Thermal Evolution of C-Fe-Bi Nanocomposite System: From Nanoparticle Formation to Heterogeneous Graphitization Stage.

Carbon xerogel nanocomposites with integrated Bi and Fe particles (C­Bi­Fe) represent an interesting model of carbon nanostructures decorated with multifunctional nanoparticles (NPs) with applicability for electrochemical sensors and catalysts. The present study addresses the fundamental aspects of the catalyzed growth of nano-graphites in C­Bi­Fe systems, relevant in charge transport and thermo-chemical processes. The thermal evolution of a C­Bi­Fe xerogel is investigated using different pyrolysis treatments. At lower temperatures (~750°C), hybrid bismuth iron oxide (BFO) NPs are frequently observed, while graphitization manifests under more specific conditions such as higher temperatures (~1,050°C) and reduction yields. An in situ heating TEM experiment reveals graphitization activity between 800 and 900°C. NP motion is directly correlated with textural changes of the carbon support due to the catalyzed growth of graphitic nanoshells and nanofibers as confirmed by HR-TEM and electron tomography (ET) for the graphitized sample. An exponential growth model for the catalyst dynamics enables the approximation of activation energies as 0.68 and 0.29­0.34 eV during reduction and graphitization stages. The results suggest some similarities with the tip growth mechanism, while oxygen interference and the limited catalyst­feed gas interactions are considered as the main constraints to enhanced growth.

The Effect of the Reducing Sugars in the Synthesis of Visible-Light-Active Copper(I) Oxide Photocatalyst.

In the present work, shape tailored Cu2O microparticles were synthesized by changing the nature of the reducing agent and studied subsequently. d-(+)-glucose, d-(+)-fructose, d-(+)xylose, d-(+)-galactose, and d-(+)-arabinose were chosen as reducing agents due to their different reducing abilities. The morpho-structural characteristics were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS), while their photocatalytic activity was evaluated by methyl orange degradation under visible light (120 min). The results show that the number of carbon atoms in the sugars affect the morphology and particle size (from 250 nm to 1.2 µm), and differences in their degree of crystallinity and photocatalytic activity were also found. The highest activity was observed when glucose was used as the reducing agent.

The Impact of Composites with Silicate-Based Glasses and Gold Nanoparticles on Skin Wound Regeneration.

The silver content of the skin regeneration ointments can influence its regeneration process but in the meantime, it can take the benefit of the antibacterial properties of silver by avoiding the bacterial infection of an open wound. In the current study, the skin healing and regeneration capacity of bioactive glass with spherical gold nanocages (BGAuIND) in the Vaseline ointments were evaluated in vivo comparing the bioactive glass (BG)-Vaseline and bioactive glass with spherical gold (BGAuSP)-Vaseline ointments. Spherical gold nanocages are stabilized with silver and as a consequence the BGAuIND exhibits great antibacterial activity. Histological examination of the cutaneous tissue performed on day 8 indicates a more advanced regeneration process in rats treated with BGAuSP-Vaseline. The histopathological examination also confirms the results obtained after 11 days post-intervention, when the skin is completely regenerated at rats treated with BGAuSP-Vaseline compared with the others groups where the healing was incomplete. This result is also confirmed by the macroscopic images of the evolution of wounds healing. As expected, the silver content influences the wound healing process but after two weeks, for all of the post-interventional trials from the groups of rats, the skin healing was completely.

Multi-analyses of gallstones and correlation between their properties with the laboratory results.

This study explores the morpho-structure of gallstones (GSs) removed from 36 patients in NW Romania and correlate it with the laboratory results of the patients. GSs were analyzed by SEM-EDS, X-ray diffraction and IR, UV-Vis and X-ray photoelectron spectroscopy. The laboratory studies consisted in hematological, coagulation, biochemistry, immunological and tumor markers tests. The morphological and structural investigations allowed to classify the GS in five different types and to establish their mechanism of formation. Only macroscopic evaluation, SEM microscopy, FTIR and UV-Vis spectroscopy give different easily noticeable information for each GS type. EDS, XPS and XRD diffraction are recommended to distinguish pigment and carbonate stones from the other GS types and a carefully examination is needed to establish the differences between the pure cholesterol, the mixed cholesterol and the composite cholesterol stones, due to the high similarities. The variation of specific markers cannot differentiate the patients with pure cholesterol GS from those with mixed cholesterol and pigment GS and those with mixed cholesterol from those with composite cholesterol stones. Seven laboratory parameters (RDW-CV, MPV, PCT, GLUC-HK, WBC, PT, GPT) are the key indicators for the GS disease and trend to present generally higher values than normal.

