Ruthenium/reduced graphene oxide nanocomposites (Ru/rGO NCs) were synthesized via an electrostatic self-assembly approach. Polyvinylpyrrolidone (PVP) stabilized and positively charged metallic ruthenium nanoclusters about 1.2 nm were synthesized and uniformly loaded onto negatively charged graphene oxide (GO) sheets via strong electrostatic interactions. The as-prepared Ru/rGO NCs exhibited superior performance in catalytic hydrolysis of sodium borohydride (NaBH4) to generate H2. The hydrogen generation rate was up to 14.87 L H2 min?1 gcat?1 at 318 K with relatively low activation energy of 38.12 kJ mol?1. Kinetics study confirmed that the hydrolysis of NaBH4 was first order with respect to concentration of catalysts. Besides, the conversion of NaBH4 remained at 97% and catalytic activity retained more than 70% after 5 reaction cycles at room temperature. These results suggested that the Ru/rGO NCs have a promising prospect in the field of clean energy.
Although number of stimuli-responsive drug delivery systems based on mesoporous silica nanoparticles (MSNs) have been developed, the simultaneous real-time monitoring of carrier in order to guarantee proper drug targeting still remains as a challenge. GQDs-MSNs nanocomposite nanoparticles composed of graphene quantum dots (GQDs) and MSNs are proposed as efficient doxorubicin delivery and fluorescent imaging agent, allowing to monitor intracellular localization of a carrier and drug diffusion route from the carrier.Graphene quantum dots (average diameter 3.65?±?0.81 nm) as a fluorescent agent were chemically immobilized onto mesoporous silica nanoparticles (average diameter 44.08?±?7.18 nm) and loaded with doxorubicin. The structure, morphology, chemical composition, and optical properties as well as drug release behavior of doxorubicin (DOX)-loaded GQDs-MSNs were investigated. Then, the in vitro cytotoxicity, cellular uptake, and intracellular localization studies were carried out. Prepared GQDs-MSNs form stable suspensions exhibiting excitation-dependent photoluminescence (PL) behavior. These nanocomposite nanoparticles can be easily DOX-loaded and show pH- and temperature-dependent release behavior. Cytotoxicity studies proved that GQDs-MSNs nanocomposite nanoparticles are nontoxic; however, when loaded with drug, they enable the therapeutic activity of DOX via its active delivery and release. GQDs-MSNs owing to their fluorescent properties and efficient in vitro cellular internalization via caveolae/lipid raft-dependent endocytosis show a high potential for the optical imaging, including the simultaneous real-time optical tracking of the loaded drug during its delivery and release.
Carbon-coated ZnFe2O4 spheres with sizes of ~110–180 nm anchored on graphene nanosheets (ZF@C/G) are successfully prepared and applied as anode materials for lithium ion batteries (LIBs). The obtained ZF@C/G presents an initial discharge capacity of 1235 mAh g?1 and maintains a reversible capacity of 775 mAh g?1 after 150 cycles at a current density of 500 mA g?1. After being tested at 2 A g?1 for 700 cycles, the capacity still retains 617 mAh g?1. The enhanced electrochemical performances can be attributed to the synergetic role of graphene and uniform carbon coating (~3–6 nm), which can inhibit the volume expansion, prevent the pulverization/aggregation upon prolonged cycling, and facilitate the electron transfer between carbon-coated ZnFe2O4 spheres. The electrochemical results suggest that the synthesized ZF@C/G nanostructures are promising electrode materials for high-performance lithium ion batteries.
Barium titanate (BT) nanoparticles are coated by titania and modified by fluoroalkylsilane. The BT nanoparticles are incorporated into polyvinylidene fluoride (PVDF) films to obtain highly dielectric and transparent nanocomposite films at low filler loadings. Incorporation of BT nanoparticles having average sizes of 12 and 22 nm is performed. Incorporation of BT nanoparticles enhances the permittivity of PVDF films. Higher transparency of nanocomposite films is achieved by incorporating 12-nm nanoparticles compared to that by 22-nm nanoparticles. The polarisation mechanism in the nanocomposite films is examined using the Vo–Shi model. The result indicates that even a slight increase in the thickness of titania-coating layer on the BT nanoparticles increase the permittivity of the nanocomposite films. Comparison of the measured and calculated permittivities showed that the incorporation of BT nanoparticles coated with titania provides a practical approach to create transparent nanocomposite films having high permittivity.
Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) were stabilized by the self-assembly of nitrile molecules onto the ruthenium colloid surface by virtue of the formation of Ru?N≡C interfacial bonding linkages. Thermogravimetric analysis showed that there were about 63 nitrile ligands per nanoparticle, corresponding to an average molecular footprint of 22.4 Å2. Proton nuclear magnetic resonance (NMR) studies suggested an end-on configuration of the nitrile moiety on the metal core surface. Meanwhile, infrared measurements showed that the C≡N stretch red-shifted from 2246 to 1944 cm?1 upon adsorption on the nanoparticle surfaces, as confirmed by 15N isotopic labeling. This apparent red-shift suggests extensive intraparticle charge delocalization, which was further manifested by photoluminescence measurements of 1-cyanopyrene-functionalized ruthenium nanoparticles that exhibited a red shift of 40 nm of the emission maximum, in comparison to that of free monomers. The results further highlight the significance of metal?organic contacts in the manipulation of the dynamics of intraparticle charge transfer and the nanoparticle optical and electronic properties.
Porous polyacrylamide hydrogel (PAM) was prepared by polymerization at room temperature. Cadmium sulfide/polyacrylamide hydrogels (CdS/PAM) was synthesized by in situ loading CdS nanoparticles and used for photocatalytic decomposition of water for the first time. The size distribution of the loaded CdS nanoparticles is 3–12 nm. We studied the enhanced photocatalytic activity and photo-corrosion inhibition of CdS/PAM the compared with pure CdS and probed the mechanism of the improvement. In particular, the CdS/PAM prepared in 0.003 M CdCl2 solution exhibited the highest hydrogen production efficiency of 2.929 mmol g?1 h?1, about 79 times that of pure CdS. The results demonstrate that the formation of new N–Cd bond and high transmittance of CdS/PAM dramatically enhance photocatalytic activity. The electron cloud of nitrogen atom can attract holes and repel photogenerated electrons, which lowers the carrier recombination probability. The results also reveal that the excellent hydrophilicity of hydrogel plays an important role in the inhibition of photocorrosion. In addition, CdS/PAM is easily recycled and processed. The present work will pave a good way for the application of smart hydrogels in the field of photocatalytic hydrogen production.
A novel core–shell nanocomposite Ni–Ca@mSiO2 was first prepared by a modified Stöber method in this paper. It has a core–shell structure with Ni (about 8 nm in diameter) and Ca as the cores and mesoporous silica as the outer shell, as proven by the transmission electron microscopy. This nanocomposite exhibited good catalytic performance in the selective hydrogenation of benzophenone, with 96.1% conversion and 94.9% selectivity for benzhydrol under relatively mild reaction conditions. It was demonstrated that addition of small amounts of alkaline Ca can not only markedly improve the dispersion of the active species but also tune the acid–base property of this nanocomposite, resulting in the efficient suppression of benzhydrol dehydration to achieve a high selectivity. Furthermore, the core–shell nanocomposite Ni–Ca@mSiO2 can be recycled four runs without appreciable loss of its initial activity, more stable than the traditional supported nanocatalyst Ni–Ca/mSiO2. It was suggested that the outer mesoporous silica shell of Ni–Ca@mSiO2 can prevent both the aggregation and the leaching of the active Ni species, accounting for its relatively good stability.
Graphical abstract A magnetic core–shell nanocomposite Ni–Ca@mSiO2 exhibited good activity, selectivity, and reusability in benzophenone selective hydrogenation.
Nitrilimine cycloadditions to ethylenes, acetylenes, and activated nitriles have been exploited in the presence of catalytic amounts of oleic-acid-coated iron oxide nanoparticles (diameter?=?11.9?±?1.0 nm). The reactions were fully regioselective with monosubstituted ethylenes and ethyl cyanoformiate, while mixtures of cycloadducts were obtained in the presence of methyl propiolate. The intervention of iron oxide nanoparticles allowed carrying out the cycloadditions at milder conditions compared to the metal-free thermal processes. A labile intermediate has been proposed to explain this behavior.
Graphical abstract Nitrilimine cycloadditions to ethylenes, acetylenes, and activated nitriles have been exploited in the presence of catalytic amounts of oleic-acid-coated iron oxide nanoparticles.
Layered zinc-based metal-organic framework ([Zn(4,4′-bpy)(tfbdc)(H2O)2], Zn-LMOF) nanosheets were synthesized by a facile hydrothermal method (4,4′-bpy = 4,4′-bipyridine, H2tfbdc = tetrafluoroterephthalic acid). The materials were characterized by IR spectrum, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, transmission electron microscope (TEM), scanning electron microscope (SEM), and the Brunauer–Emmett–Teller (BET) surface. When the Zn-LMOF nanosheets with the thickness of about 24 ± 8 nm were used as an anode material of lithium-ion batteries, not only the Zn-LMOF electrode shows a high reversible capacity, retaining 623 mAh g?1 after 100 cycles at a current density of 50 mA g?1 but also exhibits an excellent cyclic stability and a higher rate performance.
