Pure PBS Research Articles

Enhancing sustainability and biodegradability of poly(butylene succinate) (PBS) composite filaments reinforced with cocoa bean shell residues

AbstractIn this research, we have successfully produced biodegradable composite filaments using Poly(butylene succinate) (PBS) and cocoa bean shell residues (CBS). These composite filaments, fabricated by incorporating up to 20 wt% of the natural filler into the PBS matrix through extrusion processing, have undergone rigorous rheological, mechanical, thermal, morphological, and soil disintegration characterizations. The results have unveiled the potential of printing biodegradable biocomposite filaments, with the materials demonstrating thermal stability in the printing process temperature range. However, a reduction in thermal stability was observed with the incorporation of the natural filler. Differential scanning calorimetry (DSC) analyses indicated a small crystallinity variation for the composites concerning the pure PBS matrix. Furthermore, incorporating the natural filler improved the disintegration rate in the composites' soil, suggesting that CBS can increase and modulate the biodegradation rate of the PBS matrix, thereby expanding its applications in sustainable packaging, 3D printed parts for consumer goods, and agriculture.Highlights Sustainable innovation by using PBS‐CBS filaments for eco‐conscious production. CBS boosts biodegradation and soil disintegration. Shaping a greener future with eco‐friendly 3D printing of PBS‐CBS biocomposites.

Improved decolorization of MB using CeCoO3/PbS heterojunction as a superior‐excellent photocatalyst

Developing effective and inexpensive photocatalysts is considered a helpful approach to pollution degradation. Herein, CeCoO3/PbS photocatalyst was synthesized via the hydrothermal procedure and described by XRD, IR, SEM, EDS, PL, and DRS analyses. The results revealed the deposition of PbS on the CeCoO3 surface, as illustrated by the FE‐SEM images. The influence of photocatalyst dosage, temperature, electron acceptor, and pH toward the decolorization of MB under the irradiation of a UV lamp was considered. By CeCoO3/PbS photocatalyst, the conversion percentage achieved 98% within 10 min, around two times more than pure CeCoO3 and PbS. According to the experimental and calculated results, the Type‐II heterojunction formation was observed, which boosted the photoactivity of CeCoO3/PbS by its higher charge separation rate compared with perovskite and PbS and the stronger redox capability of charges. In addition, CeCoO3/PbS nanocomposites have impressive stability and efficiency after five cycles of experiments. Consequently, the coupling of CeCoO3 with PbS provides a favorable pathway to remove contamination.

Study of Galena Ore Powder Sintering and Its Microstructure

Galena is a natural mineral enriched with lead sulfide (PbS). It typically forms in hydrothermal veins associated with igneous rocks and can also occur as a gangue mineral in other ore deposits. PbS is of special importance for scientific research applications due to the possibility of tuning its semiconductor energy gap using nanotechnology in conjunction with powder metallurgy as an easy, controllable production route. In this paper, almost pure PbS was successfully produced starting from a high ratio of PbS phase galena ore. As-received galena lumps were roughly pulverized and milled to produce four particle size ranges of 38, 63, 125, and 250 µm prior to compaction and sintering in a vacuum (pre-flushed with argon gas). SEM coupled with the EDAX analysis unit was employed to investigate the microstructure and chemical composition of the as-received galena and the subsequent products after sintering. The chemical analysis confirmed the high ratio of PbS compound in the as-received galena and sintered products with approximately 85% Pb and 13% S mass ratio. The sintering process of the galena powder was carried out at different values of temperature, time, and compaction pressure. Additionally, the effect of length to diameter ratio of compacted and sintered samples was investigated. XRD analysis confirmed the existence of the PbS phase in the as-received and sintered samples at 700 °C with approximately 98 wt.%, as well as a new phase that is formed at 800 °C with a lower percentage. The micro-hardness of the as-received and sintered samples was measured and compared with the as-received galena ore. The results showed a significant reduction in the hardness of sintered galena powder compared with the bulk as-received galena by 52%. Furthermore, a relative sintered density of 99.3% for the as-received galena density signifies a novel result using powder metallurgy techniques.

