Sulfur Nanoparticles Research Articles

Seed Priming with Greenly Synthesized Sulfur Nanoparticles Enhances Antioxidative Defense Machinery and Restricts Oxidative Injury Under Manganese Stress in Helianthus annuus (L.) Seedlings

Increased urbanization detrimentally affects crop plants. Heavy metals pollution sharply threatens food security. However, greenly synthesized nanoparticles were recently proposed as growth bioregulators. To investigate the evolved mechanisms by which sulfur nanoparticles (SNPs) could improve cellular defense against manganese toxicity, the present experiment was applied on Helianthus annuus (L.) seedlings. The experimental design was based on priming of sunflower seeds for 18 h in different (12.5–200 μM) SNPs, while 100 mM manganese sulfate (MnSO4) was implemented as irrigation treatment. The 14-day-old seedlings manifested Mn noxiousness and oxidative stress indications such as increased reactive oxygen species (O2·− and H2O2) and lipid peroxidation. Manganese exposure severely lowered the activity of some antioxidant enzymes like superoxide dismutase (SOD) and catalase (CAT), while induced ascorbate peroxidase (APX), guaiacol peroxidase (POX), polyphenol oxidase (PPO), and glutathione reductase (GR) activities. An evident decline in the pool of antioxidant compounds, such as ascorbic acid (ASA), glutathione (GSH), and total flavonoids content (TFC), was attained with Mn stress. Priming with SNPs significantly stimulated CAT and SOD activities and enhanced the antioxidant compounds (ASA, TFC, and total phenolic compounds) level in Mn-stressed seedlings. Consequently, SNPs caused a significant decrease in O2·−, H2O2, and lipid peroxidation and their oxidative damage. However, a significant reduction in GSH was detected with SNPs that might be consumed and incorporated into biosynthesis of other chelating ligands. Therefore, SNPs manifested a vital role in Mn detoxification through counterbalancing oxidative damage and elevating the antioxidant defense machinery.

Photocatalytic decontamination of toxic hexavalent chromium in water over graphitic carbon nitride supported sulfur nanoparticles

We report here for the first time a facile strategy for the preparation of graphitic carbon nitride (gCN) composited with different weight percentages of sulfur (SNPs) nanoparticles (SCN-x), and their remarkable photocatalytic decontamination of toxic hexavalent chromium. Fabrication of the binary hybrid photocatalysts were carried out via two facile steps: conventional thermal polycondensation of melamine into bulk gCN and its delamination, followed by disproportionation of thiosulfate to produce fine SNPs dispersed on gCN in the presence of weak organic acids. Absorption intensity of gCN was markedly expanded into visible region after composition with sulfur nanoparticles. Photocatalytic reduction efficiency of Cr(VI) by SCN-x was remarkably higher than bare gCN; and the optimum SNPs content on gCN was 8.7 wt% (SCN-2) with photoreduction efficiency of ca. 99 % after 15 min of visible light illumination. Electrochemical characterizations of SNP and SCN-2 samples indicated that the glassy carbon electrode (GCE) modified with SCN-2 enhanced formation of Cr(III) at 65.4 % compared to SNP-modified electrode at ∼36 %. BET results indicated that the presence of sulfur nanoparticles on gCN resulted in higher surface areas (influencing catalytic active sites that improve visible-light absorption), thus, facilitating electron transfer from the conduction band to sulfur species, whilst preventing the electron from recombining with holes. This work opens up the importance of sulfur utilization as promoter for photocatalytic applications.

Synthesis of sulfur doped carbon nanoparticle for the improvement of supercapacitive performance

In this article, the synthesis of sulfur-doped carbon nanoparticle (S-CNP) by using sulfur powder, carbon disulfide and cow margarine through a simple flame pyrolysis technique, as an efficient energy storage material is reported. The as-prepared S-CNP with a high amount of sulfur atom exhibited excellent electrochemical properties. In electrochemical energy storage application of as prepared S-CNP shows maximum specific capacitance of 337 F g-1 at 1.0 A g-1 current density with excellent specific energy of 37.9 Wh kg-1 and specific power of 1796 W kg-1 in a symmetrical two-electrode cell configuration. The material exhibited magnificent cyclic stability at higher current density of 15 A g-1, retaining up to 89.6% of its initial capacitance after more than 20,000 repetitive charge−discharge cycles. This acceptable process of the direct production of sulfur functionalized CNP is a simplistic, inexpensive and bulk production of the nanomaterial prototype for variety of applications together with supercapacitor applications.

