Label-Free Detection of Unbound Bilirubin and Nitrophenol Explosives in Water by a Mechanosynthesized Dual Functional Zinc Complex: Recognition of Picric Acid in Various Common Organic Media.

High levels of unconjugated bilirubin (UB) in serum lead to asymptomatic and neonatal jaundice and brain dysfunctions. Herein, we have reported the detection of UB at as low as 1 µM in an aqueous alkaline medium using a Zn(II) complex. The specificity of the complex has been validated by the HPLC in the concentration window 6-90 µM, which is rare. The sensory response of the probe at physiological pH against nitro explosives developed it as an instant-acting fluorosensor for picric acid (PA) and 2,4-dinitrophenol (2,4-DNP). Spectroscopic titration provided a binding constant of 4×105  M-1 with PA. The naked eye detection was found to be 15 µM. The solid-state photoluminescent nature of the complex enabled it for PA sensing in the solid phase. Interestingly, the probe remained fluorescent in various volatile and non-volatile organic solvents. As a result, it can also detect PA and 2,4-DNP in a wide range of common organic media. NMR studies revealed the coordination of PA, 2,4-DNP, and UB to the Zn(II) center of the probe, which is responsible for the observed quenching of the probe with the analytes.

Highly Sensitive and Selective Recognition of Zn2⁺ and Fe2⁺ Ions Using a Novel Thiophene-Derived Hydrazone Dual Fluorometric Sensor.

The selective detection of Zn2⁺ and Fe2⁺ ions is critical in environmental and biological studies. Schiff base chemosensors hold promise, but exploration of thiophene-derived variants remains limited. This work introduces a novel thiophene-derived Schiff base sensor (TBH), synthesized through the condensation reaction of thiophene-2-carboxaldehyde with benzil-bis-hydrazone, for the selective detection of Zn2⁺ and Fe2⁺ ions. TBH exhibits remarkable selectivity, with a significant 185-fold fluorescence enhancement for Zn2⁺ and complete quenching 99% for Fe2⁺, allowing for distinct detection of both ions. Notably, TBH demonstrates high binding affinity towards Zn2⁺ and Fe2⁺, even in the presence of competing cations, forming stable 1:1 complexes. This finding is supported by absorption and emission titration studies and FT-IR analysis as well. This easily synthesized, rapid and cost-effective sensor offers a promising approach for sensitive and differentiated dual detection of Zn2⁺ and Fe2⁺ in environmental and biological systems.

Constructing ESIPT-Capable α-Cyanostilbene Luminogens: Influence of Different Aromatic Substitutions Tethered to H-Acceptor (CH = N) on Photophysical Properties, Cu2+ and Fe3+ Detection.

Herein, two excited-state intramolecular proton transfer (ESIPT)-capable α-cyanostilbene luminogens were synthesized by Schiff base reaction of salicylaldehyde-like α-cyanostilbene candidate with 1-naphthylamine and 3-biphenylamine, respectively. We systematically analyzed their photophysical properties compared with their analogue, and demonstrated that their fluorescence behaviors could be elaborately modulated by different aromatic substitutions tethered to H-acceptor (CH = N). In virtue of the outstanding solid fluorescence, the 3-biphenylamine-decorated fluorophore was applied for monitoring Cu2+/Fe3+ qualitatively on the TLC-based test strip in real time and sensing Cu2+/Fe3+ quantitatively in the THF/H2O medium (fw = 90%, pH = 7.4). When the probe chelated with Cu2+/Fe3+, similar "turn-off" fluorescence signal outputs were triggered. From the fluorescence titration experiments, the detection limits were evaluated as 7.97 × 10- 8 M for Cu2+ and 8.24 × 10- 8 M for Fe3+, and the binding constant (Kα) values of the complexes were found to be 7.80 × 104 M-1 for Cu2+ and 9.06 × 104 M-1 for Fe3+. Job's plots indicated that probe complexed with Cu2+/Fe3+ in a 2:1 binding stoichiometry ratio. Furthermore, the probe was used to accurately quantify the Fe3+ spiked in real water specimens. This study offered a new perspective to construct ESIPT-capable α-cyanostilbene luminogen as the potential luminescent probe.

