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RISS 인기검색어
- 검색키워드
- 저자 : Stavrakis, Stavros (검색결과 4 건)
- 무료
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Scalable production of CuInS2/ZnS quantum dots in a two-step droplet-based microfluidic platform
Yashina, A.,Lignos, I.,Stavrakis, S.,Choo, J.,deMello, A. Royal Society of Chemistry 2016 Journal of Materials Chemistry C Vol.4 No.26
<P>We report the scalable formation of CuInS2/ZnS nanocrystals using a two-stage microfluidic reactor integrated with a real-time optical detection system, which is able to monitor reaction parameters prior and subsequent to the addition of the shell material. By injecting a ZnS single source precursor in droplets containing CuInS2 cores and without the need of purification steps, we are able to obtain core-shell nanocrystal populations emitting between 580 and 760 nm with significant narrower size distributions (90-95 nm) than for the same material systems synthesized on the macroscale. In-line monitoring allowed for rapid assessment of optimum reaction parameters (Cu/In, S/(Cu + In), Zn/(Cu + In) molar ratios, temperatures and reaction time) and enabled the formation of CuInS2/ZnS nanocrystals with high photoluminescence quantum yields (similar to 55%) within a few seconds. We believe that this synthetic methodology will be of significant utility in controllable production of ternary and quaternary metal chalcogenides, complex core-shell and doped nanostructures.</P>
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Hess, David,Rane, Anandkumar,deMello, Andrew J.,Stavrakis, Stavros American Chemical Society 2015 ANALYTICAL CHEMISTRY - Vol.87 No.9
<P>Droplet-based microfluidic systems offer a range of advantageous features for the investigation of enzyme kinetics, including high time resolution and the ability to probe extremely large numbers of discrete reactions while consuming low sample volumes. Kinetic measurements within droplet-based microfluidic systems are conventionally performed using single point detection schemes. Unfortunately, such an approach prohibits the measurement of an individual droplet over an extended period of time. Accordingly, we present a novel approach for the extensive characterization of enzyme–inhibitor reaction kinetics within a single experiment by tracking individual and rapidly moving droplets as they pass through an extended microfluidic channel. A series of heterogeneous and pL-volume droplets, containing varying concentrations of the fluorogenic substrate resorufin β-<SMALL>d</SMALL>-galactopyranoside and a constant amount of the enzyme β-galactosidase, is produced at frequencies in excess of 150 Hz. By stroboscopic manipulation of the excitation laser light and adoption of a dual view detection system, “blur-free” images containing up to 150 clearly distinguishable droplets per frame are extracted, which allow extraction of kinetic data from all formed droplets. The efficiency of this approach is demonstrated via a Michaelis–Menten analysis which yields a Michaelis constant, <I>K</I><SUB>m</SUB>, of 353 μM. Additionally, the dissociation constant for the competitive inhibitor isopropyl β-<SMALL>d</SMALL>-1-thiogalactopyranoside is extracted using the same method.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2015/ancham.2015.87.issue-9/acs.analchem.5b00766/production/images/medium/ac-2015-00766c_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac5b00766'>ACS Electronic Supporting Info</A></P>
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An optofluidic system with integrated microlens arrays for parallel imaging flow cytometry
Holzner, Gregor,Du, Ying,Cao, Xiaobao,Choo, Jaebum,J. deMello, Andrew,Stavrakis, Stavros The Royal Society of Chemistry 2018 Lab on a chip Vol.18 No.23
<P>In recent years, high-speed imaging has become increasingly effective for the rapid analysis of single cells in flowing environments. Single cell imaging methods typically incorporate a minimum magnification of 10× when extracting sizing and morphological information. Although information content may be significantly enhanced by increasing magnification, this is accompanied by a corresponding reduction in field of view, and thus a decrease in the number of cells assayed per unit time. Accordingly, the acquisition of high resolution data from wide field views remains an unsolved challenge. To address this issue, we present an optofluidic flow cytometer integrating a refractive, microlens array (MLA) for imaging cells at high linear velocities, whilst maximizing the number of cells per field of view. To achieve this, we adopt an elasto-inertial approach for cell focusing within an array of parallel microfluidic channels, each equipped with a microlens. We characterize the optical performance of the microlenses in terms of image formation, magnification and resolution using both ray-tracing simulations and experimental measurements. Results demonstrate that the optofluidic platform can efficiently count and magnify micron-sized objects up to 4 times. Finally, we demonstrate the capabilities of the platform as an imaging flow cyclometer, demonstrating the efficient discrimination of hB and Jurkat cells at throughputs up to 50 000 cells per second.</P>
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