Time-resolved imaging of latent fingerprints with nanosecond resolution

Imaging of latent fingerprints using time-resolved (TR) method offers a broader platform to eliminate the unwanted background emission. In this paper, a novel TR imaging technique is demonstrated and implemented, which facilitates the detection of latent fingerprints with nanosecond resolution. Simulated experiments were carried out with two overlapping fingerprints treated with two fluorescent powders having different lifetimes in nanosecond range. The dependence of the fluorescence emission intensity in nanosecond resolution of TR imaging is also revealed.     

An integrated phase-resolved fluorescence imaging system with sub-nanosecond lifetime resolution

In this paper, a novel configuration of an integrated phase-resolved (PR) fingerprint fluorescence imaging system is proposed and implemented. In this integrated PR imaging system, a current modulated 402 nm dual diode laser is proposed to be the light source, to obtain both high laser power and easy modulability. To estimate the lifetime resolution of this PR imaging system, a novel method of using distance-selective suppression of fluorescence signals from two identical fluorescing samples is proposed. Detailed theoretical and experimental analyses are presented. The experimental results demonstrate that this integrated PR imaging system has a lifetime resolution of 0.1 ns. Fingerprint detection experiments are also carried out using this system with latent fingerprints deposited on substrates of aluminum foil and currency.     

Topological structures of complex belief systems (II): Textual materialization

Mythical and religious belief systems in a social context can be regarded as a conglomeration of sacrosanct rites, which revolve around substantive values that involve an element of faith. Moreover, we can conclude that ideologies, myths and beliefs can all be analyzed in terms of systems within a cultural context. The significance of being able to define ideologies, myths and beliefs as systems is that they can figure in cultural explanations. This, in turn, means that such systems can figure in logic‐mathematical analyses. © 2013 Wiley Periodicals, Inc. Complexity 19: 50–62, 2013     

Matrix-bounded enzyme: Potato esterase entrapped in polyacrylamide gel after gel electrophoresis

Summary An isoenzyme of potato esterase has been entrapped in situ after polyacrylamide (PAA)-electrophoresis, using PAA of different concentrations and crosslinking. Best results in respect to diffusion, flow rates and yield (77%) have been found for a gel containing 6% acrylamide with 6% methylen-bis-acrylamide, penetrating a gel of cyanogum with esterase. The latter is stabilized during polymerization by the gel. Properties of the entrapped enzyme (pH_i, K _m, MW etc.) have been determined, 100 fold better storage stability is achieved.

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Matrix-gebundenes Enzym: Kartoffelesterase, inkludiert in Polyacrylamidgel nach Gelelektrophorese

Zusammenfassung Von den Kartoffelesterasen wurde ein Isoenzym durch Gel-Elektrophorese in Polyacrylamid (PAA) getrennt. Das entsprechende Gelstück mit dem durch das Netzwerk stabilisierten Enzym tränkte man mit AA und Vernetzer (BIS) unterschiedlicher Konzentration und polymerisierte mit Licht das Enzym ein. Die Mischungen AA/BIS sind in einem bestimmten Verhältnis (60,36) optimal., eine Ausbeute von 77% der Anfangsaktivität kann erreicht werden. Einige Eigenschaften (pH_i, K _m, MG u.ä.) werden beschrieben, insbesondere ist die 100fach bessere Lagerstabilität hervorzuheben.

We are indebted to Professor Dr. G. Schuhmann, President of the BBA, for the encouragement to this work.For SDS-gel eleetrophoresis and the photographic work we thank Mrs. Knackstedt and Miss Krögerrecklenfort.     

Enhancement in SERS intensity with hierarchical nanostructures by bimetallic deposition approach

We investigate the plasmonic enhancement arising from bimetallic (Au/Ag) hierarchical structure and address the fundamental issues relating to the design of multilayered nanostructures for surface‐enhanced Raman scattering (SERS) spectroscopy. SERS‐active nanosphere arrays with Ag underlayer and Au overlayer were systematically constructed, with the thickness of each layer altered from 40 to 320 nm. The SERS responses of the resultant bimetallic structures were measured with 2‐naphthalenethiol dye as the test sample. The results confirm the dependency of SERS enhancement on the thickness ratio (Au : Ag). Compared with Au‐arrays, our optimized bimetallic structures, which exhibit nanoprotrusions on the nanospheres, were found to be 2.5 times more SERS enhancing, approaching the enhancement factor of an Ag‐array. The elevated SERS is attributed to the formation of effective hot‐spots associated with increased roughness of the outer Au film, resulting from subsequent sputtering of Au granules on a roughened Ag surface. The morphology and reflectance studies suggest that the SERS hot‐spots are distributed at the junctions of interconnected nanospheres and over the nanosphere surface, depending on the thickness ratio between the Au and Ag layers. We show that, by varying the thickness ratio, it is possible to optimize the SERS enhancement factor without significantly altering the operating plasmon resonance wavelength, which is dictated solely by the size of the underlying nanospheres template. In addition, our bimetallic substrates show long‐term stability compared with previously reported Ag‐arrays, whose SERS efficiency drops by 60% within a week because of oxidation. These findings demonstrate the potential of using such a bimetallic configuration to morphologically optimize any SERS substrate for sensing applications that demand huge SERS enhancement and adequate chemical stability. Copyright © 2011 John Wiley & Sons, Ltd.     

