PbS Nanoparticles Research Articles

Synthesis and crystal structures of Pb(II) dithiocarbamates complexes: precursors for PbS nanophotocatalyst

ABSTRACT Pb(II) complexes of N-ethyl-N-phenyl dithiocarbamate [Pb(EtPhdtc)2] and N-benzylmethyl dithiocarbamate [Pb(BzyMedtc)2] were synthesized and characterized by single crystal X-ray crystallography. The molecular structures of compounds reveal a distorted tetrahedral geometry around the Pb(II) ions. [Pb(EtPhdtc)2] crystalized as a dimeric structure with Pb … Pb and Pb … S interactions while [Pb(BzyMedtc)2] crystallized as monomeric complex with weak C–H interactions. Thermogravimetric analysis of the Pb(II) complexes shows they decomposed to give lead sulphide (PbS). The complexes were thermolysed in oleic acid (OA) at 120°C, 160°C and 200°C to study the influence of temperature on OA capped PbS nanoparticles. Powder X-ray diffraction patterns confirms that the as-prepared PbS are cubic rock salt crystalline phase of PbS. High resolution transmission electron microscopy (HRTEM) micrographs crystallite average size of 2.64 nm for particles prepared at 120°C, 4.12 nm for particles prepared at 160°C, and 1.93 nm for particles prepared at 200°C from [Pb(EtPhdtc)2]. The average crystallite sizes of PbS nanoparticles obtained from [Pb(BzyMedtc)2] are 6.61 nm at 120°C, 13.88 nm at 160°C, and 10.82 nm at 200°C. The as-prepared PbS nanocrystals were used as photocatalyst for the degradation of methylene blue with the highest degradation efficiency of 73.89% recorded for OAPbS1a.

Hot‐Injection Synthesis of PbE (E= S, Se) Nanoparticles from Dichalcogenoimidophosphinato Lead (II) Complexes

AbstractDichalcogenoimidodiphoshinato lead complexes, [Pb((EPiPr2)2N)2] (E=S, Se) have been synthesized and characterized. The crystal structure of [Pb((SeSPiPr2)2N)2]), has been solved by single‐crystal X‐ray crystallography and reported. These complexes have been used as single‐source precursors to synthesise PbS and PbSe nanoparticles by hot‐injection method in an oleylamine/trioctylphosphine mixture. Powder X‐ray diffraction (p‐XRD) studies indicate that the nanoparticles produced are cubic. The optical band gaps estimated from the absorption spectrum fitting curve indicate significant tuning of the bulk band gap, blue shifting towards the visible region of the electromagnetic spectrum.

Synthesis and crystal structure of bis(O-methyl hydrogenato carbonodithioate)-Pb(II): structural, optical and photocatalytic studies of PbS nanoparticles from the complex

Lead(II) methyl xanthate [Pb(S2COMe)2] was synthesized and characterized by single crystal X-ray crystallography. The molecular structure showed a distorted tetrahedral geometry around Pb(II) with each monomeric unit linked with another through Pb···S interactions. The compound was used to prepare hexadecylamine capped PbS (HDA-PbS) and oleylamine capped PbS (OLA-PbS) nanoparticles. The PbS nanoparticles were indexed to the cubic PbS crystalline phase with particle sizes of 4.5 – 34.5 nm. The estimated optical bandgaps obtained from the tauc’s plots were 3.47 and 3.30 eV for HDA-PbS and OLA-PbS, respectively, which are blue shifted in comparison to bulk PbS. The photodegradation of methylene blue using PbS as photocatalyst shows that HDA-PbS have the best degradation efficiency of 77.70% after 240 min.

