Simultaneous Optical Detection Research Articles

LIBS experiments for quantitative detection of retained fuel

Laser Induced Breakdown Spectroscopy (LIBS) provides chemical information from atomic and ionic plasma emissions generated by laser vaporization of a sample. At the ENEA research center, in collaboration with IPPLM, an equipment has been set up to qualitatively and quantitatively determine the chemical composition of impurities deposited on Plasma Facing Components (PFC). The strength of the LIBS, for its capability of light elements detection, is fully exploited to determine the deuterium content since this element can be considered as the best choice proxy for tritium; the latter being is of great importance in assessing safe conditions to assure the continuous operation in nuclear fusion tokamak.Here we present the results of the Double Pulse LIBS (DP-LIBS) probing of deuterated samples with the simultaneous optical detection by medium-resolution and high-resolution spectrometer. Deuterium emission at 656.1nm has been detected then the elemental composition has been quantified by applying the Calibration Free (CF) approach. The obtained results demonstrate that the DP-LIBS technique combined with CF analysis is suitable for the quantitative determination of tritium content inside the PFCs of next fusion devices like ITER.

NIR upconversion fluorescence glucose sensing and glucose-responsive insulin release of carbon dot-immobilized hybrid microgels at physiological pH.

This work reports the preparation of multifunctional hybrid microgels based on the one-pot free radical dispersion polymerization of hydrogen-bonding complexes in water, formed from hydroxyl/carboxyl bearing carbon dots with 4-vinylphenylboronic acid and acrylamide comonomers, which can realize the simultaneous optical detection of glucose using near infrared light and glucose-responsive insulin delivery.

Coupling shell-isolated nanoparticle enhanced Raman spectroscopy with paper chromatography for multi-components on-site analysis

By coupling shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) with paper chromatography, two birds with one stone method were developed for simultaneous on-site separation and optical detection of multiple components. The established method features high sensitivity of plasmon-enhanced sensing strategies and sufficient temporal and spatial resolution of planar chromatographic techniques.

Optical particle detection in liquid suspensions with a hybrid integrated microsystem

In this work, we present an optical microsystem for particle flow detection, based on hybrid integration and silicon micromachining. Sensing principle is light obscuration. We demonstrate the feasibility of integrating commercial components such as light sources (850nm near infrared Vertical-Cavity-Surface-Emitting Lasers VCSELs) and optics (an array of microlenses) into a silicon fabricated structure to create an optoelectronic package of reduced dimensions (14mm×12mm) and low power consumption (≈7.2mW) that satisfies optical requirements and provides four collimated laser beams with reduced diameter spots (minimum radius of 124μm measured as 1/e2 standard). Besides this microoptical system, the detection system is completed with a double linear array imaging sensor of 256 pixels, designed and fabricated in 0.35μm CMOS technology, and a microfluidic platform. The designed set-up allows the simultaneous optical detection of singly aligned microbeads flowing in liquid suspensions through several parallel microfluidic channels, which share the pitch of the laser emitting sources, i.e. 250μm. While the throughput of the system is increased up to 5000 particles/s thanks to the possibility of performing parallel measurements, the double array of the imaging sensor improves the detection process discarding false detected events. Experimental results prove that the system is able to detect and distinguish microparticles of several sizes in a mixed solution, with detection limit set at 10μm diameter. In conclusion, the fabricated microsystem is presented as a miniaturized and robust alternative to current optical microflow cytometers based on the use of optical fibre, and the complete system, including fluidics and imaging sensor stages, represents a portable solution packaged in less than 5cm3. These features make it an interesting choice to consider in the field of point-of-care biosensing applications.

Comparison of simultaneous on-line optical and acoustic laser damage detection methods in the nanosecond pulse duration domain

We carried out single-shot laser-induced damage threshold measurements on dielectric high reflectors guided by the corresponding ISO standard. Four simultaneous on-line detection techniques were tested and compared using 532 nm, 9 ns and 266 nm, 6 ns laser pulses. Two methods, microscope aided visual inspection and detection of scattered light off the damaged surface, were based on optical signals. The other two techniques exploited the acoustic waves accompanying a damage event in ambient air and in the substrate by a microphone and a piezoelectric sensor, respectively. A unified criterion based on the statistical analysis of the detector signals was applied to assign an objective and unambiguous damage threshold value for all of our diverse detection methods. Microscope aided visual inspection showed the lowest damage thresholds for both wavelengths. However, the sensitivity of the other three techniques proved to be only slightly lower.

Multifunctional rare-Earth vanadate nanoparticles: luminescent labels, oxidant sensors, and MRI contrast agents.

