PbS Particles Research Articles

Aqueous-solution synthesis of uniform PbS nanocubes and their optical properties

PbS nanocubes with uniform size were generated conveniently in aqueous solution at 100 °C. The products were characterized by XRD, FESEM, TEM, UV–Vis–NIR, PL, DLS, Raman, and FT-IR techniques. The mean edge length of the nanocubes is 60 nm and is in high yield. UV–Vis–NIR absorption spectrum indicated that the sample exhibits a blue-shift from 3024 to 288 nm and PL spectrum also indicated that the sample exhibits a blue-shift from 3200 to 328 nm, compared with bulk PbS, respectively. Dark-field light scattering measurements showed that the nanocubes-scattered orange light have a broad absorption band around 610 nm. Such a special property demonstrates that the PbS nanocubes may find potential application in molecular imaging and in vivo cancer diagnosis and therapy. By investigating the intermediates of the reaction process, we observed the important coarse rod-like structures that formed by PbS particles attached to one another at the initial stage of reaction. Then the particle-joint structures decomposed and finally formed PbS nanocubes. Such a morphology evolution of PbS crystals could be summarized as “particle–rod–cube mechanism,” which might be model systems for understanding the growth process of other kinds of nanocubes and directing their synthesis. High-yield PbS nanocubes with an edge length of 60 nm were fabricated successfully in aqueous solution at 100 °C by the assistance of surfactant CTAB. It has been found that the reaction time, temperature, and CTAB play important roles in the formation of uniform PbS nanocubes. A possible growth mechanism called “particle–rod–cube” has been discussed.

Facile preparation of PbS nanostructures and PbS/f-CNT nanocomposites using xanthate as sulfur source: Thermal and optical characterization

PbS nanostructures with different morphologies were fabricated using a new sulfur source through a facile and low cost hydro(solvo)thermal method. The influence of different reaction factors such as sulfur source, temperature, reactant, solvent and surfactant on the size and morphology of the obtained PbS particles were investigated. Beside, a simple hydrothermal process at low temperature (60 °C) for little time (4 h), has been used for preparation of PbS nanoparticles (NPs)/functionalized multi wall carbon nanotubes (f-MWCNTs) nanocomposite. The as-prepared nanocomposite possesses excellent thermal and optical properties. Thermal stability increases by depositing PbS nanoparticles on the surface of CNT. The structure, morphology, thermal and optical properties of the as-prepared nanocompounds were studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy, Thermogravimetric analysis (TGA), Pl spectra and UV–Vis absorption spectra. Photoluminescence spectra of PbS NPs and nanocomposite are consist of two emission peaks which centered at around 402 and 423 nm, when excited at 350 nm. It was noteworthy that the blue luminescence intensity over PbS/f-CNT nanocomposite is very lower than that of pure PbS NPs. Remarkable blue-shift from bulk material was observed on the PbS nanoparticles using UV–Vis spectrum. Furthermore, possible growth mechanism of PbS nanostructures is presented.

Some features of luminescent properties of PbS suspensions, stabilized by high‐molecular polyvinylpyrrolidone

The results of the investigations of optical and luminescent properties of PbS suspensions stabilized by high‐molecular polyvinylpyrrolidone are described. Suspensions prepared by liquid colloidal method from sodium sulfide and lead nitrate demonstrate strong luminescence in near infrared spectral range at the excitation by visual light with different wavelengths. It was proposed that Förster resonant energy transfer plays the important role in luminescence properties of closed packed PbS particles. The model, which describes the observed luminescent properties of the suspensions PbS‐stabilized high‐molecular polymer, is proposed. The combination of very wide spectral range of excitation of the luminescence with rather narrow range of light radiation in near infrared spectral range determine wide perspectives of the materials in solar luminescent concentrators and photodetectors. Copyright © 2015 John Wiley & Sons, Ltd.

Impact electrochemistry: colloidal metal sulfide detection by cathodic particle coulometry.

