dong Li

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.

Self-Assembly of Conjugated Polymer-Ag@SiO2 Hybrid Fluorescent Nanoparticles for Application to Cellular Imaging

A novel fluorescent nanoparticle was prepared via a simple self-assembly technique based on water-soluble conjugated polymers (CPs) and Ag@SiO(2) core-shell nanoparticles. Core-shell nanoparticles with silver NPs core show a unique property referred to as metal-enhanced fluorescence (MEF). In the present work, the cationic conjugated polymer poly[9,9-bis(6-(N,N,N-trimethylammonium)-hexyl) fluorene-2,7-ylenevinylene-co-alt-1,4-phenylene dibromide] (PFV) was hybridized with Ag@SiO(2) NPs via simple self-assembly procedure, and given high stability, monodispersity. The fluorescence intensity of PFV after assembling on Ag@SiO(2) core-shell NPs is enhanced 1.3-fold compared with the fluorescence intensity of PFV assembled on silica NPs without silver cores for the MEF property of the Ag@SiO(2) nanostructure. Nanocomposite with bright fluorescence was obtained. Moreover, the nanocomposition exhibits good monodispersity and low cytotoxicity, which promote their application in cellular imaging. Furthermore, fluorescent nanoparticles with amendable peripheral surfaces can also be potentially obtained because of the easy modification property of CPs and give potential application in selective biological sensing and imaging.

New alkylthienyl substituted benzo[1,2-b:4,5-b′]dithiophene-based polymers for high performance solar cells

Three new alkylthienyl substituted benzodithiophene (BDT)-based polymers, poly{4,8-bis(2′-ethylhexylthiophene)benzo[1,2-b;3,4-b′]dithiophene-alt-5,5-(4′,7′-di-2-thienyl-5′,6′-dioctyloxy-benzo[c][1,2,5]oxadiazole)}(PBDTTDTBO), poly{4,8-bis(2′-ethylhexylthiophene)benzo[1,2-b;3,4-b′]dithiophene-alt-5,5-(4′,7′-di-2-thienyl-5′,6′-dioctyloxy-2′,1′,3′-benzothiadiazole)}(PBDTTDTBT) and poly{4,8-bis(2′-ethyl hexylthiophene)benzo[1,2-b;3,4-b′]dithiophene-alt-5,5-(4′,7′-di-2-thienyl-2-octyl-2′,1′,3′-benzotriazole)} (PBDTTDTBTz), were synthesized by Stille coupling polymerization reactions. All of the polymers were found to be soluble in common organic solvents such as chloroform, tetrahydrofuran and chlorobenzene with excellent film forming properties. Their structures were verified by elemental analysis and NMR spectroscopy, the molecular weights were determined by gel permeation chromatography (GPC) and the thermal properties were investigated by thermogravimetric analysis (TGA). The polymers exhibited tunable absorptions and energy levels on incorporation of different electron accepting units. All the copolymers showed high field hole mobility up to 10−2 order, and their blends with PCBM exhibited mobility as high as 10−1 order by the space-charge-limited current (SCLC) method. Preliminary photovoltaic cells based on the device structure of ITO/PEDOT:PSS/PBDTTDTBO:PC71BM (1u2006:u20061.5, w/w)/Ca/Al showed a power conversion efficiency of 5.9% with a high open-circuit voltage (Voc) of 0.84 V and a short circuit current density (Jsc) of 11.45 mA cm−2. To the best of our knowledge, this is the highest efficiency for dithienyl benzooxadiazole (DTBO)-based polymer solar cells.

Control of metal-enhanced fluorescence with pH- and thermoresponsive hybrid microgels.