Collecting information on multiple pathophysiological parameters is essential for understanding complex pathologies, especially given the large interindividual variability. We report here multifunctional nanoparticles which are luminescent probes, oxidant sensors, and contrast agents in magnetic resonance imaging (MRI). Eu(3+) ions in an yttrium vanadate matrix have been demonstrated to emit strong, nonblinking, and stable luminescence. Time- and space-resolved optical oxidant detection is feasible after reversible photoreduction of Eu(3+) to Eu(2+) and reoxidation by oxidants, such as H2O2, leading to a modulation of the luminescence emission. The incorporation of paramagnetic Gd(3+) confers in addition proton relaxation enhancing properties to the system. We synthesized and characterized nanoparticles of either 5 or 30 nm diameter with compositions of GdVO4 and Gd0.6Eu0.4VO4. These particles retain the luminescence and oxidant detection properties of YVO4:Eu. Moreover, the proton relaxivity of GdVO4 and Gd0.6Eu0.4VO4 nanoparticles of 5 nm diameter is higher than that of the commercial Gd(3+) chelate compound Dotarem at 20 MHz. Nuclear magnetic resonance dispersion spectroscopy showed a relaxivity increase above 10 MHz. Complexometric titration indicated that rare-earth leaching is negligible. The 5 nm nanoparticles injected in mice were observed with MRI to concentrate in the liver and the bladder after 30 min. Thus, these multifunctional rare-earth vanadate nanoparticles pave the way for simultaneous optical and magnetic resonance detection, in particular, for in vivo localization evolution and reactive oxygen species detection in a broad range of physiological and pathophysiological conditions.

Label-free optical detection of biomolecular translocation through nanopore arrays.

In recent years, nanopores have emerged as exceptionally promising single-molecule sensors due to their ability to detect biomolecules at subfemtomole levels in a label-free manner. Development of a high-throughput nanopore-based biosensor requires multiplexing of nanopore measurements. Electrical detection, however, poses a challenge, as each nanopore circuit must be electrically independent, which requires complex nanofluidics and embedded electrodes. Here, we present an optical method for simultaneous measurements of the ionic current across an array of solid-state nanopores, requiring no additional fabrication steps. Proof-of-principle experiments are conducted that show simultaneous optical detection and characterization of ssDNA and dsDNA using an array of pores. Through a comparison with electrical measurements, we show that optical measurements are capable of accessing equivalent transmembrane current information.

An approach towards 3D sensitive AFM cantilevers

The atomic force microscope (AFM) tapping mode is a highly sensitive local probing technique that is very useful to study and measure surface properties down to the atomic scale. The tapping mode is mostly implemented using the resonance of the first bending mode of the cantilever and therefore provides sensitivity mainly along the direction of this oscillation. Driven by the semiconductor industry, there is an increasing need for accurate measurements of nanoscale structures for side wall characterization by AFM that requires additional sensitivity in the lateral direction. The conventional tapping mode has been augmented by various authors, for example by tilting the cantilever system (Cho et al 2011 Rev. Sci. Instrum. 82 023707) to access the sidewall or using a torsion mode (Dai et al 2011 Meas. Sci. Technol. 22 094009) of the cantilever to provide additional lateral sensitivity. These approaches however trade lateral sensitivity for vertical sensitivity or still lack sensitivity in the remaining lateral direction. We present an approach towards true 3D sensitivity for AFM cantilevers based on simultaneous excitation and optical detection of multiple cantilever resonance modes along three axes. Tuning the excitation of the cantilever to specific frequencies provides a mechanism to select only those cantilever modes that have the desired characteristics. Additionally, cantilever engineering has been used to design and create a substructure within the cantilever that has been optimized for specific resonance behavior around 4 MHz. In contrast to the conventional approach of using a piezo to actuate the cantilever modulation, we present results on photo-thermal excitation using an intensity modulated low-power laser source. By tightly focusing the excitation spot on the cantilever we were able to attain a deflection efficiency of 0.7 nm µW−1 for the first bending mode. The presented approach results in an efficient all optical excitation and deflection detection scheme where both the position of the spot to excite the cantilever and the spot position of the read-out beam provide additional parameters to fully control and optimize the multi-mode structure required for 3D AFM measurements.

