Enhanced Photocatalytic Properties of All-Organic IDT-COOH/O-CN S-Scheme Heterojunctions Through π-π Interaction and Internal Electric Field.

Herein, we present a distinct methodology for the in situ electrostatic assembly method for synthesizing a conjugated (IDT-COOH)/oxygen-doped g-C3N4 (O-CN) S-scheme heterojunction. The electron delocalization effect due to π-π interactions between O-CN and self-assembled IDT-COOH favors interfacial charge separation. The self-assembled IDT-COOH/O-CN exhibits a broadened visible absorption to generate more charge carriers. The internal electric field between the IDT-COOH and the O-CN interface provides a directional charge-transfer channel to increase the utilization of photoinduced charge carriers. Moreover, the active species (•O2-, h+, and 1O2) produced by IDT-COOH/O-CN under visible light play important roles in photocatalytic disinfection. The optimum 40% IDT-COOH/O-CN can kill 7-log of methicillin-resistant Staphylococcus aureus (MRSA) cells in 2 h and remove 88% tetracycline (TC) in 5 h, while O-CN only inactivates 1-log of MRSA cells and degrades 40% TC. This work contributes to a promising method to fabricate all-organic g-C3N4-based S-scheme heterojunction photocatalysts with a wide range of optical responses and enhanced exciton dissociation.

Metal Oxide-Related Dendritic Structures: Self-Assembly and Applications for Sensor, Catalysis, Energy Conversion and Beyond.

In the past two decades, we have learned a great deal about self-assembly of dendritic metal oxide structures, partially inspired by the nanostructures mimicking the aesthetic hierarchical structures of ferns and corals. The self-assembly process involves either anisotropic polycondensation or molecular recognition mechanisms. The major driving force for research in this field is due to the wide variety of applications in addition to the unique structures and properties of these dendritic nanostructures. Our purpose of this minireview is twofold: (1) to showcase what we have learned so far about how the self-assembly process occurs; and (2) to encourage people to use this type of material for drug delivery, renewable energy conversion and storage, biomaterials, and electronic noses.

Transdermal nanotherapeutics: Panax quinquefolium polysaccharide nanoparticles attenuate UVB-induced skin cancer.

Ultraviolet (UV) radiation is known to cause an imbalance of the endogenous antioxidant system leading to an increase in skin cancer. Panax quinquefolium (American ginseng) polysaccharides (GPS) can inhibit such an imbalance due to its anti-oxidative and anti-inflammatory properties. The aim of this study was to investigate the therapeutic effects of topical formulations containing GPS nanoparticles (NPs) to inhibit UVB induced oxidative damage and skin cancer. Photoaging was conducted under UVB irradiation with a dose of 300 mJ/cm2 on SKH1 hairless mice. The treatment groups (n = 5) were as follows: sham control, native GPS, GPS NPs and fluorescent labeled GPS NPs. To compare the photoprotective performance, the topical formulations were applied before and after UVB induction (pre-treatment and post-treatment), followed by sacrificing the animals. Then, skin and blood samples were collected, and inflammatory cytokines production was measured using ELISA. Compared to the sham control, GPS NPs pre-treated mice skin and blood samples exhibited a significant lowering in all cytokine production. In addition, skin histology analysis showed that pre-treatment of GPS NPs prevented epidermal damage and proliferation. The results support that topical formulation containing GPS NPs can inhibit UVB induced oxidative damage and skin cancer.

Synthesizing 1D and 2D metal oxide nanostructures: using metal acetate complexes as building blocks.

