Optogenetic Calcium Ion Influx in Myoblasts and Myotubes by Near-Infrared Light Using Upconversion Nanoparticles

Bioactuators made of cultured skeletal muscle cells are generally driven by electrical or visible light stimuli. Among these, the technology to control skeletal muscle consisting of myoblasts genetically engineered to express photoreceptor proteins with visible light is very promising, as there is no risk of cell contamination by electrodes, and the skeletal muscle bioactuator can be operated remotely. However, due to the low biopermeability of visible light, it can only be applied to thin skeletal muscle films, making it difficult to realize high-power bioactuators consisting of thick skeletal muscle. To solve this problem, it is desirable to realize thick skeletal muscle bioactuators that can be driven by near-infrared (NIR) light, to which living tissue is highly permeable. In this study, as a promising first step, upconversion nanoparticles (UCNPs) capable of converting NIR light into blue light were bound to C2C12 myoblasts expressing the photoreceptor protein channelrhodopsin-2 (ChR2), and the myoblasts calcium ion (Ca2+) influx was remotely manipulated by NIR light exposure. UCNP-bound myoblasts and UCNP-bound differentiated myotubes were exposed to NIR light, and the intracellular Ca2+ concentrations were measured and compared to myoblasts exposed to blue light. Exposure of the UCNP-bound cells to NIR light was found to be more efficient than exposure to blue light in terms of stimulating Ca2+ influx.

Phases evolution and photocatalytic activity of Cu2O films electrodeposited from a non-pH-adjusted solution

A pure-phase Cu₂O film photocatalyst was successfully prepared by the electrodeposition technique from a non-pH-adjusted solution. To investigate the phase evolution and photocatalytic activity of the film, the electrodeposition was conducted at different deposition temperatures. Photocatalytic activity of the films was evaluated from methylene blue (MB) dye degradation. The Cu₂O phase initially appeared at room temperature and its fraction was found to increase with increasing the deposition temperature, while the impurity phase was successfully diminished. A pure Cu₂O film with a narrow optical bandgap energy of 1.96 eV was obtained at 75°C. The multi-faceted crystals were found to form at 45°C and became a truncated octahedral structure that possessed {111} and {100} facets as deposition temperature further increased. A preferred orientation growth of {110} facet, which is known to possess a relatively high surface energy, was produced at 75°C. The performance of MB photodegradation enhanced gradually by increasing the deposition temperature. The increase of photocatalytic activity could be attributed to the rise of photoelectrochemical response and the decrease of resistance charge transfer because of narrowing bandgap energy, increasing Cu₂O fraction, and growing a relatively high catalytic activity facet which had escalated redox reaction that decomposed MB at the photocatalyst-solution interface.

Multifunctional Au@Ag@SiO2 Core-Shell-Shell Nanoparticles for Metal-Enhanced Fluorescence, Surface-Enhanced Raman Scattering, and Photocatalysis Applications

Au@Ag@SiO₂ core-shell-shell nanoparticles (NPs) were prepared by a facile one-pot synthetic technique. The Au@Ag core size and SiO₂ shell thicknesses are readily controlled by adjusting the precursor concentration. The multilayered NPs with dielectric SiO₂ outer shells and bimetallic Au@Ag cores exhibited both the chemical stability of Au with the high scattering efficiency of Ag. Furthermore, the SiO₂ shell is beneficial to the metal-enhanced fluorescence for biomedical applications. Metal-enhanced fluorescence, surface-enhanced Raman scattering, and photocatalytic activities of silica-coated Au@Ag, Ag, Au, and Au/Ag core-shell NPs were compared and discussed. The size and structure of Au@Ag@SiO₂ core-shell-shell NPs were optimized to maximize their optical and catalytic activities.

Mechanistic insights into efficient peroxymonosulfate activation by NiCo layered double hydroxides

The efficient removal of organic refractory pollutants such as dyes and antibiotics in wastewater is crucial for protecting the environment and human health. In this work, a NiCo-layered double hydroxide (NiCo-LDH) with a uniform microspherical, hierarchical structure and a high surface area was successfully synthesized as an effective peroxymonosulfate (PMS) activator for the degradation of various organic dyes and antibiotics. The influence of various parameters on the catalytic activity of the NiCo-LDH was determined. Radical scavenger studies unveiled the major reactive oxygen species (ROSs) generated in the NiCo-LDH/PSM system to be ¹O₂, SO₄^•-, and O₂^•-. Ex-situ X-ray photoelectron spectroscopy (XPS) analysis uncovered the role of Co sites and oxygen vacancy as active sites and revealed the reversible redox properties of NiCo-LDH based on Co²⁺/Co³⁺ cycles. The activation mechanism and Rhodamine B (RhB) degradation pathways were experimentally studied and proposed. The NiCo-LDH is highly versatile, reusable and stable as shown by post-catalysis characterizations. This work shows the excellent catalysis performances and provides insights into the activation mechanism of PMS by NiCo-LDH for organic pollutant remediation.

