GO-Enabled Bacterial Cellulose Membranes by Multistep, In Situ Loading: Effect of Bacterial Strain and Loading Pattern on Nanocomposite Properties.

This paper presents the results of research on the preparation and properties of GO/BC nanocomposite from bacterial cellulose (BC) modified with graphene oxide (GO) using the in situ method. Two bacterial strains were used for the biosynthesis of the BC: Komagataeibacter intermedius LMG 18909 and Komagataeibacter sucrofermentans LMG 18788. A simple biosynthesis method was developed, where GO water dispersion was added to reinforced acetic acid-ethanol (RAE) medium at concentrations of 10 ppm, 25 ppm, and 50 ppm at 24 h and 48 h intervals. As a result, a GO/BC nanocomposite membrane was obtained, characterized by tensile strength greater by 150% as compared with the pure BC (Ì´ 50 MPa) and lower volume resistivity of ~4 ∙ 109 Ω × cm. Moreover, GO addition increases membrane thickness up to ~10% and affects higher mass production, especially with low GO concentration. All of this may indicate the possibility of using GO/BC membranes in fuel cell applications.

Preparation of an Active Dressing by In Situ Biosynthesis of a Bacterial Cellulose-Graphene Oxide Composite.

This paper presents a simple method of obtaining a bacterial cellulose (BC) composite with the addition of graphene oxide (GO) using an in situ method and studies the influence of GO nanoparticles on the structure and properties of the obtained membranes. Microorganisms obtained from Golden Delicious apple vinegar were used to obtain the BC. During the biosynthesis, GO was introduced in the amounts of 3.7, 5.4 and 7.1% w/w. The resulting BC/GO composite was characterized by high water content (~400%), a thickness of about 1.1 mm (in wet form) and a cellulose nanofiber diameter of ~100 nm. The possibility of using the resulting composite membranes as potential active dressings with the sustained-release analgesic medicine-paracetamol-was investigated. The BC/GO composite membranes were characterized by a medicine sorption of 60 mg/g of BC, a slow desorption time, a constant medicine concentration over time and an 80% paracetamol release rate after 24 h. The morphology of membrane surfaces and cross-sections were examined by means of scanning electron microscopy (SEM). Infrared spectroscopy (FTIR), X-ray structure studies (WAXS) as well as thermal analysis (TGA) demonstrated the presence of GO in the BC matrix and interactions between the matrix and the additive.

Modification and Properties of Cellulose Nonwoven Fabric-Multifunctional Mulching Material for Agricultural Applications.

The paper describes a method of modifying a commercial viscose nonwoven fabric and its use as a modern mulching material in agriculture. The conducted research confirmed that the proposed modification of the viscose nonwoven fabric could be successfully used as a multipurpose and, above all, completely biodegradable nonwoven crop cover, which will eliminate the problem of disposal after the harvest period. Modified cellulose nonwoven fabric was obtained by staining with NB-BT helion brown, then padding with potassium nitrate (KNO3) solution (used as a fertilizer) and finally coating with polylactide (PLA) solution. The characterisation of the nonwoven fabric included structural analysis, physicochemical properties and mechanical tests. The modified cellulose nonwovens were used in the tunnel cultivation of tomatoes as a heat-retardant, water-absorbing, antiweed mulching material that prevents soil infestation and slowly releases fertilizers.

Graphene Oxide and Stabilized Ortho-Silicic Acid as Modifiers of Amnion and Burn Affected Skin: A Comparative Study.

INTRODUCTION: Oxidative tissue damage caused by reactive oxygen species results in a significant decrease in the total antioxidant capacity of the biological system. The aim of this interdisciplinary study was to answer the question of whether active antioxidants modify, at a molecular and supramolecular level, the tissue of pathological amnion and the necrotic eschar degraded in thermal burn. METHODS: A Nicolet 6700 Fourier-transform spectrophotometer with OMNIC software and the EasiDiff diffusion accessory were used in the FTIR spectroscopic analysis. A NICOLET MAGNA-IR 860 spectrometer with FT-Raman accessory was used to record the Raman spectra of the samples. The samples were exposed to bacteria capable of causing nosocomial infections, ie Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Pseudomonas aeruginosa. Whereas samples of hypotrophic amnion interacted with Staphylococcus aureus, Escherichia coli and Enterococcus faecalis. The obtained flame retardant effect of placentas was evaluated using the method of the limiting oxygen index (LOI). RESULTS: The infrared spectroscopy analysis proved that after modification of the amniotic samples in graphene oxide and ortho-silicic acid, the amide II band is split into two components. Incubation of samples in modifier solutions: graphene oxide, sodium ascorbate and L-ascorbic acid results in shifts and changes of intensity within the broadly understood lipid band 1743-1745-1747 cm-1. The oxidising changes observed within the lipid and amide bands are affected by the incubation effect of graphene oxide as a modifier, possibly adsorbing on the surface of the amniotic membrane. On the basis of microbiological studies, pathogenic bacteria commonly causing amniotic infections and growing in burn wounds were found to have particularly good resistance to stabilized ortho-silicic acid (E. coli) and lactoferrin (S.aureus). CONCLUSION: This thermogravimetric study found the highest stability of the analysed tissues (hypotrophic amnion and burnt epidermis) after modification with graphene oxide and sodium ascorbate.

