Thermally controlled wettability of a nanoporous membrane grafted with catechol-tethered poly(N-isopropylacrylamide)

A nanoporous membrane is coated with catechol-tethered poly(N-isopropylacrylamide). The thermosensitive variation of surface wettability determines the hindered diffusivity of dextran (40 kDa) through the nanopores.     

Adsorption and thermal decomposition of 2-octylthieno[3,4-b]thiophene on Au(111)

The adsorption and thermal stability of 2-octylthieno[3,4-b]thiophene (OTTP) on the Au(111) surfaces have been studied using scanning tunneling microscopy (STM), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). UHV-STM studies revealed that the vapor-deposited OTTP on Au(111) generated disordered adlayers with monolayer thickness even at saturation coverage. XPS and TPD studies indicated that OTTP molecules on Au(111) are stable up to 450K and further heating of the sample resulted in thermal decomposition to produce H(2) and H(2)S via C-S bond scission in the thieno-thiophene rings. Dehydrogenation continues to occur above 600K and the molecules were ultimately transformed to carbon clusters at 900K. Highly resolved air-STM images showed that OTTP adlayers on Au(111) prepared from solution are composed of a well-ordered and low-coverage phase where the molecules lie flat on the surface, which can be assigned as a (9×2√33)R5° structure. Finally, based on analysis of STM, TPD, and XPS results, we propose a thermal decomposition mechanism of OTTP on Au(111) as a function of annealing temperature.     

Gold-catalyzed hydrosilyloxylation driving tandem aldol and mannich reactions

The chemoselective formation of an enolate from alkyne in the presence of a carbonyl and imine group was realized, which constructed a variety of structural motifs under exceedingly mild reaction conditions in a tandem process. Reaction driving tandem hydrosilyloxylation/aldol reactions was achieved through the formation of enol silyl ethers catalytically generated in situ from readily available alkynes. These reactions were expanded to obtain β-amino enol silyl ethers in good yields via the tandem hydrosilyloxylation/isomerization/Mannich reaction.     

Application of a new microcantilever biosensor resonating at the air-liquid interface for direct insulin detection and continuous monitoring of enzymatic reactions

Here we describe the application of a recently developed high-resolution microcantilever biosensor resonating at the air-liquid interface for the continuous detection of antigen-antibody and enzyme-substrate interactions. The cantilever at the air-liquid interface demonstrated 50% higher quality factor and a 5.7-fold increase in signal-to-noise-ratio (SNR) compared with one immersed in the purified water. First, a label-free detection of a low molecular weight protein (insulin, 5.8 kDa) in physiological concentration was demonstrated. The liquid facing side of the cantilever was functionalized by coating its surface with insulin antibodies, while the opposite side was exposed to air. The meniscus membrane at the micro-slit around the cantilever sustained the liquid in the microchannel. After optimizing the process of surface functionalization, the resonance frequency shift was successfully measured for insulin solutions of 0.4, 2.0, and 6.3 ng ml(-1). To demonstrate additional application of the device for monitoring enzymatic protein degradation, the liquid facing microcantilever surface was coated with human recombinant SOD1 (superoxide dismutase 1) and exposed to various concentrations of proteinase K solution, and the kinetics of the SOD1 digestion was continuously monitored. The results showed that it is a suitable tool for sensitive protein detection and analysis.     

Infrared laser ablation sample transfer for on‐line liquid chromatography electrospray ionization mass spectrometry

We have demonstrated an on‐line laser ablation sampling system and coupling of the system to liquid chromatography (LC) using an infrared (IR) laser to ablate and transfer materials into a flowing solvent stream. With this approach, samples are deposited on a microscope slide mounted on a translation stage and ablated in transmission geometry using a pulsed mid‐IR laser. The ablated material is captured in an exposed flowing solvent stream that carries the ablated material to the electrospray source. Post‐ablation separation is accomplished using a capillary column downstream of the capture zone. The performance of the system was assessed using peptide and protein mixtures ablated from the target and analyzed with and without LC separation. Copyright © 2012 John Wiley & Sons, Ltd.     

