294 research outputs found
Surface Functionalization and Patterning by Multifunctional Resorcinarenes
Plant
phenolic compounds and catecholamines have been widely used
to obtain substrate-independent precursor nanocoatings and adhesives.
Nevertheless, there are downsides in using such phenolic compounds
for surface modification such as formation of nonuniform coatings,
need for multistep modification, and restricted possibilities for
postfunctionalization. In this study, inspired by a strong binding
ability of natural polyphenols found in plants, we used three different
macrocyclic polyphenols, known as resorcin[4]Âarenes, to modify the
surface of different substrates by simple dip-coating into the dilute
solution of these compounds. Eight hydroxyl groups on the large rim
of these resorcin[4]Âarenes provide multiple anchoring points to the
surface, whereas the lower rim decorated with different appending
groups introduces the desired chemical and physical functionalities
to the substrateâs surface. Deposition of a uniform and transparent
resorcinarene layer on the surface was confirmed by several surface
characterization techniques. Incubation of the modified substrates
in different environments indicated that the stability of the resorcinarene
layer was dependent on the type of substrate and the pH value. The
most stable resorcinarene layer was formed on amine-functionalized
substrates. The surface was modified with alkenyl functional groups
in one step using a resorcinarene compound possessing four alkenyl
appending groups on its small rim. Thiolâene photoclick chemistry
was used to site-selectively postfunctionalize the surface with hydrophilic
and hydrophobic micropatterns, which was confirmed by X-ray photoelectron
spectroscopy and time-of-flight secondary ion mass spectrometry. Thus,
we demonstrate that resorcin[4]Âarenes extend the scope of applications
of plant polyphenol and mussel-inspired precursors to tailor-made
multifunctional nanocoatings, suitable for a variety of potential
applications in biotechnology, biology, and material science
Regeneration of β-Cyclodextrin Based Membrane by Photodynamic Disulfide Exchange â Steroid Hormone Removal from Water
The occurrence of steroid hormones in water and their serious impact on human and ecosystem demand high performance materials for efficient removal of such micropollutants. Here, an affinity membrane is developed for hormone removal with regenerable binding sites. By using photodynamic disulfides as a linker, UV induced detachment of βâCD ligands from the membrane surface is demonstrated. The macroporous base membrane is first fabricated via a polymerization induced phase separation method using 2âhydroxyethyl methacrylate (HEMA) and ethylene dimethylacrylate (EDMA) monomers. Then the affinity membranes are prepared by immobilizing βâCD ligands to the poly(HEMAâcoâEDMA) base membrane through the 2âcarboxyethyl disulfide linker. The βâCD functionalized affinity membrane shows a 30% increase of E2 hormone uptake compared with the base membrane, attributed to the formation of CDâhormone hostâguest inclusion complexes. The photodynamic disulfide linkers enable UVâinduced detachment of blocked βâCD ligands from and reattachment of fresh βâCD ligands to the membrane surface after each adsorption cycle, thus conferring the affinity membrane with excellent regenerative properties. It is anticipated that the use of dynamic covalent bonds for binding ligands will be of interest for developing smart affinity membranes with regenerable and readjustable surface properties
A 16-Channel Wireless Neural Recording System-on-Chip with CHT Feature Extraction Processor in 65nm CMOS
Wireless implantable neural recording chips enable multichannel data acquisition with high spatiotemporal resolution in situ. Recently, the use of machine learning approaches on neural data for diagnosis and prosthesis control have renewed the interest in this field, and increased even more the demand for multichannel data. However, simultaneous data acquisition from many channels is a grand challenge due to data rate and power limitations on wireless transmission for implants. As a result, recent studies have focused on on-chip classifiers, despite the fact that only primitive classifiers can be placed on resource-constrained chips. Moreover, robustness of the chosen algorithm cannot be guaranteed pre-implantation due to the scarcity of patient-specific data; waveforms can change over time due to electrode micro migration or tissue reaction, highlighting the need for robust adaptive features
Substrate-Independent and Re-Writable Surface Patterning by Combining Polydopamine Coatings, Silanization, and Thiol-Ene Reaction
Polydopamine coating is a unique, simple, and substrate-independent surface functionalization strategy. Techniques for secondary functionalization, patterning, and re-functionalization of polydopamine modified materials are important to broaden the scope of applications of such materials in a variety of fields. Here, a facile and substrate-independent strategy for surface functionalization and patterning is presented. This approach combines the advantages of three important methods: facile and substrate-independent polydopamine coating, versatile gas phase silanization, and rapid thiol-ene photoclick reaction for patterning. They demonstrate equally efficient functionalization and patterning of diverse materials, such as glass, polytetrafluoroethylene, aluminum, polypropylene, or polyethylene. They also show the possibility of controlled chemical removal of the patterns or surface functionalization by treatment with tetrabutylammonium fluoride, which allows re-modification or re-patterning of the substrate. Thus, this universal and powerful approach for substrate independent surface modification and patterning can significantly facilitate the development of novel functional materials and devices useful for various applications