Enhancement of photocatalytic and photoelectrochemical properties of TiO2 nanotubes sensitized by SILAR - Deposited PbS nanoparticles

The aim of this work is to improve the photocatalytic and photoelectrochemical properties of TiO2 nanotubes (TiO2-NTAs) by sensitizing them with PbS nanoparticles (NPs) prepared by the Successive Ionic Layer Adsorption and Reaction method (SILAR). The Microstructure, surface morphology, phase composition and optical properties of the prepared structure were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM and High-resolution mode HRTEM) and X-ray photoelectron spectroscopy (XPS). The TiO2 NTAs were loaded by PbS NPs, which contents increase by increasing the number of SILAR cycles. The PbS NPs, which have a size in the order of ∼20 nm, were found to be uniformly distributed in the TiO2 NTAs without damaging the tubular ordered structure. The photocatalytic activity of the PbS/TiO2 NTAs system, toward Amido Black (AB), showed significant enhancement compared to the bare untreated TiO2 NTs. At 30 SILAR deposition cycles the PbS-NPs/TiO2 NTAs structure is able to remove 75% of BA under simulated solar light, considerably higher than the 40% removal obtained with unloaded TiO2 NTAs. A significant improvement of the Photoelectrochemical (PEC) efficiency has been also demonstrated for the PbS-NPs/TiO2 NTAs hybrid system. This improvement is mainly related to visible-light harvesting and reduced recombination of photo-generated electron-hole pairs due to the synergistic effect of the heterojunction and to the well-organized morphology of the TiO2 NTAs.

In situ incorporation of laser ablated PbS nanoparticles in CH3NH3PbI3 films by spin-dip coating and the subsequent effects on the planar junction CdS/CH3NH3PbI3 solar cells

This is the first report on in situ incorporation of lead sulfide (PbS) nanoparticles in methyl ammonium perovskite thin films (CH3NH3PbI3:PbS) by the two step spin-dip method and the successive effects on the photovoltaic properties of HTM free Glass/FTO/CdS/CH3NH3PbI3 planar junctions. PbS nanocolloids of different concentrations were prepared by pulsed laser ablation of PbS target in isopropanol. CH3NH3PbI3:PbS thin films were synthesized by two step process of dipping spin coated PbI2 thin films in a dissolution of CH3NH3I in isopropanol containing PbS nanocolloids. Analysis on the structure, composition, morphology and optoelectronic properties of CH3NH3PbI3:PbS films with varying PbS nanoparticle concentrations were done and the results were compared with that of pristine CH3NH3PbI3 films. The CH3NH3PbI3:PbS films were of higher crystallinity with improved photocurrent sensitivity. The thin films were incorporated to HTM free p-n junction solar cells using chemical bath deposited CdS as window layer. The champion cell, Glass/FTO/CdS/CH3NH3PbI3:PbS showed Voc of 0.9 V, the highest value ever reported for HTM free p-n junction solar cell. Also, the device yielded Jsc of 7.76 mA/cm2, FF of 0.4 and a power conversion efficiency of 2.9%. The stability studies for 40 days evidenced that the champion device maintained the open circuit voltage unchanged.

Study of TiO2 nanotubes decorated with PbS nanoparticles elaborated by pulsed laser deposition: microstructural, optoelectronic and photoelectrochemical properties

Titanium dioxide nanotube arrays (TiO2 NTAs) have been synthesized using the electrochemical anodization procedure. Lead sulfide nanoparticles (PbS NPs) were deposited on TiO2 NTAs (PbS NPs/TiO2 NTAs) using the pulsed laser deposition (PLD) method. The prepared samples (PbS NPs/TiO2 NTAs) were characterized using scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis spectroscopy and photoluminescence. The size of the PbS NPs was controlled by varying the number of laser pulses (NLP) during the PLD process. TEM observations show that the PbS NPs are in the range of 10–20 nm, consistent with the results obtained from XRD. HRTEM and diffuse reflectivity show that, at NLP ≥ 2500, the growth of the PbS NPs occurs on a previously formed PbS layer. Transmission and absorption spectra show that the PbS-NPs have an indirect optical bandgap which is particle size independent. This optical bandgap corresponds to excitonic transitions, which are greatly affected by oxygen defects, off-stoichiometry and other surface state defects, particularly for smaller NPs (NLP < 2500). The absorption spectra of the TiO2 NTAs show that the PbS NPs extend the absorption range of the TiO2-NTAs from the ultraviolet to the visible region, indicating that the PbS NPs/TiO2 NTAs heterojunction facilitates the separation of the photogenerated charge carriers. Photoelectrochemical analyses show that a maximum photocurrent current density of ~1.05 mA/cm2 and a photoelectrochemical conversion efficiency of 2.5% are reached for NLP = 2500 under an illumination of 100 mW/cm2 in the UV–Vis range.

