Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.analchem.3c00766

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Brown carbon (BrC) affects radiation budget and thus global climate by absorbing lights, during which photolysis can also occur and serve as an important sink of BrC. Yet, the interactive...

DOI： 10.1039/d3ea00073g

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/02786826.2022.2080042

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsearthspacechem.2c00021

researchmap

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

We report a spray-drying method to fabricate silver nanoparticle (AgNP) aggregates for application in surface-enhanced Raman spectroscopy (SERS). A custom-built system was used to fabricate AgNP aggregates of four sizes, 48, 86, 151, and 218 nm, from drying droplets containing AgNPs atomized from an AgNP suspension. Sample solutions of Rhodamine B (RhB) at 10^–6, 10^–8, and 10^–10 M concentrations were dropped onto the AgNP aggregates as probe molecules to examine the enhancement of the Raman signals of the RhB. The ordering of the analytical enhancement factors (AEFs) by aggregate size at a 10^–6 M RhB was 86 nm > 218 nm > 151 nm > 48 nm. When RhB concentrations are below 10^–8 M, the 86 and 151 nm AgNP aggregates show clear RhB peaks. The AEFs of the 86 nm AgNP aggregates were the highest in all four aggregates and higher than those of the 218-nm aggregates, although the 218-nm aggregates had more hot spots where Raman enhancement occurred. This finding was attributable to the deformation and damping of the electron cloud in the highly aggregated AgNPs, reducing the sensitivity for Raman enhancement. When RhB was premixed with the AgNP suspension prior to atomization, the AEFs at 10^–8 M RhB rose ~ 100-fold compared to those in the earlier experiments (the post-dropping route). This significant enhancement was probably caused by the increased opportunity for the trapping of the probe molecules in the hot spots.

DOI： 10.1038/s41598-022-08598-y

researchmap

Other Link： https://www.nature.com/articles/s41598-022-08598-y

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.1c07211

researchmap

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Particulate nitrate photolysis can lead to the formation of secondary inorganic and organic aerosols that affect climate, air quality, and human health.

DOI： 10.1039/d1ea00087j

researchmap

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.1c05641

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.1c04642

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Atmospheric particles experience various physical and chemical processes and change their properties during their lifetime. Most studies on atmospheric particles, both in laboratory and field measurements, rely on analyzing an ensemble of particles. Because of different mixing state of individual particles, only average properties can be obtained from studies using ensembles of particles. To better understand the fate and environmental impacts of atmospheric particles, investigations on their properties and processes at a single-particle level are valuable. Among a wealth of analytic techniques, single-particle Raman spectroscopy provides an unambiguous characterization of individual particles under atmospheric pressure in a non-destructive and in-situ manner. This paper comprehensively reviews the application of such a technique in the studies of atmospheric particles, including particle hygroscopicity, phase transition and separation, and solute-water interactions, particle pH, and multiphase reactions. Investigations on enhanced Raman spectroscopy and bioaerosols on a single-particle basis are also reviewed. For each application, we describe the principle and representative examples of studies. Finally, we present our views on future directions on both technique development and further applications of single-particle Raman spectroscopy in studying atmospheric particles.

DOI： 10.5194/acp-2021-423

researchmap

Authorship：Lead author  

DOI： 10.1039/D0FD90037K

researchmap

Publishing type：Research paper (scientific journal)  

An industrial enzyme, Cyclodextrin glucanotransferase (CGTase), was immobilised in polyvinyl alcohol (PVA) nanofiber (average diameter around 200 nm) membrane via co-electrospinning of the CGTase/ PVA mixture followed with glutaraldehyde vapour phase cross- linking Addition of enzyme with concentration ranging from 1.5 to 7.5 % to the PVA solution (8 wt%) caused significant changes to the liquid jet behaviours which consequently affected the nanofiber structures and sizes. Incorporation of CGTase in the PVA membrane was confirmed by Raman spectroscopic analysis. The Raman spectra also showed no structural changes occured to the enzyme after subjected to the electrostatic spinning and cross-linking reaction. The immobilised enzyme showed excellent catalytic efficiency with up to 3.6 times higher enzyme loading, 25 % higher activity and good reusability in comparison with CGTase/PVA film made up from the same starting solution (control).

