Dual-mode Sensor Research Articles

Smartphone-assisted hydrogel platform based on BSA-CeO2 nanoclusters for dual-mode determination of acetylcholinesterase and organophosphorus pesticides.

Adual-mode sensor was developed for detecting acetylcholinesterase (AChE) and organophosphorus pesticides (OPs) via bifunctional BSA-CeO2 nanoclusters (NCs) with oxidase-mimetic activity and fluorescence property. The dual-mode sensor has the characteristics of self-calibration and self-verification, meeting the needs of different detection conditions and provide more accurate results. The colorimetric sensor and fluorescence sensor have been successfully used for detecting AChE with limit of detection (LOD) of 0.081mU/mL and 0.056mU/mL, respectively, while the LOD forOPs were 0.9ng/mL and 0.78ng/mL, respectively. The recovery of AChE was 93.9-107.2% and ofOPs was 95.8-105.0% in actual samples. A novel strategy was developed to monitor pesticide residues and detect AChE level, which will motivate future work to explore the potential applications of multifunctional nanozymes.

A dual-mode colorimetric and fluorometric sensor for the detection of spermine and spermidine in food based on N-doped carbon dots and peroxidase-like activity of V6O13 nanobelts

Spermine (SPM) and spermidine (SPD) exist widely in food, and their excessive consumption will cause serious harm to human body, so it is significant that determine the content of them in foods. Herein, the peroxidase-like activity of V6O13 nanobelts could catalyze n-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt (TOPS) and 4-amino-antipyrine (4-AAP) to generate the purple complex (PC1). It was first found that PC1 could quench the CDs fluorescence by static quenching (SQE). The SPM and SPD can inhibit the peroxidase-like activity of V6O13, making changes in the color and fluorescence intensity of the solution. Therefore, a fluorescent and colorimetric dual-mode sensor were constructed. The quantitative analysis of SPM and SPD will be realized through the variation of dual signal. Such sensor offers good detection sensitivity for SPM and SPD. The limit of detection (LOD) of SPM and SPD on colorimetric channel were 3.42 μg·L−1 and 11.10 μg·L−1, separately. In the fluorescent channels, the LOD of SPM and SPD were individually determined as low as 1.16 μg·L−1 and 1.31 μg·L−1. Particularly, the results of the dual-channel could be mutually validated, which improved the reliability of the assay. Such method demonstrated good detection of SPM and SPD in actual samples, indicating its huge potential for practical application.

A polydiacetylene (PDA) based dual-mode optical sensor for the ppb level selective detection of biogenic polyamines

Biogenic polyamines (BPAs), specifically spermine and spermidine, play vital roles in cellular physiology, influencing processes like cell growth and proliferation. Beyond their cellular implications, these amines serve as biomarkers for cancer and aging-related diseases. This study presents a dual-output optical sensor for BPAs using polydiacetylene (PDA). The sensor utilizes alendronate's phosphate groups as recognition units for BPAs in liquid and solid phases. Ammonium groups of BPAs interact with negatively charged alendronate-modified PDA (PDAPH) liposomes causing a color change from blue to red accompanied by a gradual increase in fluorescence output at λmax 622 nm. The sensor exhibits high sensitivity with low detection limits of 4.3 ppb and 5.1 ppb for spermine and spermidine in colorimetric analysis, and lower limits of 1.6 and 1.4 ppb in fluorimetric measurements respectively, demonstrating its dual output ability. PDAPH liposomes also respond to cadaverine and putrescine indicating the probe's ability to detect key BPAs. The sensor shows minimal responses to interfering species, confirming its selective affinity towards BPAs. Practical validation in real water, urine, and serum samples demonstrates the sensor's efficiency. Immobilization of PDAPH liposomes into sodium alginate results in the creation of PDA beads. These beads exhibit a discernible color change when exposed to BPA concentrations exceeding 0.3 μM with a sufficiently low detection limit of 11.7 ppb in the solid phase. These findings highlight the efficiency of the PDAPH liposome sensor for accurate and reliable biogenic polyamine detection.

