Quaternary ammonium salts for water treatment with balanced rate of sterilization and degradation.

The growing number of infections caused by drug-resistant bacteria which arise from the overuse of antibiotics has severely affected the normal operation of human society. The high antibacterial activity of QAS makes it promising as an alternative to antibiotics, but it suffers from secondary pollution due to its non-degradation. Here we have synthesized a class of gemini quaternary ammonium salts (GQAS) with different carbon chain lengths containing ester groups by using facile methylation reaction. Quaternary ammonium groups contribute to insert negatively charged bacterial membranes, resulting in membrane damage and bacteria death. Compared with conventional single-chain QAS, except for the more efficient antibacterial efficiency attribute to the presence of the second carbon chain, GQAS with alterable antibacterial properties can minimize the possibility of bacterial resistance and reduce the accumulation of GQAS in the environment through the introduction of degradable ester groups. GQAS is completely superior to the commercial bactericide benzalkonium chloride (BAC) in both antibacterial activity and degrade performance, which can be used as a more environmentally friendly bactericide.

Preparation of a high-efficiency low-toxicity CdS/C60 bactericide and investigation of the mechanism.

Photocatalysis is considered as a promising technology to solve bacterial contamination, but the development of efficient photocatalysts with a strong generalizable light response remains a challenge. CdS has a suitable energy gap and good response to visible light, but the photogenerated carrier separation efficiency is low, and the photo-corrosion phenomenon leads to the significant release of Cd2+. In this paper, the CdS/C60 composite photocatalyst bactericide is synthesized via a simple one-step hydrothermal method. Testing via EIS, I-t, PL, and TRPL show that the C60 in the composite improves the hole-electron separation efficiency of CdS, resulting in a better photocatalytic performance. The complete inactivation of S. aureus and E. coli can be achieved within 40 min and 120 min, respectively, by dispersing 100 µg mL-1 of CdS/C60-2 in a diluted bacterial solution under simulated visible-light irradiation. Combined with ESR, SEM, fluorescence staining, DNA gel electrophoresis and ICP technology, it is believed that the high inactivation of bacteria is attributed to the ROS produced during the photocatalytic process, which destroy the integrity of the bacterial cell membrane and further destroy the DNA inside the bacteria, thus causing bacterial inactivation, rather than the inactivation being caused by Cd2+ toxicity.

In-situ polycondensate-coated cellulose nanofiber heterostructure for polylactic acid-based composites with superior mechanical and thermal properties.

Renewable yet biodegradable natural fiber (e.g., cellulose nanofiber (CNF)) reinforced bio-based polymers (e.g., polylactic acid (PLA)) are being applied for the manufacture of clean packaging products. The interface incompatibility between hydrophilic CNF and hydrophobic PLA still restricts the promotion of high-performance bio-based products. Herein, a polycondensate-coated CNF hybrid, wherein silane, aluminate, and titanate coupling agent monomers were in-situ polymerized onto the CNF surface via dehydration self-condensation, was designed and further employed as strengthening/toughening nanofillers for fabricating the CNF-reinforced PLA composite. Results showed that the polycondensate coatings could efficiently promote the dispersion of CNFs and enhance interfacial compatibility between CNFs and PLA. Attributing to the synergistic effect of polycondensate coatings and CNFs, a considerable improvement in processing, mechanical and thermal properties was obtained in resultant CNF/PLA composites. With adding 2.5 wt% polycondensate-coated CNFs, the tensile strength, Young's modulus, and tensile toughness of CNF-reinforced PLA composites was raised by about 27 %, 51 % and 68 %, respectively; also, such composite possessed greater elasticity and higher melt strength than pure PLA. This study provides a novel interface control strategy to fabricate low-cost yet high-performance PLA-based composites for sustainable packaging application.

Quaternary Ammonium Salts: Insights into Synthesis and New Directions in Antibacterial Applications.

The overuse of antibiotics has led to the emergence of a large number of antibiotic-resistant genes in bacteria, and increasing evidence indicates that a fungicide with an antibacterial mechanism different from that of antibiotics is needed. Quaternary ammonium salts (QASs) are a biparental substance with good antibacterial properties that kills bacteria through simple electrostatic adsorption and insertion into cell membranes/altering of cell membrane permeability. Therefore, the probability of bacteria developing drug resistance is greatly reduced. In this review, we focus on the synthesis and application of single-chain QASs, double-chain QASs, heterocyclic QASs, and gemini QASs (GQASs). Some possible structure-function relationships of QASs are also summarized. As such, we hope this review will provide insight for researchers to explore more applications of QASs in the field of antimicrobials with the aim of developing systems for clinical applications.

Boosting the visible-light-driven photocatalytic antibacterial performance of MoS2 nanosheets by poly(3-(4-methyl-3'-thiophenoxy))propyltrimethylammonium chloride (PThM) modification.

