Anthocyanin-functionalized biopolymer films as pH-sensitive indicators

Anthocyanins are water-soluble, non-toxic flavonoid pigments, which produce the blue, red and purple color of many plants. Color change of anthocyanin extracts is a direct consequence of the transformation of their chemical structure when exposed to different pH conditions. Optical properties investigated in UV-Vis absorption and PL spectra show a clear difference between anthocyanins in acidic and in alkaline environments. Chitosan, a natural-based, non-toxic and biodegradable polysaccharide, is chosen as an ideal matrix for nanocomposites. It is proven to be a good carrier for anthocyanins, because of its ability to entrap the indicator dyes and at the same time the ability to release anthocyanins when in contact with an acidic environment. In this research, we have developed anthocyanin-enhanced biopolymer indicator systems, which provide fast colorimetric response to alterations in pH levels of the environment. Transmittance spectra of nanocomposites show excellent light-blocking properties of the films. This opens up possibilities for advancement in future technology of smart biodegradable food packaging biomaterials. The availability of innovative and healthy materials reduces the need for using synthetic plastic in the modern food industry.IX International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; August 28 - September 1, 2023; Belgrad

Electronic structure of silver-bismuth iodide rudorffite nanomaterials studied by synchrotron radiation soft X-ray photoemission spectroscopy

Silver-bismuth iodide (Ag-Bi-I) rudorffites are chemically stable and non-toxic materials that can act as a possible replacement for methylammonium lead halide perovskites in optoelectronic devices. In this report we will present innovative routes for fabrication of AgBi-I nanomaterials, as well as the results of the investigation of the electronic structure of isolated Ag-Bi-I nanoparticles by soft X-ray aerosol photoemission spectroscopy [1, 2]. Aerosol photoemission spectroscopy allows studies of the electronic structure of submicrometer particles that are free from the influence of a substrate or solvent [1-5]. In this approach the aerosol particles can be produced directly from a solution or a colloidal dispersion, which opens a possibility for investigation of a variety of nanosystems that can be produced by wet chemistry methods. This technique relies on the interaction of focused beam of isolated particles with ionizing radiation under high vacuum conditions. In addition, by using tunable synchrotron radiation as an excitation source it is possible to obtain highresolution photoelectron spectra in the investigated photoelectron energy range.X Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 26-27, 2022; Belgrad

A fluorescent nanoprobe for single bacterium tracking: functionalization of silver nanoparticles with tryptophan to probe the nanoparticle accumulation with single cell resolution

The investigation of the interaction of silver nanoparticles and live bacteria cells is of particular importance for understanding and controlling their bactericidal properties. In this study, the process of internalization of silver nanoparticles in Escherichia coli cells was followed by means of synchrotron excitation deep ultraviolet (DUV) fluorescence imaging. Antimicrobial nanostructures that can absorb and emit light in the UV region were prepared by functionalization of silver nanoparticles with tryptophan amino acid and used as environmentally sensitive fluorescent probes. The nanostructures were characterized by morphological (TEM) and spectroscopic methods (UV-vis, FTIR, XPS, and photoluminescence). The TEM images and the analyses of the UV-vis spectra suggested that the addition of tryptophan led to the formation of hybrid nanostructures with pronounced eccentricity and larger sizes with respect to that of the initial silver nanoparticles. The DUV imaging showed that it was possible to distinguish the fluorescent signal pertaining to silver-tryptophan nanostructures from the autofluorescence of the bacteria. The spatial resolution of the fluorescence images was 154 nm which was sufficient to perform analyses of the accumulation of the nanostructures within a single bacterium. The DUV imaging results imply that the tryptophan-functionalized silver nanoparticles interact with cell membranes via insertion of the amino acid into the phospholipid bilayer and enter the cells

Roadmap on dynamics of molecules and clusters in the gas phase

This roadmap article highlights recent advances, challenges and future prospects in studies of the dynamics of molecules and clusters in the gas phase. It comprises nineteen contributions by scientists with leading expertise in complementary experimental and theoretical techniques to probe the dynamics on timescales spanning twenty order of magnitudes, from attoseconds to minutes and beyond, and for systems ranging in complexity from the smallest (diatomic) molecules to clusters and nanoparticles. Combining some of these techniques opens up new avenues to unravel hitherto unexplored reaction pathways and mechanisms, and to establish their significance in, e.g. radiotherapy and radiation damage on the nanoscale, astrophysics, astrochemistry and atmospheric science

Influence of culture activity on aroma components in yoghurts produced from goat's and cow's milk