1D and 2D metal oxide nanostructures are important for potential applications in alternative energy, batteries, supercapacitors, catalysts, biomaterials, and electronic nanodevices. Many current approaches for making the desired nanomaterials require multiple steps, which are often exotic and complex for production on a commercial scale. In contrast, the sol-gel reactions between metal alkoxides and organic acids have emerged as a simple protocol for producing metal oxides and inorganic/organic hybrid materials with a controllable 1D or 2D architecture. Our knowledge of this process continues to evolve through the fundamental goal of designing a desired nanostructure from the corresponding molecular building blocks. Our research was driven by the discovery of various morphologies by fine-tuning the synthesis parameters, such as the reaction temperature and molar ratio of the reactants, as well as switching solvents. These discoveries lead to several quesions: What are the building blocks of the 1D and 2D nanostructures and how does the self-assembly occur? What are the reaction kinetics and the mechanisms of nanostructure formation? What role does the solvent play in the assembly process? What are the effects of reaction temperature and pressure? How can we manipulate the nanostructure-for example, the parallel growth of 1D semiconductors-from a substrate surface? And lastly, what are the industrial applications of macroporous aerogels and xerogels? This minireview will highlight documented research accounts to answer these questions.

Impact of the chemical nature and position of spacers on controlling the optical properties of silicon quantum dots.

The unique properties of silicon quantum dots (SQDs), including intriguing optical properties, biocompatibility, and ease of surface modification have made them excellent candidates for a variety of optoelectronic and biomedical applications. Unfortunately, the low quantum efficiency (QE), unstable photoluminescence, and poor colloidal stability of SQDs have hindered their wide applicability. Herein, we report the synthesis of four assemblies of SQDs (1.6-1.8 nm average diameter) functionalized with fluorescein dye through isothiocyanate (-NCS) and carboxylate (COO-) spacers in the benzene ring of the fluorescein to produce the dyads Am-SQD-Fl, DiAm-SQD-Fl, urea-SQD-Fl, and SQD-Fl. The photophysical measurements showed that the spacer played a key role in directing and controlling the optical properties of SQDs dyads, with the isothiocyanate spacer leading to a significant improvement in the QE of the dyad systems up to 65% and extending their photostability for at least one year. The interactions between the SQDs and fluorescein in the dyads Am-SQD-Fl, DiAm-SQD-Fl, and SQD-Fl were found to mainly proceed through photoinduced electron transfer at different rates, while energy transfer was confirmed to be the predominant process in the dyad urea-SQD-Fl. To demonstrate the suitability of the functionalized SQDs for bioimaging applications, the water-soluble dyads were examined for fluorescence imaging of human bone cancerous U2OS cells.

Photocatalytic and antibacterial activities of silver and iron doped titania nanoparticles in solution and polyaspartic coatings.

Visible region active photocatalytic coatings are of interest for antimicrobial activity in low light applications or those employing LED lights with limited UV content. This work examined Ag and Fe doped titania nanoparticles (nTiO2) with varying dopant ranges in polyaspartic polymer coatings for potential light and dark activity. First, the Ag and Fe doped nTiO2 were synthesized by sol-gel chemistry with varying dopant concentrations, then characterized with respect to their size and aggregate size distribution, crystallinity, and surface and band gap features. The photocatalytic activity was then tested with methylene blue under both AM 1.5 G and visible light. From both sample sets (Ag and Fe doped nTiO2), the best photo catalytically active sample materials were chosen for antibacterial tests with gram-negative Escherichia coli (E. coli) and gram-positive Bacillus subtilis (B. subtilis) in (a) solution and (b) polyaspartic nanocomposites under UV and visible irradiation. The results showed that Ag doped nTiO2 samples delivered the best and excellent antibacterial action, even in the dark, attributed to both an enhanced band gap and surface area, as well as a combination of photocatalytic activity and Ag being present at the nanoparticle's surface. No leaching of Ag at room temperature was observed from the nTiO2 structure, giving potential for next generation coatings that are both light and dark active.

Immunoengineering with Ginseng Polysaccharide Nanobiomaterials through Oral Administration in Mice.

