56 research outputs found

    Recent Developments in the Field of Explosive Trace Detection

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    Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems

    Molecular Imprinted Polymers Coupled to Photonic Structures in Biosensors: The State of Art

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    Optical sensing, taking advantage of the variety of available optical structures, is a rapidly expanding area. Over recent years, whispering gallery mode resonators, photonic crystals, optical waveguides, optical fibers and surface plasmon resonance have been exploited to devise different optical sensing configurations. In the present review, we report on the state of the art of optical sensing devices based on the aforementioned optical structures and on synthetic receptors prepared by means of the molecular imprinting technology. Molecularly imprinted polymers (MIPs) are polymeric receptors, cheap and robust, with high affinity and selectivity, prepared by a template assisted synthesis. The state of the art of the MIP functionalized optical structures is critically discussed, highlighting the key progresses that enabled the achievement of improved sensing performances, the merits and the limits both in MIP synthetic strategies and in MIP coupling

    Nanoplasmonic efficacy of gold triangular nanoprisms in measurement science: applications ranging from biomedical to forensic sciences

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    Indiana University-Purdue University Indianapolis (IUPUI)Noble metal nanostructures display collective oscillation of the surface conduction electrons upon light irradiation as a form of localized surface plasmon resonance (LSPR) properties. Size, shape, and refractive index of the surrounding environment are the key features that control the LSPR properties. Surface passivating ligands on to the nanostructure can modify the charge density of nanostructures. Further, allow resonant wavelengths to match that of the incident light. This unique phenomenon called the “plasmoelectric effect.” According to the Drude model, red and blue shifts of LSPR peak of nanostructures are observed in the event of reducing and increasing charge density, respectively. However, herein, we report unusual LSPR properties of gold triangular nanoprisms (Au TNPs) upon functionalization with para-substituted thiophenols (X-Ph-SH, X = -NH2, -OCH3, -CH3, -H, -Cl, -CF3, and -NO2). Accordingly, we hypothesized that an appropriate energy level alignment between the Au Fermi energy and the HOMO or LUMO of ligands allows the delocalization of surface plasmon excitation at the hybrid inorganic-organic interface. Thus, provides a thermodynamically driven plasmoelectric effect. We further validated our hypothesis by calculating the HOMO and LUMO levels and work function changes of Au TNPs upon functionalization with para-substituted thiol. This reported unique finding then utilized to design ultrasensitive plasmonic substrate for biosensing of cancer microRNA in bladder cancer and cardiovascular diseases. In the discovery of early bladder cancer diagnosis platform, for the first time, we have been utilized to analyze the tumor suppressor microRNA for a more accurate diagnosis of BC. Additionally, we have been advancing our sensing platform to mitigate the false positive and negative responses of the sensing platform using surface-enhanced fluorescence technique. This noninvasive, highly sensitive, highly specific, also does not have false positives techniques that provide the strong key to detect cancer at a very early stage, hence increase the cancer survival rate. Moreover, the electromagnetic field enhancement of Surface-Enhanced Raman Scattering (SERS) and other related surface-enhanced spectroscopic processes resulted from the LSPR property. This dissertation describes the design and development of entirely new SERS nanosensors using a flexible SERS substrate based on the unique LSPR property of Au TNPs. The developed sensor shows an excellent SERS activity (enhancement factor = ~6.0 x 106) and limit of detection (as low as 56 parts-per-quadrillions) with high selectivity by chemometric analyses among three commonly used explosives (TNT, RDX, and PETN). Further, we achieved the programmable self-assembly of Au TNPs using molecular tailoring to form a 3D supper lattice array based on the substrate effect. Here we achieved the highest reported sensitivity for potent drug analysis, including opioids and synthetic cannabinoids from human plasma obtained from the emergency room. This exquisite sensitivity is mainly due to the two reasons, including molecular resonance of the adsorbate molecules and the plasmonic coupling among the nanoparticles. Altogether we are highly optimistic that our research will not only increase the patient survival rate through early detection of cancer but also help to battle the “war against drugs” that together are expected to enhance the quality of human life

    Plasmonic-enhanced fluorescent conjugated polymer chemosensor for ultra-sensitive detection of nitroaromatic vapors

