Photooxidation of Methacrolein in Fe(III)-Oxalate Aqueous System and Its Atmospheric Implication

Iron and oxalic acids are widely distributed in the atmosphere and easily form ferric oxalate complex(Fe(III)-Ox).The tropospheric aqueous-phase could provide a medium to enable the photo-Fenton reaction with Fe(III)-Ox under solar irradiation.Although the photolysis mechanisms of Fe(III)-Ox have been investigated extensively,information about the oxidation of volatile organic compounds(VOC),specifically the potential for Secondary Organic Aerosol(SOA)formation in the Fe(III)-Ox system,is lacking.In this study,a ubiquitous VOC methacrolein(MACR)is chosen as a model VOC,and the oxidation of MACR with Fe(III)-Ox is investigated under typical atmospheric water conditions.The effects of oxalate concentration,Fe(III)concentration,MACR concentration,and pH on the oxidation of MACR are studied in detail.Results show that the oxidation rate of MACR greatly accelerates in the presence of oxalate when compared with only Fe(III).The oxidation rate of MACR also accelerates with increasing concentration of oxalate.The effect of Fe(III)is found to be more complicated.The oxidation rate of MACR first increases and then decreases with increasing Fe(III)concentration.The oxidation rate of MACR increases monotonically with decreasing pH in the common atmospheric water pH range or with decreasing MACR concentration.The production of ferrous and hydrogen peroxide,pH,and aqueous absorbance are monitored throughout the reaction process.The quenching experiments verify that·OH and O_(2)^(+)are both responsible for the oxidation of MACR.MACR is found to rapidly oxidize into small organic acids with higher boiling points and oligomers with higher molecular weight,which contributes to the yield of SOA.These results suggest that Fe(III)-Ox plays an important role in atmospheric oxidation.

Multiscale design of stiffening and ROS scavenging hydrogels for the augmentation of mandibular bone regeneration

Although biomimetic hydrogels play an essential role in guiding bone remodeling,reconstructing large bone defects is still a significant challenge since bioinspired gels often lack osteoconductive capacity,robust mechanical properties and suitable antioxidant ability for bone regeneration.To address these challenges,we first engineered molecular design of hydrogels(gelatin/polyethylene glycol diacrylate/2-(dimethylamino)ethyl methacrylate,GPEGD),where their mechanical properties were significantly enhanced via introducing trace amounts of additives(0.5 wt%).The novel hybrid hydrogels show high compressive strength(>700 kPa),stiff modulus(>170 kPa)and strong ROS-scavenging ability.Furthermore,to endow the GPEGD hydrogels excellent osteoinductions,novel biocompatible,antioxidant and BMP-2 loaded polydopamine/heparin nanoparticles(BPDAH)were developed for functionalization of the GPEGD gels(BPDAH-GPEGD).In vitro results indicate that the antioxidant BPDAH-GPEGD is able to deplete elevated ROS levels to protect cells viability against ROS damage.More importantly,the BPDAH-GPEGD hydrogels have good biocompatibility and promote the osteo differentiation of preosteoblasts and bone regenerations.At 4 and 8 weeks after implantation of the hydrogels in a mandibular bone defect,Micro-computed tomography and histology results show greater bone volume and enhancements in the quality and rate of bone regeneration in the BPDAH-GPEGD hydrogels.Thus,the multiscale design of stiffening and ROS scavenging hydrogels could serve as a promising material for bone regeneration applications.