A Robust Nanoparticle-based Magnetic Separation Method for Intact Lysosomes

Lysosome isolation is a preresiquite for identifying lysosomal protein composition by mass spectroscopic analysis, to reveal lysosome functions, and their involvement in some diseases. Magnetic nanoparticle-based fractionation has received great attention for lysosome isolation, owing to its high efficiency, purity, and preservation of lysosomal structures. Understanding the intracellular trafficking of magnetic probes is the key point of this technique, to determine the appropriate time for magnetic isolation of lysosomes, because this parameter changes depending on different cell lines used. The traditional magnetic probes, such as superparamagnetic iron oxide nanoparticles (SPIONs), require surface modification by fluorescent dyes to enable the investigation of their intracellular trafficking, which has some disadvantages, including the possible alternation of their bio-interaction, and the instability of fluorescence properties in the lysosomal environment. To overcome those limitations, we present a protocol that employs magnetic-plasmonic nanoparticles (MPNPs) to investigate intracellular trafficking using their intrinsic imaging capability, followed by quick lysosome isolation using a magnetic column. This protocol can be easily applied to isolate the intact lysosomes of any adherent cell lines. Graphical abstract.

One-pot synthesis of Au-M@SiO2 (M = Rh, Pd, Ir, Pt) core-shell nanoparticles as highly efficient catalysts for the reduction of 4-nitrophenol

The conversion of p-nitrophenol (4-NP) to p-aminophenol (4-AP) is of great significance for pharmaceutical and material manufacturing. In this work, Au-M@SiO₂ (M = Rh, Pd, Ir, Pt) nanoparticles (NPs) with core-shell structures, which are expected to be excellent catalysts for the transformation of 4-NP to 4-AP, were synthesized by a facile one-pot one-step method. The structure and composition of the NPs were characterized through transmission electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. Au-M@SiO₂ (M = Rh, Pd, Ir, Pt) core-shell NPs showed excellent catalytic activity in the reduction of 4-NP, which is superior to most catalysts reported in the previous literature. The enhanced catalytic activity of Au-M@SiO₂ core-shell NPs is presumably related to the bimetallic synergistic effect. This study provides a simple strategy to synthesize core-shell bimetallic NPs for catalytic applications.

Environmental STEM Study of the Oxidation Mechanism for Iron and Iron Carbide Nanoparticles

The oxidation of solution-synthesized iron (Fe) and iron carbide (Fe₂C) nanoparticles was studied in an environmental scanning transmission electron microscope (ESTEM) at elevated temperatures under oxygen gas. The nanoparticles studied had a native oxide shell present, that formed after synthesis, an ~3 nm iron oxide (Fe_xO_y) shell for the Fe nanoparticles and ~2 nm for the Fe₂C nanoparticles, with small void areas seen in several places between the core and shell for the Fe and an ~0.8 nm space between the core and shell for the Fe₂C. The iron nanoparticles oxidized asymmetrically, with voids on the borders between the Fe core and Fe_xO_y shell increasing in size until the void coalesced, and finally the Fe core disappeared. In comparison, the oxidation of the Fe₂C progressed symmetrically, with the core shrinking in the center and the outer oxide shell growing until the iron carbide had fully disappeared. Small bridges of iron oxide formed during oxidation, indicating that the Fe transitioned to the oxide shell surface across the channels, while leaving the carbon behind in the hollow core. The carbon in the carbide is hypothesized to suppress the formation of larger crystallites of iron oxide during oxidation, and alter the diffusion rates of the Fe and O during the reaction, which explains the lower sensitivity to oxidation of the Fe₂C nanoparticles.

