Anomalous Lehmann Rotation of Achiral Nematic Liquid Crystal Droplets Trapped under Linearly Polarized Optical Tweezers.

Continuous rotation of a cholesteric droplet under the heat gradient was observed by Lehmann in 1900. This phenomenon, the so-called Lehmann effect, consists of unidirectional rotation around the heat flux axis. We investigate this gradient heat effect using infrared laser optical tweezers. By applying single trap linearly polarized optical tweezers onto a radial achiral nematic liquid crystal droplet, trapping of the droplet was performed. However, under a linearly polarized optical trap, instead of stable trapping of the droplet with slightly deformed molecular directors along with a radial hedgehog defect, anomalous continuous rotation of the droplet was observed. Under low power laser trapping, the droplet appeared to rotate clockwise. By continuously increasing the laser power, a stable trap was observed, followed by reverse directional rotation in a higher intensity laser trap. Optical levitation of the droplet in the laser beam caused the heat gradient, and a breaking of the symmetry of the achiral nematic droplet. These two effects together led to the rotation of the droplet under linearly polarized laser trapping, with the sense of rotation depending on laser power.

A screen-printed carbon electrode modified with gold nanoparticles, poly(3,4-ethylenedioxythiophene), poly(styrene sulfonate) and a molecular imprint for voltammetric determination of nitrofurantoin.

A molecularly imprinted polymer (MIP) and a nanocomposite prepared from gold nanoparticles (AuNP) and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) were deposited on a screen-printed carbon electrode (SPCE). The nanocomposite was prepared by one-pot simultaneous in-situ formation of AuNPs and PEDOT:PSS and was then inkjet-coated onto the SPCE. The MIP film was subsequently placed on the modified SPCE by co-electrodeposition of o-phenylenediamine and resorcinol in the presence of the antibiotic nitrofurantoin (NFT). Using differential pulse voltammetry (DPV), response at the potential of ~ 0.1 V (vs. Ag/AgCl) is linear in 1 nM to 1000 nM NFT concentration range, with a remarkably low detection limit (at S/N = 3) of 0.1 nM. This is two orders of magnitude lower than that of the control MIP sensor without the nanocomposite interlayer, thus showing the beneficial effect of AuNP-PEDOT:PSS. The electrode is highly reproducible (relative standard deviation 3.1% for n = 6) and selective over structurally related molecules. It can be re-used for at least ten times and was found to be stable for at least 45 days. It was successfully applied to the determination of NFT in (spiked) feed matrices and gave good recoveries. Graphical abstract Schematic representation of a voltammetric sensor for the determination of nitrofurantoin. The sensor is based on a screen-printed carbon electrode (SPCE) modified with an inkjet-printed gold nanoparticles-poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) nanocomposite and a molecularly imprinted polymer.

Dual-functional natural rubber latex foam composites for solar-driven clean water production and heavy metal decontamination.

Solar steam generation (SSG) offers a sustainable approach to fresh water production. Herein, a novel dual-functional natural rubber/carbon black composite foam evaporator is presented for a cost-efficient SSG system that both produces fresh water and eliminates heavy metals present in the water. The composite foam is produced using the Dunlop process, and in its optimized form, it absorbed >96 % of sunlight. The foam evaporator exhibited a thermal conductivity of 0.052 W/m⋅K, a water evaporation rate of 1.40 kg/m2/h, converted 83.38 % of light to heat under 1 sun irradiation, and showed outstanding stability. The technology required to produce this composite foam is already available to make large-scale production feasible, while the natural raw materials are abundant. On the basis of its performance qualities, the rubber foam composite appears to be an excellent candidate for application as a viable solar absorber for SSG to produce fresh, clean water for commercial purposes.

Acetylcholinesterase modified inkjet-printed graphene/gold nanoparticle/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hybrid electrode for ultrasensitive chlorpyrifos detection.

This study successfully created a portable acetylcholinesterase sensor on a printed hybrid electrode capable of detecting chlorpyrifos in the field. While a screen-printed electrode was chosen herein to enable a single-use and portable platform for the in-field application, the hybrid material was incorporated to ensure ultrasensitive detection at lower electrode potentials. The hybrid ink of gold nanoparticles (AuNPs) decorated on graphene (GP) sheets in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was synthesized through a simple completely-green one-pot process. The subsequent characterization was carried out via transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The synergy resulting from the greater surface area and enhanced transfer of electrons combined with high levels of electrocatalytic activity and superb conductivity offered by GP, AuNP, and PEDOT:PSS allows the sensor to exhibit ultrasensitive chlorpyrifos detection at the relatively low detection limit of 0.07 nM. The sensor demonstrated in this study also exhibits good reproducibility, desirable stability, and a successful application for the real sample with satisfactory recovery results of around 106 %, indicating its potential for use as a tool in the analysis of pesticides.

Zingiber cassumunar Roxb. Essential Oil-Loaded Electrospun Poly(lactic acid)/Poly(ethylene oxide) Fiber Blend Membrane for Antibacterial Wound Dressing Application.