An ultrasensitive smartphone-assisted bicolor-ratiometric fluorescence sensing platform based on a “noise purifier” for point-of-care testing of pathogenic bacteria in food

Non-specific binding in fluorescence resonance energy transfer (FRET) remains a challenge in foodborne pathogen detection, resulting in interference of high background signals. Herein, we innovatively reported a dual-mode FRET sensor based on a “noise purifier” for the ultrasensitive quantification of Escherichia coli O157:H7 in food. An efficient FRET system was constructed with polymyxin B-modified nitrogen-sulfur co-doped graphene quantum dots (N, S-GQDs@PMB) as donors and aptamer-modified yellow carbon dots (Y-CDs@Apt) as acceptors. Magnetic multi-walled carbon nanotubes (Fe@MWCNTs) were employed as a “noise purifier” to reduce the interference of the fluorescence background. Under the background purification mode, the sensitivity of the dual-mode signals of the FRET sensor has increased by an order of magnitude. Additionally, smartphone-assisted colorimetric analysis enabled point-of-care detection of E. coli O157:H7 in real samples. The developed sensing platform based on a “noise purifier” provides a promising method for ultrasensitive on-site testing of trace pathogenic bacteria in various foodstuffs.

Construction of an aptamer sensor for sensitive detection of AOH based on the enhancement of light/electric dual signaling response of Ru/Cu-THQ by Ag NCs

Precise detection of food safety is a hotspot and challenging aspect in contemporary scientific research. This study utilized Ag nanocubes (Ag NCs) to augment the electrogenerated chemiluminescence (ECL) and electrochemical (EC) dual-response signals of Ru/Cu-tetrahydroxybenzoquinone (Ru/Cu-THQ). Consequently, a novel aptamer sensor was developed for the trace detection of Alternariol (AOH). This dual-mode sensor offers several advantages: (1) The output of dual-channel signals significantly reduces the likelihood of false-positive and false-negative detection results, which are common in traditional single-mode sensing. (2) Ru/Cu-THQ effectively coordinates dual-channel outputs and exhibits excellent ECL and EC behavior. (3) Ag NCs, due to their strong K2S2O8 activation ability and excellent conductivity, further amplify the sensor's response signal. This sensor demonstrates effective detection performance for AOH in the concentration range of 0.01–100 ng/mL, offering a novel approach for accurate food safety detection and potential application in real sample analysis.

Dual-mode colorimetric electrochemical aptamer sensor based on Au@Pd bimetallic nanoparticles for the detection of Pb(II) in edible mushrooms

Dual-mode colorimetric electrochemical aptamer sensor based on Au@Pd bimetallic nanoparticles for the detection of Pb(II) in edible mushrooms

Nanozyme-induced deep learning-assisted smartphone integrated colorimetric and fluorometric dual-mode for detection of tetracycline analogs

In this work, a colorimetric and fluorescent dual-mode probe controlled by NH2-MIL-88 B (Fe, Ni) nanozymes was developed to visually detect tetracycline antibiotics (TCs) residues quantitatively, as well as accurately distinguish the four most widely used tetracycline analogs (tetracycline (TC), chrycline (CTC), oxytetracycline (OTC), and doxycycline (DC)). Colorless substrate 3,3′,5,5′-tetramethylbenzidine (TMB) may be oxidized to blue oxidized TMB by the Fe Fenton reaction, which was catalyzed by the NH2-MIL-88 B (Fe, Ni) nanozyme with POD-like activity. The colorimetric detection system allows TCs to interact with NH2-MIL-88 B (Fe, Ni). This inhibits the production of ·OH, weakens the oxidation process of TMB, and ultimately lightens the blue color in the system by blocking the electron transfer between NH2-MIL-88 B (Fe, Ni) and H2O2. Furthermore, TCs can interact with NH2-MIL-88 B (Fe, Ni) as a result of the internal filtering effect, which causes the fluorescence intensity to decrease as TCs concentration increases. Additionally, a portable instrument that combines a smartphone sensing platform with colorimetric and fluorescent signals was created for the quick, visual quantitative detection of TCs. The colorimetric and fluorescent dual-mode nano platform enables color change, with detection limits (LODs) of 0.182 μM and 0.0668 μM for the spectrometer and smartphone sensor, respectively, based on the inhibition of fluorescence and enzyme-like activities by TCs. Overall, the colorimetric and fluorescence dual-mode sensor has good stability, high specificity, and an efficient way to eliminate false-positive issues associated with a single detection mode.

