This paper describes a compact, self-contained, cost effective, and portable Raman Integrated Tunable Sensor (RAMiTs) for screening a wide variety of chemical and biological agents for homeland defense applications. The instrument is a fully-integrated, tunable, "point-and-shoot" Raman monitor based on solid-state acousto-optic tunable filter (AOTF) technology. It can provide direct identification and quantitative analysis of chemical and biological samples in a few seconds under field conditions. It also consists of a 830-nm diode laser for excitation, and an avalanche photodiode for detection. Evaluation of this instrument has been performed by analyzing several standard samples and comparing the results those obtained using a conventional Raman system. In addition to system evaluation, this paper will also discuss potential applications of the RAMiTs for detection of chemical and biological warfare agents.
Multiple methodologies exist to implement spectral imaging for tissue demarcation and disease diagnosis. In this paper, benchtop acousto-optic tunable filter (AOTF), liquid-crystal tunable filter (LCTF) and Fourier interferometric spectral imaging systems were quantitatively compared in terms of imaging speed of soft tissue autofluorescence. Optical throughput, image signal-to-noise ratio (SNR), and collagen autofluorescence imaging in chicken breast were assessed. Within this comparison, the Fourier system possessed the largest optical throughput (~50%) relative to the tunable-filter imaging systems; however, its throughput advantage failed to correlate to improved image SNR over the LCTF system. Further, while the autofluorescence imaging capability of the Fourier system exceeded that of the LCTF system for comparable total image integration times, the LCTF is capable of producing equivalent autofluorescence SNR with superior SNR when interrogations at only a few wavelengths are required and the random access filter tuning of the LCTF can be exploited. Therefore, the simple, rugged design and random-access filter-tuning capability of LCTF-based spectral imaging makes it best-suited for clinical development of soft tissue autofluorescence imaging.
This paper describes a self-contained, portable Raman instrument that has been developed for environmental and homeland defense applications. The instrument consists of a 830-nm diode laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode for detection. The primary component of this system is the AOTF and it has been selected based on its spectral range along with its high resolution, ~7.5 cm-1. Software has been developed in house using C programming language for controlling the instrument (i.e. the AOTF frequency, the signal acquisition, etc.). Evaluation of this instrument has been performed by analyzing several standard samples and comparing to a conventional Raman system. In addition to system evaluation, this paper will also discuss potential applications of this instrument to trace detection of hazardous chemicals using the Raman Integrated Tunable Sensor (RAMiTs) coupled with surface-enhance Raman scattering process.
An integrated multi-functional biochip based on integrated circuit complementary metal oxide semiconductor (CMOS) sensor array for use in medical diagnostics and pathogen detection has been described. The usefulness and potential of the biochip as a rapid, inexpensive screening tool for detection of bioenvironmental pathogens will be demonstrated. Detection of aerosolized spores was achieved by coupling the miniature system to a portable bioaerosol sampler, and the performance of the antibody-based recognition and enzyme amplification method was evaluated. The bioassay performance was found to be compatible with the air sampling device, and the enzymatic amplification was found to be an attractive amplification method for detection of low spore concentrations. The combined portable bioaerosol sampler and miniature biochip system detected 100 B. globigii spores, corresponding to 17 aerosolized spores/L of air.
Surface-enhanced Raman scattering (SERS) spectra of chemical agent simulants such as dimethyl methylphonate (DMMP), pinacolyl methylphosphonate (PMP), diethyl phosphoramidate (DEPA), and 2-chloroethyl ethylsulfide (CEES), and biological agent simulants such as bacillus globigii (BG), erwinia herbicola (EH), and bacillus thuringiensis (BT) were obtained from silver oxide film-deposited substrates. Thin AgO films ranging in thickness from 50 nm to 250 nm were produced by chemical bath deposition onto glass slides. Further Raman intensity enhancements were noticed in UV irradiated surfaces due to photo-induced Ag nanocluster formation, which may provide a possible route to producing highly useful plasmonic sensors for the detection of chemical and biological agents upon visible light illumination.
We describe the use of a biochip based on complementary metal oxide semiconductor (CMOS) technology for detection of specific genetic sequences using molecular beacons (MB) immobilized on solid surfaces as probes. The applicability of this miniature detection system for screening for the BRCA1 gene is evaluated using MB probes, designed especially for the BRCA1 gene. MB probes are immobilized on a zeta-probe membrane by biotin-streptavidin immobilization. Two immobilization strategies are investigated to obtain optimal assay sensitivity. The MB is immobilized by manual spotting on zeta-probe membrane surfaces with the use of a custom-made stamping system. The detection of the BRCA1 gene using an MB probe is successfully demonstrated and expands the use of the CMOS biochip for medical applications.