Molybdenum disulfide (MoS2) has been reported to possess photocatalytic bactericidal ability, but its efficiency is not high. In this paper, a water-soluble cationic conjugated polymer, poly(3-(4-methyl-3'-thiophenoxy))propyltrimethylammonium chloride (PThM), was designed to modify MoS2 and boost its antibacterial abilities. Another hydrophobic conjugated polymer, polythiophene (PTh), was synthesized and composited with MoS2, and this was compared with PThM/MoS2 from the perspective of composite effectiveness. Studies involving the photo-disinfection of Escherichia coli (E. coli) under visible-light irradiation (30 W) showed that the antibacterial efficiencies were in the following order: PThM/MoS2 > PTh/MoS2 > MoS2. The enhanced bactericidal activities of PThM/MoS2 and PTh/MoS2 were attributed to the conjugated polymers restraining the recombination of photogenerated carriers in MoS2, thereby increasing the generation of reactive oxygen species (ROS). PThM/MoS2 presented the best antibacterial efficiency because its cationic side-chains improved the solubility of the material and promoted contact between bacteria and the material. This work may provide some insights into the design of practical nano-antibacterial materials.

Dye adsorption and photo-induced recycling of hydroxypropyl cellulose/molybdenum disulfide composite hydrogels.

A novel environmental friendly dye adsorbent composited of hydroxypropyl cellulose (HPC) and molybdenum disulfide (MoS2) were fabricated, which can be recycled and reused by illumination due to the photo-catalytic properties of MoS2. In order to promote a more homogeneous dispersion of MoS2 nanosheets in HPC, MoS2 was functionalized with HPC chains through esterification. The successful functionalization of MoS2 was confirmed by FTIR, XRD, XPS characterizations. The morphologies of the HPC and HPC-MoS2/HPC hydrogels were compared by SEM. The obtained HPC-MoS2/HPC hydrogels exhibited enhanced adsorption performance toward methylene blue. An adsorption improvement of HPC hydrogel had been brought by the incorporation of HPC-MoS2 sheets. Adsorption kinetics was then imitated by Lagergren pseudo-first-order and pseudo-second-order models. Adsorption isotherms were imitated by Langmuir isotherm and Freundlich isotherm. The photo-regeneration experiments of HPC-MoS2/HPC hydrogel after absorption showed that the absorbent can be activated easily by illumination with little loss of dye adsorbing capacity.

Sodium alginate-assisted exfoliation of MoS2 and its reinforcement in polymer nanocomposites.

In this work, molybdenum disulfide (MoS2) nanosheets were facilely prepared by direct exfoliation of MoS2 in aqueous media with the assistance of sodium alginate (SA). Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectra results showed that the raw MoS2 was successfully exfoliated into few-layer MoS2 nanosheets (SA-MoS2). FTIR and thermal gravimetric analysis (TGA) investigations showed that the obtained MoS2 nanosheets were modified by SA after exfoliation and improved dispersion in water were achieved. The obtained SA-MoS2 nanosheets were employed to reinforce the water-soluble polymer SA. No obvious macroscopic phase separation could be found from the SA/SA-MoS2 films. Dynamic mechanical analysis (DMA) results showed that almost 9 times enhancement for the storage modulus of SA was achieved with the incorporation of only 0.5wt% of SA-MoS2, and the thermal stability of SA was also found improved with the addition of SA-MoS2 according to the thermal gravimetric analysis TGA results.

Synthesis of Highly Monodispersed CdS/SiO2 Core-Shell Nanoparticles and Their Photocatalytic Activities.

Monodispersed CdS/SiO2 core-shell composite nanoparticles with effective photocatalytic activity were successfully synthesized. The structure and morphologies of composite nanoparticles were characterized by XRD, FTIR, TEM, and high-resolution transmission electron microscopy (HRTEM). Results showed that the CdS/SiO2 composite nanoparticles exhibited obvious core-shell structure, and that the thickness of the SiO2 shell could be reduced by either increasing the water/alcohol volume ratio or decreasing TEOS amount. The photocatalytic activity of the prepared composite nanoparticles was determined by degradation of methylene blue (MB) in aqueous solution. CdS/SiO2 showed a lower photocatalytic activity compared with CdS nanoparticles. However, the residual concentration of Cd2+ in aqueous solution after MB complete degradation was reduced by half.

Fabrication of uniform "smart" magnetic microcapsules and their controlled release of sodium salicylate.

Uniform stimuli-responsive ("smart") magnetic chitosan or chitosan/poly(N-isopropylacrylamide) microcapsules were successfully prepared by using carboxyl-functionalized polystyrene particles as a core template. Magnetic nanoparticles (Fe3O4) were dispersed on the surface of microcapsules under mild conditions and the "smart" response of microcapsule shells was still retained. The structure and morphology of magnetic microcapsules were characterized by SEM, TEM, XRD and TGA. Microcapsules were prepared after removing the polystyrene core by exposing it to solvent, and the microcapsules exhibited a hollow structure. The magnetic nanoparticles also appeared on the surface of microcapsules and the chitosan/poly(N-isopropylacrylamide) composite microcapsules could be readily and quickly collected by an external magnetic field. The pH values of the aqueous dispersion and the temperature response properties of the magnetic microcapsules were investigated with sodium salicylate as the hydrophilic drug.

Golf ball-like particles fabricated by nonsolvent/solvent-induced phase separation method.

Monodisperse poly(styrene-co-acrylic acid) (P(S-co-AA)) particles having a "golf ball-like" shape were prepared by nonsolvent/solvent-induced phase separation process. The method is simple and easy operation. The nonsolvent/solvent phase was mixture of butanol, n-heptane and toluene. The dimpled surface comes from the aggregation of oil droplets on the surface of polymer spheres. The dimple's morphology can be controlled by the polymer templates, dispersion medium, reaction time, and temperature. Reverse Pickering emulsion model was suggested for the formation of golf ball-like particles.