| 1. |
- Chaudhary, Shilpi, et al.
(författare)
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Real-Time Study of CVD Growth of Silicon Oxide on Rutile TiO2(110) Using Tetraethyl Orthosilicate
- 2015
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:33, s. 19149-19161
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of the ruffle TiO2(110) surface with tetraethyl orthosilicate (TEOS) in the pressure range from UHV to 1 mbar as well as the TEOS-based chemical vapor deposition of SiO2 on the TiO2(110) surface were monitored in real time using near-ambient pressure X-ray photoelectron spectroscopy. The experimental data and density functional theory calculations confirm the dissociative adsorption of TEOS on the surface already at room temperature. At elevated pressure, the ethoxy species formed in the adsorption process undergoes further surface reactions toward a carboxyl species not observed in the absence of a TEOS gas phase reservoir. Annealing of the adsorption layer leads to the formation of SiO2, and an intermediate oxygen species assigned to a mixed titanium/silicon oxide is identified. Atomic force microscopy confirms the morphological changes after silicon oxide formation.
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| 2. |
- Kamra, Tripta, et al.
(författare)
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Covalent immobilization of molecularly imprinted polymer nanoparticles on a gold surface using carbodiimide coupling for chemical sensing.
- 2016
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 461, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- One challenging task in building (bio)chemical sensors is the efficient and stable immobilization of receptor on a suitable transducer. Herein, we report a method for covalent immobilization of molecularly imprinted core-shell nanoparticles for construction of robust chemical sensors. The imprinted nanoparticles with a core-shell structure have selective molecular binding sites in the core and multiple amino groups in the shell. The model Au transducer surface is first functionalized with a self-assembled monolayer of 11-mercaptoundecanoic acid. The 11-mercaptoundecanoic acid is activated by treatment with carbodiimide/N-hydroxysuccinimide and then reacted with the core-shell nanoparticles to form amide bonds. We have characterized the process by studying the treated surfaces after each preparation step using atomic force microscopy, scanning electron microscopy, fluorescence microscopy, contact angle measurements and X-ray photoelectron spectroscopy. The microscopy results show the successful immobilization of the imprinted nanoparticles on the surface. The photoelectron spectroscopy results further confirm the success of each functionalization step. Further, the amino groups on the MIP surface were activated by electrostatically adsorbing negatively charged Au colloids. The functionalized surface was shown to be active for surface enhanced Raman scattering detection of propranolol. The particle immobilization and surface enhanced Raman scattering approach described here has a general applicability for constructing chemical sensors in different formats.
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| 3. |
- Kamra, Tripta, et al.
(författare)
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Covalent immobilization of molecularly imprinted polymer nanoparticles using an epoxy silane.
- 2015
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 445, s. 277-284
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) can be used as antibody mimics to develop robust chemical sensors. One challenging problem in using MIPs for sensor development is the lack of reliable conjugation chemistry that allows MIPs to be fixed on transducer surface. In this work, we study the use of epoxy silane to immobilize MIP nanoparticles on model transducer surfaces without impairing the function of the immobilized nanoparticles. The MIP nanoparticles with a core-shell structure have selective molecular binding sites in the core and multiple amino groups in the shell. The model transducer surface is functionalized with a self-assembled monolayer of epoxy silane, which reacts with the core-shell MIP particles to enable straightforward immobilization. The whole process is characterized by studying the treated surfaces after each preparation step using atomic force microscopy, scanning electron microscopy, fluorescence microscopy, contact angle measurements and X-ray photoelectron spectroscopy. The microscopy results show that the MIP particles are immobilized uniformly on surface. The photoelectron spectroscopy results further confirm the action of each functionalization step. The molecular selectivity of the MIP-functionalized surface is verified by radioligand binding analysis. The particle immobilization approach described here has a general applicability for constructing selective chemical sensors in different formats.
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| 4. |
- Kamra, Tripta, et al.
(författare)
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Implementation of Molecularly Imprinted Polymer Beads for Surface Enhanced Raman Detection
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 87:10, s. 5056-5061
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) have a predesigned molecular recognition capability that can be used to build robust chemical sensors. MIP-based chemical sensors allow label-free detection and are particularly interesting due to their simple operation. In this work we report the use of thiol-terminated MIP microspheres to construct surfaces for detection of a model organic analyte, nicotine, by surface enhanced Raman scattering (SERS). The nicotine-imprinted microspheres are synthesized by RAFT precipitation polymerization and converted into thiol-terminated microspheres through aminolysis. The thiol groups on the MIP surface allow the microspheres to be immobilized on a gold-coated substrate. Three different strategies are investigated to achieve surface enhanced Raman scattering in the vicinity of the imprinted sites: (1) direct sputtering of gold nanoparticles, (2) immobilization of gold colloids through the MIPs thiol groups, and (3) trapping of the MIP microspheres in a patterned SERS substrate. For the first time we show that large MIP microspheres can be turned into selective SERS surfaces through the three different approaches of assembly. The MIP-based sensing surfaces are used to detect nicotine to demonstrate the proof of concept. As synthesis and surface functionalization of MIP microspheres and nanoparticles are well established, the methods reported in this work are handy and efficient for constructing label-free chemical sensors, in particular for those based on SERS detection.