DOI： 10.2115/fiberst.2017-0035

Scopus

researchmap

DOI： 10.1021/acs.jpca.1c00669

researchmap

Authorship：Corresponding author  

DOI： 10.1021/acs.est.0c08199

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.scitotenv.2020.142182

researchmap

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.0c01540

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.estlett.0c00368

researchmap

Publishing type：Research paper (scientific journal)  

The effect of chemical treatment of a metallic substrate on the deposition of aerosols generated by an ultrasonic nebulizer was investigated. A single substrate with areas having different "level" of hydrophilicity (or hydrophobicity) was used as a model surface. The treated (more hydrophilic) area became more negatively-charged based on a surface electric potential meter. A low-pressure analysis method (electron-microscope image) and ordinary pressure methods (Raman spectroscopy and X-ray fluorescence) analytical results indicated that in comparison with the untreated area, the treated area trapped more particles in the case of the deposition of "wet" aerosols. In the case of the deposition of more "dry" aerosols, the untreated area trapped more particles rather than that of the treated one. The efficiency of particles deposition not only depended on the degree of hydrophilicity (or hydrophobicity) of the surface but also due to the conditions (wet or dry) of incoming aerosols.

DOI： 10.11113/mjfas.v16n3.1608

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsomega.0c00311

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.9b06445

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/02786826.2020.1730298

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.est.0c00680

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.9b01623

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/02786826.2019.1597964

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsearthspacechem.9b00002

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsearthspacechem.8b00154

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.estlett.8b00681

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

This journal is © The Royal Society of Chemistry. We employed surface forces and resonance shear measurement (RSM) for studying the structure and properties of typical concentrated polymer brushes (CPBs) of poly(methylmethacrylate) (PMMA) in toluene, which are known to show very low friction. The surface forces measured between the silica surfaces bearing PMMA brush layers showed a steric repulsive force at distances between the silica surfaces of less than ca. 1050 nm (Donset). Upon retraction after compression of the PMMA brush layers, no adhesive force was observed. This indicated that the interpenetration of the polymer chain was not induced by the normal load. Based on the resonance shear measurement, the elastic (k2) and damping (viscous) (b2) parameters, which represent the dynamic properties, of the PMMA brush layers were obtained by analyzing the resonance curves. At distances below the Donset, the b2 value significantly increased and slightly decreased at the higher normal loads, and the k2 value monotonically increased with increasing load. These k2 and b2 values were greater than those obtained for a PMMA brush layer and a bare silica surface (PMMA-silica). This indicated that the mobility of the polymer chains for the PMMA-PMMA brush layers was more suppressed compared to that for the PMMA-silica, due to the interpenetration of the polymer chains. The interpenetration of the polymer chains, commonly not observed for CPBs, could be most probably induced by the application of both the normal load and oscillating shear motion. With increasing shear amplitude on the compressed PMMA-PMMA brushes (at L = 0.84, 1.34 and 4.28 mN), the b2 value first increased then decreased whilst the k2 value monotonically decreased. These tendencies can be explained by the change from the sticking condition due to interpenetration (high k2), small sliding under interpenetration (increase in b2, decrease in k2), and then smooth sliding by pulling out of interpenetrated polymer chains (decrease in b2 and k2). The obtained results indicated that the operating conditions are quite important for using polymer brush layers as tribological materials because they can exhibit both a high and low friction depending on the conditions such as the load and shear amplitude.