Quick and Mild Isolation of Intact Lysosomes Using Magnetic-Plasmonic Hybrid Nanoparticles

Rapid and efficient isolation of intact lysosomes is necessary to study their functions and metabolites by proteomic analysis. We developed a swift and robust nanoparticle-based magnetic separation method in which magnetic-plasmonic hybrid nanoparticles (MPNPs) conjugated with amino dextran (aDxt) were targeted to the lumen of lysosomes via the endocytosis pathway. For well-directed magnetic separation of the lysosomes, it is important to trace the intracellular trafficking of the aDxt-conjugated MPNPs (aDxt-MPNPs) in the endocytosis pathway. Therefore, we analyzed the intracellular transport process of the aDxt-MPNPs by investigating the time-dependent colocalization of plasmonic scattering of aDxt-MPNPs and immunostained marker proteins of organelles using the threshold Manders' colocalization coefficient (R_t). Detailed analysis of time variations of R_t for early and late endosomes and lysosomes allowed us to derive the transport kinetics of aDxt-MPNPs in a cell. After confirming the incubation time required for sufficient accumulation of aDxt-MPNPs in lysosomes, the lysosomes were magnetically isolated as intact as possible. By varying the elapsed time from homogenization to complete isolation of lysosomes (t_delay) and temperature (T), the influences of t_delay and T on the protein composition of the lysosomes were investigated by polyacrylamide gel electrophoresis and amino acid analysis. We found that the intactness of lysosomes could become impaired quite quickly, and to isolate lysosomes as intact as possible with high purity, t_delay = 30 min and T = 4 °C were optimal settings.

Heat-Up Colloidal Synthesis of Shape-Controlled Cu-Se-S Nanostructures-Role of Precursor and Surfactant Reactivity and Performance in N2 Electroreduction

Copper selenide-sulfide nanostructures were synthesized using metal-organic chemical routes in the presence of Cu- and Se-precursors as well as S-containing compounds. Our goal was first to examine if the initial Cu/Se 1:1 molar proportion in the starting reagents would always lead to equiatomic composition in the final product, depending on other synthesis parameters which affect the reagents reactivity. Such reaction conditions were the types of precursors, surfactants and other reagents, as well as the synthesis temperature. The use of 'hot-injection' processes was avoided, focusing on 'non-injection' ones; that is, only heat-up protocols were employed, which have the advantage of simple operation and scalability. All reagents were mixed at room temperature followed by further heating to a selected high temperature. It was found that for samples with particles of bigger size and anisotropic shape the CuSe composition was favored, whereas particles with smaller size and spherical shape possessed a Cu2-xSe phase, especially when no sulfur was present. Apart from elemental Se, Al2Se3 was used as an efficient selenium source for the first time for the acquisition of copper selenide nanostructures. The use of dodecanethiol in the presence of trioctylphosphine and elemental Se promoted the incorporation of sulfur in the materials crystal lattice, leading to Cu-Se-S compositions. A variety of techniques were used to characterize the formed nanomaterials such as XRD, TEM, HRTEM, STEM-EDX, AFM and UV-Vis-NIR. Promising results, especially for thin anisotropic nanoplates for use as electrocatalysts in nitrogen reduction reaction (NRR), were obtained.

Enhancing the Sensitivity of Lateral Flow Immunoassay by Magnetic Enrichment Using Multifunctional Nanocomposite Probes

For lateral flow immunoassay (LFIA), it is an important challenge to enhance the detection sensitivity to the same level as polymerase chain reaction or enzyme-linked immunosorbent assay to make LFIA pervasive in the field of on-site environmental analysis. We recently demonstrated that the LFIA sensitivity is dramatically enhanced by using Pt-nanoparticle-latex nanocomposite beads (Pt-P2VPs) as probes for the detection of the influenza A (H1N1) antigen compared with using conventional Au colloids as probes. Here, to further enhance the LFIA sensitivity using Pt-P2VPs, superparamagnetic iron oxide nanoparticles (SPIONs) were chemically conjugated to Pt-P2VPs (Pt-P2VP@SPION) to give them magnetic separation capability (enrichment and/or purification). To investigate the effect of magnetic enrichment on the LFIA sensitivity in a sandwich format, the C-reactive protein (CRP) was chosen as a model analyte and anti-CRP antibody (CRPAb)-conjugated Pt-P2VP@SPION (Pt-P2VP@SPION-CRPAb) beads were used as probes. The visual limit of detection (LOD) of LFIA was successfully lowered by increasing the magnetic enrichment factor φ. The minimum LOD under the present experimental conditions was 0.08 ng/mL for φ = 40, which is 26-fold lower than that of the standard Au-nanoparticle-based LFIA. In theory, the LOD can be unlimitedly decreased by just increasing φ. However, the times required for both the antigen-antibody binding reaction and magnetic separation dramatically increase with φ. We also propose solutions to overcome this drawback.

