Ultrasensitive Sensor Research Articles

An ultra-sensitive photoelectrochemical sensor based on ZnIn2S4/rGO nanocomposites for detection of oxytetracycline in water, food and organism samples

Residues of oxytetracycline (OTC) may cause the resistance of bacteria, and even have serious impacts on the ecosystem through the food chain. It was important to monitor OTC of low concentration for preserving human health and environmental safety. In this work, reduced graphene oxide doped ZnIn2S4 (ZnIn2S4/rGO) nanocomposites were composited by straightforward one-step solvothermal reaction. The nanocomposites had superior light absorption property and stable photocurrent response. Because rGO not only had a large specific surface area for immobilizing abundant ZnIn2S4, but also accelerated charge transfer as an electron mediator. Additionally, the oxidation potential of OTC was more negative than the valence band potential of ZnIn2S4. So, OTC can be oxidized by photogenerated holes of the ZnIn2S4 as electron donors, leading significant increase of photocurrent response. Based on this, a “signal-on” photoelectrochemical (PEC) sensor was constructed to achieve ultra-sensitive and specific detection of OTC. This sensor exhibited a wide detection range from 100 fM to 50 nM, an extremely low detection limit (61.2 fM) and excellent analytical performance in actual water, food and biological samples.

An ultrasensitive NO2 sensor based on lightweight flexible organic single crystals

There is a growing interest in developing advanced organic electronic devices as viable replacements for their inorganic counterparts. This is due to the simple and low-cost processing, versatile molecular design, and ease of control of physical properties. Organic-crystalline materials have shown superior device performance and are seen as promising candidates for future flexible electronics. Despite advancements in understanding the fundamentals governing flexibility in organic single crystals, they are rarely used in electronic devices. Herein, we fabricated a device using flexible single crystals of a Schiff base with intramolecular charge-transfer states and investigated their electrical conductivity and gas-sensing capabilities. Because the properties of charge-transfer states are influenced by their proximal environment, the device is able to selectively detect the highly toxic gas NO2 under ambient conditions with a sensitivity of 3.36 × 106 % and a detection limit of 67 ppb. The flexibility of the crystals allowed their integration into flexible substrates, expanding their potential use in the realm of wearable technology and smart electronics. This makes our findings relevant to the ecosystem and public health.

Ultrasensitive electrochemiluminescencent multivalent aptamer sensor based on energy and electron transfer dual quenching tactics.

Anefficient "on-off-on" electrochemiluminescence (ECL) aptasensor utilizing dual-mechanism quenching was constructed for detecting furanyl fentanyl (FuF). The first signal "on" state was achieved by novel dual-ligand zinc metal-organic frameworks (Zn-MOFs), which were synthesized by self-assembly reaction using zinc atom clusters as metal nodes, achieving strong and stable ECL emission. The "off" state was realized by the energy and electron quenching effect of copper-doped WO3. Specifically, in addition to the overlap of the UV-Vis spectrum, energy transfer existed between the acceptor and donor after doping copper. Therefore, copper created a "highway" for electron transfer between the donor and acceptor, which greatly improved the quenching efficiency. Simultaneously, employing multivalent aptamers as capture probes augmented the binding affinity and probability of association between aptamer and target through a synergistic multivalent effect. Consequently, the second "on" state was the ECL signal restored by introducing FuF. Benefiting from the combination of the multivalent aptamers strategy with the "on-off-on" design, the developed aptasensor showed excellent linearity (1.0 × 10-13 to 1.0 × 10-6 g/L) with a low limit of detection of 5.5 × 10-14 g/L (S/N = 3). Additionally, it demonstrates a relative standard deviation (RSD) of less than 5% and good recovery ranging from 97.6 to 102%. The proposed aptasensor presents considerable potential for rapid, sensitive, and accurate determinationof FuF.

Reversible and Ultrasensitive Detection of Nitric Oxide Using a Conductive Two-Dimensional Metal-Organic Framework.