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    "December 2014."Dissertation Supervisors: Dr. Shubhra Gangopadhyay and Dr. Luis Polo-Parada.Includes vita.Rapid degradation of fluorescent conjugated polymers in ambient conditions imposes severe restrictions on their utility for long-term, portable sensing applications. This dissertation discusses the combined use of low-density, ultra-thin oxide capping layers and plasmonic silver gratings as a means of improving the utility of fluorescent conjugated polymer ultra-thin films (<50 nm) for long-term, portable chem/bio sensing applications. Silver gratings produced by a low-cost micro-contact printing method enhanced emission of poly-[2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) by as much as 12-fold with respect to films on flat silver through a mechanism of surface plasmoncoupled emission, which directs specific emitted wavelengths toward the detection window of the fluorescence microscope. Addition of a low-density, ultra-thin silica capping layer (d = 5.07 nm, n = 1.38) improved MEH-PPV photostability significantly with respect to uncapped films under both short-term continuous illumination as well as long-term storage in dark, ambient air, while retaining a rapid quenching response to nitroaromatic vapors. Capped, plasmonic-enhanced MEH-PPV film showed a response to 2,4-dinitrotoluene vapor at a rate more than 7-fold faster than capped films on SiO2-coated silicon, attributed to a combination of sensitization effects of the silver on the conjugated polymer molecules in close proximity to the metal. Lateral diffusion of nitroaromatic vapor into the film is tracked by monitoring growth of quenched regions through fluorescence imaging. Most importantly, the devices recover fluorescence spontaneously on removal from the xvii nitroaromatic vapor source, suggesting they could be used for long-term, real-time measurements of nitroaromatic vapors.Includes bibliographical references (pages 98-117)

    Single- and Multi-Transducer Arrays Employing Nanoparticle Interface Layers as Vapor Detectors for a Microfabricated Gas Chromatograph.

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    This body of research focuses on improving microsensor arrays used as detectors in Si-microfabricated gas chromatographs (µGC) for the determination of volatile organic compounds (VOCs). By means of such improvements, µGC technology should find wider application in homeland security, disease diagnosis, and environmental monitoring. The microsensors considered here all employ thiolate-monolayer-protected gold nanoparticles (MPN) as vapor sorptive interface layers. The central hypothesis is that by altering the MPN ligand, core size, and/or the underlying transducer, the diversity of responses to VOCs provided by microsensor arrays with MPN interfaces can be improved. The first study evaluated a single transducer (ST) array of MPN-coated chemiresistors (CR) as a µGC detector for three semi-volatile markers of the explosive 2,4,6-trinitrotoluene in the presence of alkane interferences of similar volatility. The effects of flow rate and temperature on chromatographic resolution, sensitivity, and limits of detection (LOD) were assessed. Under optimized conditions, a complete analysis required 95%). These types of sensor arrays can enhance the vapor discrimination of sorption-based detectors utilized in µGC technology, making the analysis of complex VOC mixtures possible.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111430/1/lkamos_1.pd

    Applications of Graphene Quantum Dots in Biomedical Sensors

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    Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.DFG, 428780268, Biomimetische Rezeptoren auf NanoMIP-Basis zur Virenerkennung und -entfernung mittels integrierter Ansätz

    Rational Design of Peptides Derived from Odorant-Binding Proteins for SARS-CoV-2-Related Volatile Organic Compounds Recognition

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    Peptides are promising molecular-binding elements and have attracted great interest in novel biosensor development. In this study, a series of peptides derived from odorant-binding proteins (OBPs) were rationally designed for recognition of SARS-CoV-2-related volatile organic compounds (VOCs). Ethanol, nonanal, benzaldehyde, acetic acid, and acetone were selected as representative VOCs in the exhaled breath during the COVID-19 infection. Computational docking and prediction tools were utilized for OBPs peptide characterization and analysis. Multiple parameters, including the docking model, binding affinity, sequence specification, and structural folding, were investigated. The results demonstrated a rational, rapid, and efficient approach for designing breath-borne VOC-recognition peptides, which could further improve the biosensor performance for pioneering COVID-19 screening and many other applications

    Molecular Imprinting of Peptides and Proteins

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    Molecular imprinting described as a method utilized to create artificial receptors and antibodies by construction of selective recognition sites in a synthetic polymer can be a promising tool for generating peptide and protein artificial specific recognition sites. These materials, as potential antibody substitutes, have attracted great interest and attention in different fields such as peptide and protein purification and separation, chemical/electrochemical/optical sensors/biosensors, chromatographic stationary phases, and enzyme mimics. This review has focused on fundamentals of molecularly imprinted polymers in terms of selection of molecular template, functional monomer, cross linker, and polymerization format. Furthermore, several applications of peptide/protein-imprinted materials are highlighted and challenges regarding the intrinsic properties of peptide/ protein imprinting have been emphasized.HighlightsHighlights the fundamentals of peptides and proteins molecular imprinting.Summarizes the essential elements and polymer formats of peptide/protein imprinted materials.Highlights the applications of peptide/protein imprinting.Highlights the challenges in peptide/protein imprinting

    An Optical Microsensor Utilizing Genetically Programmed Bioreceptor Layers for Selective Sensing