Nanocomposite Cellulose Fibres Doped with Graphene Oxide and Their Biocidal Properties.

The paper presents a method of obtaining composite cellulose fibres (CEL) doped with graphene oxide (GO) and the influence of GO nanoparticles on the structure and properties of the obtained fibres. Composite fibres (GO/CEL) were prepared using wet method from 5% CEL solutions in 1-ethyl-3-methylimidazolium acetate (EMIMAc) containing GO (0; 0.21; 0.50; 0.98; 1.97% w/w) dispersion in N,N-dimethylformamide (DMF). The fibres were coagulated in distilled water and methanol. Optical microscopy allowed us to demonstrate a good degree of GO additive dispersion in the CEL matrix. Surface morphology was examined by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR), which indicated interactions between the matrix and the additive. Strength tests have shown that GO/CEL fibres are characterised by high values of elongation at break (7.7-19.5%) and tenacity (~133-287 [MPa]). The obtained composite fibres are characterized by good biocidal properties against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphilococcus aureus), and fungi Candida albicans, and the resistance to microorganisms depends on the surface zeta potential value and the isoelectric point (IEP) of GO/CEL fibres.

Preparation and properties of composite cellulose fibres with the addition of graphene oxide.

The paper presents the results of a study on the preparation of cellulose-based composite fibres (CEL) with graphene oxide addition (GO). Composite fibres (GO/CEL) were prepared via the wet spinning method from CEL solutions in 1-ethyl-3-methylimidazolium acetate (EMIMAc) that contained a nano-addition of GO dispersion in N,N-dimethylformamide (DMF). The GO contents of the composite fibres were 0, 0.21, 0.50, 0.98, and 1.97 % w w. The fibres were coagulated in two solvents: distilled water and methanol. The results demonstrated that the amount of GO additive and the type of coagulant significantly impact the physicochemical, mechanical and structural properties of the CEL and GO/CEL fibres. The use of distilled water in a coagulation bath causes a degree of crystallinity of 31.0-40.8 % (WAXS) and a shift in the thermal decomposition temperature (by approximately 19 °C) towards higher temperatures (TGA). The results demonstrate improvements in the mechanical properties of the GO/CEL fibres, which were at the level of 9.43-14.18 cN/tex. In addition, the GO/CEL fibres exhibit satisfactory GO dispersion throughout their volume.

The Influence of Graphene Addition on the Properties of Composite rGO/PAN Membranes and Their Potential Application for Water Disinfection.

The paper presents a method of obtaining composite polyacrylonitrile-based (PAN) membranes with the addition of reduced graphene oxide (rGO). The membranes were obtained using phase inversion method from a homogeneous rGO dispersion in a solution of PAN dissolved in N, N-dimethylformamide (DMF). The impact of the amount of rGO addition to the PAN matrix on the physicochemical, structural, transport, and separation properties and on fouling resistance was studied. Composite membranes, due to the method of preparation used and the addition of rGO, are characterized by very good transport properties (~390 L/m2 h) and by a high degree of protein retention (85%). Reduced graphene oxide has biocidal properties, which, as we have shown, depend on the size of nanoparticles and the type of microorganism. rGO/PAN membranes, on the other hand, show biostatic properties against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcuc aureus) and fungi (Candida albicans). Thus, the obtained composite membranes can be potentially used in water disinfection.

Structure-Property Relationships of Pure Cellulose and GO/CEL Membranes Regenerated from Ionic Liquid Solutions.

Two types of cellulose membranes were produced by a classical wet phase inversion method from a solution of the polymer in 1-ethyl-3-methylimidazolium acetate (EMIMAc) by coagulation in water and selected primary alcohols. The first type were membranes made from pure cellulose (CEL). The second type were membranes obtained by adding nanosized graphene oxide (GO) to the cellulose solution. The process of precipitation and selection of the coagulant affected the structure of the membranes, which in turn affected their usability and applicability. The results of the presented studies show that the physicochemical properties of the coagulant used (e.g., molecular mass and dipole moment) play important roles in this process. It was found that both the content and dimensions of the pores depended on the molecular mass of the coagulant used. It was also found that the dipole moment of coagulant molecules had a large influence on the volume content of the pores (e.g., the 1-octanol (Oc) membrane had a dipole moment of 1.71 D; Φ = 1.82%). We investigated the effect of the type of coagulant on the porous structure of CEL membranes and how this affected the transport properties of the membranes (e.g., for the distilled water (W) membrane, Jv = 5.24 ± 0.39 L/m2 h; for the Oc membrane, Jv = 92.19 ± 1.51 L/m2 h). The paper presents the results of adding GO nanoparticles in terms of the structure, morphology, and transport properties of GO/CEL membranes (e.g., for composite membrane F (containing 20% GO), Jv = 40.20 ± 2.33 L/m2 h). In particular, it describes their extremely high ability to remove heavy metal ions.

Vinylphosphonium and 2-aminovinylphosphonium salts - preparation and applications in organic synthesis.

The main synthetic routes towards vinylphosphonium salts and their wide applications in organic synthesis are discussed in this review. Particular attention is paid to the use of these compounds as building blocks for the synthesis of carbo- and heterocyclic systems after their prior transformation into the corresponding phosphorus ylides, followed by the intramolecular Wittig reaction with various types of nucleophiles containing a carbonyl function in their structures.