Graphical abstract Zinc-based layered metal-organic framework ([Zn(4,4′-bpy)(tfbdc)(H2O)2], Zn-LMOF) nanosheets have been synthesized, displaying a high capacity as anode materials for lithium-ion batteries.
Hand tools, such as a sledgehammer, are widely used in refurbishment activities; nonetheless, there is very little knowledge on nanoparticle generation. We measured particle number size distributions (PSDs) and concentrations (PNCs) in the 10–420 nm using a NanoScan scanning mobility particle sizer (SMPS) during the use of hand tools (i.e., sanding and removal of wall) in a real indoor refurbishment environment. Results indicated that refurbishment activities from removal of wall increased average PNCs by ~?6 times over the background while it was ~?1.5 times higher than sanding. The highest total PNC was 1.9?×?105 particles cm?3 that corresponded to removal of wall activities. For sanding activities, PNC was lower as the coat of the plaster was probably slightly wet. Moreover, comparison between the two principal activities showed a similar peak in the accumulation mode (~?65 nm), with a monomodal pattern. Results suggest that removal of wall activities emitted nanoparticles with a 59% of contribution in the Aitken mode. According to these data, it can be inferred that the application of hand tools in refurbishment activities generates lower total PNC than using electromechanical equipment. This study may contribute to our understanding of nanoparticle generation in refurbishment activities.
Magnesium oxide (MgO) and hydroxide [Mg(OH)2] are conventionally considered insoluble in water and stable at high temperatures. However, in this study, we found significant dissociation of MgO and Mg(OH)2 into ions when they were immersed in different physiologically relevant solutions in the form of 20-nm and 10-nm nanoparticles respectively, under standard cell culture conditions in vitro, i.e., a 37 °C, 5% CO2/95% air, sterile, humidified environment. The change in Mg2+ ion concentrations and pH measured in the physiologically relevant solutions (e.g., Dulbecco’s modified Eagle’s Medium (DMEM), simulated body fluid (SBF), relevant chloride solutions, and deionized water) confirmed their dissociation. Possible mechanisms and contributing factors for dissociation of MgO and Mg(OH)2 nanoparticles were discussed. The evidence suggests that nucleophilic substitution of OH? by Cl? in Mg(OH)2 is energetically unfavorable and it is more likely that Cl? plays a role in the stabilization of intermediate forms of MgO and Mg(OH)2 as it dissociates. The pH and buffering capability of the immersion solutions might have played the most significant role in dissociation of these nanoparticles when compared with the roles of chloride (Cl?), proteins, and different buffering agents. This article provided the first evidence on the dissociation of MgO and Mg(OH)2 nanoparticles in physiologically relevant conditions and elucidated possible factors contributing to the observed behaviors of these nanoparticles in vitro, which is important for their potential medical applications in vivo.
Electrochemical reduction of carbon dioxide is one of the methods which have the capability to recycle CO2 into valuable products for energy and industrial applications. This research article describes about a new electrocatalyst “reduced graphene oxide supported gold nanoparticles” for selective electrochemical conversion of carbon dioxide to carbon monoxide. The main aim for conversion of CO2 to CO lies in the fact that the latter is an important component of syn gas (a mixture of hydrogen and carbon monoxide), which is then converted into liquid fuel via well-known industrial process called Fischer-Tropsch process. In this work, we have synthesized different composites of the gold nanoparticles supported on defective reduced graphene oxide to evaluate the catalytic activity of reduced graphene oxide (RGO)-supported gold nanoparticles and the role of defective RGO support towards the electrochemical reduction of CO2. Electrochemical and impedance measurements demonstrate that higher concentration of gold nanoparticles on the graphene support led to remarkable decrease in the onset potential of 240 mV and increase in the current density for CO2 reduction. Lower impedance and Tafel slope values also clearly support our findings for the better performance of RGOAu than bare Au for CO2 reduction.