Flexible dual-mode sensor with accurate contact pressure sensing and contactless distance detection functions for robotic perception

Flexible dual-mode sensor with accurate contact pressure sensing and contactless distance detection functions for robotic perception

Development of a Microwave Sensor for Real-Time Monitoring of a Micro Direct Methanol Fuel Cell

Micro direct methanol fuel cells (μDMFCs) are a promising power source for microelectronic devices and systems. As the operating state and performance of a μDMFC is generally determined by both electrochemical polarization and methanol crossover, it is important to monitor the methanol concentration in μDMFCs. Here, we design and fabricate a microwave sensor and integrate it with a μDMFC for the online detection of methanol concentration in a nonintrusive way. The sensing area is set at the bottom of the anode chamber of a μDMFC which exhibits a maximum output power density of 28.8 mW cm−2 at 30 °C. With a square ring structure, the dual-mode microwave sensor shows a sensitivity of 9.5 MHz mol−1 L. Furthermore, the importance of methanol concentration monitoring is demonstrated in the long term. A relatively smooth methanol decline curve was obtained, which indicated a normal and stable operating status of the μDMFC. Derived from real-time recording data, fuel utilization was additionally calculated as 28.5%.

A Dual-Mode Detection Sensor Based on Nitrogen-Doped Carbon Dots for Visual Detection of Fe(III) and Ascorbic Acid via a Smartphone.

Accurately and promptly detecting Fe3+ and ascorbic acid (AA) is a crucial objective. In this study, nitrogen-doped carbon dots (N-CDs) were synthesized using a one-step hydrothermal synthesis method with 6,9-diamino-2-ethoxyacridine lactate as the precursor. The introduction of Fe3+ and AA resulted in both fluorescence (FL) quenching and enhancement of the synthesized N-CDs. The fluorescent response of the N-CDs probe to Fe3+ was observed in the concentration range of 5-20 µM and 25-50 µM, with a limit of detection (LOD) of 290 nM. Remarkably, the fluorescence of the N-CDs was recovered upon the addition of AA to the N-CDs-Fe3+ system. Using the "off-on" fluorescent N-CDs probe, a linear range of 40-90 µM was achieved with an LOD of 0.69 µM. Additionally, the feasibility of employing a smartphone equipped with an RGB Color Picker was demonstrated for the analysis of Fe3+ and AA concentrations, providing a novel visual detection method. Furthermore, the application of N-CDs in solution demonstrated considerable potential for visually detecting Fe3+ and AA. The proposed dual-mode detection sensor was found to be simple, efficient, and stable, enabling the successful determination of Fe3+ and AA in practical samples with satisfactory results.

Carbon fabric coated with nanostructured zinc oxide layers for use in triboelectric self-powered touch sensors

An environmentally friendly, low-cost, and lightweight biocompatible textile triboelectric material was made by in situ coating carbon fabric (CF) with nanostructured zinc oxide (ZnO) layers using the automatic Successive Ionic Layer Adsorption and Reaction (SILAR) method. Depending on the deposition mode, we created triboelectric CF/ZnO textiles with multidirectionally intergrown short ZnO nanorods or with arrays of ZnO nanosheets. The Raman spectra confirmed the hexagonal wurtzite structure of both types of ZnO layers and the unique a-axis texture of the nanosheets. In the developed triboelectric CF/ZnO/PET/ITO sensors, the upper tribonegative part was made of a polyethylene terephthalate film coated with a thin layer of indium-tin oxide, and the lower tribopositive part was made of CF/ZnO textile. In tests with repeated hand tapping at low frequency 1.3–13 Hz and a force of ∼ 5 N (pressure of ∼ 33 kPa), the open-circuit voltage pulses were ∼ 15 V for short ZnO nanorods and ∼ 30 V for ZnO nanosheets, their duration did not exceed a few milliseconds. Due to the nanosheet morphology of the ZnO layer, the maximum touch-induced surface charge density for the corresponding triboelectric textile (0.7 µC/m2) was almost twice than for the CF/ZnO textile with intergrown ZnO short nanorods (0.4 µC/m2). The touch sensor with ZnO nanosheets showed an output voltage of 3.6 V, a current density of 1.47 µA/cm2, and a power density of 1.8 µW/cm2. It can be used as a dual-mode sensor due to ability to recognize the hardness of objects by analyzing the output current peaks.

