The rapid, selective and sensitive detection of trinitrotoluene (TNT), which is widely used in te... more The rapid, selective and sensitive detection of trinitrotoluene (TNT), which is widely used in terrorist activities and also a major environmental contaminant is prime concern for the scientific community dealing with environmental problems and national security. This paper described unprecedented CAgP based multiple tier probe employing U.V.eVis., DLS & SERS techniques for highly selective, rapid and ultrasensitive detection of TNT up to 0.1 nM level. The as synthesized CAgP made possible the naked eye detection of TNT in the form of flakes in real time. The developed method due to its multiple tier approach utilizing the same sample could easily be extended to a high-throughput format and can be utilized for rapid and reliable trace detection of TNT, for on-site screenings in airports, analysis of forensic samples, and environmental analysis.
Extensive research has been pursued in the recent years for the fabrication of flexible filter pa... more Extensive research has been pursued in the recent years for the fabrication of flexible filter paper based sensors . These sensors owing to their ability to be employed in analysis of the real-world surfaces as compared to rigid substrates, have witnessed an extensive use in clinical diagnosis , food quality control [4], forensics [5] and environmental monitoring [6]. In filter paper based sensors technology, surface enhanced Raman scattering (SERS) based sensors, due to their minimal invasive nature and high sensitivity, have received special attention [7]. The prerequisite condition for an effective SERS substrate is that it should be flexible and highly sensitive for practical applications [1]. So far, a large number of flexible SERS substrates like, polymer nanofiber [8], carbon nanotubes [9], graphene [10] and cellulose paper [11-20] have been widely reported in the literature. Among all the flexible SERS substrates reported so far, cellulose paper based SERS has received significant attention due to its low-cost, biodegradability and eco-friendly nature [7]. Moreover, paper has a flexible, three-dimensional, porous and heterogeneous morphology, which made it a preferred SERS substrate. A variety of methods including dip coating [11-13], in situ reduction [14], sonochemical coating [15], electronic printing [16-18], vacuum deposition [19] and pulse-laser irradiation has been used for the impregnation of plasmonic nanoparticles onto filter paper. The method of loading plasmonic nanoparticles onto the filter paper played an important role in the distribution of nanoparticles on filter paper, and hence their SERS activity. While in situ reduction, dip-coating and sonication approaches are fast, cheaper and easy, the resultant plasmonic nanoparticles loaded paper encounter several drawbacks. In normal silver nanoparticles doped filter paper, the silver colloidal particles are loosely attached to the filter paper. The lack of sufficient adhesion to the substrate by the particles causes quick deterioration of the SERS amplification factor over time . Though vacuum deposition and pulse-laser irradiation methods offer the controlled fabrication of highly sensitive paper-plasmonic substrates, these are multi-step processes and require high power lasers or expensive equipment. Moreover, it has been shown that the distribution of plasmonic nanostructures of fabricated filterpaper based SERS substrates depends on the several factors such as, morphology, fibrils distribution and pore size of the paper used. Diffusion of analyte into porous network of filter paper due to hydrophilic nature of the paper fibrils can also affect the accuracy of the analysis. Thus, effectiveness of SERS activity of filter paper based substrate relies on controlling the nanoparticles dispersion for more SERS ''hot-spots'' creation, strong adhesion of nanoparticles and minimizing the diffusion of analyte into the filter paper, so that maximum analyte is available for analysis. These drawbacks, encountered by normal filter paper based SERS substrates, have been addressed in the present work by a simple approach of surface modification of filter paper with agarose (agar) film. The selection of agar gel was made due to its excellent molecular trapping ability, owing to its reversible stretching and contraction A B S T R A C T Highly efficient multifunctional agarose SERS test stripes has been fabricated by a convenient facile approach. SERS stripes were found to be highly sensitive, robust, and capable to alleviate the two major drawbacks of filter paper based SERS substrate i.e. the weak adhesion of plasmonic nanoparticles and the diffusion of analyte into the paper surface. The fabricated stripes have been used successfully for the ultra-trace detection of analytes of forensic interest including a dye, pesticide and explosive.
Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sens... more Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes, Forensic Science International (2013), http://dx.A c c e p t e d M a n u s c r i p t Silver nanoparticles doped agarose disc: highly sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes Abstract Raman spectroscopy is a preferred analytical tool for forensic trace analysis due to its noninvasive nature. This technique has been utilized in examination of organic colorants present in fibers and ink, but high fluorescent nature of these compounds is a problem. In the present study, silver-doped agarose gel disc, having property of quenching fluorescence and enhancing Raman signals, is found to be effective as surface-enhanced Raman scattering (SERS) substrates for analysis of rhodamine 6G (Rh 6G) and crystal violet (CV) dyes. As-prepared and well characterized by UV, TEM-EDAX and XRD techniques, the investigated silver-doped agarose gel disc proves to have minimal invasive as confirmed by the ATR-FTIR method and effective for in-situ SERS analysis of blue and red ballpoint ink. The disk is stable upon storage and hence can be re-used and re-examined. The present method offers new possibilities in trace forensic analysis with minimal destruction.
Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sens... more Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes, Forensic Science International (2013), http://dx.A c c e p t e d M a n u s c r i p t Silver nanoparticles doped agarose disc: highly sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes Abstract Raman spectroscopy is a preferred analytical tool for forensic trace analysis due to its noninvasive nature. This technique has been utilized in examination of organic colorants present in fibers and ink, but high fluorescent nature of these compounds is a problem. In the present study, silver-doped agarose gel disc, having property of quenching fluorescence and enhancing Raman signals, is found to be effective as surface-enhanced Raman scattering (SERS) substrates for analysis of rhodamine 6G (Rh 6G) and crystal violet (CV) dyes. As-prepared and well characterized by UV, TEM-EDAX and XRD techniques, the investigated silver-doped agarose gel disc proves to have minimal invasive as confirmed by the ATR-FTIR method and effective for in-situ SERS analysis of blue and red ballpoint ink. The disk is stable upon storage and hence can be re-used and re-examined. The present method offers new possibilities in trace forensic analysis with minimal destruction.
Stamp pad inks from different manufacturers across India have been analyzed to investigate the fe... more Stamp pad inks from different manufacturers across India have been analyzed to investigate the feasibility of Raman scattering as a tool for forensic analysis of questioned documents involving stamp inks. Nine different stamping inks were analyzed by both Raman spectroscopic and HPTLC methods. The results demonstrate the effectiveness of these methods in classifying the investigated stamping inks based on their spectral pattern and HPTLC chromatogram. Raman scattering tool was able to determine the sequence of heterogeneous intersection strokes involving a blue stamp pad ink and other writing instruments, such as ballpoint pen ink (red and black), pencil and laser printer toner. However, this method was unable to resolve the exact sequencing for the intersection strokes involving investigated stamp ink and blue ballpoint ink or gel pen ink (all colors).
The rapid, selective and sensitive detection of trinitrotoluene (TNT), which is widely used in te... more The rapid, selective and sensitive detection of trinitrotoluene (TNT), which is widely used in terrorist activities and also a major environmental contaminant is prime concern for the scientific community dealing with environmental problems and national security. This paper described unprecedented CAgP based multiple tier probe employing U.V.eVis., DLS & SERS techniques for highly selective, rapid and ultrasensitive detection of TNT up to 0.1 nM level. The as synthesized CAgP made possible the naked eye detection of TNT in the form of flakes in real time. The developed method due to its multiple tier approach utilizing the same sample could easily be extended to a high-throughput format and can be utilized for rapid and reliable trace detection of TNT, for on-site screenings in airports, analysis of forensic samples, and environmental analysis.
Extensive research has been pursued in the recent years for the fabrication of flexible filter pa... more Extensive research has been pursued in the recent years for the fabrication of flexible filter paper based sensors . These sensors owing to their ability to be employed in analysis of the real-world surfaces as compared to rigid substrates, have witnessed an extensive use in clinical diagnosis , food quality control [4], forensics [5] and environmental monitoring [6]. In filter paper based sensors technology, surface enhanced Raman scattering (SERS) based sensors, due to their minimal invasive nature and high sensitivity, have received special attention [7]. The prerequisite condition for an effective SERS substrate is that it should be flexible and highly sensitive for practical applications [1]. So far, a large number of flexible SERS substrates like, polymer nanofiber [8], carbon nanotubes [9], graphene [10] and cellulose paper [11-20] have been widely reported in the literature. Among all the flexible SERS substrates reported so far, cellulose paper based SERS has received significant attention due to its low-cost, biodegradability and eco-friendly nature [7]. Moreover, paper has a flexible, three-dimensional, porous and heterogeneous morphology, which made it a preferred SERS substrate. A variety of methods including dip coating [11-13], in situ reduction [14], sonochemical coating [15], electronic printing [16-18], vacuum deposition [19] and pulse-laser irradiation has been used for the impregnation of plasmonic nanoparticles onto filter paper. The method of loading plasmonic nanoparticles onto the filter paper played an important role in the distribution of nanoparticles on filter paper, and hence their SERS activity. While in situ reduction, dip-coating and sonication approaches are fast, cheaper and easy, the resultant plasmonic nanoparticles loaded paper encounter several drawbacks. In normal silver nanoparticles doped filter paper, the silver colloidal particles are loosely attached to the filter paper. The lack of sufficient adhesion to the substrate by the particles causes quick deterioration of the SERS amplification factor over time . Though vacuum deposition and