concentration were-15%, 5%, and 8%, respectively. Mineral aerosol contributed-16% to the PM2.5 aerosol mass. These data show that combustion-related particles rather than wind-blown dust dominated the light extinction budget during June 1999.

No abstract

All-inorganic CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (PeQDs) have shown great promise in optoelectronics and photovoltaics owing to their outstanding linear optical properties; however, nonlinear upconversion is limited by the small cross-section of multiphoton absorption, necessitating high power density excitation. Herein, we report a convenient and versatile strategy to fine tuning the upconversion luminescence in CsPbX3 PeQDs through sensitization by lanthanide-doped nanoparticles. Full-color emission with wavelengths beyond the availability of lanthanides is achieved through tailoring of the PeQDs bandgap, in parallel with the inherent high conversion efficiency of energy transfer upconversion under low power density excitation. Importantly, the luminescent lifetimes of the excitons can be enormously lengthened from the intrinsic nanosecond scale to milliseconds depending on the lifetimes of lanthanide ions. These findings provide a general approach to stimulate photon upconversion in PeQDs, thereby opening up a new avenue for exploring novel and versatile applications of PeQDs.

[1] The Gobi desert in northwest China is an important source of mineral aerosols over both eastern Asia and the northern Pacific Ocean. In order to determine the chemical, physical, and radiative properties of aerosols originating from the Gobi desert source region, field measurements were performed in Yulin, China, in April 2001 as part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) campaign. The means and standard deviations of the measured aerosol light absorption coefficient s ap , scattering coefficient s sp , and single-scattering albedo w are 6 Mm À1 (11 Mm À1 ), 158 Mm À1 (193 Mm À1 ), and 0.95 (0.05), respectively. A clear diurnal pattern is observed in both s ap and s sp , resulting from diurnal changes in the mixing height as well as from local combustion sources in the morning and dust sources in the afternoon. Two distinct populations of aerosol mass scattering efficiencies E scat_2.5 , one for aerosols dominated by desert dust ($1.0 m 2 g À1 ) and the other for aerosols composed primarily of local pollutants ($3.0 m 2 g À1 ), are observed. During the field study there were three significant dust events that occurred for, on average, several days at a time. The most significant dust storm resulted in a 24-hour-average PM 2.5 concentration (mass concentration of particles having aerodynamic diameters less than 2.5 mm) of 453 mg m À3 and a peak s sp of 2510 Mm À1 on 8 April. The mean PM 2.5 mass concentration during the dust storm periods is approximately 169 mg m À3 , about 4 times greater than the mean value of 44 mg m À3 observed during local pollution periods. When local pollution is the dominant source of fine particulate mass, organic matter (OM) is the major chemical component, contributing 41% to the PM 2.5 mass, followed by crustal material (29%), sulfate (17%), and elemental carbon (EC) (13%). During sand storm periods, $51% of PM 2.5 mass is crustal material, followed by CO 3 2À (11%) and OM (9.5%). The element enrichment factors indicate that coal combustion, biomass burning, and mobile source emissions are important local pollution sources. Overall, our results indicate that in addition to dust, local pollution also has a significant influence on aerosol properties in the region.

Lanthanide-doped upconversion nanoparticles (UCNPs) have shown great promise in versatile bioapplications. For the first time, organosilica-shelled β-NaLuF4:Gd/Yb/Er nanoprobes with a rattle structure have been designed for dual-modal imaging and photodynamic therapy (PDT). Benefiting from the unique rattle structure and aromatic framework, these nanoprobes are endowed with a high loading capacity and the disaggregation effect of photosensitizers. After loading of β-carboxyphthalocyanine zinc or rose Bengal into the nanoprobes, we achieved higher energy transfer efficiency from UCNPs to photosensitizers as compared to those with conventional core-shell structure or with pure-silica shell, which facilitates a large production of singlet oxygen and thus an enhanced PDT efficacy. We demonstrated the use of these nanoprobes in proof-of-concept X-ray computed tomography (CT) and UC imaging, thus revealing the great potential of this multifunctional material as an excellent nanoplatform for cancer theranostics.