Engineering CpG Deoxynucleotide-Conjugated Gold Nanoparticles for Enhanced Anti-Lymphoma Effects in an Immune Competent Lymphoma Model

Introduction: Aggressive B cell lymphomas are clinically challenging, especially in the relapsed/refractory setting. Synthetic DNAs containing the unmethylated cytosine-phosphate-guanine (CpG) deoxynucleotides motif are potent stimulants of the innate immune system. CpGs bind to toll-like receptor 9 (TLR9) in the endosomes. Activation of TLR9 leads to G1-phase arrest of lymphoma cells and induces apoptosis via the Fas ligand pathway. Class B CpGs are linear single stranded DNA that stimulate B cells, while class C CpGs form a duplex secondary structure and act on both B cells and dendritic cells. Witzig et al. (Am J Hematol 2013) used class B CpGs in combination with radioimmunotherapy for B cell lymphomas and had an overall response rate of 93% with 63% complete responses. More recently, Frank et al. (Cancer Discovery 2018) used class C CpGs in combination with radiation to treat advanced stage indolent lymphoma and found that both treated and untreated sites had significant lymph node shrinkage. However, only 7 of 29 qualified for partial response. We have previously shown that CpG conjugated gold nanoparticles (NPs) improve macrophage stimulation. Therefore, we hypothesize that CpG-conjugated gold NPs can enhance the CpG's anti-lymphoma effects though direct and immune mediated mechanisms (Figure 1A). Material and Methods: Using a previously verified triethylene glycol modified CpG (tmCpG) design, we synthesized class B tmCpG NPs (1826 for mice, 2006 for human) and class C tmCpG NPs (2395). Lymphoma cell lines (SUDHL4, Ramos, A20) and bone marrow derived dendritic cells (JAWSII) were used in in vitro and in vivo assays. Viability was measured by MTS and apoptosis by annexin V-PI flow cytometry. For dual tumor studies, A20 lymphoma cells were injected subcutaneously in both flanks of BALB/c mice. The side with the larger tumor was treated with either PBS, free CpG, or tmCpG NPs intratumorally on days 1, 4, and 8. Tumors were monitored for growth and, when either tumor reached 2 cm3, the mice were euthanized. Results: Changing the CpG sequence did not alter the monolayer formation on the nanoparticles, and 1nM of tmCpG NPs are equivalent to 0.5ug/ml of CpGs. Class C tmCpG NPs (2395) tend to form aggregates during washing and collection phases but could be sonicated back into suspension. Both class B (1826 and 2006) and class C (2395) tmCpG NPs significantly reduced viability of SUDHL4, Ramos, and A20 cells, compared with free CpGs, while having no effect on the viability of JAWSII cells. tmCpG NPs induced lymphoma cell death by apoptosis as measured by annexin V-PI. In in vivo studies, both class B free CpG and class B tmCpG NP groups had reduced tumor growth and improved survival compared with PBS controls. Nine of 15 mice (60%) in the tmCpG NP group had no detectable tumor on the treated side, while only 4 of 15 mice (27%) in the free CpG group had no tumors. On the untreated side, there was no difference in tumor growth between the three groups. In another dual tumor study, the class C tmCpG NPs trended towards a reduction of tumor growth in both the treated and untreated tumors by comparison to free CpG or PBS but the sample size was too small (n=4) to achieve statistical significance. One of the 4 mice in the class C tmCpG NP group had complete resolution of both treated and untreated tumors, while all of the PBS and free CpG mice died before day 28, suggesting that there was an abscopal effect generated by using the nanoparticle construct (Figure 1B). Conclusions: The tmCpG NP design significantly improved cytotoxicity of CpGs toward lymphoma compared with free CpGs. Class B tmCpG NPs had stronger direct cytotoxic effects at the treated tumor site compared with free CpG, while class C tmCpG NPs had immune effects at the distant untreated sites. Future studies should focus on re-engineering the platform to stabilize and optimize tmCpG NPs for improved anti lymphoma activity. Disclosures Karmali: Gilead/Kite; Juno/Celgene: Consultancy, Speakers Bureau; Takeda, BMS: Other: Research Funding to Institution; Astrazeneca: Speakers Bureau. Thaxton:Zylem: Other: Co-founder of the biotech company Zylem. Gordon:Juno/Celgene: Other: Advisory Board, Research Funding; Gilead: Other: Advisory Board; Zylem LLC: Other: co-founder; research in nanoparticles in cancer; Bayer: Other: Advisory Board.

