128 research outputs found
tuppence-based SERS for the detection of illicit materials
Deposition of silver onto British 2p coins has been demonstrated as an
efficient and cost effective approach to producing substrates capable of
promoting surface enhanced Raman scattering (SERS). Silver application to the
copper coins is undemanding taking just 20 s, and results in the formation of
multiple hierarchial dendritic structures. To demonstrate that the silver
deposition sites were capable of SERS the highly fluorescent Rhodamine 6G
(R6G) probe was used. Analyses indicated that Raman enhancement only occurs at
the silver deposition sites and not from the roughened copper surface. The
robustness of the substrate in the identification and discrimination of
illegal and legal drugs of abuse was then explored. Application of the drugs
to the substrates was carried out using spotting and soaking methodologies.
Whilst little or no SERS spectra of the drugs were generated upon spotting,
soaking of the substrate in a methanolic solution of the drugs yielded a vast
amount of spectral information. Excellent reproducibility of the SERS method
and classification of three of the drugs, 4-methylmethcathinone (mephedrone),
5,6-methylenedioxy-2-aminoindane (MDAI) and
3,4-methylenedioxy-N-methylamphetamine (MDMA) were demonstrated using
principal components analysis and partial least squares
Effect of the excitation energy, type, and amount of defects
We present a detailed Raman study of defective graphene samples containing
specific types of defects. In particular, we compared sp3 sites, vacancies,
and substitutional Boron atoms. We find that the ratio between the D and G
peak intensities, I(D)/I(G), does not depend on the geometry of the defect
(within the Raman spectrometer resolution). In contrast, in the limit of low
defect concentration, the ratio between the DⲠand G peak intensities is
higher for vacancies than sp3 sites. By using the local activation model, we
attribute this difference to the term CS,x, representing the Raman cross
section of I(x)/I(G) associated with the distortion of the crystal lattice
after defect introduction per unit of damaged area, where x = D or Dâ˛. We
observed that CS,D=0 for all the defects analyzed, while CS,DⲠof vacancies is
2.5 times larger than CS,DⲠof sp3 sites. This makes I(D)/I(Dâ˛) strongly
sensitive to the nature of the defect. We also show that the exact dependence
of I(D)/I(Dâ˛) on the excitation energy may be affected by the nature of the
defect. These results can be used to obtain further insights into the Raman
scattering process (in particular for the DⲠpeak) in order to improve our
understanding and modeling of defects in graphene
High-Yield Production and Transfer of Graphene Flakes Obtained by Anodic Bonding
We report large-yield production of graphene flakes on glass by anodic
bonding. Under optimum conditions, we counted several tens of flakes with
lateral size around 20-30 {\mu}m and few tens of flakes with larger size.
60-70% of the flakes have negligible D peak. We show that it is possible to
easily transfer the flakes by wedging technique. The transfer on silicon does
not damage graphene and lowers the doping. The charge mobility of the
transferred flakes on silicon is of the order of 6000 cm^2/V s (at carrier
concentration of 10^12 cm^-2), which is typical for devices prepared on this
substrate with exfoliated graphene.Comment: 17 pages, 6 figures; ACS Nano 201
Flexible, Print-in-Place 1D-2D Thin-Film Transistors Using Aerosol Jet Printing
In this work, we overcome temperature constraints and demonstrate 1Dâ2D thin-film transistors (1Dâ2D TFTs) in a low-temperature (maximum exposure â¤80 °C) full print-in-place process (i.e., no substrate removal from printer throughout
the entire process) using an aerosol jet printer. Semiconducting 1D CNT channels are used with a 2D hexagonal boron
nitride (h-BN) gate dielectric and traces of silver nanowires as the conductive electrodes, all deposited using the same
printer. The aerosol jet-printed 2D h-BN films were realized via proper ink formulation, such as utilizing the binder
hydroxypropyl methylcellulose, which suppresses redispersion between adjacent printed layers. In addition to an ON/
OFF current ratio up to 3.5 Ă
~ 105, channel mobility up to 10.7 cm2¡V-1¡s-1, and low gate hysteresis, 1Dâ2D TFTs exhibit
extraordinary mechanical stability under bending due to the nanoscale network structure of each layer, with minimal
changes in performance after 1000 bending test cycles at 2.1% strain. It is also confirmed that none of the device layers
require high-temperature treatment to realize optimal performance. These findings provide an attractive approach toward
a cost-effective, direct-write realization of electronics
Palladium catalysed C-H arylation of pyrenes: access to a new class of exfoliating agents for water-based graphene dispersions.
