Jian Huang

Bio: Jian Huang is an academic researcher from University of California, Riverside. The author has contributed to research in topics: Nanowire & Nanorod. The author has an hindex of 9, co-authored 20 publications receiving 448 citations. Previous affiliations of Jian Huang include Nanjing University & National University of Singapore.

The measurement of aerosol optical properties at a rural site in Northern China

Abstract: . Atmospheric aerosols constitute one of the largest sources of uncertainty in the estimation of radiative forcing for climate. From April 2003 to January 2005, in situ measurements of aerosol optical properties were conducted at a rural site in Northern China, Shangdianzi Global Atmosphere Watch (GAW) regional station (SDZ), about 150 km from Beijing. Mean values (standard deviation, S.D.) of scattering and absorption coefficients for the entire period are 174.6 Mm−1 (189.1 Mm-1) and 17.5 Mm−1 (13.4 Mm-1), respectively. These values are approximately one third of the reported values for scattering coefficients and one fifth of those for absorption coefficients obtained in the Beijing urban area. The mean single scattering albedo (SSA) for the entire period was estimated as 0.88 (0.05), which is about 0.07 higher than the values reported for the Beijing urban area, and also higher than the values (0.85) used in a reported climate simulation for China and India. Both the absorption and scattering coefficients showed a seasonal cycle with the lowest values in winter, while the highest values occurred in summer for absorption coefficients and in fall for scattering coefficients. The mean SSA values were lowest in spring and highest in winter. The daily variations of aerosol absorption and scattering coefficients were strongly influenced by synoptic changes throughout the observation period. A trajectory cluster analysis was applied to discern the source characteristics of aerosol optical properties for different air masses. The cluster-mean aerosol scattering coefficients, absorption coefficients and SSA were all high when the air masses moved from SW and SE-E directions to the site and aerosols were influenced with heavy pollution from the dense population centers and industrial areas. The cluster-mean SSA for air masses coming from the polluted areas was not only higher than those with trajectories from the "clean" directions, but also higher than the reported values for the regions with high pollution emissions (such as the Beijing urban area). This fact might reflect the substantial secondary aerosol production during transport. The characteristics of aerosol optical properties measured at this rural site suggest significant impacts of human activities on the regional aerosol.

ZnO p–n Homojunction Random Laser Diode Based on Nitrogen‐Doped p‐type Nanowires

Abstract: An electrically pumped ZnO homojunction random laser diode based on nitrogen-doped p-type ZnO nanowires is reported. Nitrogen-doped ZnO nanowires are grown on a ZnO thin film on a silicon substrate by chemical vapor deposition without using any metal catalyst. The p-type behavior is studied by output characteristics and transfer characteristic of the nanowire back-gated field-effect transistor, as well as low-temperature photoluminescence. The formation of the p–n junction is confirmed by the current–voltage characteristic and electron beam-induced current. The nanowire/thin-film p–n junction acts as random laser diode. The random lasing behavior is demonstrated by using both optical pumping and electrical pumping, with thresholds of 300 kW/cm2 and 40 mA, respectively. The angle-dependant electroluminescence of the device further proves the random lasing mechanism. An output power of 70 nW is measured at a drive current of 70 mA.

Role of oxygen for highly conducting and transparent gallium-doped zinc oxide electrode deposited at room temperature

Abstract: In this work, we found that a desirable amount of oxygen can reduce defect related scattering in enhancing carrier mobility for pulsed laser deposited zinc oxide. However, excessive oxygen can lead to formation of oxygen interstitials that can act as compensation or scattering centers. At higher oxygen pressures, structural changes that increase grain boundary scattering prove to be very important. We introduce a simple transparency index to quantify the transmission of the thin films for usage as electrodes in photovoltaic devices. An excellent resistivity of ∼3.9×10−4 Ω cm and an electron mobility of ∼19.2 cm2/V s with a transparency index of 0.84 (84% of total solar spectrum transmitted) were achieved at room temperature suggesting possible applications in plastic devices.

Current self-complianced and self-rectifying resistive switching in Ag-electroded single Na-doped ZnO nanowires

Abstract: We demonstrate current self-complianced and self-rectifying bipolar resistive switching in an Ag-electroded Na-doped ZnO nanowire device. The resistive switching is controlled by the formation and rupture of an Ag nanoisland chain on the surface along the Na-doped ZnO nanowire. Na-doping plays important roles in both the self-compliance and self-rectifying properties.

ZnO nanorods with low intrinsic defects and high optical performance grown by facile microwave-assisted solution method.

Abstract: Vertically aligned ZnO nanorods were grown at 90 °C by both microwave synthesis and traditional heated water bath method on Si (100) substrate with a precoated ZnO nanoparticle seed layer. A detailed comparison in the morphology, defects, and optical properties of the ZnO nanorods grown by the two methods across the pH range of 10.07-10.9 for microwave synthesis and conventional heated water bath method was performed using scanning electron microscopy, photoluminescence, and X-ray photoelectron spectroscopy. The results show that the microwave route leads to more uniformly distributed nanorods with a lower density of native defects of oxygen interstitials and zinc vacancies. The microwave synthesis presents a promising new approach of fabricating metal oxide nanostructures and devices toward green applications.