Preparation and Study of Structural and Optical Properties of PbS:Cu Nanostructured Thin Films

Thin films of lead sulfide (PbS) and various Cu mixing ratios (30%, 50%, and 70%) are used in this work. were made using the (PLD) method on glass substrates at a wavelength of 1064 nm and 600 mj of laser energy. X-ray diffraction experiments were used to determine the structural measurements for pure PbS, and other mixes present thin films demonstrated a face-centered-cubic structure. and discovered that the average grain size was 17.74 nm; this grew to 20.54 nm after combining with 30% Cd, 20.54 nm after mixing with 50% Cd, and 23.15 nm after mixing with 70% Cd. The optical characteristics of PbS thin films measured between 300 and 1100 nm in wavelength. For PbS thin films, the optical transmittance and transparency decrease as the o mixing ratio increases.The absorption coefficient rises as the mixing ratio does. When the mixing ratio is increased, the band gap for pure PbS thin film is 2.43, rises to 3.03, and thereafter falls to 2.01 and 1.5.

Synthesis and characterization of Mo-doped PbS thin films for enhancing the photocatalytic hydrogen production

Photocatalytic hydrogen production has gained considerable attention as a sustainable method for renewable energy production. Lead sulfide (PbS) compound has significant reserves and a suitable bandgap for the production of hydrogen gas via the water photo-splitting process. However, the charge recombination effect of the charge carriers severely limits their potential use in solar water splitting. Herein, the photoelectrodes of PbS were fabricated through the chemical bath deposition method and then doped with different Mo concentrations to optimize the hydrogen photo-production activity. Both structural and performance characterizations of the photoelectrodes have been carried out using various characterization techniques. The photoelectrochemical (PEC) performance of molybdenum (Mo)-doped PbS photoelectrodes exhibits a significant increase in the photocurrent density with the optimum photocurrent density of 1.2 mA/cm2 obtained at 0.8 % Mo doping atomic ratio which was twelve times higher than that of a pure PbS photoelectrode. The doping of Mo induces the electron-hole separation yield which results in improved electron transport characteristics. The Mo doping was as act as a donor site that increased the PbS film conductivity. The newly optimized Mo–PbS was used as a promising photoelectrode supported on commercial glass using the optimum Mo-doped PbS photoelectrode, the photoelectrochemical (PEC) hydrogen production rate was reached 122 μmol/h cm2 during the solar water splitting process and the conversion efficiency of the incident photon-to-current (IPCE) value was 7.0 % at 390 nm monochromatic exposure. Moreover, the stability of the optimum electrode was evaluated as a function of the number of runs and exposure time in addition to the electrochemical impedance study.

Vacuum-evaporated PbS:0.03 Zn thin films with varying thicknesses for environmental applications

In this research, we explore how the thickness of PbS-doped Zn thin films made through thermal vacuum evaporation affects their physical properties for environmental applications. Our x-ray diffraction (XRD) examination shows that the films consist of pure crystalline cubic PbS phase. Additionally, the energy-dispersive X-ray spectroscope (EDXS) provides confirmation that the synthesized products are of high purity. PbS films doped with Zn have spherical nanocrystals ranging from 130 nm to 250 nm in size, as observed through field emission (FE)-scanning electron microscopy (FE-SEM) analysis. The thickness of the film layer was found to correlate significantly with an increase in crystallite size and grain size, as validated by both XRD and FE-SEM analyses. The optical energy gap (Eg) of the thin films under examination exhibited variations in relation to their respective thickness. Bandgap energy was found to decrease from 1.66 eV to 1.2 eV as film thickness was increased from 50 nm to 250 nm. The Arrhenius law shows that films with varying thicknesses have thermally activated electrical conductivity and exhibit two conduction mechanisms. After analyzing the photocatalytic decomposition of methylene blue, it was observed that a thicker (PbS)0.97(Zn)0.03 film with a larger grain size demonstrated superior photocatalytic efficiency (92 % after an exposure duration of 180 min). This is due to a smaller band gap and the presence of defect sites, which enhance catalytic reactions. The study presents a framework for researching the controllable structure, thickness, and composition of chalcogenide semiconductor thin films for environmental applications.