DOI： 10.1039/c9sm01133a

Scopus

PubMed

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.est.8b00606

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

We present electrospray surface-enhanced Raman spectroscopy (ES-SERS) as a new approach to measuring the surface chemical compositions of atmospherically relevant particles. The surface-sensitive SERS is realized by electrospraying Ag nanoparticle aerosols over analyte particles. Spectral features at v(SO42-), v(C H) and v(O H) modes were observed from the normal Raman and SERS measurements of laboratory-generated supermicron particles of ammonium sulfate (AS), AS mixed with succinic acid (AS / SA) and AS mixed with sucrose (AS / sucrose). SERS measurements showed strong interaction (or chemisorption) between Ag nanoparticles and surface aqueous sulfate, [SO42- [SO42-] with [SO42-]AS / sucrose > [SO42- JAS / SA > Lok-, JAS " Enhanced spectra of the solid AS and AS / SA particles revealed the formation of surface-adsorbed water on their surfaces at 60 % relative humidity. These observations of surface aqueous sulfate and adsorbed water demonstrate a possible role of surface-adsorbed water in facilitating the dissolution of sulfate from the bulk phase into its water layer(s). Submicron ambient aerosol particles collected in Hong Kong exhibited non-enhanced features of black carbon and enhanced features of sulfate and organic matter (carbonyl group), indicating an enrichment of sulfate and organic matter on the particle surface.

DOI： 10.5194/acp-17-14025-2017

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

Immobilisation of cyclodextrin glucanotransferase (CGTase) on nanofibres was demonstrated. CGTase solution (1% v/v) and PVA (8 wt%) solution were mixed followed by electrospinning (-9 kV, 3 h). CGTase/PVA nanofibres with an average diameter of 176 ± 46 nm were successfully produced. The nanofibres that consist of immobilised CGTase were crosslinked with glutaraldehyde vapour. A CGTase/PVA film made up from the same mixture and treated the same way was used as a control experiment. The immobilised CGTase on nanofibres showed superior performance with nearly a 2.5 fold higher enzyme loading and 31% higher enzyme activity in comparison with the film.

DOI： 10.1016/j.btre.2016.03.003

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Korean Society for Atmospheric Environment  

This study focused on the measurement of the actual charging state of ambient aerosol particles, which is important for understanding the intricate process of adverse health effects caused by particulate matter (PM). The net electrostatic charging state of PM2.5 collected on filter media was measured in this study. The Faraday cage method and surface potential measurements were used in this study. The results showed that the polarities of the net charging state measured using these two methods were in agreement for 42 out of 48 samples (87.5%), and 36 samples (75%) were negatively charged. The filters were not significantly charged by friction between the filters and air not containing PM. Charge addition to or leakage from the filters was not observed over a two-month storage period. Net charging state of PM2.5 collected on the filters was concluded to be negative in most cases, based on data's support of the assumption that aerosol charging state is not altered by the process of PM collection using filter.

DOI： 10.5572/ajae.2015.9.2.137

Scopus

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A surface coated with organic molecules has been probed by a sub 100 nm resolution particulate sensor by surface-enhanced Raman scattering (SERS) technique. The spatial distribution of those molecules formed on the solid surface was altered by a dip-coating method as a function of a substrate-lifting rate. Isolated silver nanoparticles (similar to 50 nm) as "antenna" particles were deposited from the gas phase onto the surface by means of an electrostatic-assisted spray. The surface with the particles was analyzed with Raman spectroscopy technique. These analyses provide spatial information on the molecules over the surface, when SERS spectra of the molecules obtained from each measurement point are converted into the position of molecules. The occurrence frequency of SERS is found to be correlated with the two-third power law of the lifting rate which is proportional to a mass concentration of molecules per unit area, whereas the average Raman intensity is independent. A gas-phase route assisted SERS technique offers direct measurement of the molecular patterns on target surfaces.

DOI： 10.1039/c4ra03850a

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The effect of chemical treatment of a metallic substrate on the deposition behavior of charged aerosol particles derived from spraying droplets was investigated. A single substrate with areas having different hydrophilic levels was prepared as target surface. The treated (i.e., higher hydrophilic level) area, measured using a surface potential meter, showed a higher negative potential. A numerical simulation predicted that positively charged aerosol particles tended to approach and were subsequently immobilized on the high hydrophilic area. The area with higher hydrophilicity could collect particles with higher number concentration (density) than the other areas. The relationships were demonstrated in (i) the electrostatic surface potential, (ii) the hydrophilicity of surface, and (iii) the enhancement of adhesive force between the deposited particles and the surface. (C) 2014 Published by Elsevier Ltd.

