Synthesis and characteristics of poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive semi‐hollow latex particles and their application to drug carriers

In this work, the poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite semi‐hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly (MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and crosslinking agent, N,N′‐methylenebisacrylamide, in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles with solid structure. In the third process, part of the linear poly(MMA‐MAA) core of core–shell latex particles was dissolved by ammonia to form the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles. The morphologies of the semi‐hollow latex particles show that there is a hollow zone between the linear poly(MMA‐MAA) core and the crosslinked poly(MAA‐NIPAAm) shell. The crosslinking agent and shell composition significantly influenced the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) semi‐hollow latex particles. Besides, the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles were used as carriers to load with the model drug, caffeine. The processes of caffeine loaded into the semi‐hollow latex particles appeared four situations, which was different from that of solid latex particles. In addition, the phenomenon of caffeine released from the semi‐hollow latex particles was obviously different from that of solid latex particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3441–3451     

Raman investigation on carbonization process of metal–organic frameworks

Under inert gas flow and high temperature, carbonization of aluminum‐based metal–organic frameworks (MOFs) was carried out. The formation rate of carbonized MOFs (CMOFs) was monitored by the variation of the Raman D band to G band intensity ratio with heat treatment duration. Powder x‐ray diffraction (PXRD) and scanning electron microscope (SEM) techniques were used to confirm the formation of CMOFs. The activation energy was extracted from the temperature‐dependent rate constants using the Arrhenius equation and correlated with the structural properties of precursor MOFs such as pore size and the number of carbon atoms per ligand. A reaction mechanism is proposed and discussed for the formation of CMOFs based on Raman observation. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of Polynucleotide Modified Gold Nanoparticles as a High Potent Anti‐Cancer Drug Carrier

Gold nanoparticles have been developed for the photoacoustic imaging, delivery of genes and laser induced photothermal therapy. In this study, we have developed oligonucleotide conjugated gold nanoparticles as the carrier for simultaneous DNA and anti‐cancer nucleoside delivery. The polynucleotidenanoparticle complex presented higher capacity in carrying 5‐FU anti‐cancer compounds than the original gold particles. The hydrodynamic size of the gold nanoparticles increased from 25 to 35 nm with an increase in the negative surface charge from ?9.58 to 21.66 mV after polynucleotide conjugation and drug loading. A positive association between environmental pH and drug release was observed in PBS, which implied their potential use in the controlled localized drug release in the lower GI tract. The MTT assay revealed dose dependent cytotoxicity to colon cancer cell line than free compounds. These results suggest the potential use of this new polynucleotide‐gold nanoparticles complex as the environmental controlled anti‐cancer nanocapsule, especially suitable for per oral colon cancer chemotherapy.     

First‐principle calculations on CO oxidation catalyzed by a gold nanoparticle

We have elucidated the mechanism of CO oxidation catalyzed by gold nanoparticles through first‐principle density‐functional theory (DFT) calculations. Calculations on selected model show that the low‐coordinated Au atoms of the Au₂₉ nanoparticle carry slightly negative charges, which enhance the O₂ binding energy compared with the corresponding bulk surfaces. Two reaction pathways of the CO oxidation were considered: the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH). The overall LH reaction O_2(ads) + CO_(gas) → O_2(ads) + CO_(ads) → OOCO_(ads) → O_(ads) + CO_2(gas) is calculated to be exothermic by 3.72 eV; the potential energies of the two transition states ( TS_LH1 and TS_LH2 ) are smaller than the reactants, indicating that no net activation energy is required for this process. The CO oxidation via ER reaction Au₂₉ + O_2(gas) + CO_(gas) → Au₂₉–O_2(ads) + CO_(gas) → Au₂₉–CO_3(ads) → Au₂₉–O_(ads) + CO_2(gas) requires an overall activation barrier of 0.19 eV, and the formation of Au₂₉–CO_3(ads) intermediate possesses high exothermicity of 4.33 eV, indicating that this process may compete with the LH mechanism. Thereafter, a second CO molecule can react with the remaining O atom via the ER mechanism with a very small barrier (0.03 eV). Our calculations suggest that the CO oxidation catalyzed by the Au₂₉ nanoparticle is likely to occur at or even below room temperature. To gain insights into high‐catalytic activity of the gold nanoparticles, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Suzuki coupling approach for the synthesis of phenylene-pyrimidine alternating oligomers for blue light-emitting material

[reaction: see text] Conjugated oligomers with an alternating phenylene-pyrimidine structure have been synthesized by the successive Suzuki coupling reaction starting from 2-bromo-5-iodopyrimidine. The photoluminescence properties and quasi-reversible redox behavior of these oligomers make them applicable as an active material for a light-emitting device. Blue light-emitting electroluminescent devices with an external quantum efficiency up to 1.8% have been fabricated.     