Nanostructured p-PbS/p-CuO sulfide/oxide bilayer heterojunction as a promising photoelectrode for hydrogen gas generation

Abstract Recently, the photoelectrochemical (PEC) water-splitting reaction for hydrogen (H2) production has been a competitive research route to realize clean and sustainable electric power. In this work, copper oxide (CuO) and PbS thin films were fabricated on commercial glass, respectively, using the techniques of successive ionic-layer adsorption and reaction and chemical bath deposition. These nanostructured thin films served successfully as photoelectrodes for the photogeneration of H2. In addition, a p-PbS/p-CuO bilayer system was also fabricated, and a remarkable boost in PEC efficiency was observed compared to pure CuO and PbS thin films. Optical examinations showed excellent absorbance properties of the p-PbS/p-CuO bilayer in the visible range, with a bandgap of ∼1.28 eV. X-ray diffraction analysis indicated a monoclinic CuO/cubic PbS crystalline structure with a particle size of ∼18 nm. The photocurrent density (J ph) values were obtained using a three-electrode electrochemical cell in 0.3 M Na2S2O3 electrolyte. The p-PbS/p-CuO photoelectrode demonstrated a J ph value of −0.390 mA cm−2, which is significantly higher than the values of −0.120 and −0.008 mA cm−2 for the pure PbS and CuO photoelectrodes, respectively. This improvement is attributed to the p-PbS/p-CuO oxide/sulfide bilayer heterojunction, which improved the visible light absorption and reduced the electron–hole (e–h) recombination. The effects of pH value, temperature light intensity, and wavelength were all additionally studied. Remarkably, the photoelectrodes were stable under a pH of ∼7, which makes them promising for H2 production using normal drinking/seawater. These findings confirm the ability of the prepared photoelectrodes to facilitate water splitting and H2 generation under various environmental, chemical, and illumination conditions.

γ-Ray-Induced Photocatalytic Activity of Bi-Doped PbS toward Organic Dye Removal under Sunlight.

Photocatalysts based on semiconducting chalcogenides due to their adaptable physio-chemical characteristics are attracting attention. In this work, Bi-doped PbS (henceforth PbS:Bi) was prepared using a straightforward chemical precipitation approach, and the influence of γ-irradiation on PbS's photocatalytic ability was investigated. Synthesized samples were confirmed structurally and chemically. Pb(1-x)BixS (x = 0, 0.005, 0.01, 0.02) samples that were exposed to gamma rays showed fine-tuning of the optical bandgap for better photocatalytic action beneath visible light. The photocatalytic degradation rate of the irradiated Pb0.995Bi0.005S sample was found to be 1.16 times above that of pure PbS. This is due to the occupancy of Bi3+ ions at surface lattice sites as a result of their lower concentration in PbS, which effectively increases interface electron transport and the annealing impact of gamma irradiation. Scavenger tests show that holes are active species responsible for deterioration of the methylene blue. The irradiated PbS:Bi demonstrated high stability after being used repeatedly for photocatalytic degradation.

Preparation and Spectroscopic, Thermal, and Mechanical Characterization of Biocomposites of Poly(butylene succinate) and Onion Peels or Durum Wheat Bran.

The utilization of plant based fillers: onion peels (OP) and durum wheat bran (WB) to obtain sustainable biocomposite materials with poly(butylene succinate) (PBS) is presented in this paper. The biocomposites were first obtained in pellet form by extrusion method and then injection moldings were made from the pellets. Two kinds of biocomposites were fabricated containing 15% and 30% wt. of OP or WB. Additionally, pure PBS moldings were prepared for comparative purposes. The effect of the filler type and its amount on the chemical structure, density, thermal, and thermo-mechanical properties of the fabricated composite samples was studied. Fourier-transform infrared spectroscopy results showed that the composite preparation method had no effect on the chemical structure of composite components, but weak interactions such as hydrogen bonding between OP or WB and PBS was observed. The addition of OP or WB to the composite with PBS reduced its thermal stability in comparison with pure PBS, all studied composites start to degrade below 290 °C. Additionally, the mechanical properties of the composites are worse than PBS, as the impact strength dropped by about 70%. The deterioration of tensile strength was in the range 20-47%, and the elongation at maximum load of the composites was in the range 9.22-3.42%, whereas for pure PBS it was 16.75%. On the other hand, the crystallinity degree increased from 63% for pure PBS to 79% for composite with 30% wt. of WB. The Young's modulus increased to 160% for composition with 30% wt. of OP. Additionally, the hardness of the composites was slightly higher than PBS and was in the range 38.2-48.7 MPa. Despite the reduction in thermal stability and some mechanical properties, the studied composites show promise for everyday object production.