Deep-Learning-Assisted Discriminative Detection of Vitamin B12 and Vitamin B9 by Fluorescent MoSe2 Quantum Dots.

A facile and environmentally mindful approach for the synthesis of MoSe2 QDs was developed via the hydrothermal method from bulk MoSe2. In this, the exfoliation of MoSe2 was enhanced with the aid of an intercalation agent (KOH), which could reduce the exfoliation time and increase the exfoliation efficiency to form MoSe2 QDs. We found that MoSe2 QDs display blue emission that is suitable for different applications. This fluorescence property of MoSe2 QDs was harnessed to fabricate a dual-modal sensor for the detection of both vitamin B12 (VB12) and vitamin B9 (VB9), employing fluorescence quenching. We performed a detailed study on the fluorescence quenching mechanism of both analytes. The predominant quenching mechanism for VB12 is via Förster resonance energy transfer. In contrast, the recognition of VB9 primarily relies on the inner filter effect. We applied an emerging and captivating approach to pattern recognition, the deep-learning method, which enables machines to "learn" patterns through training, eliminating the need for explicit programming of recognition methods. This attribute endows deep-learning with immense potential in the realm of sensing data analysis. Here, analyzing the array-based sensing data, the deep-learning technique, "convolution neural networks", has achieved 93% accuracy in determining the contribution of VB12 and VB9.

A Dual-Mode Pressure and Temperature Sensor.

The emerging field of flexible tactile sensing systems, equipped with multi-physical tactile sensing capabilities, holds vast potential across diverse domains such as medical monitoring, robotics, and human-computer interaction. In response to the prevailing challenges associated with the limited integration and sensitivity of flexible tactile sensors, this paper introduces a versatile tactile sensing system capable of concurrently monitoring temperature and pressure. The temperature sensor employs carbon nanotube/graphene conductive paste as its sensitive material, while the pressure sensor integrates an ionic gel containing boron nitride as its sensitive layer. Through the application of cost-effective screen printing technology, we have successfully manufactured a flexible dual-mode sensor with exceptional performance, featuring high sensitivity (804.27 kPa-1), a broad response range (50 kPa), rapid response time (17 ms), and relaxation time (34 ms), alongside exceptional durability over 5000 cycles. Furthermore, the resistance temperature coefficient of the sensor within the temperature range of 12.5 °C to 93.7 °C is -0.17% °C-1. The designed flexible dual-mode tactile sensing system enables the real-time detection of pressure and temperature information, presenting an innovative approach to electronic skin with multi-physical tactile sensing capabilities.

A dual-mode wearable sensor with coupled ion and pressure sensing

Simultaneous monitoring of the body’s biochemical and biophysical signals via wearable devices can provide a comprehensive assessment of an individual’s health state. However, current multifunctional sensors for synchronous biochemical and biophysical sensing rely on discrete sensing units, posing a limitation in increased complexity in device assembly, signal processing, and system integration. In this study, we report a dual-mode and self-powered wearable sensor with ion and pressure-sensing capabilities by interfacing a hydrogel film with a solid ion-selective electrode. The hydrogel film can not only collect natural sweat from the skin but also offer a piezoionic response to pressure. We show that wrist pulse-induced pressure response can be incorporated into the noise of the response to sweat sodium ions, allowing for the simultaneous measurement of heart rate and sweat electrolytes. This work provides an example of simplifying the development of wearable multimode sensors through the rational design of classic electrochemical sensors.

Novel electrochemical/fluorescence dual-mode biosensor based on covalent organic framework for tetracycline detection

Excessive antibiotic residues increased the environmental damage and safety of animal products, leading to serious health threats. In this study, a dual-mode probe was developed and applied as an electrochemical/fluorescence sensor for tetracycline (TET) detection. The probe, comprising a fluorescent covalent organic framework, electroactive methylene blue, gold nanoparticles (AuNPs) and single-stranded DNA, was synthesized by self-assembly. A glassy carbon electrode was functionalized with molybdenum disulfide nanosheets, AuNPs, and aptamers. The probe exhibited fluorescent signals in solution and electrochemical signals after being specifically connected to the electrode via hybridization. In the presence of TET, the probe is be competitively expelled from the modified electrode, resulting in an increase in the fluorescent signal and a decrease in the electrochemical signal. The developed electrochemical/fluorescence dual-mode sensor enabled sensitive TET detection in the concentration range of 10 nM–10 mM, with minimum detection limits of 0.03 nM (electrochemical) and 0.05 nM (fluorescence). With its high selectivity, superior reproducibility, and excellent stability, the proposed dual-mode sensor demonstrates high reliability, and excellent application prospects for TET detection in milk and river water samples.