Magnetic Properties of 1D Iron–Sulfur Compounds Formed Inside Single‐Walled Carbon Nanotubes

Herein, the filling of single‐walled carbon nanotubes (SWCNTs) with sulfur is performed, and the magnetic properties of the formed nanomaterials are studied. Encapsulation of sulfur species results in the appearance of a specific magnetic ordering in the system due to the formation of nanoscopic grains composed of sulfur and residual catalytic Fe nanoparticles contained in the SWCNTs. The magnetic character of the obtained 1D nanostructures is studied using superconducting quantum interference device (SQUID) magnetometer and a sequential ferromagnetic–antiferromagnetic ordering in the material is revealed. Magnetic and optical properties are strongly dependent on the synthesis protocols. A significant Raman intensity increase related to the encapsulated nanostructures is obtained when filling is performed at high‐pressure high‐temperature conditions. Simultaneously, the magnetic susceptibility gets strongly reduced for high‐pressure filling, which is related to the escape of iron particles from the nanotube interior, and the magnetic properties of the material are governed by a weak ferromagnetic ordering of Fe–S structures remained inside SWCNTs. Sulfur encapsulation provides the new route for controlling the magnetic properties in 1D nanomaterials that pave the way for advanced magneto‐optical applications.

Reduction-responsive sulfur dioxide polymer prodrug nanoparticles loaded with irinotecan for combination osteosarcoma therapy

Combination therapy can boost the therapeutic effectiveness of monotherapies by achieving synergy between therapeutic agents. Herein, a reduction-responsive sulfur dioxide (SO2) polymer prodrug was synthesized as a nanocarrier to load irinotecan (IRN) to be used in combination osteosarcoma therapy. The SO2 prodrug (denoted as mPEG-PLG (DNs)) was synthesized by coupling a small-molecule SO2 donor, N-(3-azidopropyl)-2,4-dinitrobenzenesulfonamide (AP-DNs), to the side chains of methoxy poly (ethylene glycol)-block-poly (γ-propargyl-L-glutamate) block copolymer. The mPEG-PLG (DNs) had the ability to self-assemble into micelles while simultaneously encapsulating IRN in aqueous media. The formed micelles led to enhanced SO2 and IRN release in reductive conditions. Using nile red as a model drug, the loaded micelles were efficiently internalized by cancer cells, demonstrated by confocal laser scanning microscopy and flow cytometry. The release of SO2 within nanoparticles (NPs) in tumor cells led to enhanced intracellular reactive oxygen species amounts together with induced oxidative destruction to cancer cells. Furthermore, the IRN-loaded SO2 polymer prodrug NPs mediated synergistic therapeutic effects against osteosarcoma cells, leading to improved biodistribution and enhanced tumor growth inhibition over control groups in a murine osteosarcoma model. Taken together, this work highlights the potential of SO2 polymer prodrugs as reduction-responsive nanocarriers to load chemotherapeutics for effective combination osteosarcoma therapy.

High discharge efficiency and energy density for polymer composites filled with S-doped zinc oxide nanoparticles

Inorganic-polymer nanocomposites consisting of sulfur doped zinc oxide nanoparticles (ZOS_nps) as fillers and poly(vinylidene fluoride) (PVDF) as the polymer matrix were prepared via the solution casting method. The energy storage behaviors of PVDF/ZOS nanocomposites were studied. The results indicated that the incorporation of ZOS_nps in the polymer matrix could effectively improve breakdown strength (Eb), resulting in greatly enhanced energy density (Ue) and discharge efficiency (η). The nanocomposite with 1 vol% of ZOS_nps shows an outstanding discharge energy density of 11.5 J cm−3 and maintains a high discharge efficiency of 68.7% at 4800 kV cm−1. This reason is that S-doped zinc oxide nanoparticles with isoelectronic hope traps suppress the interfacial polarization. The present work may offer a novel way to confine the movement of charges by introducing isoelectronic impurities in polymer nanocomposites.