Plant polysaccharides (PS) such as American ginseng polysaccharide (GPS) have drawn immense interest in the field of immunoengineering, as they offer a way to actively control immune cell behavior and stimulation. These pharmacological activities have been limited by PS's inherent physicochemical properties including large molecular size, heterogeneity, and poor solubility. In this work, we hypothesized that by nanosizing and encapsulating GPSs, we could enhance their immunomodulation by increased penetration and absorption through the GI tract. Herein, GPS nanoparticles (NPs) of average size 20 nm (± 4 nm) were prepared using a microfluidic approach, then encapsulated within porous nanospheres (diameter 180 ± 10 nm) of biodegradable gelatin to enhance their oral delivery. To locate the GPS NPs inside the gelatin, we encapsulated fluorescent-labeled GPS in gelatin and analyzed using confocal microscopy. An in vitro investigation on tumor induced macrophage cell lines showed a concentration dependent enhanced immunostimulation with the encapsulated GPS NPs. The immunomodulation was then studied for different formulations of GPS through oral gavage in Swiss albino mice. The results showed that the production of proinflammatory mediators in blood samples was significantly increased for the encapsulated GPS in a dose- and time-dependent manner compared to other GPS treatments. This study shows that GPS and potentially other PS systems' immunomodulation properties can be significantly enhanced for use in simple oral drug delivery.

Syntheses, crystal structures, adsorption properties and visible photocatalytic activities of highly stable Pb-based coordination polymers constructed by 2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline and bridging linkers.

Five highly stable coordination polymers assembled by 2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline (2-HNCP) and different aromatic carboxylic acid ligands, namely, [Pb(2-NCP)(L1)]n (1), [Pb2(2-NCP)2(L2)]n·2nH2O (2), [Pb2(2-NCP)2(L2)]n (3), [Pb(2-NCP)(L3)0.5]n (4) and [Pb2(2-NCP)2(L4)]n (5), where HL1 = pyridine-4-carboxylic acid, H2L2 = 2-amino-1,4-benzenedicarboxylic acid, H2L3 = 1,4-benzenedicarboxylic acid and H2L4 = 2-hydroxy-1,4-benzenedicarboxylic acid, have been synthesized under hydrothermal conditions. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses and infrared spectroscopy. In 1, adjacent ladder-like chains are extended into a three-dimensional (3D) supramolecular architecture by π-π interactions. In 2, the neighboring layers are interconnected by π-π interactions to afford a 3D supramolecular architecture. 3-5 exhibit similar 3D frameworks with a Schläfli symbol of 412·63 topologies. The different auxiliary ligands and the pH value of the reaction system were discussed in regard to the formation of different structures. In addition, these five complexes present high thermal stabilities, the preferential adsorption of CO2 over N2 and excellent photocatalytic activities for dye degradation under visible light irradiation.

Tuning the Optical Properties of Silicon Quantum Dots via Surface Functionalization with Conjugated Aromatic Fluorophores.

Silicon Quantum Dots (SQDs) have recently attracted great interest due to their excellent optical properties, low cytotoxicity, and ease of surface modification. The size of SQDs and type of ligand on their surface has a great influence on their optical properties which is still poorly understood. Here we report the synthesis and spectroscopic studies of three families of unreported SQDs functionalized by covalently linking to the aromatic fluorophores, 9-vinylphenanthrene, 1-vinylpyrene, and 3-vinylperylene. The results showed that the prepared functionalized SQDs had a highly-controlled diameter by HR-TEM, ranging from 1.7-2.1 nm. The photophysical measurements of the assemblies provided clear evidence for efficient energy transfer from the fluorophore to the SQD core. FÓ§rster energy transfer is the likely mechanism in these assemblies. As a result of the photogenerated energy transfer process, the emission color of the SQD core could be efficiently tuned and its emission quantum efficiency enhanced. To demonstrate the potential application of the synthesized SQDs for bioimaging of cancer cells, the water-soluble perylene- and pyrene-capped SQDs were examined for fluorescent imaging of HeLa cells. The SQDs were shown to be of low cytotoxicity.

