Hydrothermal Synthesis and Photocatalytic Activity of Zinc Oxide Hollow Spheres

ZnO hollow spheres with porous crystalline shells were one-pot fabricated by hydrothermal treatment of glucose/ZnCl2 mixtures at 180 °C for 24 h, and then calcined at different temperatures for 4 h. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption−desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B aqueous solution at ambient temperature. The results indicated that the average crystallite size, shell thickness, specific surface areas, pore structures, and photocatalytic activity of ZnO hollow spheres could be controlled by varying the molar ratio of glucose to zinc ions (R). With increasing R, the photocatalytic activity increases and reaches a maximum value at R = 15, which can be attributed to the combined effects of several factors such as specific surface area, the porous structure and the crystallite size. Further results show that hollow spheres can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused than conventional powder photocatalyst. After many recycles for the photodegradation of RhB, the catalyst does not exhibit any great loss in activity, confirming ZnO hollow spheres is stability and not photocorroded. The prepared ZnO hollow spheres are also of great interest in solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology

Analysis of Atmospheric Radiosulfur at Natural Abundance by a New-Type Liquid Scintillation Counter Equipped with Guard Compensation Technology

High-sensitivity measurements of radiosulfur (cosmogenic 35S; half-life: 87.4 days) at natural abundance using ultra-low-level liquid scintillation counter (LSC) methods have been developed and optimized in the last decade, providing new details in space, atmospheric, and hydrological sciences. These LSC methods heavily rely on instruments conventionally equipped with 650 kg lead blocks that passively shield cosmic and environmental background radiation, but this type of instrument is not commercially available anymore, hindering further applications of 35S. To solve this problem, we extended the methods to a new-type LSC equipped with new mathematics-based active shielding techniques (Guard Compensation Technology; GCT). The counting efficiency of the new-type LSC for low-35S activity samples (e.g., natural samples) is low and highly variable because a portion of true signals from 35S decay events was undesirably removed by GCT. We therefore developed a new data processing protocol to determine 35S activities accurately and precisely in the range between ∼1 and ∼13 disintegrations per minute, and its validity was tested by working standards with known 35S activities. As an application example, we measured concentrations of 35S in sulfate aerosols collected in Guangzhou, a megacity in subtropical South China. The obtained values are within the range of previously reported data from various mid-latitude sampling sites. Based on these results, we conclude that our protocol allows the continuing utility of 35S measurements using a new-type LSC for a deeper understanding of the atmospheric sulfur cycle and its influences on the environment, climate, and public health

Hydrothermal Synthesis and Visible-light Photocatalytic Activity of Novel Cage-like Ferric Oxide Hollow Spheres

Fe2O3 hollow spheres with novel cage-like architectures and porous crystalline shells were successfully fabricated by a controlled hydrothermal precipitation reaction using urea as a precipitating agent and carbonaceous polysaccharide spheres as templates in a mixed solvent of water and ethanol, and then calcined at 500 °C for 4 h. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption−desorption isotherms, and UV−visible diffuse reflectance spectroscopy. The visible-light photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution at ambient temperature under visible-light illumination in the presence of H2O2. The results indicated that the diameter, shell thickness, average crystallite size, specific surface areas, pore structures, and photocatalytic activity of Fe2O3 hollow spheres could be easily controlled by changing the concentration of FeCl3 and size of carbon spheres, respectively. With increasing FeCl3 concentration, the average crystallite size, shell thickness, and pore size increase. In contrast, specific surface areas and photocatalytic activity decrease. Further results show that other experimental conditions such as hydrothermal time and solvent composition also obviously influence the formation and morphology of hollow spheres. The samples can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused compared to conventional nanosized powder photocatalysts. The prepared Fe2O3 hollow spheres are also of great interest in sensor, lithium secondary batteries, solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology

3D Droplet-Based Microfluidic Device Easily Assembled from Commercially Available Modules Online Coupled with ICPMS for Determination of Silver in Single Cell

More recently, single-cell analysis based on ICPMS has made considerable headway while a challenge remains to differentiate single cell from doublets during the analysis. One burgeoning solution is to encapsulate single cell into droplets on the platform of the microfluidic chip. However, the manufacture of the droplet-based microfluidic chip requires sophisticated fabrication and limits its potential application. In this paper, we presented an off-the-shelf three-dimensional (3D) microfluidic device by assembling commercially available parts without any proficient manufacturing process. Uniform monodisperse microdroplet was generated from the 3D microfluidic device with a size variation of 1.5%, and the innner diameter of the 3D microfluidic device was the same as the nebulizer (150 μm). The proposed 3D microfluidic device-time-resolved ICPMS system was applied to detect silver in single AgNPs (51 nm), and the result is in good agreement with conventional acid digestion method, demonstrating the accuracy of the method. Silver uptake behaviors in HepG2 cells were then studied by incubating with Ag+ or AgNPs under biocompatible conditions. The results revealed that the cell-to-cell variability in terms of the diversity of cells incubated with AgNPs was wider than those cells incubated with Ag+ from the aspect of the content distribution of silver at the single-cell level

Reversible Ionic Liquid Intercalation for Electrically Controlled Thermal Radiation from Graphene Devices

Using graphene as a tunable optical material enables a series of optical devices such as switchable radar absorbers, variable infrared emissivity surfaces, or visible electrochromic devices. These devices rely on controlling the charge density on graphene with electrostatic gating or intercalation. In this paper, we studied the effect of ionic liquid intercalation on the long-term performance of optoelectronic devices operating within a broad infrared wavelength range. Our spectroscopic and thermal characterization results reveal the key limiting factors for the intercalation process and the performance of the infrared devices, such as the electrolyte ion-size asymmetry and charge distribution scheme and the effects of oxygen. Our results provide insight for the limiting mechanism for graphene applications in infrared thermal management and tunable heat signature control