New Insights into The Photoactivity of Shape-Tailored BiVO4 Semiconductors via Photocatalytic Degradation Reactions and Classical Reduction Processes.

In the present study, additive-free, pH-driven, hydrothermal crystallization was used to obtain shape-tailored monoclinic BiVO4 photocatalysts. The as-prepared BiVO4 products were systematically characterized, uncovering their crystallographic, morphologic and optical properties, while their applicability was verified in the visible light-driven photodegradation of oxalic acid and rhodamine B. Monoclinic clinobisvanite was obtained in most cases, with their band gap values located between 2.1 and 2.4 eV. The morphology varied from large, aggregated crystals, individual microcrystals to hierarchical microstructures. It was found that the degradation efficiency values obtained in the case of oxalic acid were directly related to the presence of (040) crystallographic plane, while the degradation of rhodamine B was partially independent by the presence of this structural feature. The importance of (040) crystallographic plane was also demonstrated via the reduction of Cu2+ to Cu, by analyzing the Raman spectra of the Cu containing samples, the mean primary crystallite size of Cu and Cu content. Furthermore, the presence of (040) crystallographic plane was directly proportional with the hydrodynamic properties of the powders as well.

Carbon Xerogel Nanostructures with Integrated Bi and Fe Components for Hydrogen Peroxide and Heavy Metal Detection.

Multifunctional Bi- and Fe-modified carbon xerogel composites (CXBiFe), with different Fe concentrations, were obtained by a resorcinol-formaldehyde sol-gel method, followed by drying in ambient conditions and pyrolysis treatment. The morphological and structural characterization performed by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption/desorption porosimetry, scanning electron microscopy (SEM) and scanning/transmission electron microscopy (STEM) analyses, indicates the formation of carbon-based nanocomposites with integrated Bi and Fe oxide nanoparticles. At higher Fe concentrations, Bi-Fe-O interactions lead to the formation of hybrid nanostructures and off-stoichiometric Bi2Fe4O9 mullite-like structures together with an excess of iron oxide nanoparticles. To examine the effect of the Fe content on the electrochemical performance of the CXBiFe composites, the obtained powders were initially dispersed in a chitosan solution and applied on the surface of glassy carbon electrodes. Then, the multifunctional character of the CXBiFe systems is assessed by involving the obtained modified electrodes for the detection of different analytes, such as biomarkers (hydrogen peroxide) and heavy metal ions (i.e., Pb2+). The achieved results indicate a drop in the detection limit for H2O2 as Fe content increases. Even though the current results suggest that the surface modifications of the Bi phase with Fe and O impurities lower Pb2+ detection efficiencies, Pb2+ sensing well below the admitted concentrations for drinkable water is also noticed.

Optical Properties of Composites Based on Graphene Oxide and Polystyrene.

In this work, new optical properties of composites based on polystyrene (PS) microspheres and graphene oxide (GO) are reported. The radical polymerization of styrene in the presence of benzoyl peroxide, pentane and GO induces the appearance of new ester groups in the PS macromolecular chains remarked through an increase in the absorbance of the infrared (IR) band at 1743 cm-1. The decrease in the GO concentration in the PS/GO composites mass from 5 wt.% to 0.5 wt.% induces a diminution in the intensities of the D and G Raman bands of GO simultaneous with a down-shift of the D band from 1351 to 1322 cm-1. These variations correlated with the covalent functionalization of the GO layers with PS. For the first time, the photoluminescent (PL) properties of PS/GO composites are reported. The PS microspheres are characterized by a PL band at 397 nm. Through increasing the GO sheets' concentration in the PS/GO composite mass from 0.5 wt.% to 5 wt.%, a PS PL quenching process is reported. In addition, in the presence of ultraviolet A (UVA) light, a photo-degradation process of the PS/GO composite having the GO concentration equal to 5 wt.% is demonstrated by the PL studies.

The Comparison of the Photocatalytic Performance Shown by TiO2 and TiO2/WO3 Composites- A Parametric and Kinetic Study.