Effect of sulfur nanoparticles on properties of alginate-based films for active food packaging applications

Sulfur nanoparticles (SNPs) were prepared and embedded in calcium cross-linked alginate films in varying concentration, and their effect on the functional properties of the films were studied. The FE-SEM image showed uniform dispersion of up to 2 wt% of SNPs, above which aggregation was observed. The addition of 2 wt% of SNPs showed the best results of the tensile and water vapor barrier properties, with an increase in 12% and 41%, respectively. The surface color of the films changed significantly by the addition of SNPs with a decrease in transparency. However, the UV barrier properties showed a considerable increase of 99%. In addition, the incorporation of SNPs increased the hydrophobicity of the film, which was evident by the increased water contact angle and decreased moisture content of the film, as indicated by the thermal analysis results. The antimicrobial activity of alginate/SNPs composite film was tested against foodborne pathogenic bacteria, E. coli and L. monocytogenes. The nanocomposite film did not completely destroy E. coli but showed a bacteriostatic activity to reduce the 60% of bacterial colonies. However, the activity against L. monocytogenes was found to be highly bactericidal at the highest nanoparticle concentration, where a 100% bacterial elimination was observed after 12 h of exposure. Thus, the alginate/SNPs composite film can be used for the packaging of frozen foods with high moisture content that are susceptible to Listeria monocytogenes contamination, such as meat products.

Antimicrobial activity of sulfur nanoparticles: Effect of preparation methods

Sulfur nanoparticles (SNPs) were synthesized using elemental sulfur and sodium sulfide, capped with chitosan as a stabilizer (SNPES), and their properties were compared to SNPs prepared by acidification of sodium thiosulfate (SNPSTS). The SNPs were characterized using UV–visible spectroscopy, EDS, TEM, XRD, and TGA, and their antimicrobial activity was tested using the disk diffusion method and minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) analysis. The SNPES showed a rod-shaped morphology with an average length of 87 nm, while SNPSTS exhibited a spherical shape with an average particle size of 17 nm. The rod-shaped SNPES showed higher thermal stability than the spherical SNPSTS. Both types of SNPs did not show significant antibacterial activity against Gram-negative (E. coli) bacteria but showed significant antibacterial activity against Gram-positive (L. monocytogenes) bacteria. Between the SNPs, SNPES showed higher growth-inhibiting activity against L. monocytogenes than SNPSTS.

Crepe Cake Structured Layered Double Hydroxide/Sulfur/Graphene as a Positive Electrode Material for Li-S Batteries.

Solving the polysulfide shuttle problem is one of the core challenges for the industrialization of lithium-sulfur batteries. In this work, a triphasic composite of LDH/sulfur/rGO (LDH: layered double hydroxide, rGO: reduced graphene oxide) with a crepe cake like structure is designed and fabricated as a positive electrode material for lithium-sulfur batteries. Sulfur nanoparticles are embedded in the interlayer space of the composite and thus are well protected physically via three-dimensional wrapping and chemically via strong interaction of LDH nanoflakes with lithium polysulfides, such as ionic bonds and S···H hydrogen bonds. In addition, the flexible lamellar structure of the composite with soft graphene layers can tolerate the volume expansion of sulfur during lithiation as well as facilitate ionic permeability and electron transport, which is favorable for the redox reactions of polysulfide. The present work sheds light on the future development and industrialization of lithium-sulfur batteries.

