Effects of Different Concentrations and Exposure Time of Sodium Hypochlorite on the Structural,Compositional and Mechanical Properties of Human Dentin

This study evaluated the effects of sodium hypochlorite（NaOCl） with different concentrations and exposure time on the structural, compositional and mechanical properties of human dentin in vitro. Sixty dentin slabs were obtained from freshly extracted premolars, randomly distributed into four groups（n=15）, and treated with 1%, 5%, 10% NaOCl and distilled water（control group）, respectively, for a total of 60 min. Attenuated total reflection infrared（ATR-IR） spectroscopy, Raman spectroscopy and X-ray diffraction（XRD） were carried out before, 10 min and 60 min after the treatment. Scanning electron microscopy（SEM） and flexural strength test were conducted as well. The results showed that dentins experienced morphological alterations in the NaOCl groups, but not in the control group. Two-way repeated-measures analysis of variance revealed that the carbonate：mineral ratio（C：M）, Raman relative intensity（RRI）, a-axis, c-axis length and full width at half maximum（FWHM） with the increase of time and concentration in the NaOCl groups were not significantly different from those in the control group（P〉0.05）. Nevertheless, the mineral：matrix ratio（M：M） increased and the flexural strength declined with the increase of concentration and the extension of time in the NaOCl groups（P〈0.05）. Additionally, it was found that the M：M and the flexural strength remained unchanged after 1% NaOCl treatment（P〉0.05）, and the morphology changes were unnoticeable within 10 min in 1% NaOCl group. These results indicated that NaOCl has no significant effects on the inorganic mineral of human dentin; but it undermines and eliminates the organic content concentration-and time-dependently, which in turn influences the flexural strength and toughness of dentins. In addition, an irrigation of 1% NaOCl within 10 min can minimize the effects of NaOCl on the structural and mechanical properties of dentin during root canal treatment.

N_(2)photofixation promoted by in situ photoinduced dynamic iodine vacancies at step edge in Bi_(5)O_(7)I nanotubes

Heterogeneous photosynthesis is a promising route for sustainable ammonia production,which can utilize renewable energy and water as the hydrogen source under ambient condition.In this study,a series of Bi_(5)O_(7)I(BOI)nanosheets and nanotubes are synthesized,the surface tensile strain is formed by curling the nanosheets into nanotubes to tune the concentration and location of dynamic vacancies.Scanning transmission electron microscopy(STEM)with spherical aberration correction confirms the presence of intrinsic areal defects on the surface of the BOI nanotube resulted from surface tensile strain.The presence of areal defects lowers the formation energy of I vacancies(IV)at step edge site,thus the IV with higher concentration would be favorably generated under visible light.Rapid scan in situ Fourier transform infrared(FT-IR)analysis in the aqueous media reveals that the IV promotes photocatalytic N_(2) activation and reduction,proceeds through an associative alternating mechanism.Specially,after turning off the light,the surface vacancy sites can be reoccupied by I−ions,which enables the protection and regeneration of photocatalyst surface in an aerobic and dark environment.This work provides an innovative strategy to tune concentration and location of dynamic surface vacancies on photocatalysts by building surface tensile strain for advancing sustainable ammonia production.

Annealing and optical homogeneity of large ZnGeP_(2) single crystal

A high-quality ZnGeP_(2)(ZGP)single crystal with large size ofΦ30 mm×80 mm was grown by a modified vertical Bridgman method.ZGP wafers were annealed with ZGP polycrystalline powder for 300 h at 550,600 and 650℃,respectively.The as-grown and annealed crystals were characterized by X-ray diffraction(XRD)analysis,Fourier transform infrared spectroscopy(FTIR),IR microscope and energy-dispersive spectroscopy(EDS).Results show that the quality of all wafers is improved evidently after annealing and the optimum annealing temperature obtained is 600℃.The IR transmittance of the wafer measured by FTIR is up to 56.78%at wavelength of 2.0μm nearby and exceeds 59.00%in the wavelength range of 3.0-8.0μm.The deviations from stoichiometry decrease,and the homogeneity of the crystal is also improved after annealing.In this paper,scanning infrared map was proposed as a new nondestructive method to evaluate optical quality and homogeneity of crystal through comparing the IR transmittance with the three-dimensional IR spectral contour map.

Processing of Calamine with Modern Analytical Techniques:Processed with Huanglian Decoction(黄连汤)and Sanhuang Decoction(三黄汤)

Objective： To determine the pyrolysis characteristics of calcined and processed calamine, qualitatively and quantitatively compare the contents of related elements, morphology and functional groups of the pyrolysis products dried at different heating temperatures and explore the critical temperature and the optimal drying temperature for the process of calamine with Huanglian Decoction（HLD, 黄连汤） and San Huang Decoction（SHD, 三黄汤）. Methods： Pyrolysis products were prepared by programmable and constantly heating the calcined and processed calamine to or at different heating temperatures. Thermogravimetry（TG） was used to test their pyrolysis characteristics. Fourier transform infrared spectroscopy and scanning electron microscopeenergy dispersive spectrometer were used to determine their morphology, functional groups and element contents. Page model was used to investigate the constant drying kinetics of processed calamine. Results： The adding of HLD or SHD to calcined calamine（CC） can slow its weight loss in drying pyrolysis process. The temperature ranges where HLD and SHD can affect its weight loss were 65–150 ℃ and 74–180 ℃, respectively. The drying temperature was optimized as 90 ℃. The drying kinetic for the processed calamine fits Page model shows good linearity. Conclusions： The critical temperature and the optimal drying temperature where HLD and SHD can affect the weight loss rate in the process of calamine were explored using the theories and methods of both biophysical chemistry and processing of Chinese materia medica. This work provides a good example for the study of the process of other Chinese medicines using modern analytical techniques.

Utilization of nano/micro-size iron recovered from the fine fraction of automobile shredder residue for phenol degradation in water

The study investigates the magnetic separation of Fe from automobile shredder residue （ASR） （ 〈 0.25 mm） and its application for phenol degradation in water. The magnetically separated Fe was subjected to an ultrasonically assisted acid treatment, and the degradation of phenol in an aqueous solution using nano/micro-size Fe （n/m Fe） was investigated in an effort to evaluate the possibility of utilizing n/m Fe to remove phenol from wastewater. The prepared n/m Fe was analyzed by scanning electron microscopy （SEM） and Fourier transform infrared spectroscopy （FTIR）. The eflects of the dosages ot n/mFe, pH, concentration of phenol and amount of H2O2 on phenol removal were evaluated. The results confirm that the phenol degradation rate was improved with an increase in the dosages of n/mFe and H2O2; however, the rate is reduced when the phenol concentration is higher. The degradation of phenol by n/mFe followed the pseudo-first-order kinetics. The value of the reaction rate constant （k）was increased as the amounts of n/m Fe and H2O2 increased. Conversely, the value of k was reduced when the concentration of phenol was increased. The probable mechanism behind the degradation of phenol by n/m Fe is the oxidation of phenol through hydroxyl radicals which are produced during the reaction between H2O2 and n/m Fe.