In this paper, we report on the Ag nanoparticle-containing hybrid poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-PAA) microgels with pH- and thermoresponsive metal-enhanced fluorescence (MEF). The hybrid microgels were prepared by in situ reducing Ag salts to Ag nanoparticles in the PNIPAM-co-PAA microgels. According to the interaction distance-dependent nature of MEF effects, we can realize a controllable MEF effect by adjusting the average interaction distance between fluorophores and Ag nanoparticles due to the good stimuli-responsive swelling-shrinking behavior of the hybrid microgels. The results show that MEF effect can be well tuned in the pH region 2-12 as well as the temperature region of 20-50 °C. By this method, an enhanced fluorescence detection can possibly be manipulated by adjusting external stimuli such as pH and temperature.

Controllable metal-enhanced fluorescence in organized films and colloidal system.

In recent years, considerable efforts have been devoted to better understand the unique emission properties of fluorophores enhanced by the localized surface plasmon resonance of metal nanoparticles (NPs), due to the widespread applications of fluorescence techniques. It is demonstrated by experiment and theoretical calculation that the enhancement efficiency strongly depends on the morphology of the metal NPs, the spectral overlap between metal and fluorophores, the separation distance between them, and other factors. Among these aspects to be considered are suitable spacer material and assembling methods to control the spatial arrangement of plasmonic NPs and fluorophore with proper optical properties and interactions. In this contribution, we provide a brief overview on recent progress of metal-enhanced fluorescence in organized films and colloidal systems.

Hybrid conjugated polymer-Ag@PNIPAM fluorescent nanoparticles with metal-enhanced fluorescence

Hybrid nanoparticles with core–shell structures have shown brilliant potential application in many research fields. In this paper, a novel core–shell Ag@PNIPAM nanocomposite particle which combines the thermoresponsive property of poly(N-isopropylacrylamide) (PNIPAM) and the metal-enhanced fluorescence (MEF) effect of Ag colloids is demonstrated. The cationic conjugated polymer poly[9,9′-bis(6′′-(N,N,N-trimethylammonium)-hexyl)fluorene-2,7-ylenevinylene-co-alt-1,4-phenylene dibromide] (PFV) is then assembled onto the surface of these core–shell nanoparticles by the self-assembly technique. The fluorescence intensity of the prepared PFV/Ag@PNIPAM nanoparticles shows excellent thermostability in the temperature region from 20 °C to 50 °C, and the thermoquenching of PFV is greatly inhibited due to the MEF effects of Ag nanoparticles. Compared with the PFV solution without adding Ag@PNIPAM nanoparticles, a 1.6-fold and 3.1-fold enhancement can be observed when the temperature of the PFV/Ag@PNIPAM dispersion was 20 °C and 50 °C, respectively. In addition, the PFV/Ag@PNIPAM nanoparticles can exhibit excellent cytocompatibility, as well as strong and stable fluorescence when co-cultured with A549 lung cancer cells. These unique properties make these PFV/Ag@PNIPAM core–shell nanoparticles a desirable material especially in the field of efficient cellular imaging and biosensing.

Gold nanoflower@gelatin core-shell nanoparticles loaded with conjugated polymer applied for cellular imaging.

In the present work, a facile one-pot method is designed to fabricate a core-shell fluorescent nanoparticle (NP) for cellular imaging based on a new cationic conjugated polymer, poly[9,9-bis(6,6-(N,N,N-trimethylaminium)fluorene-2,7-ylenevinylene-co-alt-2,5-dicyano-1,4-phenylene] (PFVCN). Gold nanoflowers (AuNFs) are prepared by a seedless method, in which a gelatin layer formed through a sol-gel phase transition is deposited on the surface of each AuNF. The cationic PFVCN self-assembles onto the negative surface of the resultant (AuNF@Gelatin NPs) driven by electrostatic attraction. An obvious enhancement of fluorescence intensity is observed. The AuNF@Gelatin/PFVCN NPs exhibit excellent cytocompatibility, and their cellular imaging ability is demonstrated when cocultured with HeLa cells. AuNF@Gelatin/PFVCN hybrid NPs are expected to be a desirable material in the field of cellular imaging and biosensing.

