Antimicrobial activity of metal-based nanoparticles: a mini-review.

The resistance of pathogenic microorganisms to antibiotics is one of the main problems of world health. Of particular concern are multidrug-resistant (MDR) bacteria. Infections caused by these microorganisms affect the appearance of acute or chronic diseases. In this regard, modern technologies, such as nanomaterials (NMs), especially promising nanoparticles (NPs), can possess antimicrobial properties or improve the effectiveness and delivery of known antibiotics. Their diversity and characteristics, combined with surface functionalization, enable multivalent interactions with microbial biomolecules. This article presents an overview of the most current research on replacing antibiotics with NPs, including the prospects and risks involved.

Conducting Silicone-Based Polymers and Their Application.

Over the past two decades, both fundamental and applied research in conducting polymers have grown rapidly. Conducting polymers (CPs) are unique due to their ease of synthesis, environmental stability, and simple doping/dedoping chemistry. Electrically conductive silicone polymers are the current state-of-the-art for, e.g., optoelectronic materials. The combination of inorganic elements and organic polymers leads to a highly electrically conductive composite with improved thermal stability. Silicone-based materials have a set of extremely interesting properties, i.e., very low surface energy, excellent gas and moisture permeability, good heat stability, low-temperature flexibility, and biocompatibility. The most effective parameters constructing the physical properties of CPs are conjugation length, degree of crystallinity, and intra- and inter-chain interactions. Conducting polymers, owing to their ease of synthesis, remarkable environmental stability, and high conductivity in the doped form, have remained thoroughly studied due to their varied applications in fields like biological activity, drug release systems, rechargeable batteries, and sensors. For this reason, this review provides an overview of organosilicon polymers that have been reported over the past two decades.

2,1,3-Benzothiadiazole Small Donor Molecules: A DFT Study, Synthesis, and Optoelectronic Properties.

We herein report the design and synthesis of small-donor molecules, 2,1,3-benzothiadiazole derivatives (2a-d), by Stille or Suzuki reaction. The synthesized compounds were characterized by spectroscopic and electrochemical methods. The compounds 2a-d absorb the light in a wide range (the UV-green/yellow light (2c)) and emit from green to red/near IR light (2c). Furthermore, these compounds show a narrow energy gap (1.75-2.38 eV), and high Ea values increasing for polymers, which prove their electron-donating nature and semiconductor properties. The measurements were enhanced by theoretical modeling.

Synthesis and Properties of New Dithienosilole Derivatives as Luminescent Materials.

Three new organosilicon compounds based on dithienosilole (DTSi) were synthesized in good yields. We report the optical and electrochemical properties of the resulting derivatives. We find that these compounds absorb the light in the ultraviolet and blue light range, and they exhibit luminescence in almost the entire range of visible light. After electropolymerization were significantly lowered, the values of the energy gap (even 1.51 eV for P2) and the ionization potential of the polymers were compared to monomers. Optoelectronic properties of the obtained compounds suggest that these derivatives of DTSi may be good candidates as the emissive layers in white organic light-emitting diodes (WOLEDs), which would reduce the amount of layers.

Synthesis and Electrochromic Properties of Conducting Polymers Based on Highly Planar 2,7-Disubstituted Xanthene Derivatives.

On the basis of preliminary DFT calculations, p-type semiconducting polymers based on 2,7-substituted xanthene building blocks that show a high degree of planarity were designed. The synthesis, electrochemical characterization, and theoretical modeling of 2,7-bis(thiophen-2-yl)-9,9-dimethylxanthene (1) and 2,7-bis(3-hexylthiophen-2-yl)-9,9-dimethylxanthene (2) is described. The synthetic procedure is based on the incorporation of thiophene rings by means of Pd-catalyzed cross-coupling reactions, which lead to monomers 1 and 2. Copolymers P1 and P2 obtained by means of anodic polymerization have been characterized by spectroscopic and electrochemical methods. Electrochromism was observed for both polymers. The experimental data supported by density functional theory modeling explain the influence of alkyl chain substitution on the properties of the investigated copolymers.

Comparative study of alternating low-band-gap benzothiadiazole co-oligomers.

