Synthesis and photophysical investigation of squaraine rotaxanes by "clicked capping"

Pseudorotaxane complexes of squaraine dyes and tetralactam macrocycles are converted into permanently interlocked rotaxane structures using copper-catalyzed and copper-free cycloaddition reactions with bulky stopper groups. The photophysical properties of the encapsulated squaraine depend on the structure of the macrocycle. In one case, squaraine rotaxanes are produced in near-quantitative yields and with intense near-IR fluorescence. In another case, squaraine fluorescence is greatly diminished upon macrocyclic encapsulation but the signal can be restored by dye displacement with anions.     

Easily Scalable Shell-Structured Copper Catalyst with High Activity and Durability for Carbon Dioxide Hydrogenation

Inducing strong metal-support interaction (SMSI) has been a useful way to control the structure of surface active sites. The SMSI often causes the encapsulation of metal particles with an oxide layer. Herein, an amorphous ceria shell was formed on Cu nanoparticles under a mild gas condition with high activity and durability for surface reaction. Cu−Ce solid solution promoted the transfer of surface oxygen species, which induced the ceria shell formation on Cu nanoparticles. This catalyst was used for CO₂ hydrogenation, selectively producing CO with high low-temperature activity and good durability for operation at high temperature. CO₂ activation and H₂ spillover could occur at low temperatures, enhancing the activity. The shell prevented the sintering, assuring durability. This catalyst was applied to a bench-scale reactor without loss in performance, resulting in high CO productivity in all temperature ranges.     

Reorganization of highly preorganized hosts upon cation complexation: Ab initio study of fluorospherands

Fluorospherands (F‐spherands) are highly preorganized hosts composed of fluorobenzene or 4‐methylfluorobenzene units attached to one another at their 2,6‐positions. To understand the intrinsic factors affecting cation complexation, we investigated the complexation behavior between F‐spherands and cations using density functional theory (DFT) at the level of B3LYP/6‐31G**. The F6‐spherand (C₆H₃F)₆, ( 1 ) has a highly preorganized spherical cavity, which can encapsulate Li⁺ and Na⁺. Its cavity is not big enough for K⁺ and NH, which prefer external binding. Plausible conformations were studied for F8‐spherand (C₆H₃F)₈. Conformer of D_2d symmetry ( 2b ) is more stable than that of D_4d ( 2a ), in agreement with NMR experiments. The cavity size of F8‐spherand is big enough to encapsulate all cations studied. However, the cavity size of 2b is smaller than that of 2a , which resulted in the guest selectivity. Upon complexation, 2b conformation is more stable for Li⁺ and Na⁺, while 2a conformation is preferred for larger cations such as K⁺ and NH. Thus, the ab initio calculations over these highly preorganized fluorospherands give important insights into their host–guest chemistry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Preparation, characterization, and reactivity of Pt/SDBC catalysts for the hydrogen-water isotopic exchange reaction

Pt/SDBC catalysts, which are used for the hydrogen-water isotopic exchange reaction, were prepared. TGA experiments showed that the treatment temperature of Pt/SDBC catalysts in inert gas is limited to 400 °C and the maximum allowable heat treatment temperature in oxygen is 200 °C. From nitrogen adsorption and hydrogen chemisorption measurements, it was shown that the dispersion of platinum particles depended on the physical properties, i.e., specific surface area and pore structure of SDBC. It was found that the heat treatment could not impact the structure of SDBC and the oxygen treatment at 150 °C improved the platinum dispersion. It was shown by XPS analysis that the oxygen treatment of impregnated Pt/SDBC increased the fraction of platinum metal state and platinum dispersion. As the supported platinum area increases, the catalytic activity of Pt/SDBC for the hydrogen-water vapor isotopic exchange reaction increases. It indicates that the hydrogen chemisorption measurement can be used to estimate the catalytic activities of Pt/SDBC catalysts. It was not observed that the particle size of supported platinum affected the specific reaction rate at 60 °C. It implies that this reaction is structure insensitive.     

