Generation of reactive oxygen species (ROS) by common
sunscreen
agents such as titanium dioxide (TiO2) and zinc oxide (ZnO)
has prompted much research to incorporate effective antioxidants into
sunscreens. Nanodiamonds (NDs) and fullerenes (C60) are
potent antioxidants (radical scavengers) and effective UV filters,
making them prime candidates as additives. The radical scavenging
potentials of NDs and C60 are compared to the common antioxidant
vitamin C using the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH)
assay. In the presence of UV irradiation and ROS-generating TiO2 nanoparticles, we found that the radical scavenging potentials
of vitamin C significantly decrease, while those of NDs and C60 are enhanced. This suggests that NDs and C60 can
be used as long-lasting antioxidants to complement sunscreens. NDs
and C60 are further incorporated into prototype creams
along with TiO2 nanoparticles. When these prototype creams
are subjected to simulated solar irradiation, the transmission spectra
show that the anti-UV properties of the creams are well maintained
after prolonged irradiation. Hence, NDs and C60 are photostable
UV filters, which can supplement the sun protection efficacy of sunscreens.
Cell studies using human dermal fibroblasts are also conducted to
demonstrate the ability of NDs and C60 to scavenge the
intracellular ROS generated by TiO2 nanoparticles. Under
irradiation, ND significantly reduces intracellular oxidative stress.
This is not observed for C60 because it can behave as both
a ROS generator and scavenger when irradiated. This work establishes
the antioxidant and anti-UV benefits of adding NDs and C60 to sunscreens.
SAPO‐34 hollow fiber zeolite membranes are successfully synthesized on α‐Al2O3 hollow fiber ceramic substrates by secondary growth method, and used to separate H2 from a binary mixture (H2, C3H8) or ternary mixture (H2, C3H8, and C3H6) under a wide temperature range (25–600°C) with the aim of using them for propane dehydrogenation (PDH) reactions at high temperature. The results show excellent performance for H2/C3H8 and H2/ C3H8 & C3H6 separation, with high H2 permeance of 3.1 × 10−7 mol/m2/s/Pa and H2/C3H8 selectivity of 41 at 600°C. Additionally, the membrane shows stable performance for 140 hr of H2/C3H8 separation test at 600°C. The high performance of this membrane is mainly attributed to the thin (∼2 μm) zeolite layer and asymmetric‐wall of the hollow fiber support. So far, this membrane offers the highest hydrogen permeation and selectivity for H2/C3H8 separation at high temperature (600°C) compared to those reported in literature.
Silicoaluminophosphate (SAPO) zeolite SAPO-34 membranes with uniform pore size of 0.38 nm and unique adsorption properties have been used in natural gas purification, H2 purification, Kr/Xe separation and other gas...
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