Widespread formation of toxic nitrated bisphenols indoors by heterogeneous reactions with HONO.

With numerous structurally diverse indoor contaminants, indoor transformation chemistry has been largely unexplored. Here, by integrating protein affinity purification and nontargeted mass spectrometry analysis (PUCA), we identified a substantial class of previously unrecognized indoor transformation products formed through gas-surface reactions with nitrous acid (HONO). Through the PUCA, we identified a noncommercial compound, nitrated bisphenol A (BPA), from house dust extracts strongly binding to estrogen-related receptor γ. The compound was detected in 28 of 31 house dust samples with comparable concentrations (ND to 0.30 µg/g) to BPA. Via exposing gaseous HONO to surface-bound BPA, we demonstrated it likely forms via a heterogeneous indoor chemical transformation that is highly selective toward bisphenols with electron-rich aromatic rings. We used 15N-nitrite for in situ labeling and found 110 nitration products formed from indoor contaminants with distinct aromatic moieties. This study demonstrates a previously unidentified class of chemical reactions involving indoor HONO, which should be incorporated into the risk evaluation of indoor contaminants, particularly bisphenols.

The deposition of iron and silver nanoparticles in graphene-polyelectrolyte brushes.

The high surface area of graphene nanosheets (GNs) enables them to load metal nanoparticles (NPs) for various applications such as catalysis, sensors and biomedicine. To optimize the performance, it is desired to establish an effective approach that can tune the morphology of metal nanoparticles (NPs) on GNs. We here demonstrate that GN-poly(acrylic acid) (GN/PAA) brushes can control the size and spatial distributions of iron and silver NPs. Results of Raman, Fourier transform infrared and x-ray photoelectron spectroscopy confirm the covalent bonding between PAA chains and GNs. Thermogravimetric analysis reveals a PAA grafting density of ~0.055 chain nm(-2). Transmission electron microscopy is used to study the effect of PAA chain length and precursor concentration on the morphology of the metal NPs deposited on PAA brushes and graphene oxide (GO). Short PAA brushes are found to be effective for controlling the spatial and size distributions of the NPs, resulting in small particle sizes and homogeneous distributions compared to those deposited on GO. The concentration of precursors has a limited effect on the dimension of the NPs in the brushes due to the key role that polyelectrolyte brushes play in controlling the growth of NPs.