Rapid Millifluidic Synthesis of Stable High Magnetic Moment FexCy Nanoparticles for Hyperthermia

A millifluidic reactor with a 0.76 mm internal diameter was utilized for the synthesis of monodisperse, high magnetic moment, iron carbide (FexCy) nanoparticles by thermal decomposition of iron pentacarbonyl (Fe(CO)5) in 1-octadecene in the presence of oleylamine at 22 min nominal residence time. The effect of reaction conditions (temperature and pressure) on the size, morphology, crystal structure, and magnetic properties of the nanoparticles was investigated. The system developed facilitated the thermal decomposition of precursor at reaction conditions (up to 265 °C and 4 bar) that cannot be easily achieved in conventional batch reactors. The degree of carbidization was enhanced by operating at elevated temperature and pressure. The nanoparticles synthesized in the flow reactor had size 9-18 nm and demonstrated high saturation magnetization (up to 164 emu/gFe). They further showed good stability against oxidation after 2 months of exposure in air, retaining good saturation magnetization values with a change of no more than 10% of the initial value. The heating ability of the nanoparticles in an alternating magnetic field was comparable with other ferrites reported in the literature, having intrinsic loss power values up to 1.52 nHm2 kg-1.

Following the Formation of Silver Nanoparticles Using In Situ X-ray Absorption Spectroscopy

The formation of silver and Au@Ag core@shell nanoparticles via reduction of AgNO₃ by trisodium citrate was followed using in situ X-ray absorption near-edge structure (XANES) spectroscopy and time-resolved UV-visible (UV-vis) spectroscopy. The XANES data were analyzed through linear combination fitting, and the reaction kinetics were found to be consistent with first-order behavior with respect to silver cations. For the Au@Ag nanoparticles, the UV-vis data of a lab-scale reaction showed a gradual shift in dominance between the gold- and silver-localized surface plasmon absorbance bands. Notably, throughout much of the reaction, distinct gold and silver contributions to the UV-vis spectra were observed; however, in the final product, the contributions were not distinct.

Facile synthesis of Mn-doped NiCo2O4 nanoparticles with enhanced electrochemical performance for a battery-type supercapacitor electrode

We report the synthesis of manganese-doped nickel cobalt oxide (Mn-doped NiCo2O4) nanoparticles (NPs) by an efficient hydrothermal and subsequent calcination route. The material exhibits a homogeneous distribution of the Mn dopant and a battery-type behavior when tested as a supercapacitor electrode material. Mn-doped NiCo2O4 NPs show an excellent specific capacity of 417 C g-1 at a scan rate of 10 mV s-1 and 204.3 C g-1 at a current density of 1 A g-1 in a standard three-electrode configuration, ca. 152-466% higher than that of pristine NiCo2O4 or MnCo2O4. In addition, Mn-doped NiCo2O4 NPs showed an excellent capacitance retention of 99% after 1000 charge-discharge cycles at a current density of 2 A g-1. The symmetric solid-state supercapacitor device assembled using this material delivered an energy density of 0.87 μW h cm-2 at a power density of 25 μW h cm-2 and 0.39 μW h cm-2 at a high power density of 500 μW h cm-2. The cost-effective synthesis and high electrochemical performance suggest that Mn-doped NiCo2O4 is a promising material for supercapacitors.

Catalytic activation of peroxymonosulfate with manganese cobaltite nanoparticles for the degradation of organic dyes

