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In this work, photoluminescent (PL) carbon nano dots (CNDs) prepared from argan waste were embedded in highly optical transparent poly(styrene-co-acrylonitrile) (PSA) and cyclo-olefin copolymer (COC) matrices, which were further processed into thin films. In the first step, the luminescent CNDs were prepared through thermal processing of fine-groundargan waste, followed, in the second step, by direct dispersion in the polymer solutions, obtained by solving PSA and COC in selected solvents. These two polymer matrices were selected due to their high optical transparency, resilience to various environmental factors, and ability to be processed as quality thin films. The structural configuration of the CNDs was investigated through EDX, XPS, and FTIR, while DLS, HR-SEM, and STEM were used for their morphology investigation. The luminescence of the prepared CNDs and resulted polymer nanocomposites was thoroughly investigated through steady-state, absolute PLQY, and lifetime fluorescence. The quality of the resulted CND–polymer nanocomposite thin films was evaluated through AFM. The prepared highly luminescent thin films with a PL conversion efficiency of 30% are intended to be applied as outer photonic conversion layers on solar PV cells for increasing their conversion efficiency through valorization of the UV component of the solar radiation. [ABSTRACT FROM AUTHOR]

Among the modern oncological therapies, one of the most promising is based on tumor hyperthermia with magnetic nanoparticles resulting from the crystallization of iron and cobalt oxides. We synthesized core–shell magnetic nanoparticles of perchlorate-CoxFe3−xO4 (x = 0; 0.5; 1.0) via the co-precipitation method and stabilized them in aqueous suspensions. Fine granulation of the dispersed ferrophase was revealed by Transmission Electron Microscopy and Dynamical Light Scattering, with FTIR data detailing the surface-interaction phenomena. X-ray diffractometry revealed specific crystallization features of inverse spinel lattice, providing crystallite size and lattice parameters dependent on the cobalt content. The results of the Vibrating Sample Magnetometry investigations indicated that cobalt doping has reduced the magnetic core size and increased the nanoparticle dimension, which could be the result of crystallization defects at the nanoparticle surface related to the presence of cobalt ions. A mathematical model was applied with a focus on the quantitative description of the temperature distribution around magnetic nanoparticles. Further development of our research will consider new cobalt ferrite nanoparticles with new cobalt contents and different organic coatings to contribute to their biocompatibility and stability in aqueous suspensions, as required by administration in living organisms. [ABSTRACT FROM AUTHOR]

In this work, Carbon Dots with intense blue photo-luminescent emission were prepared through a pyrolytic processing of forestry ligno-cellulosic waste. The preparation path is simple and straightforward, mainly consisting of drying and fine grinding of the ligno-cellulosic waste followed by thermal exposure and dispersion in water. The prepared Carbon Dots presented characteristic excitation wavelength dependent emission peaks ranging within 438–473 nm and a remarkable 28% quantum yield achieved at 350 nm excitation wavelength. Morpho-structural investigations of the prepared Carbon Dots were performed through EDX, FT-IR, Raman, DLS, XRD, and HR-SEM while absolute PLQY, steady state, and lifetime fluorescence were used to highlight their luminescence properties. Due to the wide availability of this type of ligno-cellulosic waste, an easy processing procedure achieved photo-luminescent properties, and the prepared Carbon Dots could be an interesting approach for various applications ranging from sensors, contrast agents for biology investigations, to photonic conversion mediums in various optoelectronic devices. Additionally, their biocompatibility and waste valorization in new materials might be equally good arguments in their favor, bringing a truly "green" approach. [ABSTRACT FROM AUTHOR]

The paper presents several new polymer complexes based on poly(2‐hydroxyethyl) methacrylate (P‐HEMA) and transition metals including Y3+, Eu3+, Tb3+ and Dy3+. Red‐, green‐, blue‐ and yellow‐emitting polymer complexes with remarkable photoluminescent (PL) properties, high degree of transparency and excellent processability both in bulk and in thin film were prepared and investigated. In the case of the prepared P‐HEMA–Eu3+ and P‐HEMA–Tb3+ polymer complexes, divinylbenzene was used as a crosslinker resulting a markedly enhanced PL emission, most probably due to the presence of the benzene rings which improve the efficiency of the energy transfer to the cation emissive centres. The prepared polymer complexes were structurally investigated through Fourier transform infrared and X‐ray photoelectron spectroscopies while atomic force microscopy was used to study the morphology of the prepared thin films. Steady‐state fluorescence spectroscopy and absolute PL quantum yield were used for the investigation of the luminescent properties. The impressive PL emission and the convenience of preparation in bulk or thin films could be important arguments for a wide area of applications ranging from photonic conversion materials in optoelectronic devices (light‐emitting diodes, flat‐panel displays) to full‐colour watermarks on special‐purpose papers or PL inks and coatings. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Introduction. The aim of the present study was to evaluate, by atomic force microscopy (ATM), the surface condition and roughness parameters of low viscosity composite resins after exposure to Coca-Cola acidic drink under different immersion regimes. Materials and methods. The materials used in the present study were Filtek Ultimate Flowable Restorative(3M ESPE, St. Paul, MN, USA) and BrilliantFlow (COLTENE Whaledent, Switzerland). 20 cylindrical 5 mm in diameter and 2 mm thick samples were made from each material using plastic conformers placed on glass plates. The samples were light-cured for 40 s on both sides through the glass plates, to ensure complete polymerization of the material, then divided into two groups, as follows: Group I. Filtek Ultimate Flowable Restorative, and Group II. Brilliant Flow. Specimens from each group were then randomly divided into 5 subgroups: subgroup A, consisting of 4 control samples kept only in artificial saliva, and subsets B-E, consisting of 4 samples, one for each of the 4 immersion protocols in Coca Cola drink. The surface state of all samples was analyzed by atomic force microscopy and the roughness parameters were calculated. Results and discussion. The samples subjected to immersion in Coca-Cola were strongly corroded, compared to the control ones. The highest surface roughness value was determined for samples submerged 3 times/day in Coca Cola. Meantime, a higher Ra value was determined for the Filtek Ultimate Flowable composite than for Brilliant Flow. Conclusions. Evaluation of the surface condition of samples after immersion revealed in both materials a pattern of pitting corrosion, namely micro-holes and a preferential corrosion direction more obvious on the samples subjected to three immersions per day. [ABSTRACT FROM AUTHOR]