Selective dual sensing strategy for free and vitamin D3 micelles in food samples based on S,N-GQDs photoinduced electron transfer.

A reliable nanotechnological sensing strategy, based on an S,N-co-doped graphene quantum dot (GQD) platform, has been developed to distinctly detect two key variants of vitamin D3, specifically the free (VD3) and the nanoencapsulated form (VD3Ms). For this purpose, food-grade vitamin D3 micelles were self-assembled using a low-energy procedure (droplet size: 49.6 nm, polydispersity index: 0.34, ζ-potential: -33 mV, encapsulation efficiency: 90 %) with an innovative surfactant mixture (Tween 60 and quillaja saponin). Herein, four fluorescent nanoprobes were also synthesized and thoroughly characterized: S,N-co-doped GQDs, α-cyclodextrin-GQDs, ß-cyclodextrin-GQDs, and γ-cyclodextrin-GQDs. The goal was to achieve a selective dual sensing strategy for free VD3 and VD3Ms by exploiting their distinctive quenching behaviors. Thus, the four nanosensors allowed the individual sensing of both targets to be performed (except α-CD-GQD for VD3Ms), but S,N-GQDs were finally selected due to selectivity and sensitivity (quantum yield, QY= 0.76) criteria. This choice led to a photoinduced electron transfer (PET) mechanism associated with static quenching, where differentiation was evidenced through a displayed 13-nm hypsochromic (blue) shift when interacting with VD3Ms. The reliability of this dual approach was demonstrated through an extensive evaluation of analytical performance characteristics. The feasibility and accuracy were proven in commercial food preparations and nutritional supplements containing declared nanoencapsulated and raw VD3, whose results were validated by a paired Student's t-test comparison with a UV-Vis method. To the best of our knowledge, this represents the first non-destructive analytical approach addressing the groundbreaking foodomic trend to distinctly detect different bioactive forms of vitamin D3, while also preserving their native nanostructures as a chemical challenge, thus providing reliable information about their final stability and bioavailability.

1,2,3-Triazoles: Controlled Switches in Logic Gate Applications.

A 1,2,3-triazole-based chemosensor is used for selective switching in logic gate operations through colorimetric and fluorometric response mechanisms. The molecular probe synthesized via "click chemistry" resulted in a non-fluorescent 1,4-diaryl-1,2,3-triazole with a phenol moiety (PTP). However, upon sensing fluoride, it TURNS ON the molecule's fluorescence. The TURN-OFF order occurs through fluorescence quenching of the sensor when metal ions, e.g., Cu2+, and Zn2+, are added to the PTP-fluoride ensemble. A detailed characterization using Nuclear Magnetic Resonance (NMR) spectroscopy in a sequential titration study substantiated the photophysical characteristics of PTP through UV-Vis absorption and fluorescence profiles. A combination of fluorescence OFF-ON-OFF sequences provides evidence of 1,2,3-triazoles being controlled switches applicable to multimodal logic operations. The "INH" gate was constructed based on the fluorescence output of PTP when the inputs are F- and Zn2+. The "IMP" and "OR" gates were created on the colorimetric output responses using the probe's absorption with multiple inputs (F- and Zn2+ or Cu2+). The PTP sensor is the best example of the "Write-Read-Erase-Read" mimic.

Dual Fluorometric Detection of Fe3+ and Hg2+ Ions in an Aqueous Medium Using Carbon Quantum Dots as a "Turn-off" Fluorescence Sensor.