The determination of the size and concentration of colloidal nano and microparticles is of paramount importance to modern nanoscience. Application of the particle collision technique on metal and metal oxide nanoparticles has been intensively explored over the past decade owing to its ability to determine the particle size and concentration via reactions including the inherent oxidation or the reduction of nanoparticles as well as surface reactions catalysed by the nanoparticles. Transition metal dichalcogenide particles were previously quantified using the anodic (oxidative) particle coulometry method. Here we show that cathodic (reductive) particle coulometry can be favorably used for the detection of metal sulfide colloidal particles. The detection of sulfides of cobalt and lead was performed using the particle collision technique in this work. The presence of spikes confirmed the viability of detecting new and larger particles from compounds using reductive (cathodic) potentials. Such an expansion of the impact particle coulometry method will be useful and applicable to the determination of concentration and size of colloidal metal sulfide nanoparticles in general.

Local supersaturation dictated branching and faceting of submicrometer PbS particles with cubic growth habit.

Hierarchical cubelike submicrometer PbS particles consisting of truncated octahedrons, cuboctahedrons, and cubes were prepared in ethylene glycol solution under favorable high mole ratio of thiourea (Tu) to Pb(AC)2 (R(S/Pb)) via a pumping process. A qualitative analysis based on the classical nucleation theory coupled with the crystal growth theory is employed to interpret the observed experimental phenomena. By varying the concentration of reactants, R(S/Pb), and reaction temperature, it is possible to tune the local supersaturation degree (LSD), which is determined by the number of nuclei and overall growth unit (or concentration), surrounding each growing particle that dictates the branching and faceting of PbS particle. Relatively high LSD that is required for branching growth could be achieved at lower concentration of Tu and reaction temperature. Increasing the concentration of Tu and reaction temperature resulted in less LSD and yielded cubic PbS particles.

Preparation and characterization of heat-assisted PbS/TiO2 thin films

Heat-assisted PbS/TiO2 thin films with different reaction temperatures were prepared. Microstructure, morphology, optical and photoelectron-chemical properties of the as-synthesized thin films were investigated systematically. For the PbS/TiO2 thin films with reaction temperature changing from 10 to 95°C, PbS particles obtained by successive ionic layer adsorption and reaction are galena phase, the mean size of PbS particles decreases firstly and then increases, the coverage of PbS particles on surface increases. At the same time, red shift in the adsorption edges from 416 to 594nm has been detected, and the optical band gap Eg decreases from 3.58 to 2.88eV. What's more, the intensity of photoluminescence increases firstly and then decreases. The photochemistry measurement suggests that the sample prepared at 60°C possesses the highest photocurrent in the first test cycle. However, the value of photocurrent decreases immediately with increasing the test cycle. The effect of the reaction temperature on the microstructure, morphology, optical and photoelectron-chemical properties of PbS/TiO2 thin films have been discussed in detail.

Spectral characteristics and morphology of nanostructured Pb–S–O thin films synthesized via two different methods

Using two different experimental techniques, namely chemical vapor deposition (CVD) and physical vapor deposition (PVD), we deposited a lead sulphide (PbS) thin films with a very small lifetime (10−9). We investigated the morphology of the obtained PbS films using various techniques i.e. AFM, SEM, EDAX, AES and HRTEM. In the case of CVD, we found that the surface consists of grains with dimensions in the plane (diameter to 300nm and height up to 200nm), while the same order of the grain size has been observed for PVD. On the other hand, SEM investigation reveals that the PbS particles with various morphologies of both films have uniform and the particle size distribution. Small amount of sodium was obtained from EDXS studies, which may originate from the substrate where the deposition process has been produced at temperature 550–600°C and for CVD at minimum accelerating voltage 5kV silicon are presented in the spectrum, which means that the region for X-ray generation voltage data exceeds the thickness of the films (where the thickness of films about 0.4μm). AES confirms the surface layer of these films (PVD) containing carbon and oxygen and it has a thickness of 0.1μm. At a depth of 1.3μm in films these elements are again increased, which corresponds to the film thickness of 1.5μm. Layers of PVD films are seen by HRTEM and the studies confirm that oxygen-layer located on top of the structure, while the layers of CVD films not only have the oxygen along the crystallite boundaries, but also accumulate in the depth of the boundary with the substrate. Our results of morphology indicate that the change in spectral characteristics of films deposited by (CVD and PVD) is related to the structure and the crystalline size.