This paper describes the use of a highly crystalline conductive 2D copper3(hexaiminobenzene)2 (Cu3(HIB)2) as an ultrasensitive (limit of detection of 1.8 part-per-billion), highly selective, reversible, and low power chemiresistive sensor for nitric oxide (NO) at room temperature. The Cu3(HIB)2-based sensors retain their sensing performance in the presence of humidity, and exhibit strong signal enhancement towards NO over other highly toxic reactive gases, such as NO2, H2S, SO2, NH3, CO, as well as CO2. Mechanistic investigations of the Cu3(HIB)2-NO interaction through spectroscopic analyses and density functional theory revealed that the Cu-bis(iminobenzosemiquinoid) moieties serve as the binding sites for NO sensing, while the Ni-bis(iminobenzosemiquinoid) MOF analog shows no noticeable response to NO. Overall, these findings provide a significant leap in the development of crystalline metal-bis(iminobenzosemiquinoid) based conductive 2D MOFs as highly sensitive, selective, and reversible sensing materials for the low-power detection of highly toxic gases.

Reversible and Ultrasensitive Detection of Nitric Oxide Using a Conductive Two‐Dimensional Metal–Organic Framework

This paper describes the use of a highly crystalline conductive 2D copper3(hexaiminobenzene)2 (Cu3(HIB)2) as an ultrasensitive (limit of detection of 1.8 part‐per‐billion), highly selective, reversible, and low power chemiresistive sensor for nitric oxide (NO) at room temperature. The Cu3(HIB)2‐based sensors retain their sensing performance in the presence of humidity, and exhibit strong signal enhancement towards NO over other highly toxic reactive gases, such as NO2, H2S, SO2, NH3, CO, as well as CO2. Mechanistic investigations of the Cu3(HIB)2‐NO interaction through spectroscopic analyses and density functional theory revealed that the Cu‐bis(iminobenzosemiquinoid) moieties serve as the binding sites for NO sensing, while the Ni‐bis(iminobenzosemiquinoid) MOF analog shows no noticeable response to NO. Overall, these findings provide a significant leap in the development of crystalline metal‐bis(iminobenzosemiquinoid) based conductive 2D MOFs as highly sensitive, selective, and reversible sensing materials for the low‐power detection of highly toxic gases.

High‐Performance Ultrasensitive Flexible Piezoelectric Thin Film Sensors via a Cost‐Effective Transfer Strategy

AbstractCurrently, reported physical or chemical methods to produce flexible perovskite thin films rely on the use of expensive single crystal substrates or large‐scale precision equipment. Here, a high‐performance ultrasensitive piezoelectric sensor via a cost‐effective strategy is developed to enable the release of lead zirconate titanate (PZT) thin films from an inexpensive mica substrate, which are subsequently transferred to a flexible polyethylene terephthalate substrate. The weak van der Waals interaction between the mica/La0.7Sr0.3MnO3 heterostructures minimizes mechanical clamping effects and provides favorable lattice and thermal matching conditions for the growth of high‐quality thin films. The transferred thin films exhibit significantly improved mechanical and functional properties, including an outstanding piezoelectric response (474.2 pm V−1) and an excellent mechanical flexibility, with a bending radius up to 1 mm. The sensor formed via the new transfer strategy exhibits a highly sensitive response to wide‐angle bending (110 mV degree−1) and small pressure changes (1.8 V kPa−1), and is successfully employed for real‐time breathing monitoring and wireless gesture recognition, thereby demonstrating its significant potential in applications related to flexible electronics.

An Ultrasensitive Temperature Sensor in 1550 nm Communication Band Based on MoO2 Coated Microstructured Optical Fiber

An Ultrasensitive Temperature Sensor in 1550 nm Communication Band Based on MoO2 Coated Microstructured Optical Fiber

Preparation of Metal Nanocluster Supraparticles for Ultrasensitive Sensing of Tetracycline Based on Multiple Interactions between a Target and Sensor.