Photovoltaic devices using semiconducting polymers containing head‐to‐tail‐structured bithiophene,pyrene, and benzothiadiazole derivatives

An alternating copolymer composed of heal‐to‐tail‐structured 3,4′‐dihexyl‐2,2′‐bithiophene (DHBT) and pyrene units [poly(DHBT‐alt‐PYR)] was synthesized using a Stille coupling reaction for use in photovoltaic devices as a p‐type donor. For the reduction of the bandgap energy of poly(DHBT‐alt‐PYR), 4,7‐bis(3′‐hexyl‐2,2′‐bithiophen‐5‐yl)benzo[c][1,2,5]thiadiazole (BHBTBT) units were introduced into the polymer. Poly(DHBT‐co‐PYR‐co‐BHBTBT)s were synthesized using the same polymerization reaction. The synthesized polymers were soluble in common organic solvents and formed smooth thin films after spin casting. The optical bandgap energies of the polymers were obtained from the onset absorption wavelengths. The measured optical bandgap energy of poly(DHBT‐alt‐PYR) was 2.47 eV. As the BHBTBT content in the ter‐polymers increased, the optical bandgap energies of the resulting polymers decreased. The bandgap energies of poly(50DHBT‐co‐40PYR‐co‐10BHBTBT) and poly(50DHBT‐co‐20PYR‐co‐30BHBTBT) were 1.84 and 1.73 eV, respectively. Photovoltaic devices were fabricated with a typical sandwich structure of ITO/PEDOT:PSS/active layer/LiF/Al using the polymers as electron donors and [6,6]‐phenyl C₇₁‐butyric acid methyl ester as the electron acceptor. The device using poly(50DHBT‐co‐20PYR‐co‐30BHBTBT) showed the best performance among the fabricated devices, with an open‐circuit voltage, short‐circuit current, fill factor, and maximum power conversion efficiency of 0.68 V, 5.54 mA/cm², 0.35, and 1.31%, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Particle and breath figure formation of triblock copolymers having self‐complementary hydrogen‐bonding units

Novel triblock copolymers having self‐complementary hydrogen‐bonding units were synthesized by using reversible addition–fragmentation transfer polymerization. As characterized by dynamic light scattering and atomic force microscopy, these polymers formed noncovalently crosslinked polymer particles and showed an aggregation behavior by intermolecular and intramolecular interactions. At low concentration, polymers formed nanoparticles, and the particle diameter increased with increasing polymer concentration. Well‐ordered hexagonal microstructures were prepared by “Breath Figure” technique with the triblock copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Surface characteristics of Ti‐10Ta‐10Nb alloy modified by hydrogen peroxide treatment for dental implants

The use of titanium‐based alloys as biomaterials is becoming more common because they have a reduced elastic modulus, superior biocompatibility, specific strength, good corrosion resistance, superior strain control, and fatigue resistance compared to conventional stainless steel and Co? Cr alloys. However, when implanted into the human body these metals are problematic because they do not directly bond with living bone. Surface treatments play an important role in nucleating calcium phosphate deposition on a surgical titanium alloy implant. The purpose of this study is to examine whether the precipitation of apatite on Ti? 10Ta? 10Nb alloy is affected by surface modification in H₂O₂ solution. Specimens were chemically treated with a solution containing 30 wt% H₂O₂ at 80 °C for 1 h, and subsequently heat treated at 400 °C for 1 h. All specimens were immersed in SBF (Simulated Body Fluid) with a pH of 7.4 at 36.5 °C for seven days, and the surfaces were examined with XRD, SEM, EDX and in vitro testing. The microstructure analysis of the Ti? 10Ta? 10Nb alloy after etching with Keller's etchant showed a Widmanstatten pattern. The micro‐Vickers hardness number was 236.44 ± 4.99, and surface roughness was increased by the surface treatment. The wettability after surface treatment was better than on the nontreated surface. Resistance to cytotoxicity was decreased by the chemical surface treatment (P < 0.05). Copyright © 2011 John Wiley & Sons, Ltd.     

Quantitative analysis of an organic thin film by XPS,AFM and FT‐IR

We report the characterization of Firpic (iridium(III)bis[4,6‐di‐fluorophenyl]‐pyridinato‐N,C²,]picolinate) organic thin film prepared by vacuum deposition to provide a systematic route to organic film quantification. To analyze the characteristics of thin Firpic films on a Si substrate, various techniques such as XPS, Fourier transform infra‐red (FT‐IR) spectrometer, and atomic force microscopy (AFM) are utilized. The Firpic films remain stable without surface morphological or compositional change during deposition and after exposure to X‐ray irradiation or atmospheric environment, for which qualities these films are believed to be an ideal platform as a pure organic thin film. The monotonic increases in FT‐IR and XPS intensities with film thickness are matching well with each other. In particular, from the XPS intensity analysis, the relative atomic sensitivity factors of the present system, electron attenuation length, and molecular density in the organic thin film can be evaluated. Copyright © 2011 John Wiley & Sons, Ltd.