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    Protein engineering is a rich technology that holds the potential to revolutionize sensors through the creation of highly selective peptides that encode unique recognition affinities. Their robust integration with sensor platforms is very challenging. The goal of this research project is to combine expertise in micro-electro-mechanical systems (MEMS) and biological/protein engineering to develop a selective sensor platform. The key enabling technology in this work is the use of biological molecules, the Tobacco mosaic virus (TMV) and its derivative, Virus-Like-Particle (VLP), as nanoreceptor layers, in conjunction with a highly sensitive microfabricated optical disk resonator. This work will present a novel method for the integration of biological molecules assembly on MEMS devices for chemical and biological sensing applications. Particularly in this research, TMV1Cys-TNT and TMV1Cys-VLP-FLAG bioreceptor layers have been genetically engineered to bind to an ultra-low vapor pressure explosive, Trinitrotoluene (TNT), and to a widely used FLAG antibody, respectively. TNT vapor was introduce to TMV1Cys-TNT coated resonator and induced a 12 Hz resonant frequency shift, corresponding to a mass increase of 76.9 ng, a 300% larger shift compared to resonators without receptor layer coating. Subsequently, a microfabricated optical disk resonator decorated with TMV1Cys-VLP-FLAG was used to conduct enzyme-linked immunosorbent assay and label-free immunoassays on-a-chip and demonstrated a resonant wavelength shift of 5.95 nm and 0.79 nm, respectively. The significance of these developments lies in demonstrating the capability to use genetically programmable viruses and VLPs as platforms for the display and integration of receptor peptides within microsystems. The work outlined here constitutes an interdisciplinary investigation on the integration capabilities of the bio-nanostructure materials with traditional microfabrication architectures. While previous works have focused on individual components of the system, this work addresses multi-component integration, including biological molecule surface assembly and fabrication utilizing both top-down and bottom-up approaches. Integrating biologically programmable material into traditional MEMS transducers enhances selectivity, sensitivity, and simplifies fabrication and testing methodologies. This research provides a new avenue for enhancing sensor platforms through the integration of biological species as the key to remedying challenges faced by conventional systems that utilize a wide range of polymers or metals for nonspecific bindings

    Self-assembled peptide template directed synthesis of one-dimensional inorganic nanostructures and their applications

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    Ankara : The Materials Science and Nanotechnology Program of the Graduate School of Engineering and Sciences of Bilkent University, 2012.Thesis (Ph. D.) -- Bilkent University, 2012.Includes bibliographical references.Engineering at the nano scale has been an active area of science and technology over the last decade. Inspired by nature, synthesis of functional inorganic materials using synthetic organic templates constitutes the theme of this thesis. Developing organic template directed synthesis approach for inorganic nanomaterial synthesis was aimed. For this purpose, an amyloid like peptide sequence which is capable of self-assembling into nanofibers in convenient conditions was designed and decorated with functional groups showing relatively high affinity to special inorganic ions, which are presented at the periphery of the one-dimensional peptide nanofiber. These chemical groups facilitated the deposition of targeted inorganic monomers onto the nanofibers yielding one-dimensional organic-inorganic core-shell nanostructures. The physical and chemical properties of the synthesized peptide nanofibers and inorganic nanostructures were characterized using both qualitative and quantitative methods. First, silica nanotubes were obtained by silica mineralization around these peptide nanofiber templates for the construction of sensors for explosives. The fluorescence dye was used to coat the silica nanotubes to detect explosive vapor. The surface of the silica nanotubes were porous enough to adsorb more dye compared to the silica nanoparticles and silica film, and causes faster fluorescence quenching in the presence of explosives like trinitrotoluene and dinitrotoluene. The silica nanotubes which synthesized with this peptide nanofiber templates can be used in catalysis and sensors in which high surface area is advantageous. In the second part of the thesis, titanium dioxide nanotubes were obtained from titania mineralization. They are wellknown with their fascinating properties as a result of the one-dimensional nanostructure, such as more efficient electron transfer and less electron-hole recombination. The sufficient photoactivity of titanium dioxide makes them suitable materials for Dye-Sensitized Solar-Cell construction. It is demonstrated that the peptide nanofiber templated titanium dioxide nanotubes have more than two times more efficiency compared to template-free synthesized titanium dioxide particles. Finally, designed peptide sequence was conducted to a multi-step seeding mediated growth method for gold mineralization around peptide nanofibers. The gold-peptide hybrid nanostructures with different packing characteristics and sizes were synthesized and fully characterized. Further, it was demonstrated that the dry film of these nanostructures showed a resistive switching dominant conductivity, due to the nanogaps in between gold nanoparticles as a result of particle alignment driven by the peptide nanofiber. The results obtained in this thesis encourage use of a new “bottom-up” synthesis approach. Specially designed peptides with desired properties and functional groups were synthesized and peptide nanofibers formed were further used as templates for inorganic mineralization. Not only it is possible to synthesis high amount of nanostructure with this approach, but also formed one-dimensional nanostructures show advance functionalities used in several applications as a part of the thesis scope. This methodology is suitable for many metals and metal oxide based applications.Acar, HandanPh.D
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