The benzothiadiazole-arylene alternating conjugated oligomers have been designed and synthesized via Suzuki coupling reaction. The structures and properties of the conjugated oligomers were characterized by (1)HNMR, (13)CNMR, UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy. The luminescent measurements demonstrate that polybenzothiadiazoles are good chromophores able to form thin films by Langmuir-Blodgett (LB) technique, making them suitable for further applications. Also the electrical properties of obtained films confirm the good potential of these novel aryl-based π-conjugated polymers for the development of various electrical and electrochemical solid-state devices.

Phenoxazine based units--synthesis, photophysics and electrochemistry.

A few new phenoxazine-based conjugated monomers were synthesized, characterized, and successfully used as semiconducting materials. The phenoxazine-based oligomers have low ionization potentials or high-lying HOMO levels (~4.7 eV), which were estimated from cyclic voltammetry. Conjugated oligomers offer good film-forming, mechanical and optical properties connected with their wide application. These results demonstrate that phenoxazine-based conjugated mers are a promising type of semiconducting and luminescent structures able to be used as thin films in organic electronics.

A new route to light emitting organic materials based on triazine derivatives.

Novel light-emitting organic materials comprising conjugated oligomers chemically attached via a flexible spacer to an electron-or hole-conducting core were synthesized by Stille cross-coupling methodology and designed for tunable charge injection and optical properties. The hyperbranched structures have been characterized by (1)H NMR, (13)C NMR, and UV-VIS spectroscopy. The obtained structures show good stability in common organic solvents such as CHCl(3), toluene, and CH(2)Cl(2) and exhibit excellent thermal stability. A preliminary electroluminescence properties were also investigated. This class of materials will help to balance charge injection and transport and to spread out the charge recombination zone, thereby significantly improving the device efficiency and lifetime of unpolarized and polarized OLEDs.

Biocatalysts immobilized in ultrathin ordered films.

The immobilization of enzymes and other proteins into ordered thin materials has attracted considerable attention over the past few years. This research has demonstrated that biomolecules immobilized in different [Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS)] matrixes retain their functional characteristics to a large extent. These new materials are of interest for applications as biosensors and biocatalysts. We review the growing field of oxidases immobilized onto ordered Langmiur-Blodgett and Langmuir-Schaefer films. Strategies for the preparation of solid supports and the essential properties of the resulting materials with respect to the envisaged applications are presented. Basic effects of the nature of the adsorption and various aspects of the application of these materials as biosensors, biocatalysts are discussed. Outlook of potential applications and further challenges are also provided.

Structure and sensor properties of thin ordered solid films.

Miniaturized gas sensors and biosensors based on nanostructured sensing elements have attracted considerable interest because these nanostructured materials can be used to significantly improve sensor sensitivity and the response time. We report here on a generic, reversible sensing platform based on hybrid nanofilms. Thin ordered Langmuir-Blodgett (LB) films built of fluorene derivatives were used as effective gas sensors for both oxidative and reductive analytes. A novel immobilization method based on thin LB films as a matrix has been developed for construction of sensing protein layers. Biomolecules can often be incorporated into and immobilized on Langmuir-Blodgett films using adsorption methods or by covalent immobilization of proteins. The sensor sensitisation was achieved by an amphiphilic N-alkyl-bis(thiophene)arylenes admixed into the film. The interlaced derivative was expected to facilitate the electron transfer, thereby enhancing the sensor sensitivity. The results suggest that this may be very promising approach for exploring the interactions between proteins and high throughput detection of phenol derivatives in wastewater.

Theoretical studies of symmetric five-membered heterocycle derivatives of carbazole and fluorene: precursors of conducting polymers.

Structures, electron ionization and excitation energies, and electron density distribution are studied for carbazole and fluorene derivatives substituted symmetrically by thiophene, ethylenodioxythiophene, furane, or pyrrole. The calculated properties of the molecules directly or indirectly mimic molecular parameters that are important for the design of processes of polymerization or for modeling the final polymer. The studies have been focused on the variation in the properties as a function of the chemical composition of the central fragment and the external rings. The calculated properties of consecutive oligomers indicate their fast convergence to values characterizing polymers.