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The inaccurate quantification of personal exposure to air pollution introduces error and bias in health estimations, severely limiting causal inference in epidemiological research worldwide. Rapid advancements in affordable, miniaturised air pollution sensor technologies offer the potential to address this limitation by capturing the high variability of personal exposure during daily life in largescale studies with unprecedented spatial and temporal resolution. However, concerns remain regarding the suitability of novel sensing technologies for scientific and policy purposes. In this paper we characterise the performance of a portable personal air quality monitor (PAM) that integrates multiple miniaturised sensors for nitrogen oxides (NO x ), carbon monoxide (CO), ozone (O 3 ) and particulate matter (PM) measurements along with temperature, relative humidity, acceleration, noise and GPS sensors. Overall, the air pollution sensors showed high reproducibility (mean R 2 = 0.93, min-max: 0.80-1.00) and excellent agreement with standard instrumentation (mean R 2 = 0.82, min-max: 0.54-0.99) in outdoor, indoor and commuting microenvironments across seasons and different geographical settings. An important outcome of this study is that the error of the PAM is significantly smaller than the error introduced when estimating personal exposure based on sparsely distributed outdoor fixed monitoring stations. Hence, novel sensing technologies such as the ones demonstrated here can revolutionise health studies by providing highly resolved reliable exposure metrics at a large scale to investigate the underlying mechanisms of the effects of air pollution on health.
Enantioselective recognition of carboxylates has important implications in asymmetric synthesis and drug discovery. We have prepared a novel C2-symmetric receptor 1 from alpha-aminoxy acids in a high overall yield. A series of chiral recognition studies indicate that receptor 1 not only can bind to carboxylate ions tightly but also has a good ability to recognize enantiomers of a broad variety of carboxylic acids in the 1H NMR spectra. Thus, the receptor 1 can be used as a chiral shift reagent for the determination of enantiomeric purities of chiral carboxylic acids by 1H NMR directly and rapidly.
In this Article, we report the successful fabrication of large-area ordered Si nanowire arrays (NWAs) by a cost-effective and scalable wet-etching process in combination with nanospheres lithography technique. The periodical Si NWAs are further investigated as photocathode for water splitting, with excellent hydrogen evolution performances with a maximum photocurrent density of 27 mA cm(-2) achieved, which is ∼2.5 times that of planar Si and random Si nanowires electrode. The greatly improved PEC performance can be attributed to the patterned and ordered NWs structure as a result of enhancement of the light harvesting as well as charge transportation and collection efficiency.
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