Continuous Hydrothermal Decarboxylation of Fatty Acids and Their Derivatives into Liquid Hydrocarbons Using Mo/Al2O3 Catalyst.

In this study, we report a single-step continuous production of straight-chain liquid hydrocarbons from oleic acid and other fatty acid derivatives of interest including castor oil, frying oil, and palm oil using Mo, MgO, and Ni on Al2O3 as catalysts in subcritical water. Straight-chain hydrocarbons were obtained via decarboxylation and hydrogenation reactions with no added hydrogen. Mo/Al2O3 catalyst was found to exhibit a higher degree of decarboxylation (92%) and liquid yield (71%) compared to the other two examined catalysts (MgO/Al2O3, Ni/Al2O3) at the maximized conditions of 375 °C, 4 h of space time, and a volume ratio of 5:1 of water to oleic acid. The obtained liquid product has a similar density (0.85 kg/m3 at 15.6 °C) and high heating value (44.7 MJ/kg) as commercial fuels including kerosene (0.78-0.82 kg/m3 and 46.2 MJ/kg), jet fuel (0.78-0.84 kg/m3 and 43.5 MJ/kg), and diesel fuel (0.80-0.96 kg/m3 and 44.8 MJ/kg). The reaction conditions including temperature, volume ratio of water-to-feed, and space time were maximized for the Mo/Al2O3 catalyst. Characterization of the spent catalysts showed that a significant amount of amorphous carbon deposited on the catalyst could be removed by simple carbon burning in air with the catalyst recycled and reused.

Fabrication of fluorescent labeled ginseng polysaccharide nanoparticles for bioimaging and their immunomodulatory activity on macrophage cell lines.

Polysaccharides are a major active component of American ginseng root showing various biological activities including anti-carcinogenic, anti-aging, immunostimulatory and antioxidant effects. Although their biological activity has been reported by several groups, no research has explored their cellular uptake and biodistribution, owing to the lack of suitable detection techniques in living cells. This work examines a novel, simple and efficient fluorescent labeling procedure of ginseng polysaccharides (PS), in order to examine their cellular distribution using confocal microscopy. This procedure utilized a one-pot strategy with fluorescein-5-thiosemicarbazide (FTSC) to introduce a thiosemicarbazide group onto the aldehyde group at the reducing saccharide end to form a stable amino derivative through reductive amination. This polysaccharide-FTSC derivative was then characterized by GPC, UV, FTIR, photoluminescence and fluorescence microscopy to confirm attachment and any structural changes. The results demonstrated that the labeled ginseng PS nanostructure showed high fluorescence with minimal changes in PS molecular weight. The labeled PS exhibited almost no cytotoxicity effect against tumor induced macrophage cell lines (RAW 264.7) while retaining high immunostimulating activity similar to the non-labeled ginseng PS. Therefore, the developed approach provides a convenient and highly efficient fluorescent labeling procedure for understanding the mechanism of ginseng PS uptake in macrophage cell lines.

The effect of silica thickness on nano TiO2 particles for functional polyurethane nanocomposites.

In order to help reduce the agglomeration of TiO2 nanoparticles in polyurethane coatings while enhancing their photoactivity and mechanical/physical properties, this work examined encapsulating TiO2 nanoparticles in a thin layer of SiO2, prior to their nanocomposite polymerization. By applying a Stöber process, varying thicknesses of SiO2 were successfully coated onto the surface of anatase and rutile TiO2 nanoparticles. The methylene blue results showed that different loadings of SiO2 onto the TiO2 surface significantly influenced their photocatalytic activity. When the loading weight of SiO2 was lower than 3.25 wt%, the photocatalytic activity was enhanced, while with higher loadings, it gave lower photocatalytic activity. When the rutile phase TiO2 surface was fully covered with SiO2, an enhanced photocatalytic activity was observed. When these silica coated nanoparticles were applied in polyurethane coatings, increasing the amount of SiO2 on the titania surface increased the coatings contact angle from 75° to 87° for anatase phase and 70°-78° for rutile phase. The Young's modulus was also increased from 1.06 GPa to 2.77 GMPa for anatase phase and 1.06-2.17 GPa for rutile phase, attributed to the silica layer giving better integration. The thermal conductivity of the polyurethane coatings was also successfully decreased by encapsulating SiO2 on the titania surface for next generation high performance coatings.