In this work, we report the facile hydrothermal synthesis of manganese cobaltite nanoparticles (MnCo₂O_4.5 NPs) which can efficiently activate peroxymonosulfate (PMS) for the generation of sulfate free radicals (SO₄˙⁻) and degradation of organic dyes. The synthesized MnCo₂O_4.5 NPs have a polyhedral morphology with cubic spinel structure, homogeneously distributed Mn, Co, and O elements, and an average size less than 50 nm. As demonstrated, MnCo₂O_4.5 NPs showed the highest catalytic activity among all tested catalysts (MnO₂, CoO) and outperformed other spinel-based catalysts for Methylene Blue (MB) degradation. The MB degradation efficiency reached 100% after 25 min of reaction under initial conditions of 500 mg L⁻¹ Oxone, 20 mg L⁻¹ MnCo₂O_4.5, 20 mg L⁻¹ MB, unadjusted pH, and T = 25 °C. MnCo₂O_4.5 NPs showed a great catalytic activity in a wide pH range (3.5–11), catalyst dose (10–60 mg L⁻¹), Oxone concentration (300–1500 mg L⁻¹), MB concentration (5–40 mg L⁻¹), and temperature (25–55 °C). HCO₃⁻, CO₃²⁻ and particularly Cl⁻ coexisting anions were found to inhibit the catalytic activity of MnCo₂O_4.5 NPs. Radical quenching experiments revealed that sulfate radicals are primarily responsible for MB degradation. A reaction sequence for the catalytic activation of PMS was proposed. The as-prepared MnCo₂O_4.5 NPs could be reused for at least three consecutive cycles with small deterioration in their performance due to low metal leaching. This study suggests a facile route for synthesizing MnCo₂O_4.5 NPs with high catalytic activity for PMS activation and efficient degradation of organic dyes.

Catalytic degradation of organic dyes via manganese cobaltite nanoparticles-activated peroxymonosulfate.

Gram-Scale Synthesis of Tetrahedrite Nanoparticles and Their Thermoelectric Properties

Here, we report a method for facile gram-scale synthesis of tetrahedrite (Cu₁₂Sb₄S₁₃) nanoparticles (NPs) with high quality and good reproducibility. The obtained NPs had a well-defined tetrahedral shape with a mean edge length of ∼70 nm. We sintered the NPs by the hot press technique to fabricate a nanostructured pellet for thermoelectric measurements. The figure of merit (ZT) value of the pellet was 0.52 at 675 K, which was comparable with the ZT value of the non-nanostructured counterpart.

Nanobulk Thermoelectric Materials Fabricated from Chemically Synthesized Cu3Zn1-x Al x SnS5-y Nanocrystals

Direct energy conversion of heat into electricity using thermoelectric materials is an attractive solution to help address global energy issues. Developing novel materials composed of earth-abundant and nontoxic elements will aid progress toward the goal of sustainable thermoelectric materials. In this study, we chemically synthesized Cu-Zn-Sn-S nanocrystals and fabricated a Cu3ZnSnS5-y thermoelectric material using nanocrystals as building blocks. The figure-of-merit (ZT) value of the Cu3ZnSnS5-y material was found to be 0.39 at 658 K. We substituted Zn with Al in the Cu3ZnSnS5-y system to form Cu3Zn1-x Al x SnS5-y (x = 0.25, 0.5, 0.75, and 1) to lower the lattice thermal conductivity of the resulting materials. Complete substitution of Al for Zn substantially decreased the lattice thermal conductivity and dramatically increased the electrical conductivity of the material. However, the ZT value could not be significantly enhanced, which could be primarily attributed to the high carrier thermal conductivity. These results highlight the production of Cu3Zn1-x Al x SnS5-y thermoelectric materials and unveil the scope for improvement of ZT values by altering transport properties.

Plasmon induced magneto-optical enhancement in metallic Ag/FeCo core/shell nanoparticles synthesized by colloidal chemistry

The combination of magnetic and plasmonic materials and their nanostructurization have revealed a prominent pathway to develop novel photonic materials for the active control of the light polarization using a magnetic field. Until now, physical growth methods have been the only exploitable approach to prepare these types of nanostructures. Here, we demonstrate the chemical synthesis of magneto-plasmonic core/shell nanocrystals with enhanced magnetic control of optical properties comparable to the best results reported for nanostructure growth by physical methods. Ag/FeCo core/shell nanocrystals were synthesized using a combination of hot injection and polyol approaches, demonstrating that the well-defined structures of both components, their interface and the optimized morphology, where the plasmonic and magnetic components are placed in the core and the shell regions, are responsible for the observed large enhancement of magnetic control of light polarization. Therefore, there is a possibility to develop tunable magneto-optical materials from hybrid magneto-plasmonic structures synthesized by chemical methods.