The present study aimed to develop a carbon dots-based fluorescence (FL) sensor that can detect more than one pollutant simultaneously in the same aqueous solution. The carbon dots-based FL sensor has been prepared by employing a facile hydrothermal method using citric acid and ethylenediamine as precursors. The as-synthesized CDs displayed excellent hydrophilicity, good photostability and blue fluorescence under UV light. They have been used as an efficient "turn-off" FL sensor for dual sensing of Fe3+ and Hg2+ ions in an aqueous medium with high sensitivity and selectivity through a static quenching mechanism. The lowest limit of detection (LOD) for Fe3+ and Hg2+ ions was found to be 0.406 µM and 0.934 µM, respectively over the concentration range of 0-50 µM. Therefore, the present work provides an effective strategy to monitor the concentration of Fe3+ and Hg2+ ions simultaneously in an aqueous medium using environment-friendly CDs.

Flexible and reusable carbon dot decorated natural microcline membrane: a futuristic probe for multiple heavy metal induced carcinogen detection.

A flexible nano-engineered natural mineral (carbon dot doped natural microcline) based membrane (MCPV) has been developed, which can efficiently detect the presence of hexavalent chromium (Cr6+) and trivalent iron (Fe3+) ions in water by altering its fluorescence emission. Detailed characterization of the membrane was carried out using XRD, FT-IR spectroscopy, FESEM, TEM, and UV-Vis spectroscopy. Mechanical and temperature stabilities were also investigated. This new-generation sensor membrane is designed in such a way that it does not dissolve in water, keeping the water quality unaffected. The fluorescence studies were conducted at 414 nm and "turn-off" response was observed specifically for Fe3+ at 489 nm. A prominent red shift (530 nm) of the fluorescence maxima takes place when it comes to Cr6+. Figures of merit, such as LOD (8.7 µM for Cr6+ and 18.4 µM for Fe3+) and LOQ (29.1 µM for Cr6+ and 61.6 µM for Fe3+), were evaluated from the linear range (0-60 µM for Cr6+ and 0-30 µM for Fe3+) of the calibration curve (Stern-Volmer plots) showing high sensitivity of this sensing probe toward Cr6+ and Fe3+. Recovery and RSD calculations were done in various real-life water samples on intraday-interday basis to determine the accuracy of the sensor. This work validates the fact that the synthesized sensor membrane is capable of detecting these heavy metals in glutathione environment as well, which could be beneficial for early-stage carcinogen detection in living cells.

Shallow-Tapered Chirped Fiber Bragg Grating Sensors for Dual Refractive Index and Temperature Sensing.

In this work, we present a gold-coated shallow-tapered chirped fiber Bragg grating (stCFBG) for dual refractive index (RI) and temperature sensing. The stCFBG has been fabricated on a 15-mm long chirped FBG, by tapering a 7.29-mm region with a waist of 39 µm. The spectral analysis shows two distinct regions: a pre-taper region, in which the stCFBG is RI-independent and can be used to detect thermal changes, and a post-taper region, in which the reflectivity increases significantly when the RI increments. We estimate the RI and thermal sensitivities as 382.83 dB/RIU and 9.893 pm/°C, respectively. The cross-talk values are low (-1.54 × 10-3 dB/°C and 568.1 pm/RIU), which allows an almost ideal separation between RI and thermal characteristics. The stCFBG is a compact probe, suitable for long-term and temperature-compensated biosensing and detection of chemical analytes.

A fluorescence/colorimetric dual-mode sensing strategy for miRNA based on graphene oxide.

MicroRNAs (miRNAs) are small non-coding RNAs, which are involved in RNA silencing and post-transcriptional regulation of gene expression. Numerous studies have determined the expression of certain miRNAs in specific tissues and cell types, and their aberrant expression is associated with a variety of serious diseases such as cancers, immune-related diseases, and many infectious diseases. This suggests that miRNAs may be attractive and promising non-invasive biomarkers of diseases. In this study, we established a graphene oxide (GO)-based fluorescence/colorimetric dual sensing platform for miRNA by using a newly designed probe. The probe was designed to form a hairpin-like configuration with a fluorescent dye-labeled long tail, possessing a guanine (G)-rich DNAzyme domain in the loop region and target binding domain over the stem region and tail. By introducing this new hairpin-like probe in a conventional GO-based fluorescence platform, we observed both the miRNA-responsive color change by direct observation and sensitive fluorescence increase even below the nanomolar levels in a single solution without an additional separation step.