New strategies for enhancing the fluorescence emission of metal nanoclusters (MNCs) are very crucial for the highly sensitive sensing of food hazards. In this work, we prepared MNC supraparticles (Sc-CB/AuNCs) by simultaneously introducing cucurbit[7]uril (CB[7]) and Sc3+ ions into ATT-AuNCs for the first time. The obtained supraparticles exhibited strong emission enhancement due to synergistic aggregation-induced emission enhancement and restriction of intramolecular motion effects. Notably, the fluorescence of ATT-AuNCs was enhanced by 24-fold due to the combination of CB[7] and Sc3+ ions, and the quantum yield reached 69.1%. Moreover, we found that tetracycline (TC) could bind to the Sc-CB/AuNCs through simultaneous host-guest recognition and ionic complexation, which effectively quenched the Sc-CB/AuNCs through the synergy of photoinduced electron transfer and inner filter effect. Based on the above multiple interactions between TC and Sc-CB/AuNCs, an ultrasensitive sensing method for TC was constructed with an LOD of 0.3 nM. Furthermore, a portable fluorescent gel sensor was constructed and successfully used for TC detection in honey samples. The test took only 2 min. This work not only provided a simple and effective fluorescence enhancement strategy for MNCs but also offered a novel sensing strategy, which may largely extend the potential of host-guest recognition-based sensors for food and environmental hazards.

Asymmetric and Ultrasensitive Structural Color Response in Nanochain‐Embedded Photonic Composites

AbstractMechanochromic photonic crystals, capable of altering structural colors in response to external forces, are emerging intelligent materials in various fields, such as visual sensors and anti‐counterfeiting technologies. However, conventional mechanical responses of photonic crystals mainly rely on stretching or compression, resulting in symmetric and limited mechanochromic effects due to restricted changes in lattice spacing, particularly limiting the recognition of the direction of force. Here, asymmetric and ultrasensitive structural color responses are reported in colloidal photonic composites featuring embedded one‐dimensional (1D) photonic nanochains of colloidal particles based on shear‐induced lattice orientation change. It is shown that shearing deformation tilts the photonic nanochains within the polymer matrix, leading to a remarkable and asymmetric color shift depending on shear force and observing directions. The asymmetric response encourages to develop ultrasensitive twist sensors capable of detecting subtle twisting movements as low as 0.2° and twist direction. Furthermore, by integrating magnetic and deformation orientation control, dynamic optical anti‐counterfeiting labels capable of displaying highly intricate patterns are devised. This unique shear‐induced color‐shifting mechanism expands the responsiveness of mechanochromic materials, with broad implications in many other areas, including structural health monitoring, soft robotics, and artificial skin.

Insights into Target Gas-Oxygen Interactions in Highly Sensitive Gas Sensors Using Data-Driven Methods.

In the gas-sensing mechanism of a metal-oxide-semiconductor (n-type) gas sensor, oxygen adsorption or desorption on the oxide surface leads to an increase or decrease in the resistance of the gas sensor system. Additionally, oxygen can be adsorbed again at the location where initially adsorbed oxygen reacted with the target gas. Thus, the adsorption-desorption equilibrium of the reducing gas on the oxide surface is a significant factor in determining the sensitivity and reaction rate. In particular, for ultralow-concentration gas measurements, the relative concentration of oxygen was very high. To design an ultrasensitive gas sensor, not only the reaction of the target gas but also the competing reaction between the target gas and oxygen must be considered. Although qualitative investigations of these complex relationships have been performed according to the gas concentration and flow rate, reliable quantitative results are limited. In this study, a quantitative approach was used to understand the correlation between oxygen and a target gas by applying data analysis methods. We investigated the behavior of oxygen and the target molecules depending on the gas concentration and flow rate using the parts per billion level of the acetone gas sensor. Initial response data according to various detection conditions were processed using principal component analysis and K-means clustering; as a result, four types of reaction behaviors were inferred for 15 types of reaction conditions. Furthermore, the response time, depending on the detection conditions, can be distinguished using the suggested categorization. Our investigation suggests a possibility beyond simple optimization through the data analysis of the gