure, morphology and composition of the films were characterised by X-ray powder diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The XRD indicated a hexagonal phase for cadmium selenide, whilst cadmium phosphide was monoclinic. Pyrolysis gas chromatography-mass spectrometry and density functional theory were used to deduce a breakdown mechanism for the deposition that favoured the formation of a new aromatic iPr2N2P3+ ion.
RESUMO
EuS nanocrystals, with an average diameter of 9 nm, have been synthesized by the photolysis of Na[Eu(S2CEt2)4].3.5H2O; the first quantum confined particles of EuS to be reported.
RESUMO
A room temperature solid-state reaction has been used to prepare crystalline tin-doped ZnO. Zinc nitrate hexahydrate, cetyltrimethyl ammonium bromide, stannic chloride pentahydrate and sodium hydroxide with proper ratios were ground together. As-synthesized samples were characterized by inductively coupled plasma analysis (ICP), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD); The products were of different morphologies, well dispersed and exhibited good crystallinity, it is also found that the growth direction and morphology of ZnO depend on the amount of Sn doped, which is mainly caused by the difference in sizes between Zn and Sn atoms as well as the change of pH value. Moreover, gas sensing and photocatalytic properties of the obtained products were studied. The materials showed a high gas response to ethanol vapor, and the gas response can reach a maximum of R(a)/R(g) = 124. In addition, tin-doped ZnO materials exhibited improved photocatalytic performance toward methyl orange (MO) solution under a current density of 0.03 mg L(-1) comparison with undoped ZnO.
Assuntos
Gases/análise , Estanho/química , Óxido de Zinco/química , Catálise , Fotoquímica , TemperaturaRESUMO
The low temperature growth of crystalline PbS films has been achieved on plastic substrates by CVD using a xanthate. The possible mechanism involved in this low temperature deposition has been probed by density functional theory calculations.