Pulsed-laser-deposited lead sulfide nanoparticles based decoration of porous silicon layer as an effective passivation treatment for multicrystalline silicon

We report on the use of pulsed laser deposition (PLD) of PbS nanoparticles (PbS-NPs) on porous silicon layers in order to passivate multicrystalline silicon (mc-Si) substrates intended for solar cells applications. The porous silicon (PS) layer was first obtained through the electrochemical anodization of the mc-Si substrate, and then the PLD technique was used to decorate the PS layer by PbS-NPs at room temperature. By varying the number of laser ablation pulses (NLP) from 50 to 1200, the average size of the PbS-NPs was varied from ~2 nm to ~10 nm. The X-ray diffraction analysis has confirmed the crystalline quality of the PbS-NPs, whereas the transmission electron microscopy observations showed the uniform decoration of the PS by the PbS-NPs. By combining different characterization techniques, we were able to identify NLP = 200 as the optimal decoration condition that leads to the best passivation, in terms of the lowest surface reflectivity (of 15% at 500 nm wavelength), the highest PL intensity of the PS layer (centered around 633 nm) and the longest minority carrier lifetime (as long as ~430 µs versus 40 µs for the bare treated PS layer and 2.2 µs for the untreated bare mc-Si).

Влияние наполнителя на ИК-спектры полимерных нанокомпозитов поли-n-ксилилен-сульфиды

Проведены исследования ИК-спектров в области 500—4000 см-1 пленок полимерных нанокомпозитов на основе поли-п-ксилилена (ППК) и сульфидов (ППК—PbS, ППК—CdS, ППК—S) в зависимости от содержания наполнителя (С ~ 0—100 об. %). Пленки толщиной d ~ 0.5 мкм получены методом твердофазного криохимического синтеза на подложках из кремния. Выявлены общие изменения в ИК-спектрах нанокомпозитов по сравнению с пленкой чистого ППК и индивидуальные особенности для каждого наполнителя. С ростом концентрации наполнителя наблюдались низкочастотный сдвиг полосы внеплоскостных деформационных колебаний С-Н-связей ароматического кольца и изменения интенсивностей характеристических полос матрицы ППК. Для нанокомпозитов ППК—PbS и ППК—CdS обнаружены дополнительные полосы в области 1000—1800 см-1, а для пленок ППК—CdS — еще дополнительная полоса в области 3100— 3600 см-1. В пленках ППК—S зарегистрировано только сильное ослабление полос поглощения валентных колебаний С—С- и С—Н-связей ароматического кольца, а также деформационных С—Н-колебаний в СН2-группе. Появление дополнительных полос в ИК-спектрах пленок ППК— PbS обусловлено образованием как сульфооксидных фаз с участием наночастиц PbS, так и групп С—О, С=О из-за окисления полимерных цепей матрицы ППК, а в пленках ППК—CdS — наличием сложных соединений, содержащих сульфо- (SO4, гидроксильные (OH) и карбоксилатные (СОО-) группы. Кроме того, в ИК-спектрах пленок ППК—PbS и ППК—CdS обнаружены полосы, связанные с изменениями структуры замещенного бензольного кольца из-за потери им симметрии.