[1] Scattering and absorption of sunlight by anthropogenic aerosols reduce the photosynthetically active radiation (PAR) incident upon the Earth's surface, but increase the fraction of the PAR that is diffuse. These alterations to irradiance may elicit conflicting responses in terrestrial plants: photosynthesis and net primary productivity (NPP) are slowed by reductions in total PAR, but enhanced by increases in diffuse PAR. In this paper, we use two canopy photosynthesis models to estimate the net effect of aerosols on carbon assimilation by green plants during summertime at midlatitudes. The model calculations indicate that the net effect of PAR scattering and absorption by atmospheric aerosols on NPP can be positive, neutral, or negative. Two parameters that strongly influence the net effect are the aerosol optical depth (integral of light extinction with height) and the cloud cover. On cloudless days NPP peaks under moderately thick aerosol loadings. On overcast days, aerosols slow NPP. The implications of these results for various regions of the globe and possible directions for future studies on the effect of aerosols on plant growth are discussed.

[1] As part of the Atlanta Supersite 1999 study, aerosol radiative and related physical and chemical properties are examined on the basis of measurements of PM 2.5 (aerosol particles with aerodynamic diameters, D p , less than 2.5 mm) in urban Atlanta. In addition to potential compliance issues with proposed regulatory standards, PM 2.5 concentrations in Atlanta and the surrounding region are large enough to have an important impact on atmospheric radiative transfer and hence visibility and potentially regional climate. Arithmetic means and standard deviations of the light scattering by PM 2.5 (s sp at 530 nm) and absorption coefficients (s ap at 550 nm) measured at a controlled relative humidity of 49 ± 5% are 121 ± 48 and 16 ± 12 Mm À1 , respectively. Though the mean light extinction coefficient (s ep ) in Atlanta is much larger than background sites, it is comparable to nonurban areas in the interior southeast United States highlighting the contribution of a regional haze here. The single scattering albedo (w o ) in Atlanta is 0.87 ± 0.08 and is $10% lower than reported in nonurban polluted sites, likely a result of the emission of elemental carbon (EC) from mobile sources. A pronounced diel pattern in aerosol properties is observed with clear influences from mobile sources (morning rush hour maxima in concentrations, particularly soot-related indicators) and atmospheric mixing (afternoon minima). A strong linear relationship between s sp and PM 2.5 is observed, and using several techniques, gives a range of mean mass scattering efficiencies (E sp ) from = 3.5 to 4.4 m 2 g À1 . EC and s ap are observed to have a relationship though less strongly correlated than s sp and PM 2.5 . Four methods of determining the mass absorption efficiency of EC give E ap ranging from 5.3 to 18.3 m 2 g À1 . This wide range of values is a result of the variability in aerosol properties, uncertainties in the light absorption method, and in particular, differences in the EC measurement techniques. Best agreement was found using measured EC mass distributions using a multistage impactor in comparison to s ap calculated with a Mie code yielding E ap = 9.5 ± 1.5 m 2 g À1 , while EC mass summed from the impactor stages in comparison to measured s ap gives E ap = 9.3 ± 3.2 m 2 g À1 . Mie light-scattering calculations using inputs of measured mass and EC size distributions give geometric mean light scattering and absorption D p = 0.54 and 0.13 mm, respectively, and show the dominance of the submicrometer diameter particles to light extinction in the urban environment. Based on the measured aerosol optical depth in Atlanta, d a (500 nm) = 0.44 ± 0.22, and other radiative measurements, a best estimate of the average direct aerosol radiative forcing at the top of the atmosphere (a measure of the climate significance) is ÁF = À11 ± 6 W m À2 in Atlanta. This value is an order of magnitude greater than global mean estimates for aerosols underscoring the influence of aerosol particles on radiative transfer in the urban environment.

All‐inorganic lead‐free metal halides doped with ns2‐metal ions have shown great promise in optoelectronics and photovoltaics owing to their superior optical properties. Herein, a strategy is reported for tailoring the optical properties of 0D A2InX5⋅H2O and A3InX6 (A = Cs, Rb; X = Cl, Br) crystals via Sb3+ doping, and the excited‐state dynamics of Sb3+ is unveiled through temperature‐dependent photoluminescence (PL) and femtosecond transient absorption spectroscopies. Owing to the spatially confined 0D structure of the In‐based halides, Sb3+ ions experience a strong Jahn–Taller distortion on the excited state, which results in intense PL from Sb3+ with a broad emission band and a large Stokes shift. Through the control of A cation and the octahedral unit, tunable Sb3+ emissions (490−750 nm) with PL quantum yields up to 91.8% are achieved in these 0D In‐based halides. These findings provide fundamental insights into the excited‐state dynamics of Sb3+ in 0D metal halides, thus laying a foundation for future design of luminescent lead‐free 0D metal halides through ns2‐metal doping towards versatile applications.