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Nanospray processing of silver nanoparticles for formation of dried deposits
Týčová, Anna ; Jonas, Vladimír ; Přikryl, Jan ; Kotzianová, A. ; Velebný, V. ; Foret, František
Nanospray transfers liquid into an aerosol via electrostatic forces created between an emitter and a counter electrode. Herein, we present compact laboratory-made instrumentation for nanospray-processing of silver colloid. The instrumentation is based on the pressurized polysulfone chamber fixing a disposable vial with an immersed platinum electrode and a long fused silica capillary supplying the sprayed liquid to the emitter. The combination of low flow rates (70 nL/min) with a sharp emitter, fabricated on a 3D printed grinding station, resulted in a fine aerosol. The low volume of released droplets allowed full evaporation of water during their flight towards the counter electrode without any need for drying gas or the addition of volatile solvents. The constructed device was successfully used for the deposition of water-free silver colloid without any requirement of its pretreatment. The deposition of completely dried nanoparticles on planar substrates eliminated undesirable coffee ring effect and deposits of increased homogeneity could be obtained. Electron microscopy confirmed no significant changes in the character of nanospray-processed nanoparticles. Finally, we also investigated several approaches for the improvement of the surface density of nanoparticles on the substrate at preserved time scale.
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Deposition of dried colloidal suspension via nanoelectrospray
Jonas, Vladimír ; Týčová, Anna ; Přikryl, Jan ; Kotzianová, A. ; Velebný, V. ; Foret, František
Electrospray is a relatively well-established tool for the deposition of nanoparticles. In this work, we use nanoelectrospray (nES) operating at flow rates down to tens of nanoliters per minute. As a result, the formed aerosol consists of very small droplets quickly drying during the flight towards a counter-electrode. Therefore, we obtained deposits of increased homogeneous distribution without an undesirable coffee-ring effect. Moreover, the character of the aerosol plume is only a few millimeters wide, so it allows good control over the deposit localization.
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Surface modification of nanoparticles for sustaining sensitivity of surface-enhanced raman spectrometric measurements in salinated environment
Týčová, Anna ; Přikryl, Jan ; Vaňhara, P. ; Klepárník, Karel ; Foret, František
Surface-enhanced Raman spectrometry (SERS) represents a powerful method for analysis of a broad spectrum of analytes ranging from inorganic ions to biomolecules of high complexity. It combines the potential\nof Raman spectrometry for a definite identification of an analyte with remarkable sensitivity achieved by the surface enhancement effect occurring on metal nanoparticles. While low ionic strength influences positively\nthe sensitivity of the SERS measurement, a higher level of inorganic salts leads to fast ruining of colloidal character, which completely devastates the effect of the surface enhancement. The common stabilization of\nnanoparticles by a layer of polymers has a negative impact on the SERS sensitivity since it shields the nanoparticle surface from the analytes. In this work, we aim at the development of the bi-ligand system of\nnanoparticles surface modification for improved stability of colloid in saline solution at sustaining the potential for sensitive SERS analyses. The proposed system relies on the binding of 3-mercaptopropionic acid and\nthiolated polyethylene glycol in a suitable ratio onto the nanoparticle surfaces. While the short chains of the acid sustain the accessibility of the surface for analytes, the polymeric structures act as a steric barrier\npreventing colloid aggregation.
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CE-nESI/MS in electrode-free design: narrowing the separation channel to 5 μm
Týčová, Anna ; Foret, František
Capillary electrophoresis-nanospray/mass spectrometry (CE-nESI/MS) in electrodefree\narrangement represents a very simple instrumentation for analysis of biomolecules.\nSo far, CE-nESI/MS analyses in this design were limited to 10-75 μm ID of the\nseparation channel. Although the work with narrower dimensions brings several\nchallenges, there is a great potential for better sensitivity, improved separation power\nand lower sample consumption. This work is devoted to some practical aspects of\nexperiments in narrow bore channels and systematic evaluation of CE-nESI/MS\nanalyses conducted in capillaries of 25, 15 and 5 μm ID.
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