Chemiluminometric enzyme-linked immunosorbent assays (ELISA)-on-a-chip biosensor based on cross-flow chromatography

A chemiluminometric biosensor system for point-of-care testing has been developed using an immuno-chromatographic assay combined with an enzyme (e.g., horseradish peroxidase) tracer that produces a light signal measurable on a simple detector. Cross-flow chromatography, a method previously investigated by our laboratory, was utilized in order to accomplish sequential antigen-antibody binding and signal generation. This enzyme-linked immunosorbent assay (ELISA) was effectively carried out on a plastic chip that was redesigned to simplify the fabrication process. To enhance the sensitivity, biotin-streptavidin capture technology was employed in preparing an immuno-strip that was then incorporated onto the chip in order to generate the ELISA-on-a-chip (EOC) biosensor. Samples containing cardiac troponin I (cTnI) were analyzed using the EOC. A chemiluminescent signal proportional to the analyte concentration was produced by adding a luminogenic substrate to the tracer enzyme complexed with the analyte on the chip. The luminescent signal was detected in a dark chamber mounted with a cooled charge-coupled device and the signal was converted to optical density for quantification. This EOC biosensor system was capable of detecting cTnI present in serum at concentrations as low as 0.027 ng mL⁻¹, 30 times lower than those measured using the conventional rapid test kit with colloidal gold as the tracer. In addition, the final data was acquired within 30 s after the addition of the enzyme substrate, which was faster than the detection time required when using a colorimetric substrate with the same tracer enzyme.     

Fast gradient elution reversed-phase liquid chromatography with diode-array detection as a high-throughput screening method for drugs of abuse. II. Data analysis

In Part I of this work, we developed a method for the detection of drugs of abuse in biological samples based on fast gradient elution liquid-chromatography coupled with diode array spectroscopic detection (LC-DAD). In this part of the work, we apply the chemometric method of target factor analysis (TFA) to the chromatograms. This algorithm identifies the target compounds present in chromatograms based on a spectral library, resolves nearly co-eluting components, and differentiates between drugs with similar spectra. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguishes the present method from conventional library searching methods. Our library has a mean list length (MLL) of 1.255 and a discriminating power of 0.997 when both retention index and spectral factors are considered. The algorithm compares a library of 47 different compounds of toxicological relevance to unknown samples and identifies which compounds are present based on spectral and retention index matching. The application of a corrected retention index for identification rather than raw retention times compensates for long-term and column-to-column retention time shifts and allows for the use of a single library of spectral and retention data. Training data sets were used to establish the search and identification parameters of the method. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were found to be 92% and 94%, respectively.     

Impact of interstitial air holes on a wide-bandwidth rejection filter made from a photonic crystal fiber

We have investigated the spectral properties of a band rejection filter made with a long-period fiber grating written in photonic crystal fiber that has interstitial air holes. Experiments showed that only one mode was coupled strongly to the fundamental core mode over a 600 nm spectral range. The central wavelength of the filter could be tuned over that range without being appreciably affected by any other mode. By using the multipole method, we found that the interstitial air holes of the photonic crystal fiber played a critical role in limiting the number of modes that could strongly interact with the fundamental mode and in obtaining well-separated resonance peaks. Excellent agreement between theory and experiment was obtained.     

A simple and cost-effective molecular diagnostic system and DNA probes synthesized by light emitting diode photolithography

This work introduces a novel chip to be used in the future as a simple and cost-effective method for creating DNA arrays using light emission diode (LED) photolithography. The DNA chip platform contains 24 independent reaction sites, which allows for the testing of a corresponding amount of patients’ samples in hospital. An array of commercial UV LEDs and lens systems was combined with a microfluidic flow system to provide patterning of 24 individual reaction sites, each with 64 independent probes. Using the LED array instead of conventional laser exposure systems or micro-mirror systems significantly reduces the cost of equipment. The microfluidic system together with microfluidic flow cells drastically reduces the amount of used reagents, which is important due to the high cost of commercial reagents. The DNA synthesis efficiency was verified by fluorescence labeling and conventional hybridization.     

Porous SnO2/layered titanate nanohybrid with enhanced electrochemical performance for reversible lithium storage

A porous hybrid of titanate nanosheets with SnO(2) nanoparticles has been realized by an exfoliation and reassembling route. The present nanohybrid shows a large reversible capacity of 860 mA h g(-1) with a good capacity retention (about 60% retention of the initial capacity after 50 cycles).     

Reduction of the Polarization-Dependent Loss of Long-Period Fiber Gratings by Thermal Heating

The polarization-dependent loss of UV-written long-period fiber gratings was significantly reduced by increasing the pulse repetition rate of the writing UV beam. The effect is closely related with the enhanced photosensitivity induced by thermal heating.