Metal (Au, Pt) Nanoparticle-Latex Nanocomposites as Probes for Immunochromatographic Test Strips with Enhanced Sensitivity

The development of a sensitive and rapid diagnostic test for early detection of infectious viruses is urgently required to defend against pandemic and infectious diseases including seasonal influenza. In this study, we developed noble metal (Au, Pt) nanoparticle-latex nanocomposite particles for use as probes for immunochromatographic test (ICT) strips. The nanocomposite particles were conjugated with monoclonal antibody (mAb) to detect an influenza A (H1N1) antigen. For comparison, Au nanoparticles conjugated with mAb were also prepared. The lowest detectable concentrations of the influenza A antigen were found to be 6.25 × 10^-3 and 2.5 × 10^-2 HAU/mL for Au nanoparticle-latex and Pt nanoparticle-latex nanocomposite particles, respectively, whereas it was 4.0 × 10^-1 HAU/mL for Au nanoparticles. These results clearly demonstrated that the nanocomposite probes were more sensitive than conventional nanoparticle-based probes for ICT. To expand the versatility of the nanocomposite probes, the surfaces of the probes were functionalized with biotinylated proteins to enable modification of their surfaces with desired biotinylated antibodies through biotin-avidin binding.

Magnetic Separation of Autophagosomes from Mammalian Cells Using Magnetic-Plasmonic Hybrid Nanobeads

Developments in subcellular fractionation strategies have provided the means to analyze the protein and lipid composition of organelles by proteomics. Here, we developed ultrasmall magnetic-plasmonic hybrid nanobeads and applied them to the isolation of autophagosomes by applying a magnetic field. The beads were chemically synthesized and comprised an Ag/FeCo/Ag core/shell/shell structure with a mean diameter of 15 nm. The Ag core and the FeCo shell conferred imaging and magnetic separation capabilities, respectively. The nanobeads were transfected into mammalian cells by lipofection. Thirty minutes after lipofection, the nanobeads colocalized with Vps26 and subsequently with LC3. Cell lysates were prepared at the appropriate time points and were subjected to magnetic separation. The separated fraction contained LC3-II, transferrin receptor, and LAMP2, but not LC3-I, suggesting that autophagosomes engulfing endosomal origin had been isolated. The magnetic separation process was completed in less than 30 min, providing a rapid method for isolation of autophagosomes. The present organelle isolation technique using the hybrid nanobeads with imaging and magnetic separation capabilities is highly promising for isolation of other types of organelles such as endosomes and endosome-related organelles.

AuFePt Ternary Homogeneous Alloy Nanoparticles with Magnetic and Plasmonic Properties

Combining Au and Fe into a single nanoparticle is an attractive way to engineer a system possessing both plasmonic and magnetic properties simultaneously. However, the formation of the AuFe alloy is challenging because of the wide miscibility gap for these elements. In this study, we synthesized AuFePt ternary alloy nanoparticles as an alternative to AuFe alloy nanoparticles, where Pt is used as a mediator that facilitates alloying between Au and Fe in order to form ternary alloy nanoparticles. The relationship among composition, structure, and function is investigated and it was found that at an optimized composition (Au₅₂Fe₃₀Pt₁₈), ternary alloy NPs exhibit both magnetic and plasmonic properties simultaneously. The plasmonic properties are investigated in detail using a theoretical Mie model, and we found that it is governed by the dielectric constant of the resulting materials.

Doxorubicin loaded dual pH- and thermo-responsive magnetic nanocarrier for combined magnetic hyperthermia and targeted controlled drug delivery applications

Magnetic nanocarriers have attracted increasing attention for multimodal cancer therapy due to the possibility to deliver heat and drugs locally. The present study reports the development of magnetic nanocomposites (MNCs) made of an iron oxide core and a pH- and thermo-responsive polymer shell, that can be used as both hyperthermic agent and drug carrier. The conjugation of anticancer drug doxorubicin (DOX) to the pH- and thermo-responsive MNCs via acid-cleavable imine linker provides advanced features for the targeted delivery of DOX molecules via the combination of magnetic targeting, and dual pH- and thermo-responsive behaviour which offers spatial and temporal control over the release of DOX. The iron oxide cores exhibit a superparamagnetic behaviour with a saturation magnetization around 70 emu g(-1). The MNCs contained 8.1 wt% of polymer and exhibit good heating properties in an alternating magnetic field. The drug release experiments confirmed that only a small amount of DOX was released at room temperature and physiological pH, while the highest drug release of 85.2% was obtained after 48 h at acidic tumour pH under hyperthermia conditions (50 °C). The drug release kinetic followed Korsmeyer-Peppas model and displayed Fickian diffusion mechanism. From the results obtained it can be concluded that this smart magnetic nanocarrier is promising for applications in multi-modal cancer therapy, to target and efficiently deliver heat and drug specifically to the tumour.

