Determinations of geniposide using LC/MS/MS methods via forming ammonium and acetate adducts

In this paper, we report method development work to determine geniposide using LC/MS/MS via the formation of positive and negative ion adducts. Geniposide, which has been recognized to have choleretic effects, is the major iridoid glycoside component of Gardenia herbs. To enhance the sensitivity of LC/MS detection of geniposide, a small amount of volatile additives such as ammonium acetate and acetic acid are added into mobile phase solvents to form positive and negative adducts, which can then ionize via electrospray processes. The formation of positive adducts is due to the complexation between geniposide and ammonium ions ([M + NH₄]⁺). The formation of anionic adducts [M + CH₃COO]⁻ is believed to occur via hydrogen bonds bridging acetate ions and glucose groups on the geniposide molecule. Mobile phase solvents containing acetonitrile and aqueous solution (0.2 mM ammonium acetate or 0.1% acetic acid) at the ratio 15: 85 are employed to elute geniposide using C8 reverse phase liquid chromatography columns with electrospray tandem mass spectrometry determinations. Using geniposide standards, the methods are validated at the concentration ranges of 5 to 1000 ng/mL and 20 to 5000 ng/mL using ammonium and acetate adducts respectively. The correlation coefficients of the standard curves are 0.9999 using both ammonium and acetate adducts. The detection limits of using ammonium and acetate adducts are 1 and 5 ng/mL respectively. The measurement accuracy and precision of using ammonium adducts are within 12% and 3% respectively, whereas the accuracy and precision are within 6 and 11% respectively using acetate adducts. When the validated calibration curves of the ammonium adduct of geniposide are used to determine spiked control samples in rat blood dialysates, the determination errors of accuracy and precision are within 12% and 10% respectively.     

Plasmonic multilayer structure for ultrathin amorphous silicon film photovoltaic cell

A plasmonic multilayer structure (PMS) is proposed for photovoltaic cells with an ultrathin active layer that is 30 nm amorphous Si (α-Si). The optical properties of the PMS are analyzed by rigorous coupled-wave analysis (RCWA) and finite-difference time-domain (FDTD) method. Using the PMS, the incident light can be trapped into localized surface plasmon (LSP) and then the localized surface plasmon induces the surface plasmon (SP) that propagates transversely within the α-Si layer. Compared with the indium tin oxide (ITO)/α-Si/Ag structure, the photon number absorbed by PMS increase 28.7% while a normal incident transverse magnetic (TM) polarization wave is applied.     

TBAI/K2S2O8-facilitated reaction of sulfonylhydrazides with alkynes: Facile synthesis of (E)-β-iodovinyl sulfones

An efficient and convenient approach for the construction of various (E)-β-iodovinyl sulfones has been developed through potassium persulfate/tetrabutylammonium iodide-facilitated reaction of sulfonylhydrazides with alkynes. The products were obtained in good to excellent yields. The salient features of this reaction are the applications of a new iodine source, environmentally benign, safer solid oxidant, and shorter reaction time.     

Magnetic field modulation of photonic bandgap on FeCo/NiO half-shell array

FeCo/NiO half-shell arrays were fabricated based on the periodic monolayer polystyrene spheres. The two-dimensional magnetic periodic arrays form well-defined photonic crystals with pronounced stop bands. Quite interestingly, it is found that the stop bands can be tuned by an external magnetic field. The underlying mechanism is attributed to the controllable dielectric constant of the magnetic FeCo film under an applied magnetic field. The results shown here may open up an avenue for magnetically tunable photonic crystal stop bands, which may be useful for the creation of new magneto-optical devices.     