PDA-mediated colorimetric-fluorescence co-enhanced immunochromatography assay for the simultaneous and rapid detection of SARS-CoV-2 and HAdV

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and human adenovirus (HAdV) are highly contagious to humans and cause similar symptoms, with HAdV occurring mostly in children. Therefore, a flexible, sensitive, and accurate immunochromatographic assay (ICA) capable of recognizing SARS-CoV-2 and HAdV is urgently needed in the face of infected pediatric patients. Here, we developed a colorimetric-fluorescent co-enhanced dual-mode ICA sensor for the rapid and accurate detection of SARS-CoV-2 and HAdV. A multilayered composite nanomaterial named polydopamine@dual shell quantum dots nanobead (PDQB), which consisted of a polydopamine core (colorimetric) and a two-layered shell (fluorescent) integrated with thousands of small quantum dots, was prepared to replace conventional colorimetric nanotags (colloidal gold, AuNPs) and fluorescent nanotags (quantum nanobeads, QBs) while providing an easily readable colorimetric signal and an easily quantifiable fluorescent signal. The sensitivities of the PDQB-based ICA for SARS-CoV-2 and HAdV were 0.1 ng/mL and 104 copies/mL in colorimetric mode, respectively, and 0.005 ng/mL and 500 copies/mL in fluorescent mode, respectively. The limit of detection (LOD) of the PDQB-based ICA in colorimetric mode was 5 times lower than that of conventional AuNP-ICA. The LOD of the PDQB-based ICA in fluorescent mode was 10 times lower than that of commercial QB-ICA. This work provides a novel strategy for the detection of respiratory viruses, that realizes the co-enhancement and integration of colorimetric and fluorescent methods with high accuracy and convenience. Excitingly, the co-enhancement of colorimetric and fluorescent modes can enable the detection of respiratory viruses in different scenarios, thus guiding epidemic prevention and control.

Highly efficient persistent luminescent nanozymes-based luminescence-colorimetric dual-mode sensor for total antioxidant capacity assay

Total antioxidant capacity (TAC) is a vital parameter to assess the gross antioxidant activity in biological and food matrices. Accurate determination of TAC has become increasingly important for health monitoring and dietary guidance. Here, we report a persistent luminescent nanozyme (ZGO-Pt) based luminescence-colorimetric dual-mode sensor for selective determination of TAC. ZGO-Pt was fabricated based on ZnGa2O4:Cr nanoparticles (ZGO) with platinum nanoflower as synthetic additive. The prepared ZGO-Pt exhibited fascinating peroxidase-mimetic activity and persistent luminescence, and enabled effectively catalysis of the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB. Meanwhile, the generated oxTMB gave strong absorption at 652 nm to quench the luminescence of ZGO-Pt at 700 nm via the inner filter effect. Antioxidants could compete with the oxidable TMB or reduce oxTMB to TMB, resulting in the simultaneous variations of blue color and luminescence to provide the basis for dual-mode assay for TAC. The highly efficient catalysis of ZGO-Pt (Km, 3.12 mM for H2O2, 0.592 mM for TMB) allows the dual-mode sensor to realize precise determination of TAC with a wide linear range (0.5–200 μM and 1–300 μM for colorimetric and luminescence mode, respectively) and low limit of detection (LOD, 0.05 μM and 0.78 μM for colorimetric and luminescence mode, respectively). The developed dual-mode sensor was successfully applied to the determination of TAC in vitamin tablet, beverages and fruits. This work provides an efficient persistent luminescent nanoparticle-based nanozyme for a facile TAC assay with further vision in biosensing and food technology.