Synthesis of magnetic cobalt ferrite nanoparticles with controlled morphology, monodispersity and composition: the influence of solvent, surfactant, reductant and synthetic conditions

In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(III) and Co(II) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications.

Harvesting Nanocatalytic Heat Localized in Nanoalloy Catalyst as a Heat Source in a Nanocomposite Thin Film Thermoelectric Device

This report describes findings of an investigation of harvesting nanocatalytic heat localized in a nanoalloy catalyst layer as a heat source in a nanocomposite thin film thermoelectric device for thermoelectric energy conversion. This device couples a heterostructured copper-zinc sulfide nanocomposite for thermoelectrics and low-temperature combustion of methanol fuels over a platinum-cobalt nanoalloy catalyst for producing heat localized in the nanocatalyst layer. The possibility of tuning nanocatalytic heat in the nanocatalyst and thin film thermoelectric properties by compositions points to a promising pathway in thermoelectric energy conversion.

Formation of Pt decorated Ni-Pt nanocubes through low temperature atomic diffusion--time-resolved elemental analysis of nanoparticle formation

The formation process of Pt decorated Ni-Pt nanocubes was investigated by analysing the elemental distribution of Ni and Pt in the particles obtained from time-resolved in situ sampling during the synthesis in the oleylamine-1-heptanol system. The analysis confirmed the formation of Pt(core)-Ni(shell) nanoparticles at the initial stages of the reaction. However, as the reaction time progressed, the Pt atoms at the centre diffused outward and reached the corners and edges of the particle, whose shape changed from nearly spherical at the initial stages of the reaction to a perfect cube at the end of the reaction, forming a Ni rich cube (core)-Pt(cage). The cage obtained by dissolving the Ni rich cube was composed mainly of Pt and the Ni content in the frame was a mere 12%. The catalytic activity of the Pt cage was measured using cyclic voltammetry. The initial measurements suggested that the activity was comparable to some of the commercially available Pt catalysts.

Ag/FeCo/Ag core/shell/shell magnetic nanoparticles with plasmonic imaging capability

Magnetic nanoparticles (NPs) have been used to separate various species such as bacteria, cells, and proteins. In this study, we synthesized Ag/FeCo/Ag core/shell/shell NPs designed for magnetic separation of subcellular components like intracellular vesicles. A benefit of these NPs is that their silver metal content allows plasmon scattering to be used as a tool to observe detection by the NPs easily and semipermanently. Therefore, these NPs are considered a potential alternative to existing fluorescent probes like dye molecules and colloidal quantum dots. In addition, the Ag core inside the NPs suppresses the oxidation of FeCo because of electron transfer from the Ag core to the FeCo shell, even though FeCo is typically susceptible to oxidation. The surfaces of the Ag/FeCo/Ag NPs were functionalized with ε-poly-L-lysine-based hydrophilic polymers to make them water-soluble and biocompatible. The imaging capability of the polymer-functionalized NPs induced by plasmon scattering from the Ag core was investigated. The response of the NPs to a magnetic field using liposomes as platforms and applying a magnetic field during observation by confocal laser scanning microscopy was assessed. The results of the magnetophoresis experiments of liposomes allowed us to calculate the magnetic force to which each liposome was subjected.

Formation mechanism of magnetic–plasmonic Ag@FeCo@Ag core–shell–shell nanoparticles: fact is more interesting than fiction

The formation mechanism of Ag@FeCo@Ag core–shell–shell nanoparticles which are synthesized by the combination of a multi-step hot injection method and a polyol method was investigated by comparing several different derivative NPs such as Ag@FeCo, Ag@Co, Ag@Fe and FeCo NPs.

Novel nickel–palladium catalysts encased in a platinum nanocage

Synthesis of novel self-designed Ni–Pd–Pt nanocubes that possess the potential for the preparation of designed catalysts of the future.

Enhanced electronic properties of Pt@Ag heterostructured nanoparticles

Platinum coated by silver nanoparticles was synthesized, which displays a unique structure where polycrystalline platinum particles are completely encapsulated in continuous monocrystalline silver shells. These particles display accentuated electronic properties, where the silver shells gain electron density from the platinum cores, imparting enhanced properties such as oxidation resistance. This electron transfer phenomenon is highly interfacial in nature, and the degree of electron transfer decreases as the thickness of silver shell increases. The nanoparticle structure and electronic properties are studied and the implication to creating sensing probes with enhanced robustness, sensitivity and controllable plasmonic properties is discussed.

