Simultaneous Optical Detection Research Articles

Underwater object detection and temporal signal detection in turbid water using 3D-integral imaging and deep learning.

Underwater scattering caused by suspended particles in the water severely degrades signal detection performance and poses significant challenges to the problem of object detection. This paper introduces an integrated dual-function deep learning-based underwater object detection and classification and temporal signal detection algorithm using three-dimensional (3D) integral imaging (InIm) under degraded conditions. The proposed system is an efficient object classification and temporal signal detection system for degraded environments such as turbidity and partial occlusion and also provides the object range in the scene. A camera array captures the underwater objects in the scene and the temporally encoded binary signals transmitted for the purpose of communication. The network is trained using a clear underwater scene without occlusion, whereas test data is collected in turbid water with partial occlusion. Reconstructed 3D data is the input to a You Look Only Once (YOLOv4) neural network for object detection and a convolutional neural network-based bidirectional long short-term memory network (CNN-BiLSTM) is used for temporal optical signal detection. Finally, the transmitted signal is decoded. In our experiments, 3D InIm provides better image reconstruction in a degraded environment over 2D sensing-based methods. Also, reconstructed 3D images segment out the object of interest from occlusions and background which improves the detection accuracy of the network with 3D InIm. To the best of our knowledge, this is the first report that combines deep learning with 3D InIm for simultaneous and integrated underwater object detection and optical signal detection in degraded environments.

Pretreatment-free, on-site separation and sensitive identification of methamphetamine in biological specimens by SERS-active hydrogel microbeads

The worldwide abuse of illicit drugs led to severe consequences for human health, and society environment. Therefore, urgently required are effective and efficient on-site detection methods for illicit drugs of interest in various matrices, e.g., police samples, biofluids, and hairs. Although surface-enhanced Raman spectroscopy (SERS) shows power in many analytical fields, the cumbersome pretreatment of various matrices restricts its use in the easy-to-operate and on-site detection of illicit drugs. To address this problem, we adopted pore-size selectivity SERS-active hydrogel microbeads, whose meshes are adjustable to allow small molecules to access and to exclude large molecules. Meanwhile, Ag nanoparticles were uniformly dispersed and wrapped in the hydrogel matrix, providing excellent SERS performances with high sensitivity, reproducibility, and stability. By using these SERS hydrogel microbeads, one of the illicit drugs, methamphetamine (MAMP), can be rapidly and reliably detected in various biological specimens (blood, saliva, and hair) without sample pretreatment. The minimum detectable concentration is 0.1 ppm for MAMP in three biological specimens with a linear range of 0.1–100 ppm, which is lower than the maximum allowable level of 0.5 ppm set by the department of the health and human service. The SERS detection results were consistent with the gas chromatographic (GC) data. Thanks to its operational simplicity, fast response, high throughput and low cost, our established SERS hydrogel microbeads can be used as a sensing platform for facile analysis of illicit drugs through simultaneous separation, preconcentration, and optical detection, which shall be provided practically for front-line narcotics squad and resistance to the overwhelmed drug abuses.

Optical monitoring and treatment of breast cancer by a tumor hypoxia-activated multi-functional fluorescent sensor

Breast cancer is one of the most common cancers and a leading cause of death in women. Caused by the rapid growth, tumors show marked areas of hypoxia that play an important role in cancer progression and metastasis. We developed a near-infrared multifunctional azo-derivative, L4OD, to target the hypoxic environment of tumors. The release of fluorescent signals and lead compounds following its reaction with cytochrome P450 reductase allowed simultaneous optical detection and inhibited breast cancer tumor growth. The specificity of L4OD for cytochrome P450 reductase was confirmed in vitro through its reactions with tin chloride and rat liver microsomes. In HepG2 cells pre-treated with different oxygen concentrations (1%, 10%, and 21%) for 12 h, the red fluorescent intensity in the cells gradually increased as the oxygen concentration decreased, showing that L4OD can be used to image cytochrome P450 reductase enrichment and to monitor the associated hypoxic environment in cells. Using a mouse tumor xenograft model, we used L4OD successfully for in situ optical detection and tumor suppression in hypoxic regions of breast cancer tumors, with a high inhibition rate of 45%. These results indicate the high performance of L4OD for monitoring and therapy of breast cancer and the potential for further clinical application.