Kinetic and mechanistic related approaches for mostly titania were intensively studied in the literature. However, combined modelling and kinetic studies are few. Therefore, the present work focuses on modelling the dependence of the degradation kinetics of two model compounds (salicylic acid-SA and methyl orange-MO) on Evonik Aeroxide P25, hydrothermally prepared hierarchical TiO2 and P25/WO3 nanostars, obtained also by hydrothermal crystallization. The obtained individual semiconductors and the composites were characterized using XRD, DRS, SEM, while the photocatalytic degradation of the model pollutants were carried out varying the catalyst load, the initial pollutant concentration and incident light intensity. It was found that the degradation kinetics were independent from the hierarchical nature of the material, while significant dependencies of the degradation efficiency was found from the previously mentioned investigation parameters. All these parametric interdependences were successfully studied and a kinetic model was proposed for both bare TiO2 and TiO2/WO3 composite systems.

Detailed Investigation of Phenol Degradation on Au/TiO2 Composite Materials.

Photocatalytic applicability of different TiO2-based nanomaterials is a current hot topic. Therefore, our interest for the present research was to elucidate the formation of primary and secondary intermediates during the phenol degradation by photocatalysis, in the presence of Au/TiO2 nanocomposites. The composites consisted of differently shaped gold nanoparticles and commercial titania (Evonik Aeroxide P25). The obtained composites and the noble metal nanoparticles' morphology was investigated by Transmission Electron Microscopy (TEM), their optical properties were explored using Diffuse Reflectance Spectroscopy (DRS), while the crystal structure was characterized by X-ray diffraction (XRD). The photocatalytic activity was investigated by photodegradation of phenol and methyl orange. In case of phenol it was shown that, the formation of degradation intermediates, was dependent on the Au nanoparticles' shape, leading to high amounts of different intermediates as follows: hydroquinone for composites with spherical Au nanoparticles, 1,2,4-trihydroxy-benzene for triangle shaped nanoparticles, and pyrocatechol for TiO2.

TiO2-Alginate-Chitosan-Based Composites for Skin Tissue Engineering Applications.

The UV-B component of sunlight damages the DNA in skin cells, which can lead to skin cancer and premature aging. Therefore, it is necessary to use creams that also contain UV-active substances. Many sunscreens contain titanium dioxide due to its capacity to absorb UV-B wavelengths. In the present study, titan dioxide was introduced in alginate and chitosan-alginate hydrogel composites that are often involved as scaffold compositions in tissue engineering applications. Alginate and chitosan were chosen due to their important role in skin regeneration and skin protection. The composites were cross-linked with calcium ions and investigated using FT-IR, Raman, and UV-Vis spectroscopy. The stability of the obtained samples under solar irradiation for skin protection and regeneration was analyzed. Then, the hydrogel composites were assayed in vitro by immersing them in simulated body fluid and exposing them to solar simulator radiation for 10 min. The samples were found to be stable under solar light, and a thin apatite layer covered the surface of the sample with the two biopolymers and titanium dioxide. The in vitro cell viability assay suggested that the anatase phase in alginate and chitosan-alginate hydrogel composites have a positive impact.

The Impact of Ar or N2 Atmosphere on the Structure of Bi-Fe-Carbon Xerogel Based Composites as Electrode Material for Detection of Pb2+ and H2O2.

In this study, bismuth- and iron-embedded carbon xerogels (XG) were obtained using a modified resorcinol formaldehyde sol-gel synthesis method followed by additional enrichment with iron content. Pyrolysis treatment was performed at elevated temperatures under Ar or N2 atmosphere to obtain nanocomposites with different reduction yields (XGAr or XGN). The interest was focused on investigating the extent to which changes in the pyrolysis atmosphere of these nanocomposites impact the structure, morphology, and electrical properties of the material and consequently affect the electroanalytical performance. The structural and morphological particularities derived from X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements revealed the formation of the nanocomposite phases, mostly metal/oxide components. The achieved performances for the two modified electrodes based on XG treated under Ar or N2 atmosphere clearly differ, as evidenced by the electroanalytical parameters determined from the detection of heavy metal cations (Pb2+) or the use of the square wave voltammetry (SWV) technique, biomarkers (H2O2), or amperometry. By correlating the differences obtained from electroanalytical measurements with those derived from morphological, structural, and surface data, a few utmost important aspects were identified. Pyrolysis under Ar atmosphere favors a significant increase in the α-Fe2O3 amount and H2O2 detection performance (sensitivity of 0.9 A/M and limit of detection of 0.17 µM) in comparison with pyrolysis under N2 (sensitivity of 0.5 A/M and limit of detection of 0.36 µM), while pyrolysis under N2 atmosphere leads to an increase in the metallic Bi amount and Pb2+ detection performance (sensitivity of 8.44 × 103 A/M and limit of detection of 33.05 pM) in comparison with pyrolysis under Ar (sensitivity of 6.47·103 A/M and limit of detection of 46.37 pM).

