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Preparation of Bimetallic Nanoparticles Using a Facile Green Synthesis Method and Their Application

A straightforward, economically viable, and green approach for the synthesis of well-stabilized Au/Ag bimetallic nanoparticles is described; this method uses nontoxic and renewable degraded pueraria starch (DPS) as a matrix and mild reaction conditions. The DPS acted as both a reducing agent and a capping agent for the bimetallic nanoparticles. Au/Ag bimetallic nanoparticles were successfully grown within the DPS matrixes, and the bimetallic structures were characterized using various methods, including high-resolution transmission electron microscopy, energy-dispersive X-ray, and X-ray diffraction. Moreover, it was shown that these DPS-capped Au/Ag bimetallic nanoparticles could function as catalysts for the reduction of 4-nitrophenol in the presence of NaBH₄ and were more effective than Au or Ag monometallic nanoparticles

Preparation of Hybrid Hydrogel Containing Ag Nanoparticles by a Green in Situ Reduction Method

In this Article, large and uniform Ag nanoparticle-containing hybrid hydrogels were prepared by in situ reduction of Ag ions in cross-linked tapioca dialdehyde starch (DAS)–chitosan hydrogels. In the hybrid hydrogels, chitosan was chosen as a macromolecular cross-linker because of its abundant source and good biocompatibility. The hybrid hydrogel showed good water-swelling properties, which could be controlled by varying the ratio of chitosan to tapioca DAS in the hydrogel. The reductive aldehyde groups in the cross-linked hydrogels could be used to reduce Ag ions to Ag nanoparticles without any additional chemical reductants. Interestingly, by controlling the reduction conditions such as the tapioca DAS concentration, aqueous AgNO₃ concentration, reaction time, and aqueous ammonium concentration, Ag nanoparticles with different sizes and morphologies were obtained. Because of their biocompatibility, degradable constituents, mild reaction conditions, and controlled preparation of Ag nanoparticles, these tapioca DAS–chitosan/Ag nanoparticle hybrid hydrogels show promise as functional hydrogels

Synthesis of Cu-Nanoparticle Hydrogel with Self-Healing and Photothermal Properties

Copper (Cu) nanoparticles possess unusual electrical, thermal, and optical properties. However, applications of these materials are often limited by their tendency to oxidize. We prepared Cu nanoparticles by a simple polyol method, with a good control over the particle size. The reaction required no inert atmosphere or surfactant agents. The as-prepared Cu nanoparticles showed good resistance to oxidation in solution. These Cu nanoparticles were then incorporated into a biocompatible polysaccharide hydrogel, which further stabilized the nanoparticles. The hybrid hydrogel exhibited a rapid self-healing ability. Because of the excellent photothermal conversion properties of the embedded Cu nanoparticles, the hybrid hydrogel showed rapid temperature elevation under laser irradiation. The hybrid hydrogel showed limited cytotoxicity; however, under laser irradiation the hydrogel displayed antibacterial properties owing to the heating effects. This study demonstrates that our hybrid hydrogel may have applications in biomedical fields and photothermal therapy

Flexible Antibacterial Film Based on Conjugated Polyelectrolyte/Silver Nanocomposites

In this work, we report a flexible film based on conjugated polyelectrolyte/silver nanocomposites with efficient antibacterial activity. A flexible poly­(dimethylsiloxane) film served as a substrate for deposition of nanostructured silver. A light-activated antibacterial agent, based on the cationic conjugated polyelectrolyte poly­({9,9-bis­[6′-(<i>N,N</i>-trimethylamino)­hexyl]-2,7-fluorenyleneethynylene}-<i>alt</i>-<i>co</i>-1,4-(2,5-dimethoxy)­phenylene)­dibromide (PFEMO) was self-assembled on the negatively charged substrate. By changing the thickness of the poly­(l-lysine)/poly­(acrylic acid) multilayers between the metal substrate and PFEMO, we obtained concomitant enhancement of PFEMO fluorescence, phosphorescence, and reactive oxygen species generation. These enhancements were induced by surface plasmon resonance effects of the Ag nanoparticles, which overlapped the PFEMO absorption band. Owing to the combination of enhanced bactericidal effects and good flexibility, these films have great potential for use as novel biomaterials for preventing bacterial infections

Facile Synthesis of Biocompatible Fluorescent Nanoparticles for Cellular Imaging and Targeted Detection of Cancer Cells

In this work, we report the facile synthesis of functional core–shell structured nanoparticles with fluorescence enhancement, which show specific targeting of cancer cells. Biopolymer poly-l-lysine was used to coat the silver core with various shell thicknesses. Then, the nanoparticles were functionalized with folic acid as a targeting agent for folic acid receptor. The metal-enhanced fluorescence effect was observed when the fluorophore (5-(and-6)-carboxyfluorescein-succinimidyl ester) was conjugated to the modified nanoparticle surface. Cellular imaging assay of the nanoparticles in folic acid receptor-positive cancer cells showed their excellent biocompatibility and selectivity. The as-prepared functional nanoparticles demonstrate the efficiency of the metal-enhanced fluorescence effect and provide an alternative approach for the cellular imaging and targeting of cancer cells