Simultaneous Optical Detection of Multiple Bacterial Species Using Nanometer-Scaled Metal-Organic Hybrids.

This paper describes a simple strategy to identify bacteria using the optical properties of the nanohybrid structures (NHs) of polymer-coated metal nanoparticles (NPs). NHs, in which many small NPs are encapsulated in polyaniline particles, are useful optical labels because they produce strong scattered light. The light-scattering characteristics of NHs are strongly dependent on the constituent metal elements of NPs. Gold NHs (AuNHs), silver NHs (AgNHs), and copper NHs (CuNHs) produce white, reddish, and bluish scattered light, respectively. Moreover, unlike NPs, the color of the scattered light does not change even when NHs are aggregated. Introducing an antibody into NHs induces antigen-specific binding to cells, enabling the identification of bacteria based on light scattering. Multiple bacterial species adsorbed on the slide can be identified within a single field of view under a dark field microscope based on the color of the scattered light. Therefore, it is a useful development for safety risk assessments at manufacturing sites, such as those for foods, beverages, and drugs, and environmental surveys that require rapid detection of multiple bacteria.

(Invited) Immunosensing Chip of Indium Tin Oxide Interdigitated Electrode Array

We introduce three-dimensional (3D) interdigitated electrode array (IDA), which is a pair of IDAs on the ceiling and bottom in a microfluidic channel. The IDAs comprise of Indium tin oxide (ITO) microband electrodes that are alternatively biased. ITO based IDA can be easily and precisely patterned using conventional etching process to be integrated in a single microchannel in which very small volume of liquid sample is enough to fill. Correspondingly requiring extremely small amount of sample, the proposed strategy offers great opportunity for multiplex electrochemical biosensors with high sensitivity. ITO as an electrode material can make 3D IDA more attractive because the limit of detection goes down owing to substantially low background current. Additionally, this serves as a transparent electrode that allows simultaneous optical detection and thus widens the range of options for electrochemical biosensing chip. There are two key issues toward practical analysis. One is reference electrode that needs to lie as closely as possible to working electrodes to minimize iR drop for precise control of electrochemical potential. It is problematic because reference electrode can be hardly miniaturized to be put inside the microchannel with negligible iR drop due to narrow microchannel, i.e. high resistance. The other is functionalization of ITO surface for efficient plan of glass surface as well as ITO microbands. ITO is chemically inert so that few organic molecules can be anchored and any functional layer on it is readily detached to go away. In this presentation, we introduce two-electrode (2E) system that has appropriate mediator layer on ITO IDA. 2E system consists of only two complementary IDA demanding no reference electrodes while electrochemical potential can be retained owing to the mediators lying on the ITO electrodes. And we suggest a more reliable and versatile way of electrografting to firmly pin various mediators onto ITO surface for sensitive electrochemical immunosensing on a chip. Figure 1

Microscopic Structures, Dynamics, and Spin Configuration of the Charge Carriers in Organic Photovoltaic Solar Cells Studied by Advanced Time-Resolved Spectroscopic Methods.

Organic photovoltaics (OPVs) are promising solutions for renewable energy and sustainable technologies and have attracted much attention in recent years. Two types of organic semiconductors are used as donor materials to fabricate OPV cells. One type is a photoconductive polymer, and the other type is a small-molecule-based compound. The discovery of a bulk-heterojunction (BHJ) structure using a mixture of p- and n-type organic semiconductors has dramatically increased the power conversion efficiency (PCE) of OPV cells. In this feature article, we review our recent studies on organic BHJ thin films and OPVs by using advanced time-resolved spectroscopic techniques. Two topics regarding the microscopic behaviors of the charge carriers are discussed. The first topic is focused on how to quantify the local mobility of the charge carriers. Here, we discuss charge carrier dynamics in diketopyrrolopyrrole-linked tetrabenzoporphyrin (DPP-BP) BHJ thin films studied by time-resolved terahertz spectroscopy on a subpicosecond to several tens of picoseconds time scale and by transient photocurrent measurements on a microsecond time scale. The second topic concerns the spin configuration and interaction of the electron and hole of the polaron pairs in polymer-based BHJ thin films and OPV cells studied by the time-resolved electron paramagnetic resonance method, time-resolved simultaneous optical and electrical detection, and measurement of the magnetoconductance effect.