Effect of particle size on the thermal expansion of nanostructured lead sulfide films

The effect of particle size on the thermal expansion of nanostructured lead sulfide films produced by hydrochemical deposition has been studied. The coherent scattering region size and thermal expansion coefficients of PbS nanofilm have been measured depending on the annealing temperature in the interval 293–473K and on the duration of annealing at a constant temperature of 423K. It is found that the thermal expansion coefficient α of nanostructured PbS film is nearly twice as large as that of bulk lead sulfide. It is shown that the observed large difference in the coefficients α is due to the small size of PbS particles in the film that leads to the change of the phonon spectrum boundaries and to the growth of anharmonicity of atomic vibrations. The additional contribution to the thermal expansion coefficient caused by the small particle size in PbS nanofilm is estimated theoretically.

Enhancing the Flexural and Impact Properties of Bioplastic Poly(lactic acid) by Melt Blending with Poly(butylene succinate)

Bio-based biodegradable Poly (lactic acid) (PLA) suffers limitations such as brittleness and slow crystallization. This study aims to resolve the brittle nature of PLA by blending with Poly (butylene succinate) (PBS), a more ductile biodegradable polymer with superior toughness and flexural properties. In this research, a series of PLA/PBS blends was prepared at the blend ratios of 100/0, 80/20, 60/40, 40/60, 20/80 and 0/100. FTIR showed that there was no change in the functional groups of the PLA/PBS blends. Thermal stability assessed by TGA revealed that PBS degraded at higher temperature than that of PLA; the decomposition temperature (Td) at 10% weight loss of PLA and PBS were 330.8 and 356.4°C respectively. The Td of all the blends increased gradually with the addition of PBS. The flexural properties in terms of the flexural strength and the flexural modulus of the blends reduced significantly with PBS content. The PLA/PBS specimens with greater PBS content were softened and flexed more easily, thereby requiring a much lower flexural strength. The flexural modulus of the 80/20 and 60/40 blends dropped from 3.5 GPa for neat PLA to 3.2 GPa and 2.1 GPa while the flexural strength also declined from 105.3 MPa to 90.9 MPa and 69.1 MPa respectively. The toughness of all the blends was greater than that of neat PLA; in particular the 60/40 blend exhibited superior impact strength of 48.7 J/m compared with 30.9 J/m of the neat PLA. The microscopic images of all the blends showed two distinct phases; the 60/40 blend consisted of well dispersed small particles of the tough PBS, resulting in greater absorption of energy upon impact.

Geometry of lead sulfide nanoparticles with a NaCl-type structure

The analysis of X-ray diffraction patterns showed that the geometry of PbS nanoparticles with a structure of NaCl is a nonlinear function of particle size for PbS particles smaller than 82 nm.

Semiconductor nanoparticles in poly((2-dimethylamino)ethyl methacrylate-co-acrylic acid) co-polymers

Nanostructured cadmium selenide (CdSe) and lead sulfide (PbS) semiconductors were prepared in a poly(2-(dimethylamino)ethyl methacrylate-co-acrylic acid) matrix. The obtained nanoparticles were characterized by using optical and structural methods. Co-polymers were synthesized in two different molar ratios of pDMAEMA:acrylic acid monomer units (1:2, 1:1). Transmission electron microscopy analysis confirmed the presence of nano-sized CdSe and PbS particles. In the case of CdSe, a shift of the onset of the optical absorption toward lower wavelengths was observed. X-ray diffraction analysis revealed that both CdSe and PbS nanoparticles have cubic crystal structure.

