A universal femtoliter surface droplet-based platform for direct quantification of trace of hydrophobic compounds in aqueous solutions is presented. Formation and functionalization of femtoliter droplets, concentrating the analyte in the solution, are integrated into a simple fluidic chamber, taking advantage of the long-term stability, large surface-to-volume ratio, and tunable chemical composition of these droplets. In situ quantification of the extracted analytes is achieved by surface-enhanced Raman scattering (SERS) spectroscopy by nanoparticles on the functionalized droplets. Optimized extraction efficiency and SERS enhancement by tuning droplet composition enable quantitative determination of hydrophobic model compounds of rhodamine 6G, methylene blue, and malachite green with the detection limit of 10 to 10 m and a large linear range of SERS signal from 10 to 10 m of the analytes. The approach addresses the current challenges of reproducibility and the lifetime of the substrate in SERS measurements. This novel surface droplet platform combines liquid-liquid extraction and highly sensitive and reproducible SERS detection, providing a promising technique in current chemical analysis related to environment monitoring, biomedical diagnosis, and national security monitoring.
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http://dx.doi.org/10.1002/smll.201804683 | DOI Listing |
Proc Natl Acad Sci U S A
December 2024
Department of Chemistry, Purdue University, West Lafayette, IN 47907.
The curious chemistry observed in microdroplets has captivated chemists in recent years and has led to an investigation into their ability to drive seemingly impossible chemistries. One particularly interesting capability of these microdroplets is their ability to accelerate reactions by several orders of magnitude. While there have been many investigations into which reactions can be accelerated by confinement within microdroplets, no study has directly compared reaction acceleration at the liquid|liquid and gas|liquid interfaces.
View Article and Find Full Text PDFBiol Methods Protoc
July 2024
Institute of Energy Systems and Environment, Riga Technical University, 12 - K1 Āzene street, Riga, LV-1048, Latvia.
Microorganisms are widely used for the industrial production of various valuable products, such as pharmaceuticals, food and beverages, biofuels, enzymes, amino acids, vaccines, etc. Research is constantly carried out to improve their properties, mainly to increase their productivity and efficiency and reduce the cost of the processes. The selection of microorganisms with improved qualities takes a lot of time and resources (both human and material); therefore, this process itself needs optimization.
View Article and Find Full Text PDFJ Colloid Interface Sci
May 2024
Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA; Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA. Electronic address:
Interfacial effects are well-known to significantly alter chemical reactivity, especially in confined environments, where the surface to volume ratio increases. Here, we observed an inhomogeneity in the electrogenerated chemiluminescence (ECL) intensity decrease over time in a multiphasic system composed of femtoliter water droplets entrapping femtoliter volumes of the 1,2-dichloroethane (DCE) continuous phase. In usual electrochemiluminescence (ECL) reactions involving an ECL chromophore and oxalate ([CO]), the build-up of CO diminishes the ECL signal with time because of bubble formation.
View Article and Find Full Text PDFAnal Chim Acta
February 2024
Université Paris-Saclay, CNRS, Institut Galien Paris-Saclay, 91400, Orsay, France. Electronic address:
In this study, we review various strategies to couple sample processing in microfluidic droplets with different separation techniques, including liquid chromatography, mass spectrometry, and capillary electrophoresis. Separation techniques interfaced with droplet microfluidics represent an emerging trend in analytical chemistry, in which micro to femtoliter droplets serve as microreactors, a bridge between analytical modules, as well as carriers of target analytes between sample treatment and separation/detection steps. This allows to overcome the hurdles encountered in separation science, notably the low degree of module integration, working volume incompatibility, and cross contamination between different operational stages.
View Article and Find Full Text PDFSmall Methods
March 2024
Department of Precision and Microsystems Engineering, Delft University of Technology, Mekelweg 2, Delft, 2628CD, The Netherlands.
The capacity to precisely pipette femtoliter volumes of liquid enables many applications, for example, to functionalize a nanoscale surface and manipulate fluids inside a single-cell. A pressure-controlled pipetting method is the most preferred, since it enables the widest range of working liquids. However, precisely controlling femtoliter volumes by pressure is challenging.
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