Facile synthesis of sulfur@titanium carbide Mxene as high performance cathode for lithium-sulfur batteries

Abstract The design of sulfur hosts with polar, sulfurphilic, and conductive network is critical to lithium-sulfur (Li-S) batteries whose potential applications are greatly limited by the lithium polysulfide shuttle effect. Mxenes, possessing layered-stacked structures and high electrical conductivities, have a great potential in sulfur hosts. Herein, sulfur nanoparticles uniformly decorated on titanium carbide Mxene (S@Ti3C2Tx Mxene) are synthesized via a hydrothermal method and then utilized as a cathode for lithium-sulfur batteries. This unique architecture could accommodate sulfur nanoparticles expansion during cycling, suppress the shuttling of lithium polysulfide, and enhance electronical conductivity. Consequently, the S@Mxene with a high areal sulfur loading (∼4.0 mg cm−2) exhibits a high capacity (1477.2 mAh g−1) and a low capacity loss per cycle of 0.18% after 100 cycles at 0.2 C. This work may shed lights on the development of high performance sulfur-based cathode materials for Li-S batteries.

Microfluidic controllable synthesis of monodispersed sulfur nanoparticles with enhanced antibacterial activities

Sulfur nanoparticles (SNPs) have been frequently used for sterilization due to their high biocompatibility and environmental friendliness. Compared with traditional sublimed sulfur, SNPs have some superior properties, such as the smaller particle size, better dispersibility in water and even higher antibacterial performance. Therefore, the objective of this study is to prepare SNPs with a controllable particle size and uniform morphology using a microfluidic anti-solvent precipitation method, whose process is continuous and ideal for large-scale production. The SNPs with a range of 15–50 nm can be prepared in both a Y-type microchannel (YMC) and T-type microchannel (TMC). Interestingly, for the SNP preparation process, the YMC shows a better mixing effect than TMC, which has been verified by the CFD simulation. Compared with a traditional batch stirred tank (ST), these two microchannels can not only guarantee a relatively small and uniform particle size, but also reduce the solvent consumption by at least 50%. More importantly, the SNPs show a better continuous bactericidal ability for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), compared with traditional micro-sized sublimed sulfur. The SNPs together with surfactant CTAB have a synergistic effect, which can enhance their antibacterial activities. Especially, among all the control groups, the as-prepared 15 nm SNPs have a better bactericidal performance, which can reduce the S. aureus colony number from ∼ 8 log CFU/mL to below the detection limit in 15 h, and reduce the colony number of E. coli from ∼ 8 to 1.8 log CFU/mL.

Effects of green synthesis of sulfur nanoparticles from Cinnamomum zeylanicum barks on physiological and biochemical factors of Lettuce (Lactuca sativa).

In this study, the effect of green synthesized sulfur nanoparticle (SNP) at different concentration (0, 0.01, 0.1, 1 and 10mg/ml) on some physiological, phytochemical and biochemical traits of lettuce plants was investigated. For the first time, SNP were green synthesized using Cinnamomum zeylanicum barks extract. Our results indicated that the treatment of lettuce plants with 1mg/ml of SNP improved the growth and photosynthetic parameters of lettuce plants than related control. Some other physiological parameters such as proline, glycine betaine and soluble sugars levels along with some phytochemical parameters like anthocyanin, total phenol, flavonoids and tannin contents were enhanced after treatment of the plants with same concentration of SNP. On the other hand, specific activity of antioxidant enzymes (catalase, ascorbate peroxidase and polyphenol oxidase) and stress markers level, MDA and H2O2 were reduced in the same treated lettuce plants. However, a concentration of 10mg/ml of SNP exhibited toxicity on lettuce plants with inducing oxidative stress markers (H2O2 and MDA) and consequently reducing plant growth and biomass. This oxidative stress tend to diminish some physiological, phytochemical and biochemical parameters in treated lettuce plants. Overall, it can be concluded that the green synthesis SNP at an optimal concentration of 1mg/ml improved physiological parameters in the lettuce plants making thempotent to tolerate stressful conditions. However, higher concentration of SNP (10mg/ml) indicated toxic effects on all of the physiological parameters.