Simultaneous optical detection and extraction of cobalt(II) from lithium ion batteries using nanocollector monoliths

This study aims to develop novel nanocollectors for potential application in cobalt [Co(II)] detection and removal from lithium ion batteries. The optical nanocollectors were fabricated through functional immobilization of 2-nitroso-1-naphthol, bis[N,N-bis(carboxymethyl) aminomethyl]fluorescein, and pyrogallol red chromophore probes into large, open, cage-pored, three-dimensional cubic mesostructures with micrometer-sized monolith particles. The monolithic nanocollectors are stable and easy to use, and they have sensitive detection capabilities for low Co(II) ion concentrations. The construction of these probes into highly ordered pore-based monoliths transform ion sensing and removal systems into smart, stable assemblies and portable laboratory assays. The experiments were conducted to determine the effects of feed solution pH, concentration, and competing ions on the selective detection and removal of Co(II) ions. Solution pH played an important role in the selective removal of Co(II) ions. The nanocollectors were able to detect Co(II) ions selectively despite high concentrations of interfering ions. The unique features of the nanocollectors allow the visual detection, removal, and extraction of ultratrace concentrations of Co(II) ions without preconcentration. The adsorbed Co(II) was eluted/extracted with stripping agents and the nanocollectors were simultaneously regenerated for subsequent removal operations after rinsing with water. The nanocollectors retained their functionality despite several chemical treatments during the removal–extraction–regeneration cycles. Therefore, large-scale pilot studies are recommended to confirm these promising results.

Fabrication and characterization of solid-state nanopore arrays for high-throughput DNA sequencing

We report the fabrication and characterization of uniformly sized nanopore arrays, integrated into an optical detection system for high-throughput DNA sequencing applications. Nanopore arrays were fabricated using focused ion beam milling, followed by TiO2 coating using atomic layer deposition. The TiO2 layer decreases the initial pore diameter down to the sub-10 nm range, compatible with the requirements for nanopore-based sequencing using optical readout. We find that the TiO2 layers produce a lower photoluminescence background as compared with the more widely used Al2O3 coatings. The functionality of the nanopore array was demonstrated by the simultaneous optical detection of DNA–quantum dot conjugates, which were electro-kinetically driven through the nanopores. Our optical scheme employs total internal reflection fluorescence microscopy to illuminate a wide area of the TiO2-coated membrane. A highly parallel system for observing DNA capture events in a uniformly sized 6 × 6 nanopore array was experimentally realized.

Dual Photonic-Electrochemical Lab on a Chip for Online Simultaneous Absorbance and Amperometric Measurements

A dual lab on a chip (DLOC) approach that enables simultaneous optical and electrochemical detection working in a continuous flow regime is presented. Both detection modes are integrated for the first time into a single detection volume and operate simultaneously with no evidence of cross-talk. The electrochemical cell was characterized amperometrically by measuring the current in ferrocyanide solutions at +0.4 V vs gold pseudoreference electrode, at a flow rate of 200 μL min(-1). The experimental results for ferrocyanide concentrations ranging from 0.005 to 2 mM were in good agreement with the values predicted by the Levich equation for a microelectrode inside a rectangular channel, with a sensitivity of 2.059 ± 0.004 μA mM(-1) and a limit of detection (LoD) of (2.303 ± 0.004) × 10(-3) mM. Besides, optical detection was evaluated by measuring the absorbance of ferricyanide solutions at 420 nm. The results obtained therein coincide with those predicted by the Beer-Lambert law for a range of ferricyanide concentrations from 0.005 to 0.3 mM and showed an estimated LoD of (0.553 ± 0.001) × 10(-3) mM. The DLOC was finally applied to the analysis of L-lactate via a bienzymatic reaction involving lactate oxidase (LOX) and horseradish peroxidase (HRP). Here, the consumption of the reagent of the reaction (ferrocyanide) was continuously monitored by amperometry whereas the product of the reaction (ferricyanide) was recorded by absorbance. The DLOC presented good performance in terms of sensitivity and limit of detection, comparable to other fluidic systems found in the literature. Additionally, the ability to simultaneously quantify enzymatic reagent consumption and product generation confers the DLOC a self-verifying capability which in turn enhances its robustness and reliability.

Facile one-step synthesis of plasmonic/magnetic core/shell nanostructures and their multifunctionality