Highly luminescent composites were prepared through embedding newly developed carbon dots (C-Dots) derived from N-hydroxyphthalimide in PS, PVC and PC polymer matrices. N-hydroxyphthalimide was found to be an excellent precursor for obtaining C-Dots through a simple pyrolytic process. The C-Dots prepared by the described method are highly luminescent with an absolute quantum yield of 79.95 % which is among the highest values reported up to date. The resulted composites preserve the remarkable photoluminescent properties of the embedded C-Dots. The composites were processed in thin films or various shaped monoliths. Prior to embedment, the composition and morphology of the prepared C-Dots were investigated by XPS, FT-IR, P-XRD, DLS TEM and fluorescence spectroscopy whereas the prepared composites were investigated by AFM. Due to their truly remarkable photoluminescent properties and facile fabrication, the prepared C-Dots and related composites could be of interest for applications ranging from sensors to solar energy conversion and light-emitting devices. As will be described later, one suggested straightforward application is the UV protection of various sensitive surfaces provided by thin layers of prepared composites. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the surface condition, after finishing and polishing with 3 different systems, of a flowable composite material, starting from the microstructure experimentally analyzed by atomic force microscopy. Materials and method. The material tested in the present study was Filtek Ultimate Flowable Restorative (3M ESPE) composite. 20 cylindrical samples, 5 mm in diameter and 2 mm thick, were prepared by using metallic molds. The samples were randomly divided into 4 groups: a group containing 5 control samples, not subjected to finishing and 3 groups formed, each, of 5 samples for each of the three finishing and polishing systems, respectively system 1: the two-step Sof-Lex (3M ESPE), system 2: multi-step Super Snap (Shofu, Inc. Kyoto, Japan) and system 3: multi-step OptiDisc (KerrHawe SA, Switzerland). The surfaces of the samples were analyzed by atomic force microscopy. For quantitative evaluations, the rugosity parameter (Ra), and the mean deviation of the determined profile were calculated. Results. All 3 polishing systems determined an increase of the Ra parameter, comparatively with the control samples; the highest mean Ra value, of 1.19 µm, was recorded for system 3, followed by system 2 (mean Ra value = 1.12 µm), while the lowest mean value, of 1.10 µm, was registered for system 1. Conclusions. All three systems under investigation induced increased rugosity on the surfaces of the samples prepared from the Filtek Ultimate Flowable Restorative (3M ESPE) composite resin. The most abrasive system appears to be OptiDisc (KerrHawe SA, Switzerland), followed by the Super Snap (Shofu, Inc. Kyoto, Japan) system, the one recording the lowest abrasion being Sof-Lex (3M ESPE). [ABSTRACT FROM AUTHOR]

Currently most of the applications of silver nanoparticles are in antibacterial/antifungal agents in medicine and biotechnology, textile engineering, water treatment and silver-based consumer products. However, the effects of silver nanoparticles on human body, especially on the central nervous system, are still unclear. To study the mechanisms underlying the effects of silverpoly(amidehydroxyurethane) coated silver nanoparticles on brain functions, we subjected male Wistar rats to chronic treatments with silver-29 nm (5 µg/kg and 10 µg/kg) and silver-23 nm (5 µg/kg and 10 µg/kg) nanoparticles for 7 days. We evaluated the effects of nanoparticles size and structure on rat memory function. Memory processes were studied by means of two cognitive tasks (Y-maze and radial arm-maze). Exposure to silver nanoparticles significantly decreased spontaneous alternation in the Y-maze task and working memory functions in the radial arm-maze task, suggesting that nanoparticles have effects on short-term memory. We found no effects on long-term memory, which we assessed by reference memory trials in the radial arm-maze task. We found that memory deficits were significantly correlated with oxidative stress generation only in the Y-maze task. Our findings suggest that silver nanoparticles may induce an impairment of memory functions by increasing oxidative stress in the brain. The use of silver nanoparticles for medical purposes therefore requires careful consideration, particularlyif it involves exposure of the human brain. [ABSTRACT FROM AUTHOR]