The current investigation deciphers aggregation pattern of gold nanoparticles (AuNPs) and lipid-treated AuNPs when subjected to aqueous sodium chloride solution with increasing ionic strengths (100–400 nM). AuNPs were synthesized using 0.29 mM chloroauric acid and by varying the concentrations of trisodium citrate (AuNP1 1.55 mM, AuNP2 3.1 mM) and silver nitrate (AuNP3 5.3 μM, AuNP4 10.6 μM) with characteristic LSPR peaks in the range of 525–533 nm. TEM analysis revealed AuNPs to be predominantly faceted nanocrystals with the average size of AuNP1 to be 35?±?5 nm, AuNP2 15?±?5 nm, AuNP3 30?±?5 nm, and AuNP4 30?±?5 nm and the zeta-average for AuNPs were calculated to be 31.23, 63.80, 26.08, and 28 nm respectively. Induced aggregation was observed within 10 s in all synthesized AuNPs while lipid-treated AuNP2 (AuNP2-L) was found to withstand ionic interferences at all concentration levels. However, lipid-treated AuNPs synthesized using silver nitrate and 1.55 mM trisodium citrate (AuNP3, AuNP4) showed much lower stability. The zeta potential values of lipid-treated AuNPs (AuNP1-L-1x/200, ??17.93?±?1.02 mV; AuNP2-L-1x/200, ??21.63?±?0.70; AuNP3-L-1x/200, ??14.54?±?0.90; AuNP3-L-1x/200 ??13.77?±?0.83) justified these observations. To summarize, AuNP1 and AuNP2 treated with lipid mixture 1 equals or above 1x/200 or 1x/1000 respectively showed strong resistance against ionic interferences (up to 400 mM NaCl). Use of lipid mixture 1 for obtaining highly stable AuNPs also provided functional arms of various lengths which can be used for covalent coupling.
In the synthesis of nanostructures by pulsed laser deposition (PLD), a crucial role is played by the environmental deposition pressure and the substrate temperature. Due to the high temperature of nanoparticles (NPs) at landing, other factors may determine the structure of the resulting aggregates. Here, Au and TiO2 nanostructures are obtained by non-thermal fs-PLD in ambient conditions. On Si(100), only TiO2 NPs form fractals with areas up to ~ 1 × 106 nm2, while on quartz Au NPs also form fractals with areas up to ~ 5 × 103 nm2, a much smaller size with respect to the TiO2 case. The aggregation is described by a simple diffusive model, taking into account isotropic diffusion of the NPs, allowing quantitative simulations of the NPs and fractal area. The results highlight the key role of substrate thermal conductivity in determining the formation of fractals.
Mo-doped V2O5 hierarchical nanorod/nanoparticle core/shell porous microspheres (MVHPMs) were prepared via a simple hydrothermal approach using ammonium metavanadate and ammonium molybdate as precursors followed by a thermal annealing process. The samples were characterized by XRD, SEM, TEM, EDS, and XPS carefully; it confirmed that porous microspheres with uniform Mo doping in the V2O5 matrix were obtained, and it contains an inner core self-assembled with 1D nanorods and outer shell consisting of nanoparticles. A plausible growth mechanism of Mo-doped V2O5 (Mo-V2O5) porous microspheres is suggested. The unique microstructure made the Mo-V2O5 hierarchical microspheres a good cathode material for Li-ion battery. The results indicate the synthesized Mo-V2O5 hierarchical microspheres exhibit well-improved electrochemical performance compared to the undoped samples. It delivers a high initial reversible capacity of 282 mAh g?1 at 0.2 C, 208 mAh g?1 at 2 C, and 111 mAh g?1 at 10 C, and it also exhibits good cycling stabilities; a capacity of 144 mAh g?1 is obtained after 200 cycles at 6 C with a capacity retention of >?82%, which is much high than that of pure V2O5 (95 mAh g?1 with a capacity retention of 72%).
In this paper, we report synthesis and study of magneto-optic Faraday effect for dilute magnetic semiconductor nanostructure. The colloidal CdS nanocrystals were prepared via hot injection method and successfully doped with Mn2+ cations. The synthesized nanoparticles were characterized by using UV–Vis spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, and electron spin resonance spectroscopy. Systematic studies on effect of Mn2+ doping on photoluminescence, electron spin resonance, and magneto-optical properties are carried out. UV–Vis spectral analysis confirms blue shift in bandgap of CdS nanoparticles due to quantum confinement effect. The X-ray diffraction study confirms hexagonal wurtzite phase formation of CdS nanoparticles without any impurity phases. TEM analysis confirms uniform particle size, having particle size distribution around 5 nm. As-synthesized undoped CdS shows triangular-shaped nanocrystals with hexagonal structure; however, triangular shape of CdS nanoparticles is not conserved after Mn2+ doping. The photoluminescence characteristic spectra of Mn2+-doped CdS nanocrystals showed emission band at 660 nm and its intensity was found to increase with increasing Mn2+ concentration. Electron spin resonance signal, with six-line hyperfine structure splitting, confirmed doping of Mn2+ ions in CdS lattice. Magneto-optic measurements showed linear variation of Faraday rotation with respect to applied magnetic field, indicating paramagnetic behavior of Mn-doped CdS. The highest Verdet constant 24.81 deg/T cm was observed for 2% Mn-doped CdS nanocrystals, which further decreases with increasing Mn2+ concentration.