Photoinhibitive Properties of α-MoO3 on Its Composites with TiO2, ZnO, BiOI, AgBr, and Cu2O.

Orthorhombic molybdenum trioxide (α-MoO3) is well known as a photocatalyst, adsorbent, and inhibitor during methyl orange photocatalytic degradation via TiO2. Therefore, besides the latter, other active photocatalysts, such as AgBr, ZnO, BiOI, and Cu2O, were assessed via the degradation of methyl orange and phenol in the presence of α-MoO3 using UV-A- and visible-light irradiation. Even though α-MoO3 could be used as a visible-light-driven photocatalyst, our results demonstrated that its presence in the reaction medium strongly inhibits the photocatalytic activity of TiO2, BiOI, Cu2O, and ZnO, while only the activity AgBr is not affected. Therefore, α-MoO3 might be an effective and stable inhibitor for photocatalytic processes to evaluate the newly explored photocatalysts. Quenching the photocatalytic reactions can offer information about the reaction mechanism. Moreover, the absence of photocatalytic inhibition suggests that besides photocatalytic processes, parallel reactions take place.

Ultrasensitive Electroanalytical Detection of Pb2+ and H2O2 Using Bi and Fe-Based Nanoparticles Embedded into Porous Carbon Xerogel-The Influence of Nanocomposite Pyrolysis Temperatures.

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension.

Anionic Polysaccharide Cryogels: Interaction and In Vitro Behavior of Alginate-Gum Arabic Composites.

In the present study, polysaccharide-based cryogels demonstrate their potential to mimic a synthetic extracellular matrix. Alginate-based cryogel composites with different gum arabic ratios were synthesized by an external ionic cross-linking protocol, and the interaction between the anionic polysaccharides was investigated. The structural features provided by FT-IR, Raman, and MAS NMR spectra analysis indicated that a chelation mechanism is the main process linking the two biopolymers. In addition, SEM investigations revealed a porous, interconnected, and well-defined structure suitable as a scaffold in tissue engineering. The in vitro tests confirmed the bioactive character of the cryogels through the development of the apatite layer on the surface of the samples after immersion in simulated body fluid, identifying the formation of a stable phase of calcium phosphate and a small amount of calcium oxalate. Cytotoxicity tests performed on fibroblast cells demonstrated the non-toxic effect of alginate-gum arabic cryogel composites. In addition, an increase in flexibility was noted for samples with a high gum arabic content, which determines an appropriate environment to promote tissue regeneration. The newly obtained biomaterials that exhibit all these properties can be successfully involved in the regeneration of soft tissues, wound management, or controlled drug release systems.

The evaluation of the osteopromoting capabilities of composites based on biopolymers and gold/silver nanoparticles doped bioactive glasses on an experimental rat bone defect.

The most important concept behind using bone scaffolds is the biocompatibility of the material to avoid a local inflammatory response and must have the following properties: osteoinduction, osteoconductivity, angiogenesis, and mechanical support for cell growth. Gold nanoparticles/gold and silver nanoparticles -containing bioactive glasses in biopolymer composites have been used to enhance bone regeneration. These composites were testedin vitroon fibroblast and osteoblast cell lines using MTT tests, immunofluorescence, scanning electron microscopy analysis, andin vivoin an experimental bone defect in Sprague-Dawley rats. Both composites promoted adequate biological effects on human fibroblastic BJ (CRL 2522TM) cell lines and human osteoblastic cells isolated from the human patella in terms of cell proliferation, morphology, migration, and attachment. Most importantly, they did not cause cellular apoptosis and necrosis. According to the histological and immunohistochemical results, both composites were osteoinductive and promoted new bone formation at 60 d. Evidence from this study suggests that the small amount of silver content does not influence negatively thein vitroorin vivoresults. In addition, we obtained accurate results proving that the existence of apatite layer and proteins on the surface of the recovered composite, supports the validity ofin vitrobioactivity research.