Carbon Nanodots as Complexing Agent in the Formation of Lead(II) Sulfide Thin Films via Direct Deposition of Lead(II) Sulfide Powder

This study reveals for the first time the formation of lead(II) sulfide (PbS) thin films via direct deposition of PbS powder using carbon nanodots (Cdots) as a complexing agent. The chemical bath deposition (CBD) technique was utilized and the Cdots’ mass was varied, i.e., (in g) 3, 5, 7, and 9. The Cdots were prepared from the waste of a rice noodle production home industry via the low-temperature carbonization method. The Cdots were characterized using UV-Vis spectrophotometry, showing absorption peaks at 275 nm and 325 nm; PL, showing an emission peak at 500 nm with cyan luminescence; XRD, showing several peaks, indicating an incomplete carbonization process; FTIR, indicating the existence of C=C, C-H, C-O, and O-H functional groups; HRTEM, revealing the sizes of the Cdots in the range of 2 nm to 6 nm; and SEM, showing a smooth morphology of the Cdots’ surface. The thin films obtained were smooth with higher XRD peaks and better material distribution compared to pure PbS thin film. The band gap measurement indicated that the increase of the PbS band gap was caused by the increase of the Cdots’ mass. Hence, the thin films’ band gap may be tuned using the Cdots’ mass.

Improved Haacke's quality factor, third order nonlinear susceptibility and specific capacitance realized for PbS thin films through La3+ doping

The present study examines the third order NLO and electrochemical properties of spray deposited lanthanum doped PbS (PbS:La) thin films. FCC crystallization was confirmed by XRD patterns along the plane (2 0 0). PbS crystallites vary in size between 27 and 36 nm with La doping concentration. Surface morphology improved with La doping. La doping increases the band gap from 1.97 to 2.18 eV. Near band edge (NBE) emissions in PL spectra originates from electron-hole recombination. A low resistivity of 0.23 x10−3 Ω-m was realized for PbS film doped with 4 wt% La concentration. Figure of merit of pure PbS improves from 1.32 x 10−3 Ω−1 to 1.607 x 10−2 Ω−1 with La doping. La doping modifies the energy states and band gap of PbS favouring strong nonlinear optical absorption. PbS:La thin films demonstrate self-defocusing due to temperature effects caused by absorption of single photons or free carriers. As a result of the low cationic field strength and high polarizability of La3+ ions, PbS exhibits a higher nonlinear refractive index. The nonlinear susceptibility and refractive index were found to be in the range 3.23–5.33 x 10−6 esu and 2.74 to 3.64 x 10−9 cm2/W, respectively. From the electrochemical studies, increased specific capacitance (256.46 F/g) and decreased charge transfer resistance (12 x 103 Ω) was observed for the 4 wt% La doped film.

Thermoelectric Properties of PbS Doped with Bi2S3 and Cu2S Prepared by Hydrothermal Synthesis and Spark Plasma Sintering

Hierarchical PbS powders doped with different contents of Bi2S3 and Cu2S were synthesized using the hydrothermal method. Subsequently, the powders were subjected to spark plasma sintering (SPS) for consolidation into bulk ceramics. X-ray photoelectron spectroscopy results showed that Bi2S3 and Cu2S were doped into PbS successfully. The effect of doping with different Bi2S3 and Cu2S contents on thermoelectric performance was investigated systematically. The results showed that pure PbS was an n-type semiconductor, and Bi2S3 doping or Bi2S3-Cu2S co-doping could decrease the thermal conductivity of PbS effectively. PbS doped with 1% Bi2S3 exhibited a moderate Seebeck coefficient, high electric conductivity, and low thermal conductivity simultaneously, thus attaining a maximum figure of merit ZT of 0.55 at 773 K. PbS doped with 1% Bi2S3-1% Cu2S exhibited an enhanced power factor and reduced thermal conductivity at an elevated temperature; the maximum ZT value obtained at 773 K was 0.83, which is more than twice that of pure PbS at 758 K (0.29), as a result.