Chemical stabilization of gold coated by silver core-shell nanoparticles via electron transfer

Silver nanoparticles are notoriously susceptible to oxidation, yet gold nanoparticles coated in silver exhibit a unique electronic interaction that occurs at the interface of the two metals, leading to enhanced stability properties for the silver shell. In order to probe the phenomenon, the stability of gold nanoparticles coated by silver was studied in the presence of various chloride-containing electrolytes. It was found that a critical silver shell thickness of approximately 1 nm exists that cannot be oxidatively etched from the particle surface: this is in contrast to the observation of complete oxidative etching for monometallic silver nanoparticles. The results are discussed in terms of particle composition, structure and morphology before and after exposing the particles to the electrolytes. Raman analysis of the reporter molecule 3-amino-1,2,4-triazole-5-thiol adsorbed on the particle surface illustrates the feasibility of using gold coated by silver nanoparticle probes in sensing applications that require the presence of high levels of salt. The results provide insight into the manipulation of the electronic and stability properties for gold- and silver-based nanoparticles.

Role of base in the formation of silver nanoparticles synthesized using sodium acrylate as a dual reducing and encapsulating agent

The formation mechanism of Ag nanoparticles (NPs) synthesized with a wet-chemical reduction method using sodium acrylate as a dual reducing and capping agent was investigated with various analytical techniques. The time course of the state of the reaction solution was investigated using UV-vis and XAFS spectroscopies which showed that the NP formation rate increased with increasing concentration of sodium hydroxide (NaOH). The detailed kinetic analyses reveal that both the reduction rate of Ag ions and the nucleation rate of Ag NPs are dramatically increased with increasing NaOH concentration. XANES analyses imply that another reaction pathway via alternative Ag(+) species, such as Ag(OH)(x), was developed in the presence of NaOH. Consequently, NaOH is found to play an important role not only in creating specific intermediates in the reduction of Ag(+) to Ag(0), but also in accelerating the reduction and nucleation rates by enhancing the oxidation of sodium acrylate, thereby increasing the rate of formation of the Ag NPs.

Synthesis of core-shell gold coated magnetic nanoparticles and their interaction with thiolated DNA

Core-shell magnetic nanoparticles have received significant attention recently and are actively investigated owing to their large potential for a variety of applications. Here, the synthesis and characterization of bimetallic nanoparticles containing a magnetic core and a gold shell are discussed. The gold shell facilitates, for example, the conjugation of thiolated biological molecules to the surface of the nanoparticles. The composite nanoparticles were produced by the reduction of a gold salt on the surface of pre-formed cobalt or magnetite nanoparticles. The synthesized nanoparticles were characterized using ultraviolet-visible absorption spectroscopy, transmission electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction and super-conducting quantum interference device magnetometry. The spectrographic data revealed the simultaneous presence of cobalt and gold in 5.6±0.8 nm alloy nanoparticles, and demonstrated the presence of distinct magnetite and gold phases in 9.2±1.3 nm core-shell magnetic nanoparticles. The cobalt-gold nanoparticles were of similar size to the cobalt seed, while the magnetite-gold nanoparticles were significantly larger than the magnetic seeds, indicating that different processes are responsible for the addition of the gold shell. The effect on the magnetic properties by adding a layer of gold to the cobalt and magnetite nanoparticles was studied. The functionalization of the magnetic nanoparticles is demonstrated through the conjugation of thiolated DNA to the gold shell.

Aqueous synthesis and characterization of Ag and Ag-Au nanoparticles: addressing challenges in size, monodispersity and structure

In this paper, we demonstrate the synthesis of monodispersed silver nanoparticles (NPs) of controlled size (20.5 +/- 3.3 nm) in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing-capping agent. We then coat these NPs in a layer of gold with controllable thickness through a reduction-deposition process. The materials are characterized using several techniques including high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results show that we were able to synthesize not only monodispersed Ag NPs but also core-shell Ag-Au NPs with a discrete structure, which is significant because of the challenges associated with the creation of such materials, namely the propensity of metallic Ag to be oxidized by the presence of ionic Au. The NPs are of interest for use in a wide range of potential applications, including biomedical diagnostics and biomolecular detection as well as many others.