Synthesis of very-fine PbS nanoparticles dispersed homogeneously in MC matrix: effect of concentration on the structural and optical properties of host polymer

Well-dispersed polymer nanocomposite films based on methylcellulose (MC) and lead sulfide (PbS) were prepared by two-step methods; the fine-PbS nanoparticles are first synthesized by in situ chemical reduction method while the films are made by solution casting technique. The effect of different concentration of PbS nanoparticles on the structural, optical properties, surface morphology, and chemical composition of the host polymer matrix were studied by x-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, UV–vis absorption spectroscopy, Scanning electron microscope (SEM), and Energy-dispersive x-ray spectroscopy (EDS) techniques. XRD studies reveal that the synthesized PbS nanoparticles are in cubic nanocrystalline phase with the very-fine grain size distribution between 2.23 to 4.46 nm. The homogeneous distribution of PbS in MC matrix was supported by both UV–vis spectra analysis and SEM images. The UV–vis measurement of nanocomposite films shows high absorption in the visible range, which correlate to the characteristics of the PbS nanoparticles. The effect of various concentration of PbS nanoparticle on the energy band gap of nanocomposite films has been analysed to understand the optimum conditions for the synthesis process. Significant reduction of the direct allowed energy band gap of the MC is observed upon increasing the PbS concentration, from 6.25 eV for pure MC to 1.92 eV for 0.3 M PbS concentration. A linear correlation in the refractive index at infinite frequency with PbS concentration revealed a well-distribution of the dopant throughout the host MC. The analysis of the refractive index was correlated with the results of SEM measurement.

Revealing the Effects of the Non-solvent on the Ligand Shell of Nanoparticles and Their Crystallization

When nanoparticles (NPs) are assembled from solution, a common assembly method of choice is either solution destabilization or solvent evaporation technique. The destabilization of the NP solution by non-solvents results in the formation of faceted supercrystals (SCs) while periodic film-like assemblies are typically formed by solvent evaporation. Here, we reveal the effect of non-solvents in washing, dispersing, and crystallizing NPs. Small angle neutron scattering (SANS) is employed for monitoring the ligand shell of NPs in solutions upon introduction of various non-solvents. The SC crystallization process is traced in situ with small-angle X-ray scattering (SAXS), and the structures of the resulting single-crystalline SCs are examined in detail by mapping the reciprocal space using SAXS and wide-angle X-ray scattering. Our study suggests that the relative miscibility of the non-solvent with solvents and ligands determines the solvation and thickness of the ligand shell and thereby the resulting structure of SCs. In the early stage of crystallization, truncated octahedral PbS NPs form SCs with face-centered cubic (fcc) symmetry. In the later stage, the fcc symmetry is preserved in the SC formed by larger (5.60 nm) NPs, but the SC assembled from smaller (4.14 nm) NPs undergoes a phase transition into body-centered cubic (bcc) lattice via Bain transformation, becoming a polycrystalline SC containing three structurally correlated bcc domains and one untransformed fcc domain. Our study provides the detailed understanding of the non-solvent effect that impacts beyond the formation of SCs, enabling the judicious selection of solvent/non-solvent mixtures for NP purification.

Machine Learning Accelerates Discovery of Optimal Colloidal Quantum Dot Synthesis.