A very simple protocol, which involves the chemical reduction of AgNO3 and Fe(NO3)3 with ethylene glycol as reducing agent, has been developed for synthesizing Ag@Fe3O4 core/shell nanostructures in which the silver nanoparticle core was covered by a thicker layer of the Fe3O4 nanoparticle shell. The obtained Ag@Fe3O4 core/shell nanostructures simultaneously possess both strong magnetic responsiveness and tunable plasmonic properties. The plasmonic properties of the composite nanospheres are profoundly influenced by the high dielectric constant of the outer Fe3O4 shell layer and could be conveniently modulated over a broad spectral range spanning from the ultraviolet to near-infrared (NIR) regions (789 nm) by simply altering the thickness of the Fe3O4 shell. The localized surface plasmon resonances of the core/shell nanocomposites red-shifted with increasing thickness of the Fe3O4 shell. The morphology transformation of the Ag/Fe3O4 nanocomposites from core/shell structures with a continuous dense coating to flower-like nanostructures also allows the tuning of their plasmonic properties to be blue-shifted (to 510 nm). Catalytic degradation of rhodamine 6G (R6G) experiments show that the Ag/Fe3O4 composite nanostructures exhibit high catalytic activity by sodium borohydride. Due to the efficient optical response through localized surface plasmon resonances, the catalytic performance from the silver core and external magnetic manipulation from the Fe3O4 shell, such multifunctional nanoparticles will provide an opportunity for simultaneous optical detection and catalytic reduction with the additional benefit of relatively facile recovery and regeneration.

SURFACE MODIFICATION AND CHARACTERIZATION OF Fe3O4/Au COMPOSITE NANOPARTICLES

Fe 3 O 4/ Au composite nanoparticles were modified with α-thio-ω-carboxy poly (ethylene glycol). Results from XRD, selected area diffraction, high-resolution TEM images, and dynamic lighting scattering illustrate that the particles have a core/shell composite structure and were monodispersed. Surface plasmon resonance measured by UV–Vis indicates that the absorption peak of the modified composite particle characteristic at 532 nm can be stably suspended in a different buffer. The modified composite particles also have good response to external magnetic field. The Fe 3 O 4/ Au composite nanoparticles are magnetically and optically active, and are useful for simultaneous magnetic and optical detection. Coupled with biomolecules, the advantages of these composite particles make them very promising for biomedical applications in the near future.

Phase separated Cu@Fe3O4 heterodimer nanoparticles from organometallic reactants

Cu@Fe3O4 heteroparticles with distinct morphologies were synthesized from organometallic reactants. The shape of the magnetic domains could be controlled by the solvent and reaction conditions. They display magnetic and optical properties that are useful for simultaneous magnetic and optical detection. After functionalization, the Cu@Fe3O4 heterodimers become water soluble. The morphology, structure, magnetic and optical properties of the as-synthesized heterodimer nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), mössbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and dark field imaging. A special advantage of these heterodimers lies in the fact that the nanodomains of different composition can be used e.g. for the formation of nitric oxide (NO) through the Cu domain and heterodimer nanoparticles can be removed from the reaction mixture by means of the magnetic domain (Fe3O4).

Differential Retro-Detection for Remote Sensing Applications

A retro-detection technique is introduced for simultaneous optical retroreflection, detection, and control in bidirectional sensor links. An architecture with three orthogonal photodiodes (PDs) is used to retroreflect incident light and sample the incident optical signals. Such a system establishes a two-way (bidirectional) optical link. Moreover, the three photocurrent signals can be used in differential combinations for active control and optimization of the alignment. The theory and methodology for the optical retroreflection, detection, and control characteristics are presented, and the technique is verified experimentally with a silicon PD retro-detection prototype. The active remote sensing capabilities of the retrodetector are found to be successful.

Multifunctional Magnetic–Optical Nanoparticle Probes for Simultaneous Detection, Separation, and Thermal Ablation of Multiple Pathogens

Multifunctional nanoparticles possessing magnetization and near-infrared (NIR) absorption have warranted interest due to their significant applications in magnetic resonance imaging, diagnosis, bioseparation, target delivery, and NIR photothermal ablation. Herein, the site-selective assembly of magnetic nanoparticles onto the ends or ends and sides of gold nanorods with different aspect ratios (ARs) to create multifunctional nanorods decorated with varying numbers of magnetic particles is described for the first time. The resulting hybrid nanoparticles are designated as Fe(3)O(4)-Au(rod)-Fe(3)O(4) nanodumbbells and Fe(3)O(4)-Au(rod) necklacelike constructs with tunable optical and magnetic properties, respectively. These hybrid nanomaterials can be used for multiplex detection and separation because of their tunable magnetic and plasmonic functionality. More specifically, Fe(3)O(4)-Au(rod) necklacelike probes of different ARs are utilized for simultaneous optical detection based on their plasmon properties, magnetic separation, and photokilling of multiple pathogens from a single sample at one time. The combined functionalities of the synthesized probes will open up many exciting opportunities in dual imaging for targeted delivery and photothermal therapy.

