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.

Capuli cherry-mediated green synthesis of silver nanoparticles under white solar and blue LED light

In this article, the Capuli （Prunus serotina Ehrh. var. Capuli） cherry extract was used for the synthesis of silver nanoparticles （AgNPs） in the presence of white/visible solar and blue light-emitting diode （LED） light. For the characterization of the extract and the AgNPs, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy were employed, along with hydrodynamic particle size analysis, trans- mission electron microscopy and X-ray diffraction. The Ag nanospheres obtained using white light were 40-100 nm in diameter and exhibited an absorption peak at λmax= 445 nm, whereas those obtained using blue LED light were 20-80 nm in diameter with an absorption peak at λmax= 425 nm. Thermal analysis revealed that the content of biomolecules surrounding the AgNPs was about 55-65%, and it was also found that blue LED light AgNPs （56.28%, 0.05 mM） had a higher antioxidant efficacy than the white solar light AgNPs （33.42%, 0.05 mM） against l,l-diphenyl-2-picrylhydrazyl. The results indicate that obtaining AgNPs using a blue LED light may prove to be a simple, cost-effective and easily reproducible method for creating future nanopharmaceuticals.

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.