In this paper the experiments on microbiological quality and aroma components of yoghurt samples produced from long life goat's and cow's milk, and also from milks with 2% milk powder addition, during 9 days of refrigerated storage are described. Milk fermentation was conducted at 42 °C for 6 h. During days 1, 3, and 9 of storage the changes in acidity (pH value and lactic acid percent), viable counts of streptococci and lactobacilli and aroma components (acetaldehyde and diacetyl) were determined. Lower pH values and smaller lactic acid concentrations were found in control yoghurt samples. Viable counts of streptococci decreased during storage (from 1.01×108  to 3.97×10 7  CFU ml -1), whereas the viable counts of lactobacilli increased in all samples (from 6.95´10 6  to 2.32×10 7  CFU ml -1). The increase in count of lactobacilli was the greatest in goat's milk yoghurt samples. On the ninth day of storage, ?logN between cow's and goat's milk yoghurt samples was 0.2. Acetaldehyde in yoghurts decreased during storage time from 5.47 mg kg -1  (on day 1) to 1.05 mg kg -1  (on day 9). Both control yoghurt samples had lower acetaldehyde concentration than the supplemented samples. During nine days of storage, a significant increase in diacetyl content of yoghurt samples (from 14.20 mg kg -1  on the first day to 18.65 mg kg -1  on day 9) was noticed. goat's milk yoghurts, especially that manufactured without milk powder addition, had very soft consistency, but no syneresis was observed

The influence of milk powder, whey protein concentrate and inulin on the on the quality of cow and goat acidophilus milk

Cow and goat milk samples supplemented with milk powder, whey protein concentrate and inulin and without supplementation were fermented with Lactobacillus acidophilus La5. At the end of fermentation, the highest viable count was found in the supplemented samples, especially in those containing whey protein concentrate. Inulin did not show a notable influence on the bacterial count of samples. During 9 days of storage, the viable count, rheological characteristics and sensory properties of the samples were determined. All goat acidophilus milks had lower pH value and higher viable count of L. acidophilus La5 than the cow acidophilus milks did

Fermentation of cow’s milk and soy milk mixture with L. acidophilus probiotic bacteria with yoghurt culture

The aim of the paper was to produce a functional product and to determine the physico - chemical, microbiological and sensory properties of probiotic beverages produced from different mixtures of cow’s milk and soy milk. The ratios of cow’s milk and soy milk were 100:0%, 25:75%, 50:50%, 75:25% and 0:100%. The samples were fermented with probiotic bacteria Lactobacillus acidophilus (La5) with the addition of yogurt culture. The fermentation of samples was performed at +43 °C until coagulation and pH value of 4.6. Characteristics of the obtained beverages were monitored during storage at 1st, 7th, 14th and 21st day of storage at +4 °C. Produced probiotic beverages were observed and change in active acidity, titration acidity, change in the number od probiotic bacteria, and sensory properties and acceptability of products were tracked. After fermentation, the number of lactobacilli in the samples produced gradually decreased during 21 days, but was still above the probiotic minimum (CFU 106 mL−1) so the samples had probiotic properties. Samples of fermented beverages got the best score of their sensory properties on the seventh day of preservation. The sensory properties of the samples were mainly influenced by the type and ratio of the used milk. Mixing cow’s milk with soy milk significantly improved the sensory properties of the product. The acceptance test showed good acceptance of fermented beverages samples by potential consumers, apart from the sample that was 100% soy milk

PS-NH2 + PMMA-COOH blend: A promising substrate material for the deposition of densely packed gold nanoparticles

Densely packed gold nanoparticles with narrow size distribution were fabricated by pulsed laser deposition using a blend of amino-terminated polystyrene (PS-NH2) and carboxyl-terminated polymethylmethacrylate (PMMA-COOH) as a deposition substrate. Transmission electron microscopy showed spherical Au nanoparticles with an average size of 5 nm. UV-vis absorption spectra of the Au/blend nanocomposite films exhibited a strong resonance band at 658 nm. The analyses of the spectrum using the effective medium Bergman theory showed that the nanocomposite is comprised of isolated and randomly arranged nanoparticles. (C) 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinhei

2D silver-bismuth-iodide rudorffitenanomaterials for photovoltaic devices: a novel route for chemical synthesis of Ag3BiI6nanosheets

Silver-bismuth-iodide (Ag-Bi-I) rudorffite hybrid materials havegained an immense interest in the research for a lead-free, chemically stable and low-cost absorber material in photovoltaic devices [1].These materials can be fabricated in the form of macroscopic crystals or as thin films,in which case they can be integrated into solar cells that show good photoconversion efficiency[2]. Fabricating AgBi-I in nanocrystal form couldfacilitate further their integration in the photovoltaic devices and enhance device performance due to size confinement effects. In our previous study, we successfully fabricated ligand-free Ag3BiI6nanoparticles in the form of aerosols [3]. Here, we report on thefabricationprocedure of 2D Ag-Bi-I nanomaterials in the colloidal form. The results of the structural and morphological investigation of the nanosheets will be presented, as well as reconstruction of the electronic levels of the Ag3BiI6nanoparticles from the combined UV-vis absorption andX-ray photoelectron spectroscopy data.In addition, an analysis that shows the relation between the positions of the bands in the Ag3BiI6nanosheet absorption spectra and the thickness of the nanosheet will be discussed.VIII International School and Conference on Photonics and HEMMAGINERO workshop : PHOTONICA2021 : book of abstracts; August 23-27, 2021; Belgrad