Trench field-effect transistors integrated in a microfluidic channel and design considerations for charge detection.

Field-effect transistors (FETs) combined with a microfluidic system allow for the electrical detection of charged materials moving in a microfluidic channel. Here, we demonstrate trench-shaped silicon FETs with the combination of a microfluidic channel that can be used for simultaneous electrical and optical detection of charged fluorescent beads. The n-channel silicon trench FETs have a maximum transconductance of 1.83 × 10-5 S at near-zero gate bias voltage, which is beneficial for the high sensitivity of electrical detection. The optical transparency and physical robustness of the integrated microfluidic channel are achieved by a polydimethylsiloxane (PDMS)/glass hybrid cover combining the good sealing characteristics of PDMS, and the thin and flat properties of glass. Device evaluation methodologies and measurement approaches are also presented demonstrating a synchronized time-lapse imaging and electronic detection of bead transport. The proposed device and design consideration could advance the promise of electronic sensing to measure potential differences induced by charged analytes.

Inhomogeneous magnetic properties characterized by simultaneous electrical and optical detection of spin-torque ferromagnetic resonance

Magnetic properties of the Pt/Py microstrip were investigated using the simultaneous electrical and optical detection of spin-torque ferromagnetic resonance. From the measured optical signal using the heterodyne-magneto-optical Kerr effect (MOKE), we found that the inhomogeneous broadening and Gilbert damping constant were modified along the transverse direction of the microstrip. In addition, a difference in the precession phase was also observed owing to the non-uniform out-of-plane microwave field. Our study shows that the ferromagnetic resonance measurement based on the heterodyne-MOKE technique is a powerful tool for characterizing the static and dynamic magnetic properties of magnetic thin films with sub-micrometer spatial resolution.

Realtime Observation of Carrier Trapping and Recombination in a Bulk Heterojunction Film by Simultaneous Optical and Electrical Detection

Realtime Observation of Carrier Trapping and Recombination in a Bulk Heterojunction Film by Simultaneous Optical and Electrical Detection

Bifunctional Europium(III) and Niobium(V)-Containing Saponite Clays for the Simultaneous Optical Detection and Catalytic Oxidative Abatement of Blister Chemical Warfare Agents.

For the first time, the co-presence in the saponite structure of luminescent EuIII and catalytic NbV metal sites was exploited for the simultaneous detection and catalytic abatement of sulfur-containing blister chemical warfare agents. Metal centers were introduced in structural positions of the saponite (in the interlayer space or inside the inorganic framework) following two different synthetic methodologies. The functionalized saponites were able to reveal the presence of a sulfur mustard simulant (2-chloroethyl)ethyl sulfide (CEES) after few seconds of contact time and more than 80 % of the substrate was catalytically decomposed after 24 h in the presence of aqueous hydrogen peroxide.

Dual electrical and optical detection of ionizing radiation: Radiation-induced currents and radioluminescence in NaMgF3:Sm

Simultaneous optical and electrical detection of ionizing radiation was achieved using near tissue-equivalent NaMgF3:Sm. The electrical characteristics of the system were capacitive and ohmic and the resistivity of the compound was on the order of 1013 Ω cm. During exposure to X-rays, the compound exhibited both radiation-induced electrical conductivity and radioluminescence from Sm2+ and Sm3+. Initially, strong dose history dependences were observed for both detection methods. The radiation-induced current stabilized after a priming dose and increased with dose rate according to a power law with an exponent Δ = 0.73, and the radioluminescence intensities increased linearly with dose rate. The mobility-lifetime product of the dominant charge carriers was high and estimated to be 1.6 × 10−4 cm2/V. Our results show that dual detection of ionizing radiation is possible using NaMgF3:Sm where the minimum detectable dose rates were 46 μGys−1 and 1.5 mGys−1 for the electrical and optical detection techniques, respectively.

Simultaneous optical detection of human serum albumin and transferrin in body fluids.