High-Performance Photodetector with a-IGZO/PbS Quantum Dots Heterojunction

Low cost, high absorption coefficient, tunable band gap, and compatibility with flexible devices make lead sulfide (PbS) quantum dots (QDs) based photoconductors promising candidates for next-generation near-infrared (NIR) photodetectors. However, the detection performance of PbS QDs-based photoconductors still needs to be further improved, because there is a trade-off among the responsivity/detectivity/bandwidth in the device development process, that is, it is difficult to improve the three parameters simultaneously. Inspired by the design idea of sensitized phototransistor, a kind of amorphous indium gallium zinc oxide (a-IGZO)/PbS QDs heterojunction photoconductor is reported in this paper. The most prominent feature of this work is that a-IGZO, like a photocurrent “amplifier”, increases the photocurrent by several orders of magnitude without generating additional noise, and thus improves the sensitivity and responsiveness of the device. Compared with the initial pure PbS QDs-based photoconductor, the heterojunction device is able to increase the photocurrent by 3000 times together with a low dark current, and improve the response speed of the device with the help of interface-assisted carrier separation and recombination. In the NIR band, the device exhibits an exciting performance with a detectivity of 1.53 × 1013 Jones, a responsivity of 19070 mA/W and a decay time of 0.39 ms, respectively. By applying the a-IGZO/PbS QDs heterojunction to paper-based devices, a flexible device with bending resistance can be obtained, and the detection performance of the device does not deteriorate after 1000 times of bending.

Facile low temperature development of Ag-doped PbS nanoparticles for optoelectronic applications

The present article is based on Silver (Ag) doped Lead sulfide (PbS) nanoparticles for optoelectronic applications. Structural and morphological properties of pristine PbS and 0.5, 1.0, 2.5 and 5.0 wt% Ag doped PbS nanoparticles (NPs) were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray diffraction (XRD) patterns of pure PbS, 0.5, 1.0, and 2.5 wt% Ag: PbS NPs were marginally shifted towards a lower diffraction angle and XRD profile of 5.0 wt% Ag: PbS NPs was shifted to the right side with respect to JCPDS card. The crystallite sizes of pristine PbS and Ag: PbS NPs were obtained in the range of 17–18.7 nm. The phase and substitution of Ag into the PbS lattice were confirmed by the Fourier transform (FT) Raman spectra of Ag:PbS NPs. Scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy was employed to observe the morphology and to confirm the homogeneous doping of pristine PbS and Ag-doped PbS NPs. The optical band gaps were determined in the range of 3.011–3.378 eV and 1.201–1.286 eV, respectively from diffused reflectance spectra of pristine PbS and Ag: PbS NPs. Urbach energies were evaluated as 1.5687, 1.8879, 2.8020, 1.6425, and 1.2799 eV from the slopes of the fitted straight lines near the absorption band edge region of pure, 0.5, 1.0, 2.5, and 5.0 wt %, respectively. Current (I)-voltage (V) characteristics of the prepared NPs were carried out in the presence of an applied voltage (±4 V). The enhancement in I–V characteristics of 2.5 and 5.0 wt % was caused by the increment in the injected charge density. The optical transition states were examined by the second-order derivative of the absorbance spectra. The high carrier density in Ag: PbS has been attributed to the bottleneck effect, which is confirmed by the BM shift and I–V characteristics. It was found that Ag: PbS NPs exhibited an increase in electrical properties compared to the pristine PbS NPs.