Siloxane based copolymer sulfur as binder-free cathode for advances lithium-sulfur batteries

One of the reasons why lithium-sulfur batteries have not yet been commercialized is a great attenuation of the capacity, although their theoretical capacity is ultrahigh. To alleviate this problem, we developed multifunctional organic matter, 3-aminopropyltriethoxysilane (APS), for preparing a uniform hybrid consists of silica 3D network skeleton and copolymerized sulfur nanoparticles (cpS). In this hybrid, abundant amidogen in APS induced polymerization with sulfur, which formed uniform copolymerized sulfur nanoparticles (nano sulfur), restraining the shuttle effect of polysulfides. Meanwhile, polycondensation APS not only acted as an efficiently binder, affording compact cathodes, but also formed a stable 3D silica structure to encapsulate sulfur nanoparticles, relieving the volume change of sulfur. Consequently, this binder-free cpS composite exhibited much enhanced electrochemical performances, including a high capacity of 1187.8 mAh·g−1 at 0.1 C and a low capacity fading of 0.0654% per cycle for 500 cycles at 1 C. This study paved the way for high-energy-density batteries by simply applying a low-cost, environmentally-friendly, powerful network polymer cathode material.

A novel chemical reduction/co-precipitation method to prepare sulfur functionalized reduced graphene oxide for lithium-sulfur batteries

The higher theoretical specific capacity with considerable cell potential, Lithium–Sulfur batteries (LSBs) are considered to be high-energy storage strategies near future. However, the practical realization of LSBs is being hindered owing to low cell capacity risen from poor electronic-conductivity of elemental sulfur. To enhance the electronic-conductivity and thus to improve the specific cell capacity, commonly conducting carbons such as reduced graphene oxide, carbon nanotubes etc. are used as additives in the electrodes. Here, we report a unique in-situ synthesis strategy to prepare a composite of sulfur-functionalized reduced graphene oxide (SFRGO) encapsulating monodisperse sulfur nanoparticles using a low-cost deep eutectic solvent (DES) derived from choline chloride and sodium thiosulfate. The DES serves as an effective reductant as well as dopant. Moreover, during formation of SFRGO, a major fraction of the DES degrades to elemental sulfur. The SFRGO composite has been applied as cathode material in LSBs. The cathode material delivered a maximum specific capacity of 1265 mA h g−1 during initial cycle and retains 903 mA h g−1 after 100 cycles, with a usual capacity decay rate 0.28% each cycle. This facile chemical reduction method is an alternative to the large-scale and cost-effective production of high-quality graphene for energy storage application.

Comparative antibacterial and antifungal activities of sulfur nanoparticles capped with chitosan

The antimicrobial activity of sulfur nanoparticles (SNPs) was compared with elemental sulfur and sulfur-containing salts (sodium thiosulfate and sodium metabisulfite) against bacteria (Escherichia coli, Staphylococcus aureus) and fungi (Aspergillus flavus, Candida albicans) using the paper disc, broth microdilution, and time-kill assay methods. The results of the paper disc and MIC tests showed stronger antimicrobial activity of SNPs compared to the elemental sulfur and sulfur-containing salts. SNPs showed more potent activity against bacteria than fungi. Among the test microorganisms, E. coli (Gram-negative) was the most susceptible to SNPs, followed by S. aureus (Gram-positive), C. albicans (yeast), and A. flavus (mold). Scanning electron micrographs of microorganisms treated with SNPs showed different cell disruption patterns depending on the type of microorganisms.

Direct Visualization of Lithium Polysulfides and Their Suppression in Liquid Electrolyte.

Understanding of lithium polysulfide (Li-PS) formation and the shuttle phenomenon is essential for practical application of the lithium/sulfur (Li/S) cell, which has superior theoretical specific energy (2600 Wh/kg). However, it suffers from the lack of direct observation on behaviors of soluble Li-PS in liquid electrolytes. Using in situ graphene liquid cell electron microscopy, we have visualized formation and diffusion of Li-PS simultaneous with morphological and phase evolutions of sulfur nanoparticles during lithiation. We found that the morphological changes and Li-PS diffusion are retarded by ionic liquid (IL) addition into electrolyte. Chronoamperometric shuttle current measurement confirms that IL addition lowers the experimental diffusion coefficient of Li-PS by 2 orders of magnitude relative to that in IL-free electrolyte and thus suppresses the Li-PS shuttle current, which accounts for better cyclability and Coulombic efficiency of the Li/S cell. This study provides significant insights into electrolyte design to inhibit the polysulfide shuttle phenomenon.