A nanocurcumin (NCur)-VO2+ ensemble-based optical nanoprobe is proposed for monitoring of human serum albumin (HSA) and transferrin (TF) in biofluids of serum and urine. The determination strategy of HSA and TF is based on the decrease of the absorbance/color intensity of NCur in the presence of VO2+ due to the formation of NCur-VO2+ ensemble. This leads to aggregation of the NCur and the color change of solution from orange to pale pink. Upon addition of HSA or TF, release of VO2+ from NCur-VO2+ ensemble occurs due to their stronger binding affinities to VO2+ in competition with the NCur. This leads to deaggregation of the NCur and recovery of the decreased absorption/color intensity within a defined time range. The absorption changes atλ = 455 and the color of NCur solution can be monitored spectrophotometrically or visually by a smartphone camera, respectively. Under optimal conditions, the analytical signals increase linearly in the ranges 50-200nM (LOD = 11nM) and 20-140nM (LOD = 8nM) for HSA and TF, respectively. The difference in the different affinities between the HSA and the TF for binding to VO2+ produces the unique time profiles of each protein. Therefore, the simultaneous determination of HSA and TF is provided by using the least-square support-vector machine (LS-SVM) model. The good recoveries and small errors of predicted values suggest that the nanoprobe is capable to resolve binary mixtures of HSA and TF. The method was applied tothe simultaneous determination of HSA and TF in serum and urine samples. Graphical abstract.

Core-Shell-Heterostructured Magnetic-Plasmonic Nanoassemblies with Highly Retained Magnetic-Plasmonic Activities for Ultrasensitive Bioanalysis in Complex Matrix.

Herein, a facile self‐assembly strategy for coassembling oleic acid‐coated iron oxide nanoparticles (OC‐IONPs) with oleylamine‐coated gold nanoparticles (OA‐AuNPs) to form colloidal magnetic–plasmonic nanoassemblies (MPNAs) is reported. The resultant MPNAs exhibit a typical core–shell heterostructure comprising aggregated OA‐AuNPs as a plasmonic core surrounded by an assembled magnetic shell of OC‐IONPs. Owing to the high loading of OA‐AuNPs and reasonable spatial distribution of OC‐IONPs, the resultant MPNAs exhibit highly retained magnetic–plasmonic activities simultaneously. Using the intrinsic dual functionality of MPNAs as a magnetic separator and a plasmonic signal transducer, it is demonstrated that the assembled MPNAs can achieve the simultaneous magnetic manipulation and optical detection on the lateral flow immunoassay platform after surface functionalization with recognition molecules. In conclusion, the core–shell‐heterostructured MPNAs can serve as a nanoanalytical platform for the separation and concentration of target compounds from complex biological samples using magnetic properties and simultaneous optical sensing using plasmonic properties.

Optically probing Schwinger angular momenta in a micromechanical resonator

We report an observation of phononic Schwinger angular momenta, which fully represent twomode states in a micromechanical resonator. This observation is based on simultaneous optical detection of the mechanical response at the sum and difference frequency of the two mechanical modes. A post-selection process for the measured signals allows us to extract a component of phononic Schwinger angular momenta. It also enables us to conditionally prepare two-mode squeezed (correlated) states from a randomly excited (uncorrelated) state. The phononic Schwinger angular momenta could be extended to high-dimensional symmetry (e.g. SU(N) group) for studying multipartite correlations in non-equilibrium dynamics with macroscopic objects.

Imaging Laser-Induced Fluorescence Detection at the Taylor Cone of Electrospray Ionization Mass Spectrometry.

Laser-induced fluorescence detection (LIF) is a powerful tool for the quantitative analysis of fluorescent molecules, widely used in glycan analysis with fluorophore labeled carbohydrates where each species has a common response factor. Electrospray ionization mass spectrometry (ESI-MS), on the other hand, while revealing important structural information about individual analytes, generally can have different response factors for different species. For simpler and improved quantitation with ESI-MS, laser-induced fluorescent images were collected at the Taylor cone of the electrospray interface, enabling simultaneous and robust optical (quantitative) and MS (qualitative) detection of fluorophore labeled sugars. The performance of this universally applicable, interface design independent imaging laser-induced fluorescent (iLIF) system was demonstrated using capillary electrophoresis (CE)-ESI-MS in the analysis of aminopyrene-trisulfonate labeled linear maltooligosaccharides and branched glycans from human immunoglobulin. The limit of detection (LOD) of the iLIF system was in this case 40 attomole. The intra- and interday quantitative (peak area) reproducibilities of the system (RSD) were 4.15% and 6.79%, respectively.