Colloidal quantum dots (CQDs) allow broad tuning of the bandgap across the visible and near-infrared spectral regions. Recent advances in applying CQDs in light sensing, photovoltaics, and light emission have heightened interest in achieving further synthetic improvements. In particular, improving monodispersity remains a key priority in order to improve solar cells' open-circuit voltage, decrease lasing thresholds, and improve photodetectors' noise-equivalent power. Here we utilize machine-learning-in-the-loop to learn from available experimental data, propose experimental parameters to try, and, ultimately, point to regions of synthetic parameter space that will enable record-monodispersity PbS quantum dots. The resultant studies reveal that adding a growth-slowing precursor (oleylamine) allows nucleation to prevail over growth, a strategy that enables record-large-bandgap (611 nm exciton) PbS nanoparticles with a well-defined excitonic absorption peak (half-width at half-maximum (hwhm) of 145 meV). At longer wavelengths, we also achieve improved monodispersity, with an hwhm of 55 meV at 950 nm and 24 meV at 1500 nm, compared to the best published to date values of 75 and 26 meV, respectively.

Rapid microwave-assisted synthesis of Ag-doped PbS nanoparticles for optoelectronic applications

Herein, novel Ag-doped PbS (Ag:PbS) nanoparticles (NPs) were synthesized via a facile and rapid microwave route. Field emission scanning electron microscopy (FESEM)/energy-dispersive X-ray (EDX) spectroscopy were employed to confirm the homogeneous doping of Ag in PbS. The transmission electron microscopy (TEM) exposed that the PbS NPs were fully encapsulated with Ag. X-ray diffraction (XRD) analysis revealed that all the samples possessed cubic crystal structures whereas the peak positions for the Ag:PbS were slightly shifted towards lower angle compared to pure PbS, further confirm the Ag doping in NPs. Fourier-transform Raman (FT-Raman) spectra also confirmed the phase and doping of Ag in PbS NPs. The grain sizes of the synthesized NPs were found to be in the range of 15–40 nm while calculated crystallite sizes of these samples were in the range of 18–26 nm. The zeta potential for 5.0 wt% Ag:PbS NPs was found to be approximately 10 times higher than that for pure PbS NPs, signifying the high stability of the doped NPs in aqueous media. The optical band gap of Ag:PbS NPs were evaluated from diffused reflectance spectra and found to be in range of 1.95–2.51 eV; increases with Ag doping. The quenching in photoluminescence (PL) intensity was observed with the increase of Ag doping concentration attributed to the charge transfer between Ag and PbS. Moreover, Ag doping also improve the electrical and dielectric properties of PbS NPs. Finally, optoelectrical properties of synthesized materials were investigated under 633 nm laser-light illumination to determine their applicability as visible-light photodetectors. It was found that the Ag doped PbS NPs exhibited enhanced photodetector figures of merit compared to the pure PbS NPs.

Tuning the optoelectronic properties of PEDOT:PSS-PVP core–shell electrospun nanofibers by solvent-quantum dot doping and phase inversion

In the present study core–shell PEDOT:PSS-polyvinylpirrolidone nanofibers were synthesized by coaxial electrospinning. These fibers were doped with different solvents (dimethylsulphoxide, dimethyl sulfoxide (DMSO), isopropyl alcohol (IPA), and ethylene glycol), and PbS nanoparticles at different concentrations; additionally, the coaxial electrospinning setup process was inverted in order to exchange the phases comprising the core–shell morphology. Experimental results showed that DMSO and IPA solvents produced a change in the PEDOT:PSS phase from its benzoid structure to a more conjugated (quinoid) one. The synthesized samples displayed an increment in the conductance of the composite nanofibers, based on a more conjugated structure of the PEDOT:PSS phase, and a better dispersion of the PbS nanoparticles within the nanofibers; this increment was, under certain synthesis conditions, up to three orders of magnitude higher than in the case of the nanofibers with no solvent, nor nanoparticles, added. Photoresponse also showed a clear increment in the value of the photogenerated current as the concentration of the nanoparticles increased. Inverting the arrangement of the core–shell phases in the nanofibers increased the conductance and the photogenerated current in the cases analyzed. These results show novel evidence on the capability of tuning the conductance and photoresponse of composite core–shell nanofibers, based on the doping of the PEDOT:PSS phase with different solvents and PbS nanoparticles, and the arrangement of the core–shell phases. Tailoring the optoelectronic properties of conductive, flexible nanofibers is a desirable competence in technological areas such as transparent flexible conductors, biosensors and tissue engineering.