Distributed Fiberoptic Sensor for Simultaneous Humidity and Temperature Monitoring Based on Polyimide-Coated Optical Fibers.

Along temperature, humidity is one of the principal environmental factors that plays an important role in various application areas. Presented work investigates possibility of distributed fiberoptic humidity monitoring based on humidity-induced strain measurement in polyimide (PI)-coated optical fibers. Characterization of relative humidity (RH) and temperature response of four different commercial PI- and one acrylate-coated fiber was performed using optical backscattering reflectometry (OBR). The study addresses issues of temperature-humidity cross-sensitivity, fiber response stability, repeatability, and the influence of annealing. Acrylate-coated fiber exhibited rather unfavorable nonlinear RH response with strong temperature dependence, which makes it unsuitable for humidity sensing applications. On the other hand, humidity response of PI-coated fibers showed good linearity with fiber sensitivity slightly decreasing at rising temperatures. In the tested range, temperature sensitivity of the fibers remained humidity independent. Thermal annealing was shown to considerably improve and stabilize fiber RH response. Based on performed analysis, a 20 m sensor using the optimal PI-coated fibers was proposed and constructed. The sensor uses dual sensing fiber configuration for mutual decoupling and simultaneous measurement of temperature and RH variations. Using OBR, distributed dual temperature-RH monitoring with cm spatial resolution was demonstrated for the first time.

Simultaneous detection of bioavailable arsenic and cadmium in contaminated soils using dual-sensing bioreporters.

Whole-cell bioreporters (WCBs) have attracted increasing attention during the last few decades because they allow fast determination of bioavailable heavy metals in contaminated sites. Various WCBs to monitor specific heavy metals such as arsenic and cadmium in diverse environmental systems are available. However, currently, no study on simultaneous analysis of arsenic and cadmium has been reported, even though soils are contaminated by diverse heavy metals and metalloids. We demonstrated herein the development of dual-sensing WCBs to simultaneously quantify bioavailable arsenic and cadmium in contaminated sites by employing the promoter regions of the ars and znt operons as separate metal-sensing domains, and egfp and mcherry as reporter genes. The dual-sensing WCBs were generated by inserting two sets of genes into E. coli DH5α. The capability of WCBs was successfully proved to simultaneously quantify bioavailable arsenic and cadmium in amended Landwirtschaftliche Untersuchungs und Forschungsanstalt (LUFA) soils, and then, it was applied to contaminated field soils collected from a smelter area in Korea. As a result, it was noticed that the bioavailable portion of cadmium was higher than that of arsenic while the absolute amount of bioavailable arsenic and cadmium level was opposite. Since both cadmium and arsenic were assessed from the same E. coli cells, the data obtained by using dual-sensing WCBs would be more efficient and convenient than that from comparative WCB assay. In spite of advantageous aspects, to our knowledge, this is the first report on a dual-sensing WCB for rapid and concurrent quantification of bioavailable arsenic and cadmium in contaminated soils.

A Highly Robust, Multifunctional, and Breathable Bicomponent Fibers Thermoelectric Fabric for Dual-Mode Sensing.