Analysis of Dynamic and Thermodynamic Adsorption of Nanoparticles on Solid Surfaces by Dark‐Field Light Scattering Measurements

We have constructed a dark‐field light scattering microscope using a very low‐cost digital camera to investigate the adsorption of gold nanoparticles (AuNPs) on four different substrates at various pH values. The substrates used are glass, polycarbonate (PC), poly(dimethylsiloxane) (PDMS), and poly(methyl methacrylate) (PMMA). The coverage of AuNPs on hydrophobic substrates such as PDMS is greater than that on hydrophilic substrates like glass. The adsorption and aggregation of AuNPs on a particular substrate increased upon decreasing the pH (from 9.0 to 4.0). A greater coverage percentage of AuNPs, but less aggregation, occurs on glass treated with poly(diallyldimethylammonium) (PDDA) than on bare glass. The scattering intensity increases upon increasing the number of layers of adsorbed AuNPs on glass that was treated sequentially with AuNPs and PDDA. When compared to UV‐Vis absorption, dark‐field microscope provides greater sensitivity and qualitative surface information.     

Applications of Aziridinium Ions: Selective Syntheses of Pyrazolidin‐3‐ones and Pyrazolo[1,2‐a]pyrazoles

Reaction of ethyl (2S*,3R*)‐3‐chloro‐2‐(dialkylamino)‐3‐phenylpropanoates ( 4 ) with hydrazine monohydrate gave pyrazolidin‐3‐ones ( 5 ) via selective opening of the in situ generated aziridinium ions, followed by intramolecular amidation. (1Z,4S*,5S*)‐1‐Arylmethylidene‐4‐(dialkylamino)‐3‐oxo‐5‐phenylpyrazolidinium‐1‐ide ( 6 ), prepared from pyrazolidin‐3‐ones ( 5 ) and aromatic aldehydes under acid catalysis, reacted with a variety of 1,3‐dipolarophiles to afford good yields of pure cycloadducts 7 – 11 . The cycloaddition regio‐ and/or stereoselectivities, in all relevant cases, were also high.     

Synthesis,Optical Properties,and Sensing Applications of Gold Nanodots

In this Personal Account, we briefly address our journey in developing photoluminescent nanomaterials for sensing purposes, with a focus on gold nanodots (Au NDs). Their synthetic strategies, optical properties, and sensing applications are emphasized. The Au NDs can be simply prepared from the etching of small‐sized Au nanoparticles (<3 nm in diameter) by thiol compounds such as 11‐mercaptoundecanoic acid under alkaline conditions. This simple approach allows the preparation of various functional Au NDs by choosing different thiol compounds as etching agents. Since the optical properties of Au NDs are highly dependent on the core and shell of each Au ND, the selection of etching reagents is important. Over the years we have developed various sensing systems using Au NDs for the detection of metal ions, anions, and proteins, based on analyte‐induced photoluminescence quenching/enhancement of Au NDs as a result of changes in their oxidation state, shell composition, and structure.     

Proton shock acceleration in laser-plasma interactions

The formation of strong, high Mach number (2-3), electrostatic shocks by laser pulses incident on overdense plasma slabs is observed in one- and two-dimensional particle-in-cell simulations, for a wide range of intensities, pulse durations, target thicknesses, and densities. The shocks propagate undisturbed across the plasma, accelerating the ions (protons). For a dimensionless field strength parameter a(0)=16 (Ilambda(2) approximately 3 x 10(20) W cm(-2) microm(2), where I is the intensity and lambda the wavelength), and target thicknesses of a few microns, the shock is responsible for the highest energy protons. A plateau in the ion spectrum provides a direct signature for shock acceleration.