The Pressurized Porous Surface Model: An improved tool to study bacterial behavior under a wide range of environmentally relevant matric potentials

To study bacterial behavior under varying hydration conditions similar to surface soil, we have developed a system called the Pressurized Porous Surface Model (PPSM). Thin liquid films created by imposing a matric potential of − 0.4 MPa impact gene expression and colony development in Pseudomonas putida.     

Electric field-induced breakdown of lipid bilayers and cell membranes: A thin viscoelastic film model

Summary A simple viscoelastic film model is presented, which predicts a breakdown electric potential having a dependence on the electric pulse length which approximates the available experimental data for the electric breakdown of lipid bilayers and cell membranes (summarized in the reviews of U. Zimmermann and J. Vienken, 1982,J. Membrane Biol. 67:165 and U. Zimmermann, 1982,Biochim. Biophys. Acta 694:227). The basic result is a formula for the time of membrane breakdown (up to the formation of pores): =(/C)/( _m ² ₀ ² U ⁴/24Gh ³+T ²/Gh–1), where is a proportionality coefficient approximately equal to ln(h/2₀),h being the membrane thickness and ₀ the amplitude of the initial membrane surface shape fluctuation ( is usually of the order of unity), represents the membrane shear viscosity,G the membranes shear elasticity modules, _m the membrane relative permittivity, ₀=8.85×10^–12 Fm,U the electric potential across the membrane, the membrane surface tension andT the membrane tension. This formula predicts a critical potentialU _c ;U _c =(24Gh ³/ _m ² ₀ ² )^1/4 (for = andT=0). It is proposed that the time course of the electric field-induced membrane breakdown can be divided into three stages: (i) growth of the membrane surface fluctuations, (ii) molecular rearrangements leading to membrane discontinuities, and (iii) expansion of the pores, resulting in the mechanical breakdown of the membrane.     

Multistimuli-responsive fluorescence behaviours of aggregation-induced emission small-molecule and electrospun nanofibre films for acid–base vapour sensing

Multistimuli-responsive fluorescent materials have garnered great research interest benefited from their practical applications. Two twisted-structure compounds containing tetraphenylethylene (TPE) as the aggregation-induced emission (AIE) group and a pyridine unit as the acid reaction site to obtain new multistimuli-responsive fluorescent compounds (namely, TPECNPy: TPECNPy-2 and TPECNPy-3) were successfully synthesized through a one-step Knoevenagel condensation reaction. The multiple-stimuli response process of TPECNPy was investigated by means of photoluminescence (PL) spectra and emission colour. The results showed that both TPECNPy compounds with excellent AIE abilities displayed reversible emission wavelength and colour changes in response to multiple external stimuli, including grinding–fuming by CH₂Cl₂ or annealing and HCl-NH₃ vapour fuming. More importantly, fluorescent nanofibre films were prepared by electrospinning a solution of TPECNPy mixed with cellulose acetate (CA), and these exhibited reversible acid-induced discolouration, even with only 1 wt% TPECNPy. The results of this study may inspire strategies for designing multistimuli-responsive materials and preparing fluorescent sensing nanofibre films.     

Structure and nonlinear optical properties of copper phthalocyanine thin films

This paper describes a joint study of the structure and nonlinear optical properties of vacuum evaporated thin films of copper phthalocyanine (CuPc for brevity). Film thickness ranges from 50 to 500 nm. The anisotropic paramagnetic resonance of Cu⁺⁺ ions reveals that the Pc rings lie almost parallel to the substrate plane with however a large angular distribution (30° FWHM). Third harmonic optical generation measurements performed at 1.064 m and 1.907 m fundamental wavelengths give respectively an average value of the cubic susceptibility ⁽³⁾(-3,)=(4±0.4)·10^–12 e.s.u. and (2.1+-0.2) · 10^-12 These values, although significantly higher than for a common ionic crystal, are about one order of magnitude lower than in conjugated 1-D systems, which shows that the 2-D -electron delocalization is less profitable than the 1-D one. Besides third harmonic, we have also observed second harmonic generation. Its polarization dependence is characteristic of a quadratic susceptibility enhanced in one direction, almost perpendicular to the substrate, withd _eff comprised between 30 and 60 · 10^-9 e.s.u. The possible origins ofd _eff are discussed.     