A fluorescein-based fluorescent probe for real-time monitoring hypochlorite

Hypochlorite is an important reactive oxygen species in environment and pathophysiological processes. Abnormal level of ClO− can be destructive and lead to many diseases. Herein, to real-time and sensitively monitoring ClO−, a fluorescein-based fluorescence turn-on probe for ClO− in almost pure PBS buffer solution was successfully developed. After sensing hypochlorite, the spirolactam ring of the probe was opened and fluorescence at 525 nm greatly enhanced (∼1800 fold). The probe has a low detection limit (9.6 nM), short response time (∼1 min) and wide pH work range (5.0–9.0). Furthermore, the probe has been successfully applied to detect ClO− in disinfectant and actual water samples. Based on its fast response rate and almost pure buffer detection condition, the probe can be used to real time monitor ClO− in actual water environment.

Improving flame retardant and smoke suppression efficiency for PBS by adding a tannin surface and interfacial modified IFR/MMT synergist

A modified intumescent flame retardants/montmorillonite synergist with highly fire resistance and smoke suppression efficiency, based on the surface and interfacial modification of tannin, including bistratal microencapsulated ammonium polyphosphate particles (TFR), and Fe3+ chelated tannin exfoliated montmorillonite nanoparticles (TM), was fabricated and used to prepare PBS based composites. TM exhibited excellent flame retardant and smoke suppression efficiency. With the incorporation of 5 wt% TM (95P/5TM), 30.8 % of limited oxygen index (LOI) value and UL-94 V-1 rating of composite could be achieved, and the total smoke production (TSP) of 95P/5TM decreased by 77.4 % compared with pure PBS, indicating its excellent smoke suppression effect. When the TFR and TM loadings were 24 wt% and 1 wt%, respectively, 36.8 % of LOI value and UL-94 V-0 rating of composite (75P/24TR/1TM) could be achieved, as well as 62.9 % lowered TSP compared with pure PBS. Tannin participated in both the condensed phase and gaseous phase reactions, and improved the carbon forming capacity during combustion. The enhanced flame retardant and smoke suppression efficiency for synergist were a combined result of catalytic, synergistic and physical shielding effects. This work offers a novel routing for fabricating polymer composites with excellent flame retardant and smoke suppression efficiency with the incorporation of natural polyphenols.

Micromechanical Deformation Processes and Failure of PBS Based Composites Containing Ultra-Short Cellulosic Fibers for Injection Molding Applications.

The use of biobased thermoplastic polymers has gained great attention in the last years as a potential alternative to fossil-based thermoplastic polymers. Biobased polymers in fact offer advantages not only in terms of reduced dependence on fossil resources but they also lower the CO2 footprint in accordance with sustainability and climate protection goals. To improve the properties of these materials, reinforcement with biobased fibers is a promising solution; however, it must be kept in mind that the fibers aspect ratio and the interfacial adhesion between the reinforcement and the matrix plays an important role influencing both physical and mechanical properties of the biocomposites. In this paper, the possibility of producing composites by injection molding, based on polybutylene succinate and ultra-short cellulosic fibers has been explored as a potential biobased solution. Thermo-mechanical properties of the composites were investigated, paying particular attention to the local micromechanical deformation processes, investigated by dilatometric tests, and failure mechanisms. Analytical models were also applied to predict the elastic and flexural modulus and the interfacial properties of the biocomposites. Good results were achieved, demonstrating the that this class of biocomposite can be exploited. Compared to pure PBS, the composites with 30 wt.% of cellulose fibers increased the Young's modulus by 154%, the flexural modulus by 130% and the heat deflection temperature by 9%.

Natural and Modified Oligonucleotide Sequences Show Distinct Strand Displacement Kinetics and These Are Affected Further by Molecular Crowders.