From Europe PMC via Jisc Publications RouterHistory: ppub 2020-01-01, epub 2020-01-28Publication status: PublishedFunder: Engineering and Physical Sciences Research Council; Grant(s): 1781838, EP/P00119X/1A new and diverse family of pyrene derivatives was synthesised via palladium-catalysed C-H ortho-arylation of pyrene-1-carboxylic acid. The strategy affords easy access to a broad scope of 2-substituted and 1,2-disubstituted pyrenes. The C1-substituent can be easily transformed into carboxylic acid, iodide, alkynyl, aryl or alkyl functionalities. This approach gives access to arylated pyrene ammonium salts, which outperformed their non-arylated parent compound during aqueous Liquid Phase Exfoliation (LPE) of graphite and compare favourably to state-of-the-art sodium pyrene-1-sulfonate PS1. This allowed the production of concentrated and stable suspensions of graphene flakes in water
effect of charge, dipole and molecular structure
We study the mechanism of surface adsorption of organic dyes on graphene, and
successive exfoliation in water of these dye-functionalized graphene sheets. A
systematic, comparative study is performed on pyrenes functionalized with an
increasing number of sulfonic groups. By combining experimental and modeling
investigations, we find an unambiguous correlation between the grapheneâdye
interaction energy, the molecular structure and the amount of graphene flakes
solubilized. The results obtained indicate that the molecular dipole is not
important per se, but because it facilitates adsorption on graphene by a
âslidingâ mechanism of the molecule into the solvent layer, facilitating the
lateral displacement of the water molecules collocated between the aromatic
cores of the dye and graphene. While a large dipole and molecular asymmetry
promote the adsorption of the molecule on graphene, the stability and pH
response of the suspensions obtained depend on colloidal stabilization, with
no significant influence of molecular charging and dipole
Nanoscale insight into the exfoliation mechanism of graphene with organic dyes: effect of charge, dipole and molecular structure
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Pilot-scale Production and Viability Analysis of Freeze-Dried Probiotic Bacteria Using Different Protective Agents
The functional food industry requires an improvement of probiotic strain stability during storage, especially when they are stored at room temperature. In this study, the viability of freeze-dried Lactobacillus rhamnosus IMC 501ÂŽ and Lactobacillus paracasei IMC 502ÂŽ using different protective agents (i.e., glycerine, mannitol, sorbitol, inulin, dextrin, CrystaleanÂŽ) was determined and compared with semi skimmed milk (SSM) control. No significant differences were observed between the tested protectants and the control (SSM) during storage at refrigerated conditions. During storage at room temperature, only glycerine was found to stabilize viability better than other tested substances
Defect-free graphene enhances enzyme delivery to fibroblasts derived from patients with lysosomal storage disorders
Enzyme replacement therapy shows remarkable clinical improvement in treating lysosomal storage disorders. However, this therapeutic approach is hampered by limitations in the delivery of the enzyme to cells and tissues. Therefore, there is an urgent, unmet clinical need to develop new strategies to enhance the enzyme delivery to diseased cells. Graphene-based materials, due to their dimensionality and favourable pattern of interaction with cells, represent a promising platform for the loading and delivery of therapeutic cargo. Herein, the potential use of graphene-based materials, including defect-free graphene with positive or negative surface charge and graphene oxide with different lateral dimensions, was investigated for the delivery of lysosomal enzymes in fibroblasts derived from patients with Mucopolysaccharidosis VI and Pompe disease. We report excellent biocompatibility of all graphene-based materials up to a concentration of 100 Îźg mL in the cell lines studied. In addition, a noticeable difference in the uptake profile of the materials was observed. Neither type of graphene oxide was taken up by the cells to a significant extent. In contrast, the two types of graphene were efficiently taken up, localizing in the lysosomes. Furthermore, we demonstrate that cationic graphene flakes can be used as carriers for arylsulfatase B enzyme, for the delivery of the lacking enzyme to the lysosomes of Mucopolysaccharidosis VI fibroblasts. Arylsulfatase B complexed with cationic graphene flakes not only retained the enzymatic activity, but also exerted biological effects almost twice as high as arylsulfatase B alone in the clearance of the substrate in Mucopolysaccharidosis VI fibroblasts. This study lays the groundwork for the potential use of graphene-based materials as carriers for enzyme replacement therapy in lysosomal storage disorders
Vibrational fingerprints of residual polymer on transferred CVD-graphene
The use of vibrational sum-frequency spectroscopy (VSFS) to study transferred graphene, produced by chemical vapour deposition, is presented. The VSF spectrum shows a clear CH stretching mode at âź2924 cmâ1, which is attributed to residue of the polymer used for the transfer. This makes VSFS a powerful tool to identify adsorbates and contaminants affecting the properties of graphene
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