Angiogenic Rg1 /Sr-Doped TiO2 Nanowire/Poly(Propylene Fumarate) Bone Cement Composites.

A new approach is provided for preparing radiopaque and angiogenic poly(propylene fumarate) (PPF) bone cements by integrating Sr-doped n-TiO2 nanowires and ginsenoside Rg1 suitable for treating osteonecrosis. High aspect ratio radiopaque TiO2 -nanowires are synthesized by strontium doping in supercritical CO2 for the first time, showing a new phase, SrTiO3 . PPF is synthesized using a transesterification method by reacting diethyl fumarate and propylene glycol, then functionalized using maleic anhydride to produce terminal carboxyl groups, which are subsequently linked to the nanowires. The strong interfacial adhesion between functionalized PPF and nanowires is examined by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, thermal analysis, and mechanical testing. An angiogenic modulator, ginsenoside Rg1 , is integrated into the bone cement formulation with the mechanical properties, radiopacity, drug release, and angiogenesis behavior of the formed composites explored. The results show superior radiopacity and excellent release of ginsenoside Rg1 in vitro, as well as a dose-dependent increase in the branching point numbers. The present study suggests this new methodology provides sufficient mechanical properties, radiopacity, and angiogenic activity to be suitable for cementation of necrotic bone.

Nanostructural adsorption of vanadium oxide on functionalized graphene: a DFT study.

Rutile-monoclinic phase transitions of vanadium oxide (VO2) nanocrystals adsorbed on graphene-based substrates are of current scientific interest, although their adsorption and growth mechanisms have not been investigated theoretically. In this study, we use density functional theory (DFT) calculations for determining the binding energies and predicting the corresponding directions of growth of VO2 nanostructures (rutile and M1-monoclinic) interacting with both pure graphene and functionalized graphene nanoribbons. Several adsorption sites of pure graphene including the top, bridge, and hollow sites are considered, while additional adsorption sites of functionalized graphene nanoribbons, epoxy, alcohol and carboxylate are investigated. Vanadium oxide nanostructures are found to favor physical adsorption on the hollow sites of pure graphene, while chemical adsorption is favored on the carboxylate sites of functionalized graphene nanoribbons (FGNRs). Charge density maps showed the electron distribution originating from the interaction between VO2 and graphene substrates, helping to understand the mechanism of charge transfer. Electronic local potentials showed vertical growth tendencies for rutile VO2, while M1-monoclinic VO2 showed horizontal growth tendencies. Partial density of states (PDOS) helped examine the electronic structure of metallic rutile VO2 binding to hollow and carboxylate sites of functionalized graphene. These results provide an improved understanding of the controlled and oriented growth of VO2 nanocrystals on graphene-based substrates which can enable various properties such as the metal-insulator transition (MIT) of VO2 in light regulation applications.

Microfluidic Synthesis of Ginseng Polysaccharide Nanoparticles for Immunostimulating Action on Macrophage Cell Lines.