Chip-Based Magnetic Solid-Phase Microextraction Online Coupled with MicroHPLC–ICPMS for the Determination of Mercury Species in Cells

Trace mercury speciation in cells is critical to understand its cytotoxicity and cell protection mechanism. In this work, we fabricated a chip-based magnetic solid-phase microextraction (MSPME) system, integrating a cell lysis unit as well as a sample extraction unit, and online combined it with micro high-performance liquid chromatography (microHPLC)–inductively coupled plasma mass spectrometry (ICPMS) for the speciation of mercury in HepG2 cells. Magnetic nanoparticles with sulfhydryl functional group were synthesized and self-assembled in the microchannels for the preconcentration of mercury species in cells under an external magnetic field. The enrichment factors are ca. 10-fold, and the recoveries for the spiked samples are in the range of 98.3–106.5%. The developed method was used to analyze target mercury species in Hg²⁺ or MeHg⁺ incubated HepG2 cells. The results demonstrated that MeHg⁺ entered into the HepG2 cells more easily than Hg²⁺, and part of the MeHg⁺ might demethylate into Hg²⁺ in HepG2 cells. Besides, comprehensive speciation of mercury in incubated cells revealed different detoxification mechanisms of Hg²⁺ and MeHg⁺ in Hg²⁺ or MeHg⁺ incubated HepG2 cells

Facile Design of Phase Separation for Microfluidic Droplet-Based Liquid Phase Microextraction as a Front End to Electrothermal Vaporization-ICPMS for the Analysis of Trace Metals in Cells

The issue of quantifying trace metals in cells has drawn widespread attention but is threatened with insufficient sensitivity of the instruments, complex cellular matrix and limited cell consumption. In this study, microfluidic droplet-based liquid phase microextraction (LPME), as a miniaturized platform, was developed and combined with electrothermal vaporization (ETV)-inductively coupled plasma mass spectrometry (ICPMS) for the analysis of trace Cd, Hg, Pb, and Bi in cells. A novel and facile design of phase separation region was proposed, which made the phase separation very easily for subsequent ETV-ICPMS detection. Mechanism of the phase separation was carefully discussed using the incompressible formulation of the Navier–Stokes equations. The developed microfluidic droplet-based LPME system exhibited much higher extraction efficiency to target metals than microfluidic stratified flow-based LPME. Under the optimized conditions, the limits of detection of the proposed microfluidic droplet-based LPME-ETV-ICPMS system were 2.5, 3.9, 5.5, and 3.4 ng L^–1 for Cd, Hg, Pb, and Bi, respectively. The accuracy of the developed method was well validated by analyzing the target metals in Certified Reference Materials of GBW07601a human hair. Finally, the proposed method was successfully applied to the analysis of target metals in HeLa and HepG2 cells with the recoveries for the spiked samples ranging from 83.5 to 112.3%. Overall, the proposed design is a simple and reliable solution for the phase separation on droplet-chip and the microfluidic droplet-based LPME-ETV-ICPMS combination strategy shows great promise for trace elements analysis in cells

Facile Design of Phase Separation for Microfluidic Droplet-Based Liquid Phase Microextraction as a Front End to Electrothermal Vaporization-ICPMS for the Analysis of Trace Metals in Cells

The issue of quantifying trace metals in cells has drawn widespread attention but is threatened with insufficient sensitivity of the instruments, complex cellular matrix and limited cell consumption. In this study, microfluidic droplet-based liquid phase microextraction (LPME), as a miniaturized platform, was developed and combined with electrothermal vaporization (ETV)-inductively coupled plasma mass spectrometry (ICPMS) for the analysis of trace Cd, Hg, Pb, and Bi in cells. A novel and facile design of phase separation region was proposed, which made the phase separation very easily for subsequent ETV-ICPMS detection. Mechanism of the phase separation was carefully discussed using the incompressible formulation of the Navier–Stokes equations. The developed microfluidic droplet-based LPME system exhibited much higher extraction efficiency to target metals than microfluidic stratified flow-based LPME. Under the optimized conditions, the limits of detection of the proposed microfluidic droplet-based LPME-ETV-ICPMS system were 2.5, 3.9, 5.5, and 3.4 ng L^–1 for Cd, Hg, Pb, and Bi, respectively. The accuracy of the developed method was well validated by analyzing the target metals in Certified Reference Materials of GBW07601a human hair. Finally, the proposed method was successfully applied to the analysis of target metals in HeLa and HepG2 cells with the recoveries for the spiked samples ranging from 83.5 to 112.3%. Overall, the proposed design is a simple and reliable solution for the phase separation on droplet-chip and the microfluidic droplet-based LPME-ETV-ICPMS combination strategy shows great promise for trace elements analysis in cells

Reversible Ionic Liquid Intercalation for Electrically Controlled Thermal Radiation from Graphene Devices

Using graphene as a tunable optical material enables a series of optical devices such as switchable radar absorbers, variable infrared emissivity surfaces, or visible electrochromic devices. These devices rely on controlling the charge density on graphene with electrostatic gating or intercalation. In this paper, we studied the effect of ionic liquid intercalation on the long-term performance of optoelectronic devices operating within a broad infrared wavelength range. Our spectroscopic and thermal characterization results reveal the key limiting factors for the intercalation process and the performance of the infrared devices, such as the electrolyte ion-size asymmetry and charge distribution scheme and the effects of oxygen. Our results provide insight for the limiting mechanism for graphene applications in infrared thermal management and tunable heat signature control