Keywords: quinoxaline-walled deep cavitand, multi-walled carbon nanotubes, oxygen plasma treatment, gold nanoparticle, benzene.The unprecedented sensitivity and partial selectivity of quinoxaline-walled thioether-legged deep cavitand functionalized multiwall carbon nanotubes toward traces of benzene vapors is presented. The cavitand is grafted onto gold nanoparticle (Au-NP) decorated oxygen plasma treated multiwall carbon nanotubes (O-MWCNT) by a self-assembled monolayer process affording a product referred to as cav-Au-MWCNT. The reported technique is suitable for the mass production of hybrid nanomaterials at low cost. The cav-Au-MWCNT resistive gas sensor operates at room temperature and shows an outstanding performance toward traces of benzene vapors. The detection of 2.5 ppb of benzene in dry air is demonstrated with a limit of detection (LOD) near 600 ppt. For the first time, it is shown that a CNT nanomaterial can effectively sense the extremely harmful benzene molecule with higher sensitivity than toluene or o-xylene at the trace levels. The cavitand is well suited for binding benzene, which, being in close proximity to the MWCNT, affects its density of states (DOS) shifting the Fermi level away from the valence band. The binding of benzene is transduced in a diminution of 2 MWCNT conductance. Furthermore, the inclusion of benzene is fully reversible at room temperature, implying that the sensor can operate at very low power consumption.
Silicon nanowire chips can function as sensors for cancer DNA detection, whereby selective functionalization of the Si sensing areas over the surrounding silicon oxide would prevent loss of analyte and thus increase the sensitivity. The thermal hydrosilylation of unsaturated carbon–carbon bonds onto H-terminated Si has been studied here to selectively functionalize the Si nanowires with a monolayer of 1,8-nonadiyne. The silicon oxide areas, however, appeared to be functionalized as well. The selectivity toward the Si–H regions was increased by introducing an extra HF treatment after the 1,8-nonadiyne monolayer formation. This step (partly) removed the monolayer from the silicon oxide regions, whereas the Si–C bonds at the Si areas remained intact. The alkyne headgroups of immobilized 1,8-nonadiyne were functionalized with PNA probes by coupling azido-PNA and thiol-PNA by click chemistry and thiol–yne chemistry, respectively. Although both functionalization routes were successful, hybridization could only be detected on the samples with thiol-PNA. No fluorescence was observed when introducing dye-labeled noncomplementary DNA, which indicates specific DNA hybridization. These results open up the possibilities for creating Si nanowire-based DNA sensors with improved selectivity and sensitivity.
By exploiting a liquid biopsy approach, we developed an ultrasensitive nanoparticle-enhanced plasmonic method for detecting RAS single nucleotide variants (SNVs) in the plasma of CRC patients. The PCR-free method we developed is based on an imaging platform and allows the direct detection of ~1 attomolar RAS sequences in plasma with a sandwich hybridization assay using peptide nucleic acids probes. The assay involves a simple pre-analytical procedure that does not require the extraction of tumor DNA from plasma and detects it in volumes as low as 40 uL of plasma, which is at least an order of magnitude smaller than that required by state of the art liquid biopsy technologies. The most prevalent RAS SNVs are detected in DNA from tumor tissue with 100% sensitivity and 83.33% specificity. Spike-in experiments in human plasma further encouraged assay application on clinical specimens. Assay performances were then proven in plasma from CRC patients and healthy donors, demonstrating its promising avenue for cancer monitoring. File list (2) download file view on ChemRxiv Direct plasmonic detection RAS pre print.pdf (1.24 MiB) download file view on ChemRxiv Direct plasmonic detection RAS pre print SI.pdf (2.07 MiB)
We report the design, synthesis and characterization of a new Ru metallocavitand that is catalytically active in alkene epoxidation reactions. The elaboration of the resorcin[4]arene's aromatic cavity produced a self-folding, deep hexaamide cavitand featuring a single diverging terpyridine (tpy) group installed at its upper rim. The construction of the metallocavitand involved the initial chelation of a Ru chloride complex by the tpy ligand followed by the incorporation of 2-(phenylazo)pyridine (azpy) as an ancillary ligand. The resulting Ru chloro complex was converted into the catalytically active aqua counterpart by a ligand exchange process.
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