The essential oil from Zingiber cassumunar Roxb. (Plai) has long been used in Thai herbal remedies to treat inflammation, pains, sprains, and wounds. It was therefore loaded into an electrospun fibrous membrane for use as an analgesic and antibacterial dressing for wound care. The polymer blend between poly(lactic acid) and poly(ethylene oxide) was selected as the material of choice because its wettability can be easily tuned by changing the blend ratio. Increasing the hydrophilicity and water uptake ability of the material while retaining its structural integrity and porosity provides moisture balance and removes excess exudates, thereby promoting wound healing. The effect of the blend ratio on the fiber morphology and wettability was investigated using scanning electron microscopy (SEM) and contact angle measurement, respectively. The structural determination of the prepared membranes was conducted using Fourier-transform infrared spectroscopy (FTIR). The release behavior of (E)-1-(3,4-dimethoxyphenyl) butadiene (DMPBD), a marker molecule with potent anti-inflammatory activity from the fiber blend, showed a controlled release characteristic. The essential oil-loaded electrospun membrane also showed antibacterial activity against S. aureus and E. coli. It also exhibited no toxicity to both human fibroblast and keratinocyte cells, suggesting that the prepared material is suitable for wound dressing application.

Moisture-Resistant Electrospun Polymer Membranes for Efficient and Stable Fully Printable Perovskite Solar Cells Prepared in Humid Air.

Fully printable perovskite solar cells (PPSCs) attract attention in the photovoltaic industry and research owing to their controllable and scalable production with reduced material waste during manufacturing. However, the commercialization of PPSCs has been impeded by their inherent vulnerability to ambient moisture, leading to a rapid loss of device efficiency and lifetime. Here, we propose a novel idea to enhance the photovoltaic performance and stability of PPSCs in humid air (relative humidity exceeding 80%) using electrospun hydrophobic polymer membranes, i.e., polylactic acid (PLA), polycaprolactone (PCL), and PLA/PCL blends, as moisture-resistant layers for PPSCs. After optimizing the morphologies, hydrophobicity, and thermal properties of the electrospun membranes by varying the contents of the polymer components in the membranes, the unencapsulated devices with these membranes demonstrated power conversion efficiencies of up to 8.2%, which was significantly higher than for devices without the membranes (6.8%). Moreover, devices with the optimum electrospun membrane retained more than 85% of their original efficiency after being stored in humid air for over 35 days. In comparison, devices without the electrospun membranes lost about 50% of their initial efficiency over the same time. Our work is very useful for the development of highly efficient and stable commercial PPSCs.

Density functional theory study of adsorption geometries and electronic structures of azo-dye-based molecules on anatase TiO2 surface for dye-sensitized solar cell applications.

Structural and electronic properties of eight isolated azo dyes (ArNNAr', where Ar and Ar' denote the aryl groups containing benzene and naphthalene skeletons, respectively) were investigated by density functional theory (DFT) based on the B3LYP/6-31G(d,p) and TD-B3LYP/6-311G(d,p) methods The effect of methanol solvent on the structural and electronic properties of the azo dyes was elucidated by employing a polarizable continuum model (PCM). Then, the azo dyes adsorbed onto the anatase TiO2 (101) slab surface through a carboxyl group. The geometries and electronic structures of the adsorption complexes were determined using periodic DFT based on the PWC/DNP method. The calculated adsorption energies indicate that the adsorbed dyes preferentially take configuration of the bidentate bridging rather than chelating or monodentate ester-type geometries. Furthermore, the azo compounds having two carboxyl groups are coordinated to the TiO2 surface more preferentially through the carboxyl group connecting to the benzene skeleton than through that connecting to the naphthalene skeleton. The dihedral angles (ΦB-N) between the benzene- and naphthalene-skeleton moieties are smaller than 10° for the adsorbed azo compounds containing one carboxyl group. In contrast, ΦB-N>30° are obtained for the adsorbed azo compounds containing two carboxyl groups. The almost planar conformations of the former appear to strengthen both π-electrons conjugation and electronic coupling between low-lying unoccupied molecular orbitals of the azo dyes and the conduction band of TiO2. On the other hand, such coupling is very weak for the latter, leading to a shift of the Fermi level of TiO2 in the lower-energy direction. The obtained results are useful to the design and synthesize novel azo-dye-based molecules that give rise to higher photovoltaic performances of the dye-sensitized solar cells.

Key role of hydrazine to the interaction between oxaloacetic against phosphoenolpyruvic carboxykinase (PEPCK): ONIOM calculations.

The interactions between oxaloacetic (OAA) and phosphoenolpyruvic carboxykinase (PEPCK) binding pocket in the presence and absence of hydrazine were carried out using quantum chemical calculations, based on the two-layered ONIOM (ONIOM2) approach. The complexes were partially optimized by ONIOM2 (B3LYP/6-31G(d):PM6) method while the interaction energies between OAA and individual residues surrounding the pocket were performed at the MP2/6-31G(d,p) level of theory. The calculated interaction energies (INT) indicated that Arg87, Gly237, Ser286, and Arg405 are key residues for binding to OAA with the INT values of -1.93, -2.06, -2.47, and -3.16 kcal mol(-1), respectively. The interactions are mainly due to the formation of hydrogen bonding interactions with OAA. Moreover, using ONIOM2 (B3LYP/6-31G(d):PM6) applied on the PEPCKHS complex, two proton transfers were observed; first, the proton was transferred from the carboxylic group of OAA to hydrazine while the second one was from Asp311 to Lys244. Such reactions cause the generation of binding strength of OAA to the pocket via electrostatic interaction. The orientations of Lys243, Lys244, His264, Asp311, Phe333, and Arg405 were greatly deviated after hydrazine incorporation. These indicate that hydrazine plays an important role in terms of not only changing the conformation of the binding pocket, but is also tightly bound to OAA resulting in its conformation change in the pocket. The understanding of such interaction can be useful for the design of hydrazine-based inhibitor for antichachexia agents.