Simultaneous Optical and Electrical Spin-Torque Magnetometry with Phase-Sensitive Detection of Spin Precession

Spin-based coherent information processing and encoding utilize the precession phase of spins in magnetic materials. However, the detection and manipulation of spin precession phases remain a major challenge for advanced spintronic functionalities. By using simultaneous electrical and optical detection, we demonstrate the direct measurement of the precession phase of Permalloy ferromagnetic resonance driven by the spin-orbit torques from adjacent heavy metals. The spin Hall angle of the heavy metals can be independently determined from concurrent electrical and optical signals. The stroboscopic optical detection also allows spatially measuring local spin-torque parameters and the induced ferromagnetic resonance with comprehensive amplitude and phase information. Our study offers a route towards future advanced characterizations of spin-torque oscillators, magnonic circuits, and tunnelling junctions, where measuring the current-induced spin dynamics of individual nanomagnets are required.

Transparent poly(3,4-ethylenedioxythiophene)-based microelectrodes for extracellular recording

It is well known that at the interface between neuronal tissue and recording electrode low electrical impedance is required. However, if simultaneous optical detection or stimulation is an issue, good optical transmittance of the electrode material is desirable as well. State-of-the-art titanium nitride electrodes provide superior low impedance compared to gold or iridium, but are nontransparent. Transparent electrode materials like the transparent conducting oxide, indium tin oxide (ITO), or graphene offer high light transmittance (>80%) but reveal relatively high impedance. In this paper, the authors propose the conducting polymer poly(3,4-ethylenedioxythiophene) with the counter ion NO3- as the electrode material for low impedance and good optical transmittance properties. The polymer is electrochemically deposited onto ITO improving the relatively high impedance of ITO. This multilayer electrode allows not only for electrophysiological recordings of cardiomyocytes but also for monitoring of cell contraction under the microscope. Electrochemical impedance spectroscopy and action potential recordings reveal that the new transparent electrodes are a good compromise in terms of low impedance and transparency if deposition parameters are optimized.

Continuous wave protocol for simultaneous polarization and optical detection of P1-center electron spin resonance

The ready optical detection and manipulation of bright nitrogen vacancy center spins in diamond plays a key role in contemporary quantum information science and quantum metrology. Other optically dark defects such as substitutional nitrogen atoms (`P1 centers') could also become potentially useful in this context if they could be as easily optically detected and manipulated. We develop a relatively straightforward continuous wave protocol that takes advantage of the dipolar coupling between nitrogen vacancy and P1 centers in type 1b diamond to detect and polarize the dark P1 spins. By combining mutual spin flip transitions with radio frequency driving, we demonstrate the simultaneous optical polarization and detection of the electron spin resonance of the P1 center. This technique should be applicable to detecting and manipulating a broad range of dark spin populations that couple to the nitrogen vacancy center via dipolar fields, allowing for quantum metrology using these spin populations.

4-(2-Pyridylazo)-resorcinol-functionalized polyacrylonitrile fiber through a microwave irradiation method for the simultaneous optical detection and removal of heavy metals from water

A PAR-functionalized fiber by microwave irradiation has both colorimetric detection and adsorption abilities for heavy metal ions.

A hybrid resistive pulse-optical detection platform for microfluidic experiments

Resistive-pulse sensing is a label-free method for characterizing individual particles as they pass through ion-conducting channels or pores. During a resistive pulse experiment, the ionic current through a conducting channel is monitored as particles suspended in the solution translocate through the channel. The amplitude of the current decrease during a translocation, or ‘pulse’, depends not only on the ratio of the particle and channel sizes, but also on the particle position, which is difficult to resolve with the resistive pulse signal alone. We present experiments of simultaneous electrical and optical detection of particles passing through microfluidic channels to resolve the positional dependencies of the resistive pulses. Particles were tracked simultaneously in the two signals to create a mapping of the particle position to resistive pulse amplitude at the same instant in time. The hybrid approach will improve the accuracy of object characterization and will pave the way for observing dynamic changes of the objects such as deformation or change in orientation. This combined approach of optical detection and resistive pulse sensing will join with other attempts at hybridizing high-throughput detection techniques such as imaging flow cytometry.