This work provides an overview of progress made, in our laboratory, towards the development of a practical biochipbased technology with a biofluidics system for the detection of E. coli and other pathogens. Efforts have been devoted towards efficient coupling between a compact biofluidics sample/reagent delivery system and an integrated circuit (IC) biochip, consisting of a 2-dimensional photosensor array, for on-chip monitoring of bioassays. The complementary
metal-oxide semiconductor (CMOS) technology has been implemented to design and produce the IC biochip, which features a 4x4 array of independently addressable photodiodes that are integrated with amplifiers, discriminators and logic circuitry on a single platform. The CMOS-based biochip offers the advantages of compactness and low power consumption, making it better suited for field use than other array detectors, including CCDs. The biofluidics system includes a 0.4 mL hybridization chamber, which accommodates disposable sampling platforms embedded with bioreceptors for selective capture of pathogen DNA, proteins, or antibodies in discrete zones. The independently operating photodiodes of the IC biochip offer the capability of monitoring of multiple assays. Highlights of this work
include highly sensitive detection of E. coli (<50 organisms) and quantitative capability with a linear dynamic range of 3-5 orders of magnitude for various assays.
We describe the development of a surface-enhanced Raman scattering gene (SERGen) probe technology for rapid screening for diseases and pathogens through DNA hybridization assays. The technology combines the use of gene probes labeled with SERS-active markers, and nanostructured metallic platforms for inducing the SERS effect. As a
result, SERGen-based methods can offer the spectral selectivity and sensitivity of SERS as well as the molecular specificity of DNA sequence hybridization. Furthermore, these new probe s preclude the use of radioactive labels. As illustrated herein, SERGen probes have been used as primers in polymerase chain reaction (PCR) amplifications of specific DNA sequences, hence further boosting the sensitivity of the technology. We also describe several approaches to developing SERS-active DNA assay platforms, addressing the challenges of making the SERGen technology accessible and practical for clinical settings. The usefulness of the SERGen approach has been demonstrated in the detection of HIV, BRCA1 breast cancer, and BAX genes. There is great potential for the use of numerous SERGen probes for multiplexed
detection of multiple biological targets.
This paper describes a self-contained, portable Raman instrument that has been developed for biomedical analyses. The instrument consists of a 785-nm diode laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode for detection. The primary component of this system is the AOTF and it has been selected based on its spectral range along with its high resolution, approximately 7.5 cm-1. Software has been developed in-house in the programming language of C for controlling the instrument (i.e., the AOTF frequency, the signal acquisition, etc.). Evaluation of this instrument has been performed by analyzing several standard samples and comparing their spectra to spectra acquired using a conventional laboratory system. In addition to system evaluation, this paper will also discuss potential applications of this instrument to multiplexed genechip types of analyses.
The development of a field-portable Raman instrument for environmental analyses is described. It is based on the use of a near-infrared frequency-stabilized diode laser for excitation, an acousto-optic tunable filter for wavelength selection, and an avalanche photodiode for detection. Evaluation of this instrument for the monitoring of environmentally important species will be discussed as well as its ability to be operated in room light without significantly increasing the background signal. In addition, we will also describe a baseline removal procedure based on second derivative approach that simplifies and increases the accuracy of the instrument's automated identification algorithm.
The development of a field-portable Raman instrument for environmental analyses is described. It is based on the use of a near-infrared frequency-stabilized diode laser for excitation, an acousto-optic tunable filter for wavelength selection, and an avalanche photodiode for detection. Evaluation of this instrument for the monitoring of environmentally important species will be discussed as well as its ability to be operated in room light without significantly increasing the background signal. In addition, we will also describe a baseline removal procedure based on second derivative approach that simplifies and increases the accuracy of the instrument' s automated identification algorithm
The development of fiberoptic sensors for remote in-situ environmental monitoring using surface-enhanced Raman scattering (SERS) is described. The approach to sensor development includes the initial development of SERS-active media on nanoparticle-based solid-surface substrates. These media are generally metal-coated nanoparticles that can be further modified for enhanced chemical selectivity, longevity and ruggedness. One example of surface modification is the application of a permeability-selective polymer, polyvinyl pyrrolidone (PVP). For remote environmental sensing applications, the planar solid SERS substrates have been successfully incorporated in a two-fiber probe design. We have also applied SERS-active media directly to an optical fiber as an integrated single-fiber design. Such sensors occupy much less volume and promote non intrusive monitoring systems. Linear response of the integrated sensor monitoring systems for various environmental chemicals with excellent correlation (greater than 0.99) has been observed in the part-per-billion (ppb) range.