DOI： 10.1016/j.jaerosci.2014.06.001

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

In this study, the potential of electrohydrodynamic atomization or electrospraying to produce nanometer-order CGTase particles from aqueous suspension was demonstrated. CGTase enzyme was prepared in acetate buffer solution (1% v/v), followed by electrospraying in stable Taylor cone-jet mode. The deposits were collected on aluminium foil (collector) at variable distances from the tip of spraying needle, ranging from 10 to 25 cm. The Coulomb fission that occurs during electrospraying process successfully transformed the enzyme to the solid state without any functional group deterioration. The functional group verification was conducted by FTIR analysis. Comparison between the deposit and the as-received enzyme in dry state indicates almost identical spectra. By increasing the distance of the collector from the needle tip, the average particle size of the solidified enzyme was reduced from 200 +/- 117 nm to 75 +/- 34 nm. The average particle sizes produced from the droplet fission were in agreement with the scaling law models. Enzyme activity analysis showed that the enzyme retained its initial activity after the electrospraying process. The enzyme particles collected at the longest distance (25 cm) demonstrated the highest enzyme activity, which indicates that the activity was controlled by the enzyme particle size. (C) 2014 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.enzmictec.2014.06.002

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Surface Science Society of Japan  

We demonstrate one-step deposition of submicrometer-sized particles suspended in the gas-phase onto a plate type substrate using an electrostatic-assisted spray system. The spray nozzle was set perpendicularly to the substrates (facing the front surface). The particles were deposited on plate-type metallic surfaces, on both front and rear sides of the substrate. This "both-side" deposition can be ascribed to deflection of charged particles in the front side, and then drifting of the particles around the rear side. A numerical simulation also showed that the deposition mechanism was found to be dependent on the center and the edge of the substrate. The electrostatic effect is more effective on both the center and the edge than the diffusion effect. © 2014 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2014.238

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：The Society of Powder Technology, Japan  

DOI： 10.4164/sptj.51.759

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

A detection method based on the surface-enhanced Raman spectroscopy (SERS)-active substrate derived from aerosol nanoparticles and a colloidal suspension for detecting organic molecules of a model analyte (a pesticide) is proposed. This approach can detect the molecules of the derived from its solution with the concentration levels of ppb. For substrate fabrication, a gas-phase method is used to directly deposit Ag nanoparticles on to a silicon substrate having pyramidal structures. By mixing the target analyte with a suspension of Ag colloids purchased in advance, clotianidin analyte on Ag colloid can exist in junctions of co-aggregated Ag colloids. Using (i) a nanostructured substrate made from aerosol nanoparticles and (ii) colloidal suspension can increase the number of activity spots. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.50.06GG10

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Aerosol Science and Technology  

The emission of alkali and heavy metals in combustion processes is an important contributor to environmental load. However, little is known of the mechanism by which gas-to-particle conversion occurs during cooling and dilution with the atmosphere at the exit of stacks. In the present work, particles generated from model exhaust gases derived from NaCl and CdCl₂ were investigated experimentally in the laboratory. An on-line, gas-phase measurement system showed that the mean diameters of aerosol particles in single-metal evaporation of NaCl and CdCl₂ were 35 and 30 nm, respectively, when the dilution ratio of the model gas was 1:20. However, the value was 50 nm in two-metal co-evaporation of NaCl with CdCl₂ at the same dilution ratio. FE-SEM images of aerosol particles collected with a quartz fiber filter in the two-metal system showed a morphology similar to that of NaCl. It is thus concluded that Cd-containing vapors nucleate at and grow on the surface of NaCl particles. These results may be informative for predicting phenomena related to gas-to-particle conversion at the exit of stationary emission sources, from which such condensed particles are suspected to be released into the atmosphere.<br>

DOI： 10.11203/jar.26.277

CiNii Books

researchmap

Event date： 2022.11 　 　

Presentation type：Oral presentation (general)  

File： 27th_Jpsac_Meeting_Abstract_MG.pdf

researchmap

Event date： 2022.9 　 　

Presentation type：Oral presentation (general)  

researchmap

Event date： 2022.8 　 　

Presentation type：Oral presentation (general)  

researchmap