pH- and Glucose-Responsive Core–Shell Hybrid Nanoparticles with Controllable Metal-Enhanced Fluorescence Effects

In this paper, a novel core-shell hybrid nanoparticle with a silver core and cross-linked poly(3-acrylamidephenylboronic acid-co-acrylic acid) shell (Ag@PAPBA-PAA) was reported. The prepared hybrid nanoparticles can exhibit good responsiveness to the glucose concentration and pH of the environment and exhibit a responsive swelling and shrinking behavior. Tuned by the glucose concentration or pH, a swelling of up to 15.0 nm thickness of the hybrid nanoparticle shell can be observed. These unique responsive properties can be employed to tune the metal-enhanced fluorescence (MEF) effects of the incorporated Ag cores. The fluorescence of adsorbed positively charged porphyrin molecules (Por(4+)) shows good sensitivity to the glucose concentration and pH with an enhancement of up to about 1.8-fold. These functional hybrid nanoparticles with tunable MEF effects show a great potential application in the fields of responsive fluorescent sensing and detection.

Self-Assembly of Fluorescent Organic Nanoparticles for Iron(III) Sensing and Cellular Imaging

Fluorescent organic nanoparticles have attracted increasing attentions for chemical or biological sensing and imaging due to their low-toxicity, facile fabrication and surface functionalization. In this work, we report novel fluorescent organic nanoparticles via facile self-assembly method in aqueous solution. First, the designed water-soluble fluorophore shows a weak and negligible intrinsic fluorescence in water. Upon binding with adenosine-5-triphosphate (ATP), fluorescent nanoparticles were formed immediately with strongly enhanced fluorescence. These fluorescent nanoparticles exhibit high sensitivity and selectivity toward Fe(3+) sensing with detection limit of 0.1 nM. In addition, after incubation with HeLa cells, the fluorophore shows excellent imaging performance by interaction with entogenous ATP in cells. Finally, this fluorescent system is also demonstrated to be capable of Fe(3+) sensing via fluorescence quenching in cellular environment.

Conjugated Oligomer-Based Fluorescent Nanoparticles as Functional Nanocarriers for Nucleic Acids Delivery

Oligonucleotides such as siRNA and plasmid DNA (pDNA) have great potential for gene therapies. Multifunctional, environment-resistant carriers with imaging capabilities are required to track the assembly and disassembly of oligonucleotides, monitor the delivery processes, and develop new delivery systems. Conjugated polymers and oligomers can potentially be used as novel materials for functional nanocarriers with both delivery and imaging abilities. In this work, a novel π-conjugated oligomer 4,7-(9,9-bis(6-adenine hexyl)fluorenyl)-2,1,3-benzothiadiazole (OFBT-A) modified with nucleotide adenine (A) groups in its side chains is synthesized and characterized. Fluorescent nanoparticles based on the π-conjugated oligomers OFBT-A are developed as novel functional nanocarriers for oligonucleotides. Single-stranded DNA (ssDNA) TR-T5 labeled with Texas Red (TR) fluorescent dye is selected as a model payload oligonucleotide. The capture abilities and stability of OFBT-A are investigated by monitoring the fluorescence resonance energy transfer (FRET) efficiency between the OFBT-A nanoparticles and TR labels in solution. The OFBT-A/TR-T5 composites are stable in solution at high ionic strengths (0-500 mM) and have a wide working pH range, from 3.0 to 9.5. The in vitro profile demonstrates that the release of the TR-DNA is induced by the ssDNA A43, which has a high charge density. The release process is monitored by measuring the changes in FRET efficiency and fluorescence color for the OFBT-A/TR-T5 composites. Using this carrier, the uptake of TR-DNA by A549 lung cancer cells is observed. Both the OFBT-A nanoparticles and the OFBT-A/TR-T5 composites show high cytocompatibility. We anticipate that these novel functional nanocarriers will provide a safe strategy for monitoring the gene delivery process.