Wearable thermoelectric (TE) materials are seen as excellent candidates for flexible electronics because of their unique self-powered properties, multistimulus sensing and human waste heat conversion. However, currently reported flexible TE materials still face challenges such as poor durability, uncomfortable wearing and sensing signals crosstalking each other. Herein, this study describes a hot-air cross-linking method for the preparation of multifunctional TE fabrics with enhanced durability. Poly(ethylene terephthalate) (PET) fibers with core and sheath structures having different melting points were selected as flexible substrates. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and single-walled carbon nanotubes (SWCNTs) were embedded stably on the surface of the sheath layer in the presence of heat treatment. The fiber-welded structure created by thermal cross-linking improves the durability of TE fabrics, including consistent mechanical and electrical properties after a 6 h wash test and 6000 compression cycles. The unique fiber structure of TE fabrics ensures excellent breathability (313.7 mm s-1 at 200 Pa), which meets the breathability requirements for human wear. In addition, the fiber-prepared sensors have excellent compressive strain response (20 ms response time and 30 ms recovery time) and precise temperature discrimination (0.17 K minimum discrimination temperature) for accurate real-time monitoring of the sensed signals. Thus, the TE fabrics can be used for human motion recognition, including pulse monitoring, sign language expression, and motions in joint areas. Moreover, the fabricated wearable TE device is connected to a Bluetooth module for wireless transmission, which can be used for mechanical and temperature sensing of the robot arm without signals crosstalking. This new durable TE fabric paves the way for the next generation of smart wearable technology.

Advanced Flexible Physical Sensors with Independent Detection Mechanisms of Pressure and Strain Stimuli for Overcoming Signal Interference.

Flexible and wearable physical sensors have gained significant interest owing to their potential in attachable devices, electronic skin, and multipurpose sensors. The physical stimuli of these sensors typically consist of vertically and horizontally applied pressures and strains, respectively. However, owing to their similar response characteristics, interference occurs between the two types of signals detected, complicating the distinction between pressure and strain stimuli, leading to inaccurate data interpretation and reduced sensor specificity. Therefore, we developed a dual-sensing-mode physical sensor with separate response mechanisms for the two types of physical stimuli based on a unique structural design that can independently induce changes in the piezocapacitance and piezoresistance for pressure and strain stimuli, respectively. The asterisk-shaped piezoresistive pathway (electrode), designed for multifunctionality, effectively detected the intensity and direction of tensile deformation, and an elastomeric sponge structure positioned between the two electrodes detected the pressure signals via changes in capacitance. This dual-sensing-mode sensor offers clearer signal differentiation and enhanced multifunctionality compared to those of traditional single-mode sensors. Additionally, extensive experimentation demonstrated that our sensor has a good sensitivity, high linearity, and stability in detecting signals, proving its applicability for sophisticated monitoring and control tasks that require the differential detection between pressure and deformation signals.

Recent development in dual function fluorescence probes for HOCl and interaction with different bioactive molecules.

Reactive oxygen species (ROS), reactive sulfur species (RSS), metal ions, and nitrogen species (RNS) play important roles in a variety of biological processes, such as a signal transduction, inflammation, and neurodegenerative damage. These species, while essential for certain functions, can also induce stress-related diseases. The interrelation between ROS, RSS, Metal ions and RNS underscores the importance of quantifying their concentrations in live cells, tissues, and organisms. The review emphasizes the use of small-molecule-based fluorescent/chemodosimeter probes to effectively measure and map the species' distribution with high temporal and spatial precision, paying particular attention to in vitro and in vivo environments. These probes are recognized as valuable tools contributing to breakthroughs in modern redox biology. The review specifically addresses the relationship of HOCl/ClO‾ (hypochlorous acid/Hypochlorite) with other reactive species. (Dual sensing probes).

Thermal and light-driven soft actuators based on a conductive polypyrrole nanofibers integrated poly(N-isopropylacrylamide) hydrogel with intelligent response.