North American (NA) ginseng root (Panax quinquefolium) has become of increasing scientific interest because of its immune-enhancing properties. Herein, we have developed a novel approach to synthesize ginseng polysaccharide nanoparticles (NPs) from NA ginseng for enhancing their immunostimulation. Nanoparticles of ginseng polysaccharide were prepared using a microfluidic device and compared to other conventional wet chemical processes including nanoprecipitation and reverse microemulsion. The morphology and size of the NPs were characterized by SEM, TEM, DLS and FTIR. Depending on the experimental conditions, microfluidics was found to provide unimodal polysaccharide spheres down to 20 nm (±4 nm) with very narrow particle size distributions. In addition, the immunostimulating effect of the polysaccharide NPs was investigated on Murine macrophage cell lines, with the results revealing an enhanced production of all proinflammatory mediators in a concentration dependent manner. The proposed microfluidic system has the advantages of ease of fabrication, simplicity, and a fast and low-cost process that is capable of producing ginseng polysaccharide NPs with demonstrated enhancement of immunostimulation of macrophage cell lines.

Microfluidic Synthesis and Angiogenic Activity of Ginsenoside Rg1-Loaded PPF Microspheres.

Next generation drug-loaded polymer scaffolds for hard tissue engineering require unique structures to enhance release kinetics while enabling bone cell growth (osteogenesis). This study examined the encapsulation of the pro-angiogenic mediator, ginsenoside Rg1, into biodegradable poly(propylene fumarate) (PPF) microspheres to facilitate osteogenesis, while examining the release mechanism using advanced X-ray absorption near edge structure spectroscopy (XANES). Ginsenoside Rg1-loaded PPF microspheres were prepared using both an emulsion method and a microfluidic device, with the microfluidic technique providing tunable unimodal PPF spheres ranging in size from 3 to 52 µm by varying the flow rates. The morphology and composition of the Rg1-loaded PPF microspheres were characterized using FTIR, XRD, and XANES to examine the distribution of ginsenoside Rg1 throughout the polymer matrix. Encapsulation efficiency and release profiles were studied and quantified by UV-Vis spectrophotometry, showing high encapsulation efficiencies of 95.4 ± 0.8% from the microfluidic approach. Kinetic analysis showed that Rg1 release from the more monodisperse PPF microspheres was slower with a significantly smaller burst effect than from the polydisperse spheres, with the release following Fickian diffusion. The released Rg1 maintained its angiogenic effect in vitro, showing that the PPF microspheres are promising to serve as vehicles for long-term controlled drug delivery leading to therapeutic angiogenesis in bone tissue engineering strategies.

Quantum dots/silica/polymer nanocomposite films with high visible light transmission and UV shielding properties.

The dispersion of light-absorbing inorganic nanomaterials in transparent plastics such as poly(ethylene-co-vinyl acetate) (PEVA) is of enormous current interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Nanocrystalline semiconductor or quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light, which can control plant growth in greenhouses or enhance PV panel efficiencies. This work provides a new and simple approach for loading mesoporous silica-encapsulated QDs into PEVA. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm size were synthesized using a modified facile approach based on pyrolysis of the single-molecule precursors and capping the CdS QDs with a thin layer of ZnS. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown on the QDs through a reverse microemulsion technique based on hydrophobic interactions. By careful experimental tuning, this encapsulation technique enhanced the quantum yield (∼65%) and photostability compared to the bare QDs. Both the encapsulated bare and core-shell QDs were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films with controlled thickness. The results demonstrated for the first time that mesoporous silica not only enhanced the quantum yield and photostability of the QDs but also improved the compatibility and dispersibility of QDs throughout the PEVA films. The novel light selective films show high visible light transmission (∼90%) and decreased UV transmission (∼75%).

Stimulation and suppression of innate immune function by American ginseng polysaccharides: biological relevance and identification of bioactives.