Human Health Risk Assessment of Soils Contaminated with Metal(loid)s by Using DGT Uptake: A Case Study of a Former Korean Metal Refinery Site

The human health risk of soils contaminated with As, Pb, Cu, and Zn was evaluated based on pseudo-total concentrations of metal(loid)s, the physiologically based extraction test (PBET), and diffusive gradients in thin films (DGT). Non-carcinogenic (NCR) and carcinogenic (CR) risks exceeded the U.S. Environmental Protection Agency criteria under both the residential and non-residential scenarios. Human bioavailable concentrations (PBET) were much lower than pseudo-total concentrations. The Hazardous Index of NCR (HI (NCR)) for the PBET in the studied soils was 67% and 94% less than that for pseudo-total concentration, respectively, under the non-residential and residential scenarios. Similarly, CR for the PBET was also 65% and 93% less for the two soils. The concentration of metal(loid)s accumulated in the DGT resin was highly correlated with the PBET-extractable concentration (R² > 0.649). Therefore, for both the CR and HI (NCR), the DGT-calculated risk was linearly related to the PBET-calculated risk for the studied soils under both scenarios. The results suggest that DGT uptake and PBET-extracted concentrations are good surrogates for risk estimation and that both J1 and J2 soils require remediation before their use for residential or non-residential purposes.     

Indoor Thin‐Film Photovoltaics: Progress and Challenges

Energy generation and consumption have always been an important component of social development. Interests in this field are beginning to shift to indoor photovoltaics (IPV) which can serve as power sources under low light conditions to meet the energy needs of rapidly growing fields, such as intelligence gathering and information processing which usually operate via the Internet‐of‐things (IoT). Since the power requirements for this purpose continue to decrease, IPV systems under low light may facilitate the realization of self‐powered high‐tech electronic devices connected through the IoT. This review discusses and compares the characteristics of different types of IPV devices such as those based on silicon, dye, III‐V semiconductors, organic compounds, and halide perovskites. Among them, specific attention is paid to perovskite photovoltaics which may potentially become a high performing IPV system due to the fascinating photophysics of the halide perovskite active layer. The limitations of such indoor application as they relate to the toxicity, stability, and electronic structure of halide perovskites are also discussed. Finally, strategies which could produce highly functional, nontoxic, and stable perovskite photovoltaics devices for indoor applications are proposed.     

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O₂ pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (>80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO₂, Al₂O₃, WO₃ and Ag₄O₄.     

Film forming microbial biopolymers for commercial applications—A review

Abstract

Microorganisms synthesize intracellular, structural and extracellular polymers also referred to as biopolymers for their function and survival. These biopolymers play specific roles as energy reserve materials, protective agents, aid in cell functioning, the establishment of symbiosis, osmotic adaptation and support the microbial genera to function, adapt, multiply and survive efficiently under changing environmental conditions. Viscosifying, gelling and film forming properties of these have been exploited for specific significant applications in food and allied industries. Intensive research activities and recent achievements in relevant and important research fields of global interest regarding film forming microbial biopolymers is the subject of this review. Microbial polymers such as pullulan, kefiran, bacterial cellulose (BC), gellan and levan are placed under the category of exopolysaccharides (EPS) and have several other functional properties including film formation, which can be used for various applications in food and allied industries. In addition to EPS, innumerable bacterial genera are found to synthesis carbon energy reserves in their cells known as polyhydroxyalkanoates (PHAs), microbial polyesters, which can be extruded into films with excellent moisture and oxygen barrier properties. Blow moldable biopolymers like PHA along with polylactic acid (PLA) synthesized chemically in vitro using lactic acid (LA), which is produced by LA bacteria through fermentation, are projected as biodegradable polymers of the future for packaging applications. Designing and creating of new property based on requirements through controlled synthesis can lead to improvement in properties of existing polysaccharides and create novel biopolymers of great commercial interest and value for wider applications. Incorporation of antimicrobials such as bacteriocins or silver and copper nanoparticles can enhance the functionality of polymer films especially in food packaging applications either in the form of coatings or wrappings. Use of EPS in combinations to obtain desired properties can be evaluated to increase the application range. Controlled release of active compounds, bioactive protection and resistance to water can be investigated while developing new technologies to improve the film properties of active packaging and coatings. An holistic approach may be adopted in developing an economical and biodegradable packaging material with acceptable properties. An interdisciplinary approach with new innovations can lead to the development of new composites of these biopolymers to enhance the application range. This current review focuses on linking and consolidation of recent research activities on the production and applications of film forming microbial polymers like EPS, PHA and PLA for commercial applications.     

Real‐Time Investigation of Intercalation and Structure Evolution in Printed Polymer:Fullerene Bulk Heterojunction Thin Films

The complex intermixing morphology is critical for the performance of the nanostructured polymer:fullerene bulk heterojunction (BHJ) solar cells. Here, time resolved in situ grazing incidence X‐ray diffraction and grazing incidence small angle X‐ray scattering are used to track the structure formation of BHJ thin films formed from the donor polymer poly(2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) with different fullerene derivative acceptors. The formation of stable bimolecular crystals through the intercalation of fullerene molecules between the side chains of polymer crystallites is investigated. Such systems exhibit more efficient exciton dissociation but lower photo‐conductance and faster decay of charges. On the basis of the experimental observations, intercalation obviously takes place before or with the formation of the crystalline polymer domains. It results in more stable structures whose volume remains constant upon further drying. Three distinct periods of drying are observed and the formation of unidimensional fullerene channels along the π‐stacking direction of polymer crystallites is confirmed.