DNA and RNA strand exchange is a process of fundamental importance in biology. Herein, we used a FRET-based assay to investigate, for the first time, the stand exchange kinetics of natural DNA, natural RNA, and locked nucleic acid (LNA)-modified DNA sequences in vitro in PBS in the absence or presence of molecular additives and macromolecular crowders such as diethylene glycol dimethyl ether (deg), polyethylene glycol (peg), and polyvinylpyrrolidone (pvp). The results show that the kinetics of strand exchange mediated by DNA, RNA, and LNA-DNA oligonucleotide sequences are different. Different molecular crowders further affect the strand displacement kinetics, highlighting the complexity of the process of nucleic acid strand exchange as it occurs in vivo. In a peg-containing buffer, the rate constant of displacement was slightly increased for the DNA displacement strand, while it was slightly decreased for the RNA and the LNA-DNA strands compared with displacement in pure PBS. When we used a deg-containing buffer, the rate constants of displacement for all three sequences were drastically increased compared with displacement in PBS. Overall, we show that interactions of the additives with the duplex strands have a significant effect on the strand displacement kinetics and this effect can exceed the one exerted by the chemical nature of the displacement strand itself.

Bioinspired Polysaccharide Derivative with Efficient and Stable Lubrication for Silicon-Based Devices.

It is becoming increasingly important to synthesize efficient biomacromolecule lubricants suitable for medical devices. Even though the development of biomimetic lubricants has made great progress, the current system suitable for hydrophobic silicone-based medical devices is highly limited. In this work, we synthesize one kind of novel polysaccharide-derived macromolecule lubricant of chitosan (CS) grafted polyethylene glycol (PEG) chains and catechol groups (CT) (CS-g-PEG-g-CT). CS-g-PEG-g-CT shows good adsorption ability by applying quantitative analysis of quartz crystal microbalance (QCM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and confocal fluorescence imaging technique, as well as the typical shear-thinning feature. CS-g-PEG-g-CT exhibits low and stable coefficients of friction (COFs) (0.01-0.02) on polydimethylsiloxane (PDMS) surfaces at a wide range of mass concentrations in diverse media including pure water, physiological saline, and PBS buffer solution and is even tolerant to various normal loads and sliding frequencies for complex pressurizing or shearing environments. Subsequently, systematic surface characterizations are used to verify the dynamic attachment ability of the CS-g-PEG-g-CT lubricant on the loading/shearing process. The lubrication mechanism of CS-g-PEG-g-CT can be attributed to the synergy of strong adsorption from catechol groups to form a uniform assembly layer, excellent hydration effect from PEG chains, and typical shear-thinning feature to dissipate viscous resistance. Surprisingly, CS-g-PEG-g-CT exhibits efficient lubricity on silicone-based commercial contact lenses and catheters. The current macromolecule lubricant demonstrates great real application potential in the fields of medical devices and disease treatments.

Improved linear and nonlinear optical properties of PbS thin films synthesized by spray pyrolysis technique for optoelectronics: An effect of Gd3+ doping concentrations

In the present article, the pure PbS and different concentrations of Gd doped PbS (Gd:PbS) films were developed using the spray pyrolysis route by growing thin films on the glass substrate. The estimated crystallite sizes were found from 15.5 to 20.8 nm for as-deposited films. The spherical shape morphology of grains was observed by FESEM. The obtained average grain sizes varied from 52.8 to 108.2 nm were obtained from the grain size distributions for 0.0, 0.5, 1.5, and 2.5 wt % Gd: PbS films, respectively. Extinction coefficients of as-deposited films were measured from 0.04 to 0.12 in the range of wavelength 200–2500 nm. Refractive indices of films were obtained from 5.4 to 1.22 in range of 200–2500 nm wavelength. The band gaps of 2.75, 2.64, 2.45, and 3.10 eV for 0.0, 0.5, 1.0 and 2.5 wt % Gd thin films were estimated using Tauc's relation respectively. The values of the dielectric constant, dielectric loss, and optical conductivity were recorded in the range of 1.32–29.6, 0.30–0.61, and 2.34 × 1014–3.08 × 1013 between 200 and 2500 nm wavelengths for as-deposited thin films respectively. The optimum values of linear susceptibility, non-linear susceptibility and refractive index were recorded in the range of 1.23–2.93, 5.21 × 10−10 - 120 × 10−10, 3.54 × 10−9 – 74.2 × 10−9 (esu) between 1.46 and 0.52 eV respectively for as-deposited thin films. The Gd: PbS thin films improve the physical properties and therefore, it becomes suitable candidature for the applications in optoelectronic devices.