Chemical deposition of nanocrystalline lead sulfide powders with controllable particle size

Abstract For the first time the systematic study of the effect of synthesis conditions (concentrations of reactants, the presence or lack of a complexing agent and its type, the exposure time of deposited PbS particles in the matrix solution) on the size of lead sulfide nanoparticles, their phase composition and the presence of impurity phases is performed. PbS nanopowders are synthesized by deposition from aqueous solutions of lead acetate and sodium sulfide in the presence of EDTA-H 2 Na 2 or sodium citrate. It is found that the phase composition of the deposit and the size of the nanoparticles depend on the initial concentrations of lead and sulfur ions, the presence and type of complexing agents, as well as on the quantitative ratio between the content of lead ions and complexing ions in the solution. The possibility of controllable hydrochemical deposition of PbS nanoparticles with preassigned size from 5 to 55 nm is shown.

In-situ interaction of nano-PbS with gelatin

Water-soluble gelatin-PbS bionanocomposites (BNCs) were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectra (UV-vis), Fourier transform infrared spectra (FT-IR) and circular dichroism (CD). FT-IR data were used to envisage the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2+ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less α-helix content and more open structures (β-sheet, β-turn, or expanded). A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K (298/303/308 K: 3.11/2.00/1.60 × 106 mol/L) at three different temperatures were calculated based on this formula. Thermodynamic parameters such as ΔGθ, ΔHθ and ΔSθ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous (ΔGθ < 0), and enthalpy-driven (ΔHθ < 0).

Fabrication of CuInS2 thin film by electrodeposition of Cu–In alloy

CuInS2 thin films of chalcopyrite structure were fabricated on indium tin oxide substrates by electrochemical co-deposition of copper–indium alloy layers at 1 atm, followed by sulphurization. Co-deposition potential was determined according to voltammetric study. The effect of deposition potential, concentration of complexing agent, and heat treatment temperature on the morphology and crystal structure of the obtained thin films was examined. Then the influence of heat treatment on the optical and photoelectrochemical performance of CuInS2 thin films was studied. In the electrodeposition solution containing 5 mM CuCl2, 5 mM InCl3 and 0.2 M triethanolamine at pH of 4.0, Cu2In alloy layers were observed at the deposition potential of −1000 mV (vs. saturated calomel electrode). After sulfurization, chalcopyrite CuInS1.5 thin films with the impurity elements of C and O were obtained. Those thin films exhibited p-type semiconductor behavior with the bandgap of about 1.5 eV. The conversion efficiency can be improved further by depositing PbS particles on the thin films.

Enhanced visible-light-responsive photocatalytic property of PbS-sensitized K4Nb6O17 nanocomposite photocatalysts

PbS-loaded K4Nb6O17 nanocomposite photocatalysts (hereafter designated as PbS@K4Nb6O17) were prepared via a reverse microemulsion method. The nanocomposite materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray fluorescence spectrometer, ultraviolet–visible diffuse reflection spectra, photoluminescence measurement and X-ray photoelectron spectroscopy. The nano-semiconductor PbS@K4Nb6O17 composites have the layered structure and the band gaps of the two semiconductors couple. The nanocomposite PbS@K4Nb6O17 exhibited a strong photocatalytic activity for degradation of Rhodamine B (hereafter referred as RhB) under visible light irradiation. Moreover, the nanocomposite PbS(25wt.%)@K4Nb6O17 shows the highest photocatalytic activity, the decomposition rate of RhB solution is about 71% after 120min under visible light irradiation, which is over that of the pure K4Nb6O17 and pure PbS particles. The nanocomposite photocatalysts proved to be fairly photostable through the recyclability experiments. The mechanism of separation of the photogenerated electrons and holes at the PbS@K4Nb6O17 was discussed.

