Streptavidin Fe2O3-gold nanoparticles functionalized theranostic liposome for antibiotic resistant bacteria and biotin sensing

Novel methods of sensing and treatment required to elicit potent humoral and cellular immune responses. Here, Streptavidin functionalized α-Fe2O3-Au nanoparticles (STV-Mag) loaded cationic carbomate cholesterol is used as a carrier to release antibacterial thymol drug for Staphylococcus aureus (S. aureus) infected Caenorhabditis elegans (C. elegans). Pertaining to theranostic applications, efficient antimicrobial activity, and non-stimulated drug release and biotin dependent S. aureus growth were studied in-vivo. While STV-Mag was tethered on mercaptobenzoic acid (MBA) molecular cushion for label free streptavidin-biotin electrochemical sensing, the STV-Mag-carbomate cholesterol (STV-Mag-cCHOL liposome) vesicle with loaded drug was tethered on MBA for non-stimulant drug release through specific cholesterol-S. aureus interaction and confirmed electrochemically. Selectivity was confirmed using other pathogens, E. coli, Proteus and Enterococcus bacterium through antimicrobial studies along with S. aureus. The biotin sensing showed linear range from 10-15 to 10-3 M, which was not obtained by conventional methods. Fourier-Transform Infra-red (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used to characterize the nanoparticulate system.

TEMPO-oxidized cellulose for in situ synthesis of Pt nanoparticles. Study of catalytic and antimicrobial properties

In this work, platinum nanoparticles (PtNPs) were synthesized by a modified polyol process using TEMPO-oxidized nanocellulose (TOCN) as a stabilizing and co-reducing agent. Different ratios of TOCN nanocellulose to Pt⁴⁺ ions were studied to establish the optimum stabilizing effect of PtNPs. The effect of different pH of aqueous TOCN suspensions on the morphology of PtNPs was also examined. It was proved that PtNPs can be obtained solely in the presence of TOCN without the use of an additional reducing agent or ethylene glycol. The morphology and structural properties of the nanocellulose‑platinum nanoparticles composites were assessed using spectroscopic, microscopic and diffraction techniques, The catalytic performance in 4-nitrophenol reduction was evaluated. Significant differences in reaction rate constants k were found depending on the pH of the TOCN suspension applied during Pt⁴⁺ reduction. The crucial effect of reaction conditions on PtNPs performance was confirmed in tests of antibacterial efficacy against E. coli.

DFT study on the electronic structure and optical properties of an Au-deposited α-Fe2O3 (001) surface

The electronic structure and optical properties of gold clusters deposited on an α-Fe2O3 surface were studied by using density functional theory (DFT), with a special emphasis on the influence of Au cluster sizes. There is a strong interaction between Au clusters and the α-Fe2O3 surface, and the binding energy increases with an increase of Au cluster size. The Au atoms of the gold cluster are bonded to the iron atoms of the α-Fe2O3 surface for the Au/α-Fe2O3 system, and the electrons transfer from the Au cluster to the α-Fe2O3 surface with the largest number of electrons transferred for 4Au/α-Fe2O3. The peaks of the refractive index, extinction coefficient and dielectric function induced by Au clusters appear in the visible range, which results in the enhanced optical absorption for the Au/α-Fe2O3 system. The optical absorption intensifies with increasing Au cluster size in the visible range, showing a maximum value for 4Au/α-Fe2O3. Further increasing the Au cluster size above 4Au results in a decrease in absorption intensity. The results are in good agreement with those of the refractive index, extinction coefficient and dielectric function.

Hydrothermal Synthesis of 1T-MoS2/Pelagic Clay Composite and Its Application in the Catalytic Reduction of 4-Nitrophenol

Pelagic clay is an emerging marine resource with strong hydrophilicity, fine particles and a large specific surface area. In this work, a 1T-MoS2/pelagic clay composite was fabricated by hydrothermal synthesis. In the composite, 1T-MoS2 nanosheets are evenly dispersed on the surface of the clay minerals, significantly reducing the agglomeration of MoS2. Compared with pure 1T-MoS2, the 1T-MoS2 nanosheets generated on the surface of pelagic clay have significantly smaller lateral dimensions and thicknesses. Moreover, the specific surface area is much larger than that of the pure 1T-MoS2 nanosheets fabricated by the same method, indicating that the active sites of the MoS2 sheets are fully exposed. In addition, the composite exhibited excellent hydrophilicity, leading to a high dispersibility in aqueous solutions. In this work, the composite was used as a catalyst in the reduction of 4-nitrophenol (4-NP), and the conversion of 4-NP reached up to 96.7%. This result shows that the 1T-MoS2/pelagic clay composite is a promising catalyst in a variety of reactions.