pulse-laser irradiation methods offer the controlled fabrication of highly sensitive paper-plasmonic substrates, these are multi-step processes and require high power lasers or expensive equipment. Moreover, it has been shown that the distribution of plasmonic nanostructures of fabricated filterpaper based SERS substrates depends on the several factors such as, morphology, fibrils distribution and pore size of the paper used. Diffusion of analyte into porous network of filter paper due to hydrophilic nature of the paper fibrils can also affect the accuracy of the analysis. Thus, effectiveness of SERS activity of filter paper based substrate relies on controlling the nanoparticles dispersion for more SERS ''hot-spots'' creation, strong adhesion of nanoparticles and minimizing the diffusion of analyte into the filter paper, so that maximum analyte is available for analysis. These drawbacks, encountered by normal filter paper based SERS substrates, have been addressed in the present work by a simple approach of surface modification of filter paper with agarose (agar) film. The selection of agar gel was made due to its excellent molecular trapping ability, owing to its reversible stretching and contraction A B S T R A C T Highly efficient multifunctional agarose SERS test stripes has been fabricated by a convenient facile approach. SERS stripes were found to be highly sensitive, robust, and capable to alleviate the two major drawbacks of filter paper based SERS substrate i.e. the weak adhesion of plasmonic nanoparticles and the diffusion of analyte into the paper surface. The fabricated stripes have been used successfully for the ultra-trace detection of analytes of forensic interest including a dye, pesticide and explosive.
Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sens... more Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes, Forensic Science International (2013), http://dx.A c c e p t e d M a n u s c r i p t Silver nanoparticles doped agarose disc: highly sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes Abstract Raman spectroscopy is a preferred analytical tool for forensic trace analysis due to its noninvasive nature. This technique has been utilized in examination of organic colorants present in fibers and ink, but high fluorescent nature of these compounds is a problem. In the present study, silver-doped agarose gel disc, having property of quenching fluorescence and enhancing Raman signals, is found to be effective as surface-enhanced Raman scattering (SERS) substrates for analysis of rhodamine 6G (Rh 6G) and crystal violet (CV) dyes. As-prepared and well characterized by UV, TEM-EDAX and XRD techniques, the investigated silver-doped agarose gel disc proves to have minimal invasive as confirmed by the ATR-FTIR method and effective for in-situ SERS analysis of blue and red ballpoint ink. The disk is stable upon storage and hence can be re-used and re-examined. The present method offers new possibilities in trace forensic analysis with minimal destruction.
Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sens... more Please cite this article as: A. Raza, B. Saha, Silver nanoparticles doped agarose disc: high sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes, Forensic Science International (2013), http://dx.A c c e p t e d M a n u s c r i p t Silver nanoparticles doped agarose disc: highly sensitive surface-enhanced Raman scattering substrate for in situ analysis of ink dyes Abstract Raman spectroscopy is a preferred analytical tool for forensic trace analysis due to its noninvasive nature. This technique has been utilized in examination of organic colorants present in fibers and ink, but high fluorescent nature of these compounds is a problem. In the present study, silver-doped agarose gel disc, having property of quenching fluorescence and enhancing Raman signals, is found to be effective as surface-enhanced Raman scattering (SERS) substrates for analysis of rhodamine 6G (Rh 6G) and crystal violet (CV) dyes. As-prepared and well characterized by UV, TEM-EDAX and XRD techniques, the investigated silver-doped agarose gel disc proves to have minimal invasive as confirmed by the ATR-FTIR method and effective for in-situ SERS analysis of blue and red ballpoint ink. The disk is stable upon storage and hence can be re-used and re-examined. The present method offers new possibilities in trace forensic analysis with minimal destruction.
Stamp pad inks from different manufacturers across India have been analyzed to investigate the fe... more Stamp pad inks from different manufacturers across India have been analyzed to investigate the feasibility of Raman scattering as a tool for forensic analysis of questioned documents involving stamp inks. Nine different stamping inks were analyzed by both Raman spectroscopic and HPTLC methods. The results demonstrate the effectiveness of these methods in classifying the investigated stamping inks based on their spectral pattern and HPTLC chromatogram. Raman scattering tool was able to determine the sequence of heterogeneous intersection strokes involving a blue stamp pad ink and other writing instruments, such as ballpoint pen ink (red and black), pencil and laser printer toner. However, this method was unable to resolve the exact sequencing for the intersection strokes involving investigated stamp ink and blue ballpoint ink or gel pen ink (all colors).
Uploads
Papers by Ali Raza