Structural Properties of PbS Nanoparticles Prepared by Photo Chemical Synthesis

Lead sulfide (PbS) nanoparticles have been synthesized by photo chemical method and also in the dark ambient at room temperature. The pH of the solution is maintained by adding NaOH. The as-prepared PbS nanoparticles have been characterized by X-Ray Diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersive Analysis of X-ray (EDAX) and Transmission Electron Microscopy (TEM). XRD studies reveal the crystalline nature of the particles. Grain size values are calculated using Scherrer’s formula and compared with the standard values. SEM picture shows a flower like structure in the sample synthesized at dark ambient, whereas the samples synthesized in light reveals the presence of varied nanostructures like nanorods, nanowires and nanoparticles. Size of the photo chemically synthesized PbS particles observed from TEM lies between 30nm to 60nm. From EDAX we conclude that the composition is nearly stoichiometric.

Morphology and size control of lead sulphide nanoparticles produced using methanolic lead acetate trihydrate–thiourea complex via different precipitation techniques

In this study, lead sulphide (PbS) particles were synthesized from methanolic lead acetate–thiourea (PbAc–TU) complex via various precipitation techniques based on the decomposition of methanolic PbAc–TU complex. The influence of these techniques on the morphology, size and physical properties of PbS particles was studied in details. In general, scanning electron microscopy of the PbS particles produced by conventional chemical bath deposition, sonochemical bath deposition and microwave-assisted chemical bath deposition revealed that they were nanostructured with different size and shape. X-ray diffraction confirmed their high purity, while X-ray photoelectron spectroscopy (XPS) showed that they were partially oxidized due to their high surface energy. Optical absorption, transmission electron microscopy, selective area electron diffraction and XPS of capped nanoparticles (NPs) produced via capping assisted chemical bath deposition using poly(vinyl-pyrrolidone) (PVP) and oleic acid (OA) indicated that narrow size distributed PbS NPs absorbed strongly in the visible region with cubic crystalline phase without any evidence of surface oxidation. Fourier transform infrared spectroscopy of PVP-capped PbS NPs showed strong interaction between PbS NPs and polymer matrix, while for OA-capped PbS NPs, OA was chemically absorbed on the surface of PbS NPs.

Synthesis of anisotropic PbS nanoparticles using heterocyclic dithiocarbamate complexes

We report the synthesis of lead piperidine and lead tetrahydroquinoline dithiocarbamate (DTC) complexes and their use as single source precursors for the preparation of anisotropic PbS nanoparticles. The complexes were thermolysed in coordinating solvents such hexadecylamime (HDA), tri-n-octylphosphine oxide (TOPO), oleylamine (OA) and decylamine (DA) at various reaction temperatures. The variation of the reaction conditions and precursors produced PbS particles with shapes ranging from spheres to cubes and rods. The size of the particles is generally larger than those synthesized by conventional precursor routes. The electron microscopy and X-ray diffraction data confirm the particles to be very crystalline with the dominant cubic rock salt phase present in all samples.

Room temperature synthesis of lead sulfide nanoparticles

Lead sulfide (PbS) nanoparticles were synthesized at room temperature via a simple chemical reaction. In this work, thiophenol was used as the capping agent and sodium sulfide was used as a sulfur source. The products were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible, photoluminescence and Fourier transform infrared spectroscopy. Electron microscopy studies reveal that synthesis of PbS nanoparticles using no capping agent produces PbS nanoparticles with relatively large size, whereas adding thiophenol leads to the production of nano-sized PbS particles. We found that electronic absorption spectra as well as particle sizes depend on the used capping agents. Compared with bulk PbS, the absorption spectra of the obtained PbS nanoparticles exhibit a blue shift, which can be attributed to the quantum confinement of charge carriers in the nanoparticles.

Microstructure of nanocrystalline PbS powders and films

Nanocrystalline PbS powders and nanostructured PbS films have been produced by different deposition procedures. According to scanning and transmission electron microscopy results, the average size of PbS particles in the nanopowders is 8 to 20 nm, and the average grain size in the nanofilms is 40 to 80 nm. As shown by electron diffraction, the nanocrystalline PbS powders have the B1 structure (sp. gr. \(Fm\bar 3m\)).