42 research outputs found
Microdroplet fabrication of silver–agarose nanocomposite beads for SERS optical accumulation
Microdroplets have been used as reactors for the fabrication of agarose beads with high uniformity in shape and size, and densely loaded with silver ions, which were subsequently reduced into nanoparticles using hydrazine. The resulting nanocomposite beads not only display a high plasmonic activity, but can also trap/concentrate analytes, which can be identified by means of surface-enhanced Raman scattering (SERS) spectroscopy. The size of the beads is such that it allows the detection of a single bead under a conventional optical microscope, which is very useful to reduce the amount of material required for SERS detectio
Polymer based silver nanocomposites as versatile solid film and aqueous emulsion SERS substrates
Nanocomposites containing Ag nanoparticles (average diameter similar to 11 nm) dispersed in poly(tertbutylacrylate) were prepared by in situ polymerization via miniemulsions and constitute active and versatile SERS substrates. The use of this synthetic strategy enables the dual use of the final composites as SERS substrates, both as aqueous emulsions and as cast films, shown here by several measurements using thiosalicylic acid as the testing analyte. The main advantage of these types of materials is related to the potential to scale up and the widespread use of handy substrates, using technology already available. This requires homogeneous composite substrates with SERS activity and this was demonstrated here by means of confocal Raman microscopy. Finally, a series of experiments were carried out on Ag/polymer nanocomposites submitted to temperature variations below and above the polymer glass transition temperature (T(g)) in order to conclude about the effect of temperature processing conditions on the composites' SERS activity.FCT- SFRH/BD/66460/2009FCT- SFRH/BPD/66407/2009FCT- PTDC/QUI/67712/ 2006RNME-Pole UA-FCT Project REDE/1509/RME/200
Encapsulation of Nanostructures in a Dielectric Matrix Providing Optical Enhancement in Ultrathin Solar Cells
The incorporation of nanostructures in optoelectronic devices for enhancing their
optical performance is widely studied. However, several problems related to the
processing complexity and the low performance of the nanostructures have
hindered such actions in real-life devices. Herein, a novel way of introducing gold
nanoparticles in a solar cell structure is proposed in which the nanostructures are
encapsulated with a dielectric layer, shielding them from high temperatures and
harsh growth processing conditions of the remaining device. Through optical
simulations, an enhancement of the effective optical path length of approximately
four times the nominal thickness of the absorber layer is verified with the new
architecture. Furthermore, the proposed concept in a Cu(In,Ga)Se2 solar cell
device is demonstrated, where the short-circuit current density is increased by
17.4%. The novel structure presented in this work is achieved by combining a
bottom-up chemical approach of depositing the nanostructures with a top-down
photolithographic process, which allows for an electrical contact.This work was funded in part by the Fundação para a Ciência e a Tecnologia
(FCT) under Grants IF/00133/2015, PD/BD/142780/2018 and SFRH/BD/
146776/2019. The authors also want to acknowledge the European Union’s
Horizon 2020 Research and Innovation Programme through the ARCIGS-M
project under Grant 720887, the Special Research Fund (BOF) of Hasselt
University, the FCT through the project NovaCell (PTDC/CTM-CTM/28075/
2017), and InovSolarCells (PTDC/FISMAC/29696/2017) co-funded by FCT
and the ERDF through COMPETE2020. The authors also want to acknowledge Sandra Maya for the production of images used in this work.info:eu-repo/semantics/publishedVersio
Single-cell screening of photosynthetic growth and lactate production by cyanobacteria
Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study
This is the final version. Available on open access from the American Chemical Society via the DOI in this recordThe variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a 'primary' setup and the test data are generated on 'replicate' setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies.COST (European Cooperation in Science and Technology)Portuguese Foundation for Science and TechnologyNational Research Fund of Luxembourg (FNR)China Scholarship Council (CSC)BOKU Core Facilities Multiscale ImagingDeutsche Forschungsgemeinschaft (DFG, German Research Foundation
“Elastic” Property of Mesoporous Silica Shell: For Dynamic Surface Enhanced Raman Scattering Ability Monitoring of Growing Noble Metal Nanostructures via a Simplified Spatially Confined Growth Method
SERS chiral recognition and quantification of enantiomers through cyclodextrin supramolecular complexation
We introduce here a simple approach in which a cyclodextrin, functionalized with thiols in the narrower rim, is assembled onto the silver surface of a SERS platform composed of polystyrene beads coated with silver nanoparticles. Trapping properties of the fabricated sensor are demonstrated through the retention of different enantiomers (R,R or/and S,S) of hydrobenzoin (HBZ), a molecule that has not been reported before in SERS because it has no affinity for coinage metal surfaces. Further, selective recognition of each enantiomer and semiquantification of its proportion in a racemic mixture are provided by the analysis of the SERS spectra of the HBZ-cyclodextrin complex, in full agreement with the surface selection rules. Enantioselective sensor: We introduce a simple approach in which a cyclodextrin is assembled onto the silver surface of a SERS platform for chiral recognition of enantiomers (see picture). Trapping properties, chiral discrimination and quantification of the R,R- and S,S-enantiomers of hydrobenzoin by surface-enhanced Raman scattering (SERS) spectroscopy are demonstrated
Quantitative analysis of the growth of individual Bacillus coagulans cells by microdroplet technology
Surface-enhanced Raman scattering biomedical applications of plasmonic colloidal particles
This review article presents a general view of the recent progress in the fast developing area of surface-enhanced Raman scattering spectroscopy as an analytical tool for the detection and identification of molecular species in very small concentrations, with a particular focus on potential applications in the biomedical area. We start with a brief overview of the relevant concepts related to the choice of plasmonic nanostructures for the design of suitable substrates, their implementation into more complex materials that allow generalization of the method and detection of a wide variety of (bio)molecules and the strategies that can be used for both direct and indirect sensing. In relation to indirect sensing, we devote the final section to a description of SERS-encoded particles, which have found wide application in biomedicine (among other fields), since they are expected to face challenges such as multiplexing and high-throughput screening
Heterogeneous-surface-mediated crystallization control
The crystallization of matter at interfaces has long been a significant issue in science and technology, but surface-directed crystallization with controlled kinetics remains a matter of challenge. Here, we demonstrate a conceptual novel mechanism to steer liquid?solid phase transformation at interfaces by tailoring the chemical and structural inhomogeneity of a glass substrate through self-limited nanocrystallization of the glassy phase. Importantly, this approach enables large-scale development of metastable crystallization products, such as nanowire membranes. The thorough studies of the intermediate stages of crystallization reveal a unique cooperative mechanism in which the intricate interplays between inherent nanoscale forces and unique heterogeneous surfaces contribute to the mesoscale structural transformation from isolated units to superstructures. We further show that the constructed superstructures offer unprecedented opportuntities for the development of functional membrane systems possessing the combination of robust trace-detection performance and molecular trapping function. These findings not only present clear technological implications, but also provide an improved understanding of the fundamental mechanisms of surface-induced geological and biological processes