Electrospray (ES) technique is one of the few known schemes capable of atomizing a liquid into ultrafine droplets. By this method, a meniscus of conducting solution formed at the tip of a capillary tube becomes conical in shape when high voltage is applied between the tip and the counter electrode. Droplets are generated by the continuous breakup of a liquid jet at the apex of the cone. The most common use of ES has been as the ion source for mass spectrometry. This paper first reviews various applications of ES in nanoparticle synthesis. ES is also a tool to transfer inorganic or/and organic matters in a liquid into a gas-phase. In the present work, the size distribution of the generated aerosol was determined by a differential mobility analyzer (DMA) and a counter system. The results show that the ES-DMA system is a convenient and reliable tool for the rapid size determination of colloidal nanoparticles or water-soluble polymers, being capable of simultaneously measuring the mobility distribution and concentration of total residue present in the sample waters.

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Abstract Recently, the importance of electrostatic charging state to particle deposition in the human airways has been suggested. In this study, we developed a measurement method of electrostatic charging state of individual ambient aerosol particles using Kelvin probe force microscopy (KPFM). For KPFM substrates, glass plates were more suitable than PTFE or polycarbonate filters. We collected charged polystyrene latex standard particles with the number of elementary charges between 4 to 11 on the glass plate, and measured the topography and the surface potential using KPFM. The difference in surface potential between the particle top and the glass substrate surface was determined as the particle surface potential. The particle surface potential for positively charged particle was＋50 mV and that for negatively charged particle was approximately－45 mV. For the ambient aerosol particles, the surface potential ranged from－56.6 mV to＋156.7 mV, indicating that the number of elementary charges of ambient aerosol particles analyzed in this study was more than 4. Sequential analysis of KPFM followed by SEM/EDX for a single aerosol particle would be useful to find the relationship between the surface potential and chemical composition of individual particles.

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Water scarcity can make plants experience drought stress. This can happen from the germination stage. The seed priming method with silica nanoparticles was used to overcome this issue. Tomato seeds were soaked in a suspension of silica particles (average size of 10 nm). Drought stress was simulated by using polyethylene glycol (20,000) with concentration of 10–20 wt% in germination media. The results showed that the method of priming with silica nanoparticles was able to withstand drought stress and improve seed germination performance.

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Fertilizers, which are essential for food production, are absorbed by plants in less than half of the amount applied to the soil. As an efficient method of absorbing fertilizer, there is a method of absorbing fertilizer from the leaves of plants (i.e. foliar route). However, the method of transportation in the form of an aqueous solution in which the fertilizer is dissolved is not applicable to macronutrients. In the present study, the goal is to control the dissolution of particles on leaves during the particle transport in the solid state. The effect of properties such as crystal structure of the synthesized multicomponent particles on the dissolution properties was investigated.

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In the past few decades, enormous advances have been achieved in the field of particle technology and the trend has been shifted from macro to micro and recently to the nanoscale. Integration of nanotechnology and biotechnology has paved the way to the development of biological nanoparticles, derived from biomolecules, and biomolecule-nanoparticle conjugates for numerous applications. This review provides an overview of various types of biological nanoparticles and the methods of their fabrication with primary emphasis on the drying methods, particularly on the newly emerging technique, the electrospraying. Recent advances in the integration of biomolecules with nanoparticles in the past five years to present are also discussed. Finally, the application of the biomolecule-nanoparticle conjugates in various fields including medicals and pharmaceuticals, biosensors and bioelectronics, foods, and agricultures are also highlighted.