Simultaneous use of electrochemistry and chemiluminescence to detect reactive oxygen species produced by human neutrophils

A novel approach for the simultaneous optical and electrochemical detection of biologically produced reactive oxygen species has been developed and applied. The set-up consists of a luminol-dependent chemiluminescence assay combined with two amperometric biosensors sensitive to superoxide anion radicals (O(2)(-)) and hydrogen peroxide (H(2)O(2)), respectively. The method permits direct, real-time in vitro determination of both extra- and intracellular O(2)(-) and H(2)O(2) produced by human neutrophil granulocytes. The rate of O(2)(-) production by stimulated neutrophils was calculated to about 10(-17)mol s(-1) per single cell. With inhibited NADPH oxidase, a distinct extracellular release of H(2)O(2) instead of O(2)(-) was obtained from stimulated neutrophils with the rate of about 3 x 10(-18)mol s(-1) per single cell. When the H(2)O(2) release was discontinued, fast H(2)O(2) utilisation was observed. Direct interaction with and possibly attachment of neutrophils to redox protein-modified gold electrodes, resulted in a spontaneous respiratory burst in the population of cells closely associated to the electrode surface. Hence, further stimulation of human neutrophils with a potent receptor agonist (fMLF) did not significantly increase the O(2)(-) sensitive amperometric response. By contrast, the H(2)O(2) sensitive biosensor, based on an HRP-modified graphite electrode, was able to reflect the bulk concentration of H(2)O(2), produced by stimulated neutrophils and would be very useful in modestly equipped biomedical research laboratories. In summary, the system would also be appropriate for assessment of several other metabolites in different cell types, and tissues of varying complexity, with only minor electrode modifications.

Au-Fe3O4 dumbbell nanoparticles as dual-functional probes.

Heavy lifting: Dumbbell-shaped Au–Fe3O4 nanoparticles are made biocompatible and suitable for attachment to A431 cells. The particles are magnetically and optically active and are useful for simultaneous magnetic and optical detection (see picture). The Au–Fe3O4 nanoparticles are promising as a new type of multifunctional probe for diagnostic and therapeutic applications. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z704392_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Electrochemiluminescent/voltammetric toxicity screening sensor using enzyme-generated DNA damage

Simultaneous optical and voltammetric detection of bioactivated genotoxicity is reported for the first time employing ultrathin films of DNA, model metabolic enzymes, and electrochemiluminescence (ECL) generating metallopolymer [Ru(bpy) 2PVP 10] 2+ on pyrolytic graphite (PG) electrodes. Cytochrome P450 cam and myoglobin were used as model monoxygenase enzymes to mimic in vivo processes. Sensor film growth and component amounts were monitored using a quartz crystal microbalance (QCM). Subsequent to the enzyme reaction, DNA damage in the sensor films was measured simultaneously using a simple apparatus combining a standard voltammetry cell coupled with an optical fiber and photomultiplier tube. The model enzyme reaction converted styrene to styrene oxide, which reacts with DNA nucleobases. ECL and SWV signals increased with enzyme reaction time on the scale of several min, and provided relative enzyme turnover rates for DNA damage suitable for toxicity screening applications. Within 1 min, the sensor detects ∼3 damaged bases per 10,000 DNA bases using this simultaneous detection.

Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device. 20. Detection of Metal Ions in Different Oxidation States

Spectroelectrochemical sensing a metal in two different oxidation states, both of which are weakly absorbing in the visible wavelength range, was demonstrated with ferrous and ferric ion. The sensor consisted of an indium tin oxide optically transparent electrode (ITO OTE) coated with a thin film of Nafion preloaded with the ligand 2,2'-bipyridine (bipy). Fe2+ in the sample partitioned into the film where it reacted with bipy to form Fe(bipy)3(2+), which absorbs strongly at 520 nm. The change in absorbance (DeltaA) at 520 nm associated with the accumulation of Fe(bipy)3(2+) complex in the film was measured by attenuated total reflectance spectroscopy and was proportional to the concentration of Fe2+ in the sample. Iron in the Fe3+ form can also be determined, but it has a more complex coordination chemistry involving formation of [Fe2(bipy)4O(H2O)2]4+ as well as Fe(bipy)3(3+) in the film. Fe3+ was detected indirectly by reducing the nonabsorbing Fe3+-bipy complexes that accumulated in the film to absorbing Fe(bipy)3(2+) and monitoring DeltaA at 520 nm. The effects of film thickness and ligand concentration in the film on sensor sensitivity and response time for Fe2+ were evaluated. Detection limits of 0.6 x 10(-6) M for Fe2+ and 2 x 10(-6) M for Fe3+ were obtained with 300 nm thick films after 30 min of exposure to a quiescent sample. Careful manipulation of the potential applied with simultaneous optical detection enables Fe2+ to be distinguished from Fe3+, which is the first step in developing a sensor for speciating the two oxidation states in a mixture.