Insights into the Stability of Graphene Oxide Aqueous Dispersions.

Understanding graphene oxide's stability (or lack thereof) in liquid solvents is critical for fine-tuning the material's characteristics and its potential involvement in future applications. In this work, through the use of structural and surface investigations, the alteration of the structural and edge-surface properties of 2D graphene oxide nanosheets was monitored over a period of eight weeks by involving DLS, zeta potential, XRD, XPS, Raman and FT-IR spectroscopy techniques. The samples were synthesized as an aqueous suspension by an original modified Marcano-Tour method centred on the sono-chemical exfoliation of graphite. Based on the acquired experimental results and the available literature, a phenomenological explanation of the two underlying mechanisms responsible for the meta-stability of graphene oxide aqueous dispersions is proposed. It is based on the cleavage of the carbon bonds in the first 3-4 weeks, while the bonding of oxygen functional groups on the carbon lattice occurs, and the transformation of epoxide and hydroxyl groups into adsorbed water molecules in a process driven by the availability of hydrogen in graphene oxide nanosheets.

Bioactive Properties of Composites Based on Silicate Glasses and Different Silver and Gold Structures.

Using an ideal biomaterial to treat injured bones can accelerate the healing process and simultaneously exhibit antibacterial properties; thus protecting the patient from bacterial infections. Therefore, the aim of this work was to synthesize composites containing silicate-based bioactive glasses and different types of noble metal structures (i.e., AgI pyramids, AgIAu composites, Au nanocages, Au nanocages with added AgI). Bioactive glass was used as an osteoconductive bone substitute and Ag was used for its antibacterial character, while Au was included to accelerate the formation of new bone. To investigate the synergistic effects in these composites, two syntheses were carried out in two ways: AgIAu composites were added in either one step or AgI pyramids and Au nanocages were added separately. All composites showed good in vitro bioactivity. Transformation of AgI in bioactive glasses into Ag nanoparticles and other silver species resulted in good antibacterial behavior. It was observed that the Ag nanoparticles remained in the Au nanocages, which was also beneficial in terms of antibacterial properties. The presence of Au nanoparticles contributed to the composites achieving high cell viability. The most outstanding result was obtained by the consecutive addition of noble metals into the bioactive glasses, resulting in both a high antibacterial effect and good cell viability.

Rapid Synthesis Method of Ag3PO4 as Reusable Photocatalytically Active Semiconductor.

The widespread use of Ag3PO4 is not surprising when considering its higher photostability compared to other silver-based materials. The present work deals with the facile precipitation method of silver phosphate. The effects of four different phosphate sources (H3PO4, NaH2PO4, Na2HPO4, Na3PO4·12 H2O) and two different initial concentrations (0.1 M and 0.2 M) were investigated. As the basicity of different phosphate sources influences the purity of Ag3PO4, different products were obtained. Using H3PO4 did not lead to the formation of Ag3PO4, while applying NaH2PO4 resulted in Ag3PO4 and a low amount of pyrophosphate. The morphological and structural properties of the obtained samples were studied by X-ray diffractometry, diffuse reflectance spectroscopy, scanning electron microscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity of the materials and the corresponding reaction kinetics were evaluated by the degradation of methyl orange (MO) under visible light. Their stability was investigated by reusability tests, photoluminescence measurements, and the recharacterization after degradation. The effect of as-deposited Ag nanoparticles was also highlighted on the photostability and the reusability of Ag3PO4. Although the deposited Ag nanoparticles suppressed the formation of holes and reduced the degradation of methyl orange, they did not reduce the performance of the photocatalyst.

Gypsum Composite Boards Incorporating Phase Change Materials: A Review.

The purpose of this review is to provide an overview of the available gypsum based composite including various phase change materials employed to increase the thermal energy storage capacity of building materials. A wide range of materials such as n-alkane, saturated fatty acid, fatty acid esters etc are used as phase change materials. Adding carbonaceous material (carbon nanofibers, activated nanocarbon, graphite nanosheets etc.) to augment some properties is also a common practice. In addition, there are presented the methods of obtaining the nano/macro-composites together with some thermal characteristics of the newly prepared materials.