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An aerosol flow system has been constructed to mimic the delivery of particles to the air-liquid interface. A colloidal suspension of submicron fluorescent core-shell silica-based particles was sprayed by an ultrasonic nebulizer. The dynamics of the aerosol settling was investigated by numerical simulation to determine the carrier gas flow rate, which was further verified through experimentation. Fluorescent microscopy, a non-vacuum imaging technique, was used to observe the particles deposited on the substrate. It was found that the apparent (fluorescent) size distribution was shifted from 2.9 ± 6.0 μm to 1.7 ± 2.2 μm, which is correlated to the shift in the aggregate size from 0.70 μm to 0.24 μm due to the changes in the colloidal suspension concentration. In addition, the uniformity of the particles dispersed on the substrate was not significantly affected by the suspension’s concentration, as confirmed by the inter-particle distance analysis. It is therefore suggested that the method presented here may potentially be applied for the deposition and analysis of submicron particles on various types of substrate (i.e. air-liquid interface) without the need for vacuum imaging analysis (e.g. electron microscopy).

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An additive salt, LiNO3, was used as a shield in the preparation of single crystalline ZnO particles via an ultrasonic spray pyrolysis route in order to prevent particle-agglomeration and enhance the crystallinity of the product. LiNO3 was added to a precursor solution of zinc acetate dihydrate prior to its atomization by means of an ultrasonic transducer. Agglomerate-free particles having a mean particle size of 26 nm were successfully obtained after washing the product. Powder X-ray diffractometry, field-emission scanning electron micrograph and transmission electron micrograph data indicate that the size and morphology of ZnO were strongly influenced by the operating temperature used and the residence time of the particle in the reactor.
Also using the same apparatus, i.e. ultrasonic spray pyrolysis method, europium doped ZnO (ZnO:Eu) phosphor particle was directly synthesized. The crystal structure of product was designated by europium ions concentration and the synthesis temperature. We identified the coexistence of Eu²⁺ and Eu³⁺ in the as prepared ZnO, which was strongly influenced by the doping concentration and the synthesis temperature. With the addition of 0.5 mol % concentration of europium ion, only Eu²⁺ ion existed in the particles, while both Eu²⁺ and Eu³⁺ ions existed in the particles when using 1 mol % or higher concentration of europium ions. We also found that by changing the wavelength of excitation source, both of blue luminescence and red luminescence can be obtained.

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Synthesis of europium ion doped yttrium oxide (Y₂O₃:Eu³⁺) phosphor nanoparticles using a relatively high molecular weight polyethylene glycol is reported. Y₂O₃: Eu³⁺ materials could be prepared by simply heating in air provided that, water-soluble polymer be added into solutions containing metal nitrates. The polymer was expected to form carbonaceous materials around the produced primary particles to reduce the tendency of those particles to agglomerate. The carbonaceous materials could be removed by heating at higher temperatures, resulting in softly-agglomerated particles in the size range of 20-100 nm. The effect of synthesis parameters on particle morphology, crystallinity, and photoluminescence properties was investigated.

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Lithium manganese oxide (LiMn₂O₄) powders with particle sizes in the range of 100–600 nm have been synthesized through glucose-assisted combustion synthesis. The presence of glucose increases the stability of the precursor solution, purity of the heat-treated powders, and decreasing on size of the synthesized particle. The formation of complex metal salts-glucose in the precursor solution and effect of the methods for preparing solid precursors on the final product were investigated.

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Submicron- and nanometer-sized red luminescent particles (Y₂O₃:Eu³⁺) were successfully generated by flame spray pyrolysis (FSP) and the effect of the type of the atomizer, i.e., the ultrasonic nebulizer (UN) and the two-fluid nozzle (TFN) sprayer, on the particle characteristics was investigated. The prepared particles were characterized by field emission-scanning electron microscopy (FE-SEM), an X-ray diffractometry (XRD) analysis and spectrophotometry. UN-FSP produced non aggregated particles with a mean diameter of 754 nm and the relative photoluminescence (PL) intensity (ratio of emission intensity of generated particles to that of commercial particles) varied from 0.36 to 1.01. The Y₂O₃:Eu³⁺ particles generated by TFN-FSP were softly agglomerated with a mean diameter of 24 nm and the relative PL intensity ranged from 0.21 to 0.24. Regardless of the type of the atomizer used, the generated particles were dense and spherical in the cubic phase and highly crystalline. These results show that TFN-FSP is a versatile method of producing Y₂O₃:Eu³⁺ nanometer-sized particles compared with UN-FSP.

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