Tuning the band gap of M-doped titanate nanotubes (M = Fe, Co, Ni, and Cu): an experimental and theoretical study

Herein, we report a systematic experimental and theoretical study about a wide-ranged band gap tuning of protonated titanate nanotubes H₂Ti₃O₇ (Ti-NT) by an easy ion-exchange method using a low concentration (1 wt%) of transition metal cations. To characterize and describe the effect of M doping (M = Cu²⁺, Ni²⁺, Co²⁺, and Fe³⁺) on the electronic, optical and structural properties, semiconductors were analyzed by a combination of experimental methods and density functional theory (DFT) calculations. The nanotube band gap can be modified from 1.5 to 3.3 eV, which opens the possibility to use them in several optoelectronic applications such as photocatalysts under solar light irradiation.

Room temperature blooming of CeO2 3D nanoflowers under sonication and catalytic efficacy towards CO conversion

Carbon monoxide (CO), being a highly toxic gas, bears hazardous effects on human health and contributes majorly to environmental pollution. It is mostly produced by automobile exhausts and incomplete combustion of carbon-containing substances. Thus, the development of catalysts for CO conversion is highly imperative and has always gained interest for real field applications. Besides the high oxygen storage capacity and facile transitions between oxidation states, the huge abundance of cerium on earth makes CeO2 a low-cost and highly effective alternative to noble metal catalysts for CO oxidation. The present work delineates the room temperature synthesis of flower-shaped 3D CeO2 nanostructures using a sonication-assisted simple synthesis method within 2 hours under the pivotal importance of a structure-directing agent, polyvinylpyrrolidone (PVP). The bifunctional contributions of PVP as a surfactant and as a capping agent are discussed with a plausible mechanism. The method leading to the formation of hierarchical CeO2 nanoflowers provides an appreciable surface area of 132.69 cm2 g-1. The morphological and structural characterizations of the catalyst were thoroughly investigated using FESEM, TEM, XRD, UV-visible spectroscopy, photoluminescence spectroscopy, FTIR spectroscopy and X-ray photoelectron spectroscopy. The structural efficacies of flower-like CeO2 nanostructures have also been correlated to the narrowing of the band gap and the generation of the corresponding oxygen vacancies, resulting in surface catalytic properties towards 80% conversion of CO.

Hematite/Graphitic Carbon Nitride Nanofilm for Fenton and Photocatalytic Oxidation of Methylene Blue

Hematite (α-Fe2O3)/graphitic carbon nitride (g-C3N4) nanofilm catalysts were synthesized on fluorine-doped tin oxide glass by hydrothermal and chemical vapor deposition. Scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses of the synthesized catalyst showed that the nanoparticles of g-C3N4 were successfully deposited on α-Fe2O3 nanofilm. The methylene blue degradation efficiency of the α-Fe2O3/g-C3N4 composite catalyst was 2.6 times greater than that of the α-Fe2O3 single catalyst under ultraviolet (UV) irradiation. The methylene blue degradation rate by the α-Fe2O3/g-C3N4 catalyst increased by 6.5 times after 1 mM of hydrogen peroxide (H2O2) was added. The photo-Fenton reaction of the catalyst, UV, and H2O2 greatly increased the methylene blue degradation. The results from the scavenger experiment indicated that the main reactants in the methylene blue decomposition reaction are superoxide radicals photocatalytically generated by g-C3N4 and hydroxyl radicals generated by the photo-Fenton reaction. The α-Fe2O3/g-C3N4 nanofilm showed excellent reaction rate constants at pH 3 (Ka = 6.13 × 10−2 min−1), and still better efficiency at pH 7 (Ka = 3.67 × 10−2 min−1), compared to other methylene blue degradation catalysts. As an immobilized photo-Fenton catalyst without iron sludge formation, nanostructured α-Fe2O3/g-C3N4 are advantageous for process design compared to particle-type catalysts.

Direct hydrothermal synthesis of amine-functionalized cubic hematite (C-Fe2O3) and sonochemical deposition of nanosized Au for its application as a visible-light photocatalyst