Synthesis of PbS/TiO2 nano-tubes photoelectrode and its enhanced visible light driven photocatalytic performance and mechanism for purification of 4-chlorobenzoic acid

In this study, highly ordered TiO2 nano-tubes (TiO2 NTs) were synthesized by anodization. Subsequently, PbS nanoparticles were successfully decorated onto the surface of TiO2 NTs by successive ionic layer adsorption and reaction strategy in the presence of lead acetate (Pb(Ac)2) and thiourea. Afterwards, morphologies and chemical structures of PbS/TiO2 NTs photoelectrode were systematically studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results showed that PbS nanoparticles were uniformly dispersed on the surface of TiO2 NTs, and a small amount of PbS nanoparticles gathered together. Besides, their optical properties were investigated by ultraviolet–visible diffuse reflectance spectroscopy (DRS), transient photocurrent density, open potentials, electrochemical impedance spectroscopy (EIS) and Mott-schottky measurements. Compared with the pristine TiO2 NTs photoelectrode that only could utilize ultraviolet light, The PbS/TiO2 NTs photoelectrode presented absorption properties of visible light, which improved the utilization of solar energy. What’s more, the photocatalytic degradation performance of PbS/TiO2 NTs photoelectrode was studied by using 4-chlorobenzoic acid as the target pollutant, finding that 80.37% of 4-chlorobenzoic acid could be removed within 7 h. After these, based on the electrochemical and fluorescence spectra, the enhanced photocatalytic performance mechanism of PbS/TiO2 NTs was proposed. In addition, the PbS/TiO2 NTs possessed excellent stability for 4-chlorobenzoic acid degradation after consecutive utilization for five cycles. This study illustrated that the novel PbS/TiO2 NTs photoelectrode was a promising photocatalyst with many potential applications, which could be used in sewage treatment process. Most importantly, this study provided a theoretical support for the practical application of photocatalytic technology.

Influence of Crystallization Temperature–Time Technological Factors on Structure and Photoluminescent Properties of Polymer Nanocomposites on the Base of Isotactic Polypropylene (PP) and Lead Sulphide (PbS) Nanoparticles

In this paper, we reported on obtaining and study of polymer nanocomposites based on isotactic polypropylene and lead sulfide nanoparticles. SEM analysis showed that the average size of nanoparticles of lead sulphide based on PP + 1%PbS 7–13 nm; PP + 3% PbS is 13–18 nm, for PP + 5%PbS 11–20 nm and for nanocomposites PP + 10%PbS 13–24 nm. UV–Vis spectroscopy determined that the band gap for nanocomposites based on PP + 1%PbS is 2.2 eV; for PP + 3%PbS 2.1 eV; for PP + 5%PbS 2.3 eV, and for PP + 10% PbS 1.7 eV. The photoluminescence properties of nanocomposites based on PP + PbS are investigated. It is established that the intensity of photoluminescence increases with increasing concentration of nanoparticles of PbS to 3% of content, and then decreases. The effect of temperature–time crystallization on the structure and photoluminescent properties of nanocomposites based on PP + PbS was also studied. It is established that in the case of cooling of PP + PbS films in liquid nitrogen, the intensity of the photoluminescence increases sharply compared with cooling in water and with slow spontaneous cooling.