Graphene-based flexible temperature/pressure dual-mode sensor as a finger sleeve for robotic arms

The design of sensors with multiple sensing functions has become a new challenge to meet the measurement of multiple stimulus signals in people's productive lives. In this article, a sandwich type dual-mode flexible sensor is designed to achieve simultaneous detection of pressure and temperature by constructing different sensing model structures. The dual-mode flexible sensor essentially comprises graphene, melamine sponge and Ag nanoparticle ink. Graphene is coated on the melamine sponge to form a 3D conductive sponge using the dip coating method, while Ag nanoparticle ink is printed on PET to form a serpentine electrode through inkjet printing technology. The sensor has high sensitivity (1.937 × 10−4 Pa−1, R2 = 0.953), a wide operating range (from 0 to 40 kPa), speedy response time (248 ms) and remarkable stability in pressure measurement. It also shows high linearity (TCR = 1.035 × 10−3 °C−1, R2 = 0.987) from 10 to 60 °C and is pressure insensitive in temperature measurement. Experimental results show that the different sensing mechanisms and structural configurations allow the sensors to detect pressure and temperature signals independently or simultaneously without signal coupling. The fabricated sensor has applications in health monitoring, rehabilitation therapy, human-machine interaction and intelligent prosthetics.

The development of a dual-mode optical temperature sensor based on fluorescence intensity ratio and lifetime

The utilization of optical parameters is crucial for achieving accurate temperature detection, which in turn facilitates the development of new phosphors used for non-contact optical thermometers. In this study, a series of phosphors of KSrGdTeO6 (KSGT) co-doping Mn4+ and Sm3+ luminescent centers, were synthesized through high temperature solid-state reactions. Notably, the temperature-dependent emission spectra and attenuation curves of KSGT:Mn4+/Sm3+ were measured across a wide temperature range of 298–573 K. In the absence of energy transfer between Mn4+ and Sm3+, Mn4+ and Sm3+ activators can emit their characterized emissions by 405 nm excitation. With increasing temperature, the fluorescence intensity of Mn4+ ions decreases at a faster rate compared to that of Sm3+ ions as the temperature increases. Consequently, by utilizing the fluorescence intensity ratio (FIR) between the two activators Mn4+ and Sm3+, the optimal temperature sensing relative sensitivity (Sr) and absolute sensitivities of (Sa) of KSGT:Mn4+/Sm3+ were found to be 2.591 % K−1 at 298 K and 0.0246 K−1 at 573 K. Moreover, the luminescent lifetime of Mn4+ emission decreases rapidly with increasing temperature, which makes it also possible to be a lifetime-based thermometry with Sa and Sa of 2.3233 %K−1 at 448 K and 0.1444 K−1 at 398 K. The dual-mode sensing properties of KSGT:Mn4+/Sm3+ make it a highly sensitive temperature thermometer, which provides design ideas for future researchers in this field.

Enhanced braille recognition based on piezoresistive and piezoelectric dual-mode tactile sensors

Human Tactile perception can be divided into pressure perception and slip perception according to the mode of contact. At present, however, tactile sensors can not have the same good performance as human pressure and slip perception. In this paper, a piezoresistive and piezoelectric dual-mode tactile sensing scheme is proposed based on human finger tactile skin structure. PVDF polymer is used as the sensitive material in piezoelectric layer, which has good dynamic response and high sensitivity. Graphene and carbon black are used as the sensitive material in piezoresistive layer, the array process is simple and high resolution can be achieved. The fast response of piezoelectric signal can be used to segment the piezoresistive signal and improve the recognition accuracy when the tactile sensor is used for slip sensing. At the same time, the piezoelectric layer can also reflect the velocity information and direction information. In recognition method, according to the feature that the continuous tactile signal has both temporal and spatial features in the process of sliding, CNN-LSTM is proposed in this paper. The tactile sensors is integrated into the robot arm to detect 20 kinds of braille. At the same speed and the same force, the recognition rate of bimodal braille recognition is 90.58%. In addition, the model can be well recognized at different speeds and sliding directions, and the recognition rate is 84.2%. Finally, the tactile sensor is wore on the index finger of human hand, the average recognition rate of touch braille is 77.5%, which shows that the algorithm has good robustness, and the speed of recognition is twice as fast as that of the normal blind. In the future, it can be applied to blind reading, surface detection, texture identification and other fields.