An inventory of gaseous and primary aerosol emissions in Asia in the year 2000 : NASA global tropospheric experiment transport and chemical evolution over the pacific (TRACE-P): Measurements and analysis (TRACEP1)

Abstract: [i] An inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE-P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE-Asia experiment funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia. We estimate total Asian emissions as follows: 34.3 Tg SO 2 , 26.8 Tg NO x , 9870 Tg CO 2 , 279 Tg CO, 107 Tg CH 4 , 52.2 Tg NMVOC, 2.54 Tg black carbon (BC), 10.4 Tg organic carbon (OC), and 27.5 Tg NH 3 . In addition, NMVOC are speciated into 19 subcategories according to functional groups and reactivity. Thus we are able to identify the major source regions and types for many of the significant gaseous and particle emissions that influence pollutant concentrations in the vicinity of the TRACE-P and ACE-Asia field measurements. Emissions in China dominate the signature of pollutant concentrations in this region, so special emphasis has been placed on the development of emission estimates for China. China's emissions are determined to be as follows: 20.4 Tg SO 2 , 11.4 Tg NO x , 3820 Tg CO 2 , 116 Tg CO, 38.4 Tg CH 4 , 17.4 Tg NMVOC, 1.05 Tg BC, 3.4 Tg OC, and 13.6 Tg NH 3 . Emissions are gridded at a variety of spatial resolutions from 1° × 1° to 30 s x 30 s, using the exact locations of large point sources and surrogate GIS distributions of urban and rural population, road networks, landcover, ship lanes, etc. The gridded emission estimates have been used as inputs to atmospheric simulation models and have proven to be generally robust in comparison with field observations, though there is reason to think that emissions of CO and possibly BC may be underestimated. Monthly emission estimates for China are developed for each species to aid TRACE-P and ACE-Asia data interpretation. During the observation period of March/ April, emissions are roughly at their average values (one twelfth of annual). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±16% for SO 2 to a high of ±450% for OC.

Characteristics of concentrations and chemical compositions for PM 2.5 in the region of Beijing, Tianjin, and Hebei, China

Abstract: . In order to study the temporal and spatial variations of PM2.5 and its chemical compositions in the region of Beijing, Tianjin, and Hebei (BTH), PM2.5 samples were collected at four urban sites in Beijing (BJ), Tianjin (TJ), Shijiazhuang (SJZ), and Chengde (CD), and also one site at Shangdianzi (SDZ) regional background station over four seasons from 2009 to 2010. The samples were weighted for mass concentrations and analyzed in the laboratory for chemical profiles of 19 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, Sr, Ti, V, and Zn), eight water-soluble inorganic ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, and SO42−, and carbon fractions (OC and EC). The concentrations of PM2.5 and its major chemical species were season dependent and showed spatially similar characteristics in the plain area of BTH. The average annual concentrations of PM2.5 were 71.8–191.2 μg m−3 at the five sites, with more than 90% of sampling days exceeding 50 μg m−3 at BJ, TJ, and SJZ. PM2.5 pollution was most serious at SJZ, and the annual concentrations of PM2.5, secondary inorganic ions, OC, EC, and most crustal elements were all highest. Due to stronger photochemical oxidation, the sum of concentrations of secondary inorganic ions (NH4+, NO3−, and SO42− was highest in the summer at SDZ, BJ, TJ, and CD. Analysis of electric charges of water-soluble inorganic ions indicated the existence of nitric acid or hydrochloric acid in PM2.5. For all five sites, the concentrations of OC, EC and also secondary organic carbon (SOC) in the spring and summer were lower than those in the autumn and winter. SOC had more percentages of increase than primary organic carbon (POC) during the winter. The sums of crustal elements (Al, Ca, Fe, Mg, Ti, Ba, and Sr) were higher in the spring and autumn owing to more days with blowing or floating dust. The concentrations of heavy metals were at higher levels in the BTH area by comparison with other studies. In Shijiazhuang and Chengde, the PM2.5 pollution was dominated by coal combustion. Motor vehicle exhausts and coal combustion emissions both played important roles in Tianjin PM2.5 pollution. However, motor vehicle exhausts had played a more important role in Beijing owing to the reduction of coal consumption and sharp increase of cars in recent years. At SDZ, regional transportation of air pollutants from southern urban areas was significant.

Transition metal oxides with one-dimensional/one-dimensional-analogue nanostructures for advanced supercapacitors

Abstract: With the increasing energy demand and the overconsumption of fossil fuels, renewable energy-storage devices with higher efficiency are of great interest. In particular, supercapacitors have recently gained significant attention due to their excellent charge–discharge performance, long-term cycle lifetimes, and high specific power. In addition, supercapacitors could also make up the difference in energy and power between batteries and traditional capacitors. In the future, the promising family of transition metal oxides (TMOs) will play a significant role in environmentally friendly, low-cost, and high-powered energy storage. Furthermore, one-dimensional (1D) and one-dimensional-analogue nanostructures could remarkably enhance the characteristic properties of TMOs. In this review, we focused on the recent progress in the preparation and electrochemical properties of the next-generation supercapacitors.

Why nitrogen cannot lead to p-type conductivity in ZnO

Abstract: Based on electronic structure and atomic size considerations, nitrogen has been regarded as the most suitable impurity for p-type doping in ZnO. However, numerous experimental efforts by many different groups have not resulted in stable and reproducible p-type material, casting doubt on the efficacy of nitrogen as a shallow acceptor. Based on advanced first-principles calculations we find that nitrogen is actually a deep acceptor, with an exceedingly high ionization energy of 1.3 eV, and hence cannot lead to hole conductivity in ZnO. In light of this result, we reexamine prior experiments on nitrogen doping of ZnO.