Cubic-shaped hematite (C-Fe2O3) functionalized with amine groups was directly prepared via one-pot hydrothermal reaction of Fe3+ with 1,12-diaminododecane (DA-12) in aqueous solution (50% ethanol). Herein, DA-12 (as a Lewis acid) promoted the aggregation of α-FeOOH nanorods with Lewis base sites, leading to the rapid recrystallization and conversion into uniform C-Fe2O3. C-Fe2O3 was subsequently deposited with nanosized Au via sonochemical reduction of 1.0 wt% HAuCl4 (0.1-0.8 mL), hereafter referred to as Au-deposited C-Fe2O3 (C-Fe2O3@Au). X-ray diffraction patterns of C-Fe2O3@Au confirmed the hexagonal crystalline phases of hematite and crystalline Au (111) and showed a weak broad band attributed to the amorphous carbon of DA-12. C-Fe2O3@Au was tested as a visible-light photocatalyst towards the degradation of methylene blue (MB) dye. C-Fe2O3@Au (0.1-0.4 mL of 1.0 wt% HAuCl4) exhibited 6-8 times higher photocatalytic activity than the Au-free counterpart (C-Fe2O3). The enhanced photocatalysis was mainly attributed to the improved separation efficiency of photo-excited charge carriers, i.e., the facilitated transport of electrons from the conduction band to the lower lying Fermi level of Au. However, the photocatalytic activity of C-Fe2O3@Au (0.8 mL of 1.0 wt% HAuCl4) was decreased probably due to the reduction of active sites for MB adsorption by the high coverage of the Au layer. The combined hydrothermal and sonochemical methods provided the direct synthetic route to cubic-shaped hematite decorated with nanosized Au and surface amine functionality as a promising visible-light photocatalyst.

Photocatalytic Oxygen Evolution from Water Splitting

Photocatalytic water splitting has attracted a lot of attention in recent years, and O2 evolution is the decisive step owing to the complex four-electrons reaction process. Though many studies have been conducted, it is necessary to systematically summarize and introduce the research on photocatalytic O2 evolution, and thus a systematic review is needed. First, the corresponding principles about O2 evolution and some urgently encountered issues based on the fundamentals of photocatalytic water splitting are introduced. Then, several types of classical water oxidation photocatalysts, including TiO2, BiVO4, WO3, α-Fe2O3, and some newly developed ones, such as Sillén-Aurivillius perovskites, porphyrins, metal-organic frameworks, etc., are highlighted in detail, in terms of their crystal structures, synthetic approaches, and morphologies. Third, diverse strategies for O2 evolution activity improvement via enhancing photoabsorption and charge separation are presented, including the cocatalysts loading, heterojunction construction, doping and vacancy formation, and other strategies. Finally, the key challenges and future prospects with regard to photocatalytic O2 evolution are proposed. The purpose of this review is to provide a timely summary and guideline for the future research works for O2 evolution.

Size- and shape-dependent catalytic performances of oxidation and reduction reactions on nanocatalysts

Heterogeneous catalysis is one of the most important chemical processes of various industries performed on catalyst nanoparticles with different sizes or/and shapes. In the past two decades, the catalytic performances of different catalytic reactions on nanoparticles of metals and oxides with well controlled sizes or shapes have been extensively studied thanks to the spectacular advances in syntheses of nanomaterials of metals and oxides. This review discussed the size and shape effects of catalyst particles on catalytic activity and selectivity of reactions performed at solid-gas or solid-liquid interfaces with a purpose of establishing correlations of size- and shape-dependent chemical and structural factors of surface of a catalyst with the corresponding catalytic performances toward understanding of catalysis at a molecular level.

A simple route to diverse noble metal-decorated iron oxide nanoparticles for catalysis

Developing facile synthetic routes to multifunctional nanoparticles combining the magnetic properties of iron oxides with the optical and catalytic utility of noble metal particles remains an important goal in realizing the potential of hybrid nanomaterials. To this end, we have developed a single route to noble metal-decorated magnetic nanoparticles (Fe3O4@SiO2-M; M = Au, Pd, Ag, and PtAg) and characterized them by HRTEM and STEM/EDX imaging to reveal their nanometer size (16 nm Fe3O4 and 1-5 nm M seeds) and uniformity. This represents one of the few examples of genuine multifunctional particles on the nanoscale. We show that these hybrid structures have excellent catalytic activity for the reduction of 4-nitrophenol (knorm = 2 × 10(7) s(-1) mol(Pd)(-1); 5 × 10(6) s(-1) mol(Au)(-1); 5 × 10(5) s(-1) mol(PtAg)(-1); 7 × 10(5) s(-1) mol(Ag)(-1)). These rates are the highest reported for nano-sized comparables, and are competitive with mesoparticles of similar composition. Due to their magnetic response, the particles are also suitable for magnetic recovery and maintain >99% conversion for at least four cycles. Using this synthetic route, Fe3O4@SiO2-M particles show great promise for further development as a precursor to complicated anisotropic materials or for applications ranging from nanocatalysis to biomedical sensing.