Non-labeling multiplex surface enhanced Raman scattering (SERS) detection of volatile organic compounds (VOCs)

In this paper, we report multiplex SERS based VOCs detection with a leaning nano-pillar substrate. The VOCs analyte molecules adsorbed at the tips of the nano-pillars produced SERS signal due to the field enhancement occurring at the localized surface plasmon hot spots between adjacent leaning nano-pillars. In this experiment, detections of acetone and ethanol vapor at different concentrations were demonstrated. The detection limits were found to be 0.0017 ng and 0.0037 ng for ethanol and acetone vapor molecules respectively. Our approach is a non-labeling method such that it does not require the incorporation of any chemical sensing layer for the enrichment of gas molecules on sensor surface. The leaning nano-pillar substrate also showed highly reproducible SERS signal in cyclic VOCs detection, which can reduce the detection cost in practical applications. Further, multiplex SERS detection on different combination of acetone and ethanol vapor was also successfully demonstrated. The vibrational fingerprints of molecular structures provide specific Raman peaks for different VOCs contents. To the best of our knowledge, this is the first multiplex VOCs detection using SERS. We believe that this work may lead to a portable device for multiplex, specific and highly sensitive detection of complex VOCs samples that can find potential applications in exhaled breath analysis, hazardous gas analysis, homeland security and environmental monitoring.     

Surface-enhanced Raman scattering (SERS)-based volatile organic compounds (VOCs) detection using plasmonic bimetallic nanogap substrate

In this paper, we present surface-enhanced Raman scattering (SERS)-based volatile organic compounds (VOCs) detection with bimetallic nanogap structure substrate. Deep UV photolithography at the wavelength of 250 nm is used to pattern circular shape nanostructures. The nanogap between adjacent circular patterns is 30 ± 5 nm. Silver (30 nm) and gold (15 nm) plasmonic active layers are deposited on the nanostructures subsequently. SERS measurements on different concentrations of acetone vapor ranged from 0.7, 1.5, 3.5, 10.3, 24.5 % and control have been performed with the substrate. The measurement results are found reproducible, and the detection limit is found to be 9.5 pg (acetone molecule). The detection sensitivity is 28.7 % higher than that of the recent reported leaning silicon nanopillar substrate. With further system miniaturization, the sensing technique can work as a portable SERS-based VOCs detection platform for point-of-care breath analysis, homeland security, chemical sensing and environmental monitoring.     

Diagnosis of colon cancer using frequency domain fluorescence imaging technique

Early detection and treatment of colon cancer has been associated with better disease prognosis. Conventional and reported optical techniques have limitations in detecting early stages of colon cancer growth. In this paper, a homodyne signal processing assisted frequency domain (FD) fluorescence imaging methodology is proposed for the early diagnosis of colon cancer. Simulated phantom tissues representing the biopsy samples at different stages of colon cancer growth are prepared and used for the imaging study. Selective imaging of healthy and diseased sites simulated in the samples was achieved even for fluorescence emissions having close lifetimes and wavelength values. Possible extension of the methodology for in vivo investigations is also discussed.     

Nanosphere Templated Metallic Grating Assisted Enhanced Fluorescence

In this paper, enhanced fluorescence from a silver film coated nanosphere templated grating is presented. Initially, numerical simulation was performed to determine the plasmon resonance wavelength by varying the thickness of the silver film on top of a monolayer of 400 nm nanospheres. The simulation results are verified experimentally and tested for enhancing fluorescence from fluorescein isothiocyanate whose excitation wavelength closely matches with the plasmon resonance wavelength of the substrate with 100 nm silver film over nanosphere. The 12 times enhancement in the intensity is attributed to the local field enhancement in addition to the excitation of surface plasmon polaritons along the surface.