The development of soft hydrogel actuators with outstanding mechanical properties, fast actuation speed, and available quantification of self-sensing actuation remains a challenging endeavor. In this work, dopamine-decorated polypyrrole nanofibers (DAPPy) were introduced into the polyethylene glycol diacrylate (PEGDA)-crosslinked poly(N-isopropyl acrylamide) network to generate a stretchable, NIR-responsive, and strain sensitive DAPPy/PNIPAM hydrogel layer. Besides, this active layer was combined with the passive ligninsulfonate sodium/polyacrylamide (LS/PAAM) to give DAPPy/PNIPAM//LS/PAAM bilayer hydrogel actuator, which exhibits ultrafast thermo-responsive actuation (19°/s) and underwater grasping and lifting performance. Moreover, the DAPPy/PNIPAM layer has excellent electrical conductivity (0.29 S/m) and thermal conversion ability (10.8 °C/min), which enable such a conductive hydrogel to act as a highly sensitive strain and temperature sensor with real-time resistance change in response to tensile strain (gauge factor up to 3.4), applied pressure, temperature, and remote NIR light irradiation. More importantly, the bilayer hydrogel actuator can integrate both actuation and self-sensing functions through the bending angle-surface temperature-relative resistance change relationship of the photothermal process. With excellent mechanical actuation and self-sensing ability, the resulting bilayer hydrogel showed a promising application potential as soft biomimetic actuating materials and soft intelligent actuators.

A Wide-Range-Response Piezoresistive-Capacitive Dual-Sensing Breathable Sensor with Spherical-Shell Network of MWCNTs for Motion Detection and Language Assistance.

It is still a challenge for flexible electronic materials to realize integrated strain sensors with a large linear working range, high sensitivity, good response durability, good skin affinity and good air permeability. In this paper, we present a simple and scalable porous piezoresistive/capacitive dual-mode sensor with a porous structure in polydimethylsiloxane (PDMS) and with multi-walled carbon nanotubes (MWCNTs) embedded on its internal surface to form a three-dimensional spherical-shell-structured conductive network. Thanks to the unique spherical-shell conductive network of MWCNTs and the uniform elastic deformation of the cross-linked PDMS porous structure under compression, our sensor offers a dual piezoresistive/capacitive strain-sensing capability, a wide pressure response range (1-520 kPa), a very large linear response region (95%), excellent response stability and durability (98% of initial performance after 1000 compression cycles). Multi-walled carbon nanotubes were coated on the surface of refined sugar particles by continuous agitation. Ultrasonic PDMS solidified with crystals was attached to the multi-walled carbon nanotubes. After the crystals were dissolved, the multi-walled carbon nanotubes were attached to the porous surface of the PDMS, forming a three-dimensional spherical-shell-structure network. The porosity of the porous PDMS was 53.9%. The large linear induction range was mainly related to the good conductive network of the MWCNTs in the porous structure of the crosslinked PDMS and the elasticity of the material, which ensured the uniform deformation of the porous structure under compression. The porous conductive polymer flexible sensor prepared by us can be assembled into a wearable sensor with good human motion detection ability. For example, human movement can be detected by responding to stress in the joints of the fingers, elbows, knees, plantar, etc., during movement. Finally, our sensors can also be used for simple gesture and sign language recognition, as well as speech recognition by monitoring facial muscle activity. This can play a role in improving communication and the transfer of information between people, especially in facilitating the lives of people with disabilities.

Development of highly sensitive, flexible dual L-glutamate and GABA microsensors for in vivo brain sensing.

Real-time tracking of neurotransmitter levels in vivo has been technically challenging due to the low spatiotemporal resolution of current methods. Since the imbalance of cortical excitation/inhibition (E:I) ratios are associated with a variety of neurological disorders, accurate monitoring of excitatory and inhibitory neurotransmitter levels is crucial for investigating the underlying neural mechanisms of these conditions. Specifically, levels of the excitatory neurotransmitter L-glutamate, and the inhibitory neurotransmitter GABA, are assumed to play critical roles in the E:I balance. Therefore, in this work, a flexible electrochemical microsensor is developed for real-time simultaneous detection of L-glutamate and GABA. The flexible polyimide substrate was used for easier handling during implantation and measurement, along with less brain damage. Further, by electrochemically depositing Pt-black nanostructures on the sensor's surface, the active surface area was enhanced for higher sensitivity. This dual neurotransmitter sensor probe was validated under various settings for its performance, including in vitro, ex vivo tests with glutamatergic neuronal cells and in vivo test with anesthetized rats. Additionally, the sensor's performance has been further investigated in terms of longevity and biocompatibility. Overall, our dual L-glutamate:GABA sensor microprobe has its unique features to enable accurate, real-time, and long-term monitoring of the E:I balance in vivo. Thus, this new tool should aid investigations of neural mechanisms of normal brain function and various neurological disorders.

