Photo-oxidation studies of 4-(chloromethyl)phenyltrichlorosilane on silicon and titanium oxide

The rates of photo-oxidation of 4-(chloromethyl)phenyltrichlorosilane (CMPS) formed on titanium oxide (TiO2) and silicon oxide (SiO2) substrates were studied. The optimized self-assembly of CMPS films on SiO2 and TiO2 were investigated which subsequently used for comparing photochemical reactions by exposing samples under deep UV of 254 nm. Upon the UV irradiation, the tail group of CMPS monolayers; chloro benzyl group is converted to aldehyde group and further exposure leads to the formation of polar group (carboxylic acid) which generates surfaces with a high surface free energy and a hydrophilic character. Analyses of contact angle, Fourier transform infrared and X-ray photoelectron spectroscopy (XPS) were performed to monitor the products generated upon UV irradiation. It was found that highly efficient and rapid photo-oxidation was observed for CMPS on TiO2, a complete conversion within minutes compared to CMPS on SiO2. The use of TiO2 has shown that the rate is thrice faster than SiO2 which is efficient as a photocatalytic oxidation. The resulting carboxylic group terminated surface was subsequently derivatized using 2-amino-1,1,1-trifluoroethane (TFEA). Contact angle and XPS measurements of post-derivatization indicated that the surface functionalization was extensive

Thiol capped gold nanoparticles-based colorimetric sensor for mercury detection

Conjugation of mercaptopropionic acid (MPA) as a thiol-capping agent linked with gold nanoparticles (AuNPs) enables colorimetric heavy metal detection. The synthesized AuNPs followed by thiol-capped AuNPs shows a color changes from red wine to deep color of gold nanoparticles. The quantitative measurement was performed with UV-Vis absorption spectrum, indicating a sharp peak centered at range of 520 nm to 540 nm shifted to 561.50 nm upon linked capping agent. Fourier transform infrared (FT-IR) analysis further confirmed the presence of ligand capped on AuNPs. For this project, thiol-capped AuNPs was used to detect Hg (II). The color changes were observed as the various concentration of Hg (II). Further characterization was performed with UVVis, showing the shifting of the maximum absorption peak. This indicates the method used to determine Hg (II) was simple and fast which can detect as low as 0.1 mM

Electrochemical determination of lead & copper ions using thiolated calix[4]arene-modified screen-printed carbon electrode

This study used a thiolated calix[4]arene derivative modified on gold nanoparticles and a screen-printed carbon electrode (TC4/AuNPs/SPCE) for Pb2+ and Cu2+ determination. The surface of the modified electrode was characterised via Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Differential pulse voltammetry (DPV) was used for the detection of Pb2+ and Cu2+ under optimum conditions. The limit of detection (LOD) for detecting Pb2+ and Cu2+ was 0.7982 × 10−2 ppm and 1.3358 × 10−2 ppm, respectively. Except for Zn2+ and Hg2+, the presence of competitive ions caused little effect on the current response when detecting Pb2+. However, all competitive ions caused a significant drop in the current response when detecting Cu2+, except Ca2+ and Mg2+, suggesting the sensing platform is more selective toward Pb2+ ions rather than copper (Cu2+) ions. The electrochemical sensor demonstrated good reproducibility and excellent stability with a low relative standard deviation (RSD) value in detecting lead and copper ions. Most importantly, the result obtained in the analysis of Pb2+ and Cu2+ had good recovery in river water, demonstrating the applicability of the developed sensor for real samples

Protein patterning by UV-induced photodegradation of poly(oligo(ethylene glycol) methacrylate) brushes

The UV photodegradation of protein-resistant poly(oligo(ethylene glycol) methacrylate) (POEGMA) bottle-brush films, grown on silicon oxide by surface-initiated atom radical transfer polymerization, was studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Exposure to light with a wavelength of 244 nm caused a loss of polyether units from the brush structure and the creation of aldehyde groups that could be derivatized with amines. An increase was measured in the coefficient of friction of the photodegraded polymer brush compared to the native brush, attributed to the creation of a heterogeneous surface film, leading to increased energy dissipation through film deformation and the creation of new polar functional groups at the surface. Exposure of the films through a photomask yielded sharp, well-defined patterns. Analysis of topographical images showed that physical removal of material occurred during exposure, at a rate of 1.35 nm J−1 cm2. Using fluorescence microscopy, the adsorption of labeled proteins onto the exposed surfaces was studied. It was found that protein strongly adsorbed to exposed areas, while the masked regions retained their protein resistance. Exposure of the film to UV light from a scanning near-field optical microscope yielded submicrometer-scale patterns. These data indicate that a simple, rapid, one-step photoconversion of the poly(OEGMA) brush occurs that transforms it from a highly protein-resistant material to one that adsorbs protein and can covalently bind amine-containing molecules and that this photoconversion can be spatially addressed with high spatial resolution

A novel DNA nanosensor based on CdSe/ZnS quantum dots and synthesized Fe3O4 magnetic nanoparticles

Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices

Micro- and nano-structured poly(oligo(ethylene glycol)methacrylate) brushes grown from photopatterned halogen initiators by atom transfer radical polymerization.