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| 5. |
- Kamra, Tripta, et al.
(författare)
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Photoconjugation of Molecularly Imprinted Polymer Nanoparticles for Surface-Enhanced Raman Detection of Propranolol
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:49, s. 27479-27485
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Tidskriftsartikel (refereegranskat)abstract
- We report a simple and versatile method to covalently immobilize molecularly imprinted polymer (MIP) nanoparticles on a Raman active substrate (Klarite) using a disulfide-derivatized perfluorophenylazide (PFPA-disulfide). Gold-coated Klarite was functionalized with PFPA-disulfide via a gold sulfur bond. Upon light radiation, the available azido groups were converted to highly reactive singlet perfluorophenyl nitrene that undergoes a CH insertion reaction and form covalent bonds with the MIP nanoparticles. The resulting surfaces were characterized using scanning electron microscopy and surface enhanced Raman spectroscopy to study the morphology and template affinity of the surfaces, respectively. The Raman measurements clearly show a dose-responsive signal when propranolol binds to the MIP surface. Because the MIP particles were covalently attached to the Raman active substrate, the sensing surface was stable and could be reused after regeneration in acetic acid solution. The MIP-based Raman sensor was used successfully to detect propranolol in urine samples (7.7 X 10(-4) M). Our results show that the high selectivity of MLPs and the fingerprint Raman identification can be integrated into a compact sensing unit using high-efficiency photoconjugation. Thus, the method proposed is reliable, efficient and fast for fabricating label-free chemical sensors.
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| 6. |
- Pankratov, Dmitry, et al.
(författare)
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Scalable, high performance, enzymatic cathodes based on nanoimprint lithography
- 2015
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Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 6, s. 1377-1384
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Tidskriftsartikel (refereegranskat)abstract
- Here we detail high performance, enzymatic electrodes for oxygen bio-electroreduction, which can be easily and reproducibly fabricated with industry-scale throughput. Planar and nanostructured electrodes were built on biocompatible, flexible polymer sheets, while nanoimprint lithography was used for electrode nanostructuring. To the best of our knowledge, this is one of the first reports concerning the usage of nanoimprint lithography for amperometric bioelectronic devices. The enzyme (Myrothecium verrucaria bilirubin oxidase) was immobilised on planar (control) and artificially nanostructured, gold electrodes by direct physical adsorption. The detailed electrochemical investigation of bioelectrodes was performed and the following parameters were obtained: open circuit voltage of approximately 0.75 V, and maximum bio-electrocatalytic current densities of 18 mu A/cm(2) and 58 mu A/cm(2) in air-saturated buffers versus 48 mu A/cm(2) and 186 mu A/cm(2) in oxygen-saturated buffers for planar and nanostructured electrodes, respectively. The half-deactivation times of planar and nanostructured biocathodes were measured to be 2 h and 14 h, respectively. The comparison of standard heterogeneous and bio-electrocatalytic rate constants showed that the improved bio-electrocatalytic performance of the nanostructured biocathodes compared to planar biodevices is due to the increased surface area of the nanostructured electrodes, whereas their improved operational stability is attributed to stabilisation of the enzyme inside nanocavities.
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| 7. |
- Pankratov, Dmitry, et al.
(författare)
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Transparent and flexible, nanostructured and mediatorless glucose/oxygen enzymatic fuel cells
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 1873-2755 .- 0378-7753. ; 294, s. 501-506
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Tidskriftsartikel (refereegranskat)abstract
- Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 mu W cm(-2) maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 mu W cm(-2) after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses. (C) 2015 Elsevier B.V. All rights reserved.
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| 8. |
- Suyatin, Dmitry, et al.
(författare)
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Concept for assembling individual nanostructure-based components into complex devices
- 2015
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Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 33:6
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Tidskriftsartikel (refereegranskat)abstract
- Minute electronic (bio) devices will likely play an increasingly important role in everyday life and beyond, as overall device size often limits device functionality and applicability, a factor especially critical for brain implants. Recent progress in micro-and nanoelectronics has enabled the production of nanoscale electronic components; however, overall device size is often defined by technical and technological limitations, in particular, the ability to combine heterogeneous components made using incompatible processes on different substrates. Here, the authors suggest and evaluate a concept and approach aimed at the direct three-dimensional assembly of individual nanoscale-based components into complex devices for brain implants. They demonstrate this assembly possibility via the transfer of free-standing GaP nanowires, as well as test devices made of gold film which exhibit good quality electrical contacts. The key features essential for such a functional assembly process are discussed. The authors expect this approach to be generic and to enable the development of complex minute electronic (bio) devices based on nanoscale components. The proposed type of assembly may be especially beneficial for devices with strict size constraints, such as implantable neural interfaces. (C) 2015 American Vacuum Society.
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