BACKGROUND: Polysaccharides constituting about 10% by weight of ginseng root are known to stimulate the immune system but have recently been shown to also suppress induced proinflammatory responses. Our study aims to determine whether American ginseng root polysaccharides (AGRPS) stimulates basal innate immune function and at the same time can suppress response to lipopolysaccharide (LPS) induced proinflammatory response. An in vitro mechanistic study was used to identify the bioactive fraction(s) responsible for AGRPS immunomodulatory effects. METHODS: The ex vivo and in vivo immunomodulatory effects after oral administration of AGRPS extract was studied in adult rats by measuring cultured alveolar macrophage production of NO and changes of plasma cytokine level, modification of LPS proinflammatory immune response by AGRPS extract was also examined. To identify the bioactive fraction(s) responsible for AGRPS extract immunomodulatory effects, the immunobioactivities of the extract fractions (isolated by ion exchange and size exclusion chromatography) was investigated in an in vitro mechanistic study. RESULTS: Culture of alveolar macrophages obtained from AGRPS extract treated rats resulted in an increase of ex vivo production of NO and also reduced alveolar macrophage responsiveness to ex vivo LPS challenge. Oral treatment with AGRPS extract elevated plasma TNF-α concentration in vivo. This treatment also suppressed LPS induced elevation of plasma TNF-α in vivo. AGRPS extract immunostimulatory and immunosuppressive effects were mediated primarily by acid PS and its species with molecular weights ≥ 100 kDa and 50-100 kDa. CONCLUSION: AGRPS extract exerted immunostimulation and suppressed LPS immune response under basal and LPS induced proinflammatory conditions respectively.

Hydroxyapatite-TiO(2)-based nanocomposites synthesized in supercritical CO(2) for bone tissue engineering: physical and mechanical properties.

Calcium phosphate-based nanocomposites offer a unique solution toward producing scaffolds for orthopedic and dental implants. However, despite attractive bioactivity and biocompatibility, hydroxyapatite (HAp) has been limited in heavy load-bearing applications due to its intrinsically low mechanical strength. In this work, to improve the mechanical properties of HAp, we grew HAp nanoplates from the surface of one-dimensional titania nanorod structures by combining a coprecipitation and sol-gel methodology using supercritical fluid processing with carbon dioxide (scCO2). The effects of metal alkoxide concentration (1.1-1.5 mol/L), reaction temperature (60-80 °C), and pressure (6000-8000 psi) on the morphology, crystallinity, and surface area of the resulting nanostructured composites were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and Brunauer-Emmet-Teller (BET) method. Chemical composition of the products was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure (XANES) analyses. HAp nanoplates and HAp-TiO2 nanocomposites were homogeneously mixed within poly(ε-caprolactone) (PCL) to develop scaffolds with enhanced physical and mechanical properties for bone regeneration. Mechanical behavior analysis demonstrated that the Young's and flexural moduli of the PCL/HAp-TiO2 composites were substantially higher than the PCL/HAp composites. Therefore, this new synthesis methodology in scCO2 holds promise for bone tissue engineering with improved mechanical properties.

Fe doped TiO2-graphene nanostructures: synthesis, DFT modeling and photocatalysis.

In this work, Fe-doped TiO(2) nanoparticles ranging from a 0.2 to 1 weight % were grown from the surface of graphene sheet templates containing -COOH functionalities using sol-gel chemistry in a green solvent, a mixture of water/ethanol. The assemblies were characterized by a variety of analytical techniques, with the coordination mechanism examined theoretically using the density functional theory (DFT). Scanning electron microscopy and transmission electron microscopy images showed excellent decoration of the Fe-doped TiO(2) nanoparticles on the surface of the graphene sheets >5 nm in diameter. The surface area and optical properties of the Fe-doped photocatalysts were measured by BET, UV and PL spectrometry and compared to non-graphene and pure TiO(2) analogs, showing a plateau at 0.6% Fe. Interactions between graphene and Fe-doped anatase TiO(2) were also studied theoretically using the Vienna ab initio Simulation Package based on DFT. Our first-principles theoretical investigations validated the experimental findings, showing the strength in the physical and chemical adsorption between the graphene and Fe-doped TiO(2). The resulting assemblies were tested for photodegradation under visible light using 17ß-estradiol (E2) as a model compound, with all investigated catalysts showing significant enhancements in photocatalytic activity in the degradation of E2.