Electrochemical Epitaxial Growth of TiO2/CdS/PbS Nanocables

Electrochemical deposition as a liquid phase epitaxial growth method is widely used to fabricate different kinds of hierarchical structures. As a typical heterostructure, TiO2/PbS is widely utilized in the areas of photovoltaics and photocatalysis. Oriented TiO2 nanorod (NR) arrays can provide direct pathways for the electron transport of photoanode. However, the lattice mismatch between TiO2 NR sides and PbS is very large; PbS nanoparticles (NPs) only formed on the top of TiO2 NRs. To solve this problem, TiO2/CdS core/shell nanocables were firstly prepared electrochemically because the lattice ratio between TiO2 and CdS was 0.916; and then, PbS NPs were successfully deposited over CdS shells (the lattice ratio between CdS and PbS was 0.697) to form TiO2/CdS/PbS hierarchical heterostructures. Experimental results demonstrated that the CdS interlayer could effectively promote the growth of PbS NPs on the surface and improve the fill factor and short current density of the photoanodes.

A facilely one pot low temperature synthesis of novel Pt doped PbS nanopowders and their characterizations for optoelectronic applications

Different concentrations of Pt doped PbS nanostructures synthesis has been attained facilely by chemical route. X-ray diffraction (XRD) and FT-Raman spectroscopy analyses confirms the structure. After close inspection and indexing of diffraction peaks, the absence of additional peak owing to any contamination or free Pt in final products was confirmed. XRD data was further used to evaluate the lattice constants, crystallite size, density and strain to see the effect of Pt on these. Calculated lattice parameters confirm the single cubic phase, which was in correlation with vibrational modes analysis. The crystallite size was calculated in range from 9 to 11 nm. For further confirmation of Pt doping and its homogeneity in final product the EDX/SEM mapping was carried out and approved the homogeneous presence of Pt in PbS. SEM study revealed that the morphology is changing from nanoparticles (NPs) to nanosheets (NSs). Diffused reflectance spectra (DRS) were measured for powdered samples and energy gap was estimated up to 1.32 eV. Photoluminescence spectra was recorded and shows an intense green and broad red emission bands at 518 and 700 nm, correspondingly. The values of dielectric constant are found in range of 18–28. Total ac electrical conductivity is rising with applied frequency. The energy gap value suggest the application of synthesized Pt:PbS NPs and NSs in solar cell.

Tunable passively Q-switched Dy3+-doped fiber laser from 2.71 to 3.08 μm using PbS nanoparticles.

We present the first widely tunable passively Q-switched Dy3+-doped ZBLAN fiber laser around 3μm pumped at 1.1μm using PbS nanoparticles as the saturable absorber (SA) to our knowledge. At 2.87μm, the modulation depth and saturation intensity of the SA were measured to be 12.5% and 1.10 MW/cm2, respectively. Stable Q-switching was achieved over a wavelength range of 2.71-3.08μm (∼370 nm), which is a record tuning range from a pulsed rare-earth-doped fiber laser, to our knowledge. A maximum output power of 252.7mW was obtained, with a pulse energy of 1.51μJ, a pulse width of 795ns, and a repetition rate of 166.8kHz. This demonstration implies that Dy3+ is a promising gain medium for tunable pulsed sources in the 3μm band and shows for the first time, to the best of our knowledge, the potential of PbS as a mid-infrared SA.

Effect of Thermal Annealing on Structure and Optical Properties of Poly(p-xylylene)–PbS Thin Films

In this study, wide-angle X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy were employed to address the crystalline structure and morphology of poly(p-xylylene)–PbS nanocomposite thin films prepared by vapor deposition polymerization as well as their evolution upon thermal annealing. It was found that as-synthesized samples with different PbS contents demonstrate similar diffraction patterns that cannot be fully ascribed to a decrease in crystallite size, indicating distorted crystal structure of PbS nanoparticles compared to the bulk PbS. X-ray absorption spectroscopy reveals wide distribution of Pb–S bond lengths with a minimum value of 2.67 A, which can be attributed to the presence of molecular (PbS)n clusters in the studied films. It was shown that thermal annealing can be used to control the size of PbS nanoparticles and, as a consequence, optical properties of the composite films. The UV–vis absorption spectra demonstrate pronounced red shift of the absorption ...