Ecology of Phlebotomine Sand Flies in the Rural Community of Mont Rolland (Thiès Region, Senegal): Area of Transmission of Canine Leishmaniasis
BACKGROUND: Different epidemiological studies previously indicated that canine leishmaniasis is present in the region of Thiès (Senegal). However, the risks to human health, the transmission cycle and particularly the implicated vectors are unknown. METHODOLOGY/PRINCIPAL FINDINGS: To improve our knowledge on the population of phlebotomine sand flies and the potential vectors of canine leishmaniasis, sand flies were collected using sticky traps, light traps and indoor spraying method using pyrethroid insecticides in 16 villages of the rural community of Mont Rolland (Thiès region) between March and July 2005. The 3788 phlebotomine sand flies we collected (2044 males, 1744 females) were distributed among 9 species of which 2 belonged to the genus Phlebotomus: P. duboscqi (vector of cutaneous leishmaniasis in Senegal) and P. rodhaini. The other species belonged to the genus Sergentomyia: S. adleri, S. clydei, S. antennata, S. buxtoni, S. dubia, S. schwetzi and S. magna. The number of individuals and the species composition differed according to the type of trap, suggesting variable, species-related degrees of endophily or exophily. The two species of the genus Phlebotomus were markedly under-represented in comparison to the species of the genus Sergentomyia. This study also shows a heterogeneous spatial distribution within the rural community that could be explained by the different ecosystems and particularly the soil characteristics of this community. Finally, the presence of the S. dubia species appeared to be significantly associated with canine leishmaniasis seroprevalence in dogs. CONCLUSIONS/SIGNIFICANCE: Our data allow us to hypothesize that the species of the genus Sergentomyia and particularly the species S. dubia and S. schwetzi might be capable of transmitting canine leishmaniasis. These results challenge the dogma that leishmaniasis is exclusively transmitted by species of the genus Phlebotomus in the Old World. This hypothesis should be more thoroughly evaluated
The Multisensor Array Based on Grown-On-Chip Zinc Oxide Nanorod Network for Selective Discrimination of Alcohol Vapors at Sub-ppm Range
We discuss the fabrication of gas-analytical multisensor arrays based on ZnO nanorods grown via a hydrothermal route directly on a multielectrode chip. The protocol to deposit the nanorods over the chip includes the primary formation of ZnO nano-clusters over the surface and secondly the oxide hydrothermal growth in a solution that facilitates the appearance of ZnO nanorods in the high aspect ratio which comprise a network. We have tested the proof-of-concept prototype of the ZnO nanorod network-based chip heated up to 400 °C versus three alcohol vapors, ethanol, isopropanol and butanol, at approx. 0.2â5 ppm concentrations when mixed with dry air. The results indicate that the developed chip is highly sensitive to these analytes with a detection limit down to the sub-ppm range. Due to the pristine differences in ZnO nanorod network density the chip yields a vector signal which enables the discrimination of various alcohols at a reasonable degree via processing by linear discriminant analysis even at a sub-ppm concentration range suitable for practical applications
Impact of particle size, oxidation state and capping agent of different cerium dioxide nanoparticles on the phosphate-induced transformations at different pH and concentration
The potential hazard posed by nanomaterials can be significantly influenced by transformations which these materials undergo during their lifecycle, from manufacturing through to disposal. The transformations may depend on the nanomaterialsâ own physicochemical properties as well as the environment they are exposed to. This study focuses on the mechanisms of transformation of cerium oxide nanoparticles (CeO NPs) in laboratory experiments which simulate potential scenarios in which the NPs are exposed to phosphate-bearing media. We have experimented with the transformation of four different kinds of CeO NPs, in order to investigate the effects of nanoparticle size, capping agent (three were uncapped and one was PVP capped) and oxidation state (two consisted mostly of Ce and two were a mix of Ce/Ce). They were exposed to a reaction solution containing KHPO, citric acid and ascorbic acid at pH values of 2.3, 5.5 and 12.3, and concentrations of 1mM and 5mM. The transformations were followed by UV-vis, zeta potential and XRD measurements, which were taken after 7 and 21 days, and by transmission electron microscopy after 21 days. X-ray photoelectron spectroscopy was measured at 5mM concentration after 21 days for some samples. Results show that for pH 5 and 5mM phosphate concentration, CePO NPs were formed. Nanoparticles that were mostly Ce did not dissolve at 1mM reagent concentration, and did not produce CePO NPs. When PVP was present as a capping agent it proved to be an extra reducing agent, and CePO was found under all conditions used. This is the first paper where the transformation of CeO NPs in the presence of phosphate has been studied for particles with different size, shapes and capping agents, in a range of different conditions and using many different characterisation methods
- âŚ