Angle-independent plasmonic infrared band-stop reflective filter based on the Ag/SiO₂/Ag T-shaped array

A plasmonic infrared (IR) filter assisted by localized surface plasmon polaritons (LSPPs) in a Ag/SiO?/Ag T-shaped array was theoretically and experimentally investigated. By using a Fourier transform infrared (FTIR) spectrometer, an angle-independent LSPP resonant mode caused by a Fabry-Pérot resonance in the structure was observed in agreement with the prediction from the rigorous coupled-wave analysis (RCWA) simulation. The resonant wavelength of the mode can also be controlled by modifying the geometry of the T-shaped structure. Such LSPP property can be used as an IR reflection-type band-stop filter with a single spectral bandwidth and an ultrahigh immunity to incident angles.     

Highly bent crystals formed by restrained π-stacked columns connected via alkylene linkers with variable conformations

A reproducible formation of strongly bent crystals was accomplished by structurally restraining macrocyclic π-conjugated molecules. The model π-units consist of two 9,10-bis(2-thienylethynyl)anthracenes with a strong propensity for stacking, which are connected in a macrocyclic fashion via two alkylene linkers. The correlation between the crystalline morphology and the macrocyclic structures restrained by a variety of flexible alkylene linker combinations was systematically studied. Bent crystals were obtained only with specific alkylene linkers of appropriate chain length. The alkylene linkers can adopt different conformations in the crystal packing, so as to fill voids within the macrocycle. The ability to form several similar molecular structures with different alkylene conformations gives rise to contaminations of different crystalline phases within a single crystal, and it is these phase contaminations which are responsible for the bending of the crystals.     

Optical and structural characteristics of yttrium doped ZnO films using sol–gel technology

Yttrium-doped ZnO gel was spin-coated on the SiO₂/Si substrate. The as-prepared ZnO:Y (YZO) thin films then underwent a rapid thermal annealing (RTA) process conducted at various temperatures. The structural and photoluminescence characteristics of the YZO films were discussed thereafter. Our results indicated that the grain size of YZO thin films being treated with various annealing temperatures became smaller as compared to the ones without being doped with yttrium. Furthermore, unlike other ZnO films, the grains of YZO thin films appeared to separate from one another rather than aggregating together as both types of the films were annealed under the same environment. The photoluminescence characteristic measured showed that the UV emission was the only radiation obtained. However, the UV emission intensity of YZO thin film was much stronger than that of the ZnO thin film after annealing them with the same condition. It was also found that the intensity increased with an increase in the annealing temperature, which was caused by the exciton generated and the texture surface of the YZO thin film.     

Comparison of the angular selectivity characteristics for an off-axis holographic storage system calculated by Born approximation and coupled-wave theory

The first Born approximation is applied to calculate the angular selectivity for different positions on the reconstructed image as a function of the object beam's optical axis angle theta(ob) and reference beam angle theta(rw) for a holographic data storage system that records the Fourier transform holograms in a medium with an infinite plane-wave reference beam. Results are compared with those calculated by the coupled-wave theory.     

Asymmetric Synthesis of Axinellamines A and B

Axinellamines A and B are broad‐spectrum antibacterial pyrrole–imidazole alkaloids that have a complex polycyclic skeleton. A new asymmetric synthesis of these marine sponge metabolites is described herein, featuring an oxidative rearrangement and an anchimeric chlorination reaction.     

Measurements of wall shear stress of a turbulent boundary layer using a micro-shear-stress imaging chip

Measurements of wall shear-stress streaks of a turbulent boundary layer in the channel flow were carried out using a MEMS-based micro-shear-stress imaging chip, which contains about 100 sensors. The chip is designed and fabricated by surface micromachining technology. One arrray of 25 micro-shear-stress sensors in the chip that covers a length of 7.5 mm is used to measure the instantaneous spanwise distribution of the surface shear stress. The statistics of high shear-stress streaks were established. Based on the measurement, the physical quantities associated with the high shear-stress streaks, such as their length, width and peak shear-stress level, were obtained. We found out that a high correlation exists between the peak shear-stress level and front-end shear-stress slope of a high shear-stress streak. This important property is currently being applied to the deisgn of a real-time flow control logic.