Differential Detection of Bioavailable Mercury and Cadmium Based on a Robust Dual-Sensing Bacterial Biosensor.

Genetically programmed biosensors have been widely used to monitor bioavailable heavy metal pollutions in terms of their toxicity to living organisms. Most bacterial biosensors were initially designed to detect specific heavy metals such as mercury and cadmium. However, most available biosensors failed to distinguish cadmium from various heavy metals, especially mercury. Integrating diverse sensing elements into a single genetic construct or a single host strain has been demonstrated to quantify several heavy metals simultaneously. In this study, a dual-sensing construct was assembled by employing mercury-responsive regulator (MerR) and cadmium-responsive regulator (CadR) as the separate sensory elements and enhanced fluorescent protein (eGFP) and mCherry red fluorescent protein (mCherry) as the separate reporters. Compared with two corresponding single-sensing bacterial sensors, the dual-sensing bacterial sensor emitted differential double-color fluorescence upon exposure to 0-40 µM toxic Hg(II) and red fluorescence upon exposure to toxic Cd(II) below 200 µM. Bioavailable Hg(II) could be quantitatively determined using double-color fluorescence within a narrow concentration range (0-5 µM). But bioavailable Cd(II) could be quantitatively measured using red fluorescence over a wide concentration range (0-200 µM). The dual-sensing biosensor was applied to detect bioavailable Hg(II) and Cd(II) simultaneously. Significant higher red fluorescence reflected the predominant pollution of Cd(II), and significant higher green fluorescence suggested the predominant pollution of Hg(II). Our findings show that the synergistic application of various sensory modules contributes to an efficient biological device that responds to concurrent heavy metal pollutants in the environment.

Surface-Enhanced Raman Spectroscopy and Electrochemistry: The Ultimate Chemical Sensing and Manipulation Combination.

One of the lessons we learned from the COVID-19 pandemic is that the need for ultrasensitive detection systems is now more critical than ever. While sensors' sensitivity, portability, selectivity, and low cost are crucial, new ways to couple synergistic methods enable the highest performance levels. This review article critically discusses the synergetic combinations of optical and electrochemical methods. We also discuss three key application fields-energy, biomedicine, and environment. Finally, we selected the most promising approaches and examples, the open challenges in sensing, and ways to overcome them. We expect this work to set a clear reference for developing and understanding strategies, pros and cons of different combinations of electrochemical and optical sensors integrated into a single device.

Smart Contact Lens with Dual-Sensing Platform for Monitoring Intraocular Pressure and Matrix Metalloproteinase-9.

Contact lenses have become a popular health-monitoring wearable device due to their direct contact with the eyes. By integrating biosensors into contact lenses, real-time and noninvasive diagnoses of various diseases can be realized. However, current contact lens sensors often require complex electronics, which may obstruct the user's vision or even damage the cornea. Moreover, most of the reported contact lens sensors can only detect one analyte. Therefore, an optical-based dual-functional smart contact lens sensor has been introduced to monitor intraocular pressure (IOP) and detect matrix metalloproteinase-9 (MMP-9), both of which are key biomarkers in many eye-related diseases such as glaucoma. Specifically, the elevated IOP is continuously monitored by applying an antiopal structure through color changes, without any complex electronics. Together with the peptide modified gold nanobowls (AuNBs) surface-enhanced Raman scattering (SERS) substrate, the quantitative analysis of MMP-9 at a low nanomolar range is achieved in real tear samples. The dual-sensing functions are thus demonstrated, providing a convenient, noninvasive, and potentially multifunctional sensing platform for monitoring health and diagnostic biomarkers in human tears.