Influence of Surfactant Bilayers on the Refractive Index Sensitivity and Catalytic Properties of Anisotropic Gold Nanoparticles

Shape-controlled synthesis of gold nanoparticles generally involves the use of surfactants, typically cetyltrimethylammonium (CTAX, X = Cl(-) , Br(-)), to regulate the nucleation growth process and to obtain colloidally stable nanoparticles. The surfactants adsorb on the nanoparticle surface making further functionalization difficult and therefore limit their use in many applications. Herein, the influence of CTAX on nanoparticle sensitivity to local dielectric environment changes is reported. It is shown, both experimentally and theoretically, that the CTAX bilayer significantly reduces the refractive index (RI) sensitivity of anisotropic gold nanoparticles such as nanocubes and concave nanocubes, nanorods, and nanoprisms. The RI sensitivity can be increased by up to 40% by removing the surfactant layer from nanoparticles immobilized on a solid substrate using oxygen plasma treatment. This increase compensates for the otherwise problematic decrease in RI sensitivity caused by the substrate effect. Moreover, the removal of the surfactants both facilitates nanoparticle biofunctionalization and significantly improves their catalytic properties. The strategy presented herein is a simple yet effective universal method for enhancing the RI sensitivity of CTAX-stabilized gold nanoparticles and increasing their potential as transducers in nanoplasmonic sensors, as well as in catalytic and biomedical applications.

Interfaced heterogeneous nanodimers

Dimerization of different nanocomponents in single nanoparticles becomes interesting due to not only inheritance of properties of both components but also generation of new properties associated with strong coupling of the two components. As a class of emerging nanomaterials, interfaced heterogeneous nanodimers (IHNDs) are attracting more attentions in the field of materials research, in particular, nanoscience and nanotechnology. This review provides a timely and comprehensive overview on the general principles for the synthesis of IHNDs and typical examples of IHNDs made of various compositional combinations. The current challenges related to the synthesis and characterization of IHNDs are summarized at the end of the review and future research directions are also discussed.

Sonochemical fabrication of dual-targeted redox-responsive smart microcarriers

In the present study, the molecular and magnetic dual-targeted redox-responsive folic acid-cysteine-Fe3O4 microcapsules (FA-Cys-Fe3O4 MCs) have been synthesized via the sonochemical technique, and targeting molecule (folic acid) and Fe3O4 magnetic nanoparticles are introduced into the microcapsule shells successfully. The obtained FA-Cys-Fe3O4 MCs show excellent magnetic responsive ability by the oriented motion under an external magnetic field. The hydrophobic fluorescent dye (Coumarin 6) is successfully loaded into the FA-Cys-Fe3O4 MCs, demonstrating that it could be also easily realized to encapsulate hydrophobic drugs into the FA-Cys-Fe3O4 MCs when the drugs are dispersed into the oil phase before sonication. Cellular uptake demonstrates that FA-Cys-Fe3O4 MCs could target selectively the cells via folate-receptor-mediated endocytosis. Moreover, the FA-Cys-Fe3O4 MCs show their potential ability to be an attractive carrier for drug controlled release owing to the redox responsiveness of the disulfide in the microcapsule shells.

Multifunctional Co(0.85)Se-Fe(3)O(4) nanocomposites: controlled synthesis and their enhanced performances for efficient hydrogenation of p-nitrophenol and adsorbents

A new kind of multifunctional Co0.85 Se-Fe3 O4 nanocomposites is synthesized by loading Fe3 O4 nanoparticles (NPs) with a size of about 5 nm on the surface of Co0.85 Se nanosheets under hydrothermal conditions without using any surfactant or structure-directing agents. The Co0.85 Se-Fe3 O4 nanocomposite exhibits remarkable catalytic performance for hydrogenation of p-nitrophenol (4-NP) at room temperature and good adsorption behavior for methylene blue trihydrate in water. This nanocomposite also shows a high specific surface area and magnetic separation capability for recyclable utilization. The enhanced performances both in catalysis and adsorption are better than either individual component of Co0.85 Se nanosheets or Fe3 O4 nanoparticles, demonstrating the possibility for designing new multifunctional nanocomposites with improved performances for catalysis, adsorbents, and other applications.

Controllable synthesis of Ni nanotube arrays and their structure-dependent catalytic activity toward dye degradation

Ni nanotube (nanorod) arrays are controllably fabricated by a one-step approach, the GDDATG and DDCG growth mechanisms are introduced. The Ni nanostructures present higher catalytic activities for dye degradation, the relationship between structures and catalytic properties is also studied.

Surfactant-free sub-2 nm ultrathin triangular gold nanoframes

Ultrathin triangular gold nanoframes are synthesized in high yield through selective gold deposition on the edges of triangular silver nanoprisms and subsequent silver etching with mild wet etchants. These ultrathin gold nanoframes are surfactant-free with tailorable ridge thickness from 1.8 to 6 nm and exhibit adjustable and distinct surface plasmon resonance bands in the visible and near-IR region. In comparison, etching of the nanoprism template by galvanic replacement can only create frame structures with much thicker ridges, which have much lower catalytic activity for 4-nitrophenol reduction than the ultrathin gold nanoframes.