Photolithographic techniques have been used to fabricate polymer brush micro- and nanostructures. On exposure to UV light with a wavelength of 244 nm, halogens were selectively removed from films of chloromethylphenyltrichlorosilane and 3-(2-bromoisobutyramido)propyl-triethoxysilane on silicon dioxide. Patterning was achieved at the micrometer scale, by using a mask in conjunction with the incident laser beam, and at the nanometer scale, by utilizing interferometric lithography (IL). Friction force microscopy images of patterned surfaces exhibited frictional contrast due to removal of the halogen but no topographical contrast. In both cases the halogenated surface was used as an initiator for surface atom-transfer radical polymerization. Patterning of the surface by UV lithography enabled the definition of patterns of initiator from which micro- and nanostructured poly[oligo(ethylene glycol)methacrylate] bottle brushes were grown. Micropatterned brushes formed on both surfaces exhibited excellent resistance to protein adsorption, enabling the formation of protein patterns. Using IL, brush structures were formed that covered macroscopic areas (approximately 0.5 cm²) but exhibited a full width at half maximum height as small as 78 nm, with a period of 225 nm. Spatially selective photolytic removal of halogens that are immobilized on a surface thus appears to be a simple, rapid, and versatile method for the formation of micro- and nanostructured polymer brushes and for the control of protein adsorption

Sensitive and selective detection of DNA fragments associated with Ganoderma boninense by DNA-nanoparticle conjugate hybridisation

From Springer Nature via Jisc Publications RouterHistory: received 2020-05-04, accepted 2020-07-05, registration 2020-07-05, pub-electronic 2020-07-20, online 2020-07-20, pub-print 2020-10Publication status: PublishedFunder: Newton Fund; doi: http://dx.doi.org/10.13039/100010897; Grant(s): British Council 216196834Funder: Engineering and Physical Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000266; Grant(s): EP/K024485/1Funder: Higher Education Funding Council for England; doi: http://dx.doi.org/10.13039/100011722; Grant(s): N8 Agrifood NetworkAbstract: A colourimetric assay for the detection of DNA fragments associated with the oil palm pathogen Ganoderma boninense and other fungi DNA is reported. The assay is based on the aggregation of DNA-nanoparticle conjugates in the presence of complementary DNA from the target organism. Here, various designs of DNA-nanoparticle conjugates were evaluated, and it was found that the best design gave a visually observable colour change with as little as 2 pmol of double-stranded DNA analyte even in the presence of a large excess of a mixture of non-complementary DNA. Overall, this label-free system is rapid, sensitive, selective, simple in design, and easy to carry out. It does not require specialist equipment or specialist training for the interpretation of the results, and therefore has the potential to be deployed for agricultural diagnostics in the field. Graphic abstract: Development of a colourimetric assay based on DNA-nanoparticle conjugates for the oil palm pathogen Ganoderma boninense

The snomipede : a parallel platform for scanning near-field photolithography.

Using scanning near-field lithography (SNP), it is possible to pattern molecules at surfaces with a resolution as good as 9 nm [M. Montague, R. E. Ducker, K. S. L. Chong, R. J. Manning, F. J. M. Rutten, M. C. Davies and G. J. Leggett, Langmuir 23 (13), 7328–7337 (2007)]. However, in common with other scanning probe techniques, SNP has previously been considered a serial process, hindering its use in many applications. IBM’s “Millipede” addresses this problem by utilizing an array of local probes operating in parallel. Here, we describe the construction of two instruments (Snomipedes) that integrate near-field optical methods into the parallel probe paradigm and promise the integration of top–down and bottom–up fabrication methods over macroscopic areas. Both are capable of performing near-field lithography with 16 probes in parallel spanning approximately 2 mm. The instruments can work in both ambient and liquid environments, key to many applications in nanobiology. In both, separate control of writing is possible for each probe. We demonstrate the deprotection of self-assembled monolayers of alkylsilanes with photocleavable protecting groups and subsequent growth of nanostructured polymer brushes from these nanopatterned surfaces by atom-transfer radical polymerization

A review on the determination heavy metals ions using calixarene-based electrochemical sensors

In aquatic environment, the presence of heavy metal in excess than permissible limits set by the World Health Organization (WHO) can cause problems to human being and aquatic life. Hence, various analytical methods have been developed to monitor the water quality by tracing different heavy metal ions in water samples. The present review summarizes the body of work (143 studies) on heavy metal determination in the past 20 years using electrochemical sensors and calixarene derivatives. The potential of calixarene derivatives to sense heavy metal ions using different electrochemical techniques were discussed. The review begins with the introduction of various electrochemical methods including potentiometry, amperometry, voltammetry and electrochemical impedance spectroscopy along with the general setup. This review provides an overview of the mechanism, main parameters of studies and application of calixarene derivatives in selective and sensitive detection. The detection of various target analytes, concentration range, and detection limit using calixarene derivative-based sensors, with different electrochemical techniques, are presented. The strengths and weaknesses of different electrochemical techniques based on calixarene derivatives are also discussed. The review shows that calixarene derivatives have great potential in sensing technology applications, specifically in heavy metal ion determination. In the end, present challenges and future prospects for translating developed sensors into portable sensing in commercial purposes is highlighted

Enhancement the electrochemical conductivity of a modified reduced graphene oxide/calixarene screen-printed electrode using response surface methodology.

In this paper, Response Surface Methodology with central composite design (RSM/CCD) was used to optimize a modified electrode for improved electron transfer rate and electrochemical performance. The modification was done on a screen-printed carbon electrode (SPCE) with reduced graphene oxide (ERGO)/calix [4] arene (ERGOC4-SPCE). The properties of the modified electrodes were analyzed via cyclic voltammetry, Raman spectroscopy, and Fourier-Transform Infrared (FT-IR) spectroscopy. Then, different variables were optimized, namely, the concentration of graphene oxide, GO (A), the number of scan cycles of graphene oxide (B), and the deposition time (C). The effect of the optimized variables on the reduction-oxidation peak current response of the potassium ferricyanide redox system was analyzed. By using statistical analysis, it shows a significant effect of the concentration of GO, the deposition time, and the number of scans cycles on the peak current response. The coefficient of determination (R2) value of 0.9987 produced indicated a good fit of the model with experimental finding