Sulfur nanoparticles transform montmorillonite into an inorganic surfactant applicable in thermoplastics processing

We report on the modification of montmorillonite (MMT) with sulfur nanoparticles (S NPs) that yields a MMT/S nanocomposite exhibiting surfactant-like amphiphilic behavior at 80:20 MMT:S weight-to-weight ratio. The new material was successfully used as an inorganic surfactant for the dispergation of carbon black (CB) in High-Density Polyethylene (HDPE). Both the novel inorganic surfactants and the HDPE-based nanocomposite products were characterized rigorously by XRD, TGA-DSC, SEM, TEM, zeta potential measurement, static contact angle measurement, tensile strength analysis, particle charge measurement, and X-ray micro-computed tomography. It was found that the presence of 0.5 wt% MMT/S has no adverse effects on HDPE product quality. On the contrary, the MMT/S additive improves the homogeneity of the distribution of CB particles in the HDPE matrix, which is very important because of the UV stabilization properties of CB. The industrial relevance of this finding is that it demonstrates how the right composite of two cheap and readily available inorganic materials can improve the properties of one of the most widely used thermoplastics.

Green synthesis of sulfur nanoparticles using Ocimum basilicum leaves and its prospective effect on manganese-stressed Helianthus annuus (L.) seedlings.

A novel green approach was utilized to fabricate sulfur nanoparticles (SNPs) with the aid of Ocimum basilicum leaves extract. The effective formation of the synthesized SNPs was examined and approved using UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The average particle size was 23nm with spherical shape and crystalline in nature. In the pot experiment, the synthesized SNPs were applied with different concentrations (12.5, 25, 50, 100 and 200μM) as pre-soaking to Helianthus annuus seeds and irrigated with 100mM MnSO4. As a result of manganese (Mn) exposure, the harvested 14-day sunflower seedlings showed a significant decline in the growth parameters (shoot length, leaf area and the relative water content of both shoot and root), photosynthetic pigments, mineral content (N, P, K, Ca, and Mg), and protein content compared to the control. The root length, electrolyte leakage, Na and Mn levels, metabolites content (amino acids, protein, glycine betaine, proline, and cysteine) were greatly raised as affected by Mn stress. Mn toxicity reduction using SNPs was demonstrated, as the medium doses enhanced seedlings growth, photosynthetic pigments, and mineral nutrients. Application of SNPs decreased Mn uptake and enhanced S metabolism through increasing cysteine level. Likewise, SNPs elevated seedlings water content and eliminated physiological drought via increasing osmolytes such as amino acids and proline. It can be concluded that green-synthesized SNPs had the potential to limit the deleterious effects of Mn stress.

Confining sulfur particles in clay nanotubes with improved cathode performance of lithium–sulfur batteries

Lithium–Sulfur batteries have high energy storage capacity while their sulfur cathode suffers large volume change, polysulfides dissolution and shuttle effect, and capacity fading during long-term cycling. To help lock sulfur and mitigate these problems, we introduce halloysites, a natural clay material with nanotube format, to disperse and confine sulfur nanoparticles as well as to suppress the dissolution and migration of polysulfides. Halloysites are firstly made conductive by covering with a glucose-derived carbon skin. Sulfur nanoparticles are then trapped in both lumen and outside surface of individual nanotubes with a loading dosage up to 80 wt%. In this new halloysite/sulfur composites cathode, the hollow nanostructure of halloysites provides space to allow dimension changes of encapsulated sulfur nanoparticles during repeated lithiation while limit their size up to the diameter of nanotube lumen (i.e., 25 nm or less). The stacked halloysite clusters further create many nanoscale voids to divide the sulfur-electrolyte interface into isolated domains and increase the migration tortuosity in electrolytes to suppress the dissolution and shuttle effect of polysulfides. These features together contribute to improved cycling stability, retaining nearly ~84% of the starting capacity over 250 cycles, though the diffusion of lithium ions into and out of nanotubes show some differences.

A metal-free catalyst: sulfur-doped and sulfur nanoparticle-modified CMK-3 as an electrocatalyst for enhanced N2-fixation

S/CMK-3 was fabricated by sulfur-doped and sulfur nanoparticles modified by a one-pot method for enhanced N2reduction.