KEYWORDS: Data storage, Molecules, Surface enhanced Raman spectroscopy, Raman scattering, Molecular interactions, Molecular lasers, Optical storage, Signal detection, 3D optical data storage, Near field optics
A new optical dada storage technology based on the surface- enhanced Raman scattering (SERS) effect has been developed for high-density optical memory and three-dimensional data storage. With the surface-enhanced Raman optical data storage (SERODS) technology, the molecular interactions between the optical layer molecules and the nanostructured metal substrate are modified by the writing laser, changing their SERS properties to encode information as bits. Since the SERS properties are extremely sensitive to molecular nano- environments, very small 'spectrochemical holes' approaching the diffraction limit can be produced for the writing process. The SERODS device uses a reading laser to induce the SERS emission of molecules on the disk and a photometric detector tuned to the frequency of the RAMAN spectrum to retrieve the stored information. The results illustrate that SERODS is capable of three-dimensional data storage and has the potential to achieve higher storage density than currently available optical data storage systems.
A novel separations-based fiberoptic sensor (SBFOS) is described for remote analysis that incorporates capillary electrophoresis (CE). High sensitivity is possible with laser induced fluorescence detection and a unique and powerful element of selectivity is afforded by the exceptional separation power of CE. Speed of analysis and the possibility of remote control are further attributes which render the system useful for sensing applications. Details are given in this report for a SBFOS that employs a single-fiber optical configuration and a single buffer reservoir CE arrangement. The fiberoptic probes the outlet of a short separation capillary in a simple frontal mode of operation. Design considerations and the results of preliminary evaluations of the separation and detection characteristics of the SBFOS are presented.
A new sensor design for remote surface-enhanced Raman scattering (SERS) measurements has been developed for environmental applications. The design features the modification of an optical fiber using layers of alumina microparticles and silver coatings for inducing the SERS effect at the sensing probe. A single fiber caries both the laser excitation and the SERS signal radiation, keeping optical parameters at the remote tip simple and consistent. The small tip size achievable with this configuration also demonstrates potential of this new design as a microsensor for in-situ measurement in microenvironments. Details of sensor tip fabrication and optical system design are described. SERS spectra of aqueous environmental samples acquired in-situ using the SERS sensor are also presented to illustrate the effectiveness of the SERS sensor.
This paper presents an overview of the development of chemical monitors using the surface- enhanced raman scattering (SERS) technique. The SERS effect is based on recent experimental observations, which have indicated enhancement of the Raman scattering efficiency by factors up to 108 when a compound is adsorbed on rough metallic surfaces having submicron protrusions. The focus of our research efforts is on the development of SERS-active sensors and instrumentation capable of field analysis and remote sensing.
GAMMA-METRICS and Oak Ridge National Laboratory (ORNL) have developed a prototype portable Toxic Chemical Analyzer (TCA) for environmental screening using surface enhanced aman scattering (SERS) technology. The focus is on detection of anthropogenic chemicals such as polycyclic aromatic compounds. In this instrument a laser illuminates a small sample of analyte on a substrate of silver coated particles. Light scattered from the illuminated spot is analyzed to determine the chemicals in the analyte. The development process involved miniaturizing the instrument from a large laboratory table-top device to a small portable package, then ruggedizing the components and the packaging to withstand field conditions. A reference design for a commercial instrument has been developed. The instrument employs internal direct optics or, optionally, an external, in-situ probe connected by fiber optics to internal components. A substrate
dispenser is used to refresh the substrate in preparation for a new measurement. Measurement results to date show that high quality spectra can be obtained with the portable system. A prototype instrument is currently undergoing field trials. Data from these trials are used to refine a reference instrument design. Measurements with the prototype show that the design is capable of screening for a wide variety of environmental contaminants. Trends toward miniaturization of components and increased sensitivity
of measurement procedures lead to growth and increased optimization of the TCA.
In this paper we report on the development of a fiberoptic sensor using a new detection method based on the Surface-Enhanced Raman Scattering (SERS) technique. The SERS effect is based on recent experimental observations which have indicated enhancement of the Raman scattering efficiency by factors up to 108 when a compound is adsorbed on rough metallic surfaces having submicron protrusions. In this report we describe the development of the SERS probes for in situ remote sensing.
Conventional Raman spectroscopy is often limited by its low sensitivity due to the
inherently weak Raman cross section of organic chemicals. A relatively new detection
technique, Surface-Enhanced Raman Scattering (SERS) spectroscopy is based on recent
experimental observations, which have indicated enhancement of the Raman scattering
efficiency by factors of up to 106 when a compound is adsorbed on rough metallic surfaces
that have submicron-scale protrusions. In this report we discuss the development of the
SERS technique as a tool for monitoring hazardous chemical emissions and its application
to in situ remote sensing.