Novel water-soluble anionic p-tert-butylthiacalix[4]arene with propanesulfonate fragments has been synthesized. Alkylation of the lower rim of thiacalix[4]arene in the presence of NaH/THF led to cone conformation instead of the expected 1,3-alternate conformer due to metal template effect. The presence of supramolecular associates at the critical micelle concentration of 1.65 · 10?5 M were investigated in aqueous solutions by a combination of different techniques (DLS and conductivity). It was observed that the macrocyclic platform decreases the CMC by tenfold as compared with non-macrocycle analogs. A simple approach for the design of stable monodisperse Ag-based nanoaggregates (near 95 nm) containing ionic Ag and organic ligand–thiacalix[4]arene sulfo derivative in water has been developed. Self-assembled fractal hybrid nanodendrites consisting of water-soluble anionic (thia)calix[4]arenes and Ag+ have been obtained in a single step under mild conditions.
BaWO4 nanoparticles were successfully used as the photocatalysts in the degradation of methylthioninium chloride (MTC) dye at different pH levels of aqueous solution. Pure phase of barium tungstate (BaWO4) nanoparticles was synthesized by modified molten salt process at 500 °C for 6 h. Structural and morphological characterizations of BaWO4 nanoparticles (average particle size of ~40 nm) were studied in details using powder x-ray diffraction (XRD), FTIR, Raman, energy-dispersive, electron microscopic, and x-ray photoelectron spectroscopy (XPS) techniques. Direct band gap energy of BaWO4 nanoparticles was found to be ~3.06 eV from the UV–visible absorption spectroscopy followed by Tauc’s model. Photocatalytic properties of the nanoparticles were also investigated systematically for the degradation of MTC dye solution in various mediums. BaWO4 nanoparticles claim the significant enhancement of the photocatalytic degradation of aqueous MTC dye to non-hazardous inorganic constitutes under alkaline, neutral, and acidic mediums.
Silver nanoparticles (AgNPs) are a potential class of nanomaterial for antibiosis and chemotherapeutic effects against human carcinoma cells. However, the DNA-damaging ability of free AgNPs pose the critical issues in their biomedical applications. Herein, we demonstrated a facile method to capture Ag+ ions and reduce them into active AgNPs within Zr-based metal-organic frameworks (MOFs) of UiO-66 with a mild reductant of DMF (AgNPs@UiO-66(DMF)). The average diameters of UiO-66 carriers and AgNPs were facilely controlled to be 140 and 10 nm, respectively. The obtained UiO-66 nanocarriers exhibited excellent biocompatibility and could be effectively endocytosed by cancer cells. Additionally, the AgNPs@UiO-66(DMF) could rapidly release Ag+ ions and efficiently inhibit the growth of cancer cells. The half maximal inhibitory concentration (IC50) values of the encapsulated AgNPs were calculated to be 2.7 and 2.45 μg mL?1 for SMMC-7721 and HeLa cells, respectively, which were much lower than those of free AgNPs in the reported works. Therefore, the developed AgNPs@UiO-66(DMF) not only maintained the therapeutic effect against cancer cells but also reduced the dosage of free AgNPs in chemotherapy treatment.
Graphical abstract A mild reduction process was developed for the fabrication of AgNPs@UiO-66, which exhibited efficient induction of apoptosis in cancer cells.
This paper reported a one-step synthesis of Ag2S/Ag@MoS2 nanocomposites and its applications in the surface-enhanced Raman scattering (SERS) detection and photocatalytic degradation of organic pollutants. The nanocomposites were well characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammograms (CV), the Brunauer-Emmett-Teller (BET), and Fourier transforms infrared spectra (FTIR). The AgNPs were uniformly dispersed on the MoS2 nanosheets and the particle size of the AgNPs was about 10–30 nm. These Ag2S/Ag@MoS2 nanocomposites offered sensitive SERS signals for the detection of R6G with the limit of detections as low as 10?10 M. The photocatalytic activity of the composite catalyst was studied by the degradation of methylene blue (MB) dye under light illumination. The apparent rate constant of MB degradation for the obtained catalyst could reach 6.6?×?10?2 min?1, indicating that the novel Ag2S/Ag@MoS2 nanocomposites can be explored for organic pollutant’s detection and degradation.