Flexible Free-Standing Graphene/SnO₂ Nanocomposites Paper for Li-Ion Battery

A flexible free-standing graphene/SnO₂ nanocomposites paper (GSP) was prepared by coupling a simple filtration method and a thermal reduction together for the first time. Compared with the pure SnO₂ nanoparticles, the GSP exhibited a better cycling stability, because the graphene with high mechanical strength and elasticity can work as a buffer to prevent the volume expansion and contraction of SnO₂ nanoparticles during the Li⁺ insertion/extraction process. Meanwhile, compared with single graphene paper, the GSP showed a higher capacity because of the hybridizing with higher capacity SnO₂ nanoparticles. The excellent electrochemical performance of the GSP as an anode material in Li-ion battery was obtained. The as-prepared GSP shows a great potential for flexible Li-ion batteries

Fluorescence Resonance Energy Transfer in a Binary Organic Nanoparticle System and Its Application

Fluorescent organic nanoparticles have a much better photostability than molecule-based probes. Here, we report a simple strategy to detect chemicals and biomolecules by a binary nanoparticle system based on fluorescence resonance energy transfer (FRET). Poly­(9,9-di-<i>n</i>-octylfluorenyl-2,7-diyl) (PFO, energy donor) and poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV, energy acceptor) are utilized to prepare the binary nanoparticle system through a reprecipitation method. Since the FRET process is strongly distance-dependent, a change in the interparticle distance between the two kinds of nanoparticles after introduction of analytes will alter the FRET efficiency. The response of the binary nanoparticle system to cationic polyelectrolytes was investigated by monitoring the FRET efficiency from PFO to MEH-PPV nanoparticles and the fluorescence color of the nanoparticle solutions. Furthermore, the cationic polyelectrolyte pretreated binary nanoparticle system can be used to detect DNA by desorption of nanoparticles from the polyelectrolyte’s chains and the detection concentration can go down to 10^–14 M. Thus, the binary nanoparticle system shows great promise for applications in chemical sensing or biosensing

Fluorescent Organic Nanoparticles Based on Branched Small Molecule: Preparation and Ion Detection in Lithium-Ion Battery

Fluorescent organic nanoparticles (FONs) as a new class of nanomaterials can provide more advantages than molecule based probes. However, their applications in specific metal ion detection have rarely been exploited. We design and synthesize a branched small-molecule compound with triazole as a core and benzothiadiazole derivative as branches. By a facile reprecipitation method, nanoparticles (NPs) of this compound can be prepared in aqueous solutions, which can show high selectivity and sensitivity to Fe­(III) ions based on fluorescence quenching. In addition, the fluorescence intensity of these NPs is resistant to pH changes in solutions. Such characters of this kind of NPs can be utilized in Fe³⁺ impurity detection in a promising cathode material (LiFePO₄) for lithium ion batteries. When exposed to Fe³⁺, both the triazole and benzothiadiazole groups contribute to the fluorescence quenching of NPs, but the former one plays a more important role in Fe³⁺ impurity detection. The sensing mechanism has also been investigated which indicates that a Fe-organic complex formation may be responsible for such sensing behavior. Our findings demonstrate that specific metal ion detection can be realized by FONs and have extended the application field of FONs for chemical sensing in aqueous solutions

Self-Assembly of Conjugated Polymer on Hybrid Nanospheres for Cellular Imaging Applications

A new kind of hybrid core–shell nanosphere was fabricated by combining the in situ formation of Au nanoparticles and covalent cross-linking of biocompatible carboxymethyl starch dialdehyde (CMSD) and chitosan (CTS). When the fluorescent dye poly­[9,9′-bis­(6″-(<i>N</i>,<i>N</i>,<i>N</i>-trimethylammonium)-hexyl)­fluorene-2,7-ylenevinylene-<i>co</i>-alt-1,4-phenylene dibromide] (PFV) was assembled on the surface of the hybrid nanospheres through electrostatic attraction, these biocompatible hybrid nanospheres exhibited metal-enhanced fluorescence effects. The fluorescence intensity of (CTS–Au)@CMSD/PFV hybrid nanosphere is 1.43 times that of CTS–CMSD/PFV hybrid nanospheres lacking Au nanoparticle. In addition, the (CTS–Au)@CMSD/PFV hybrid nanospheres exhibit excellent biodegradability upon exposure to enzymatic aqueous solution and good biocompatibility when cocultured with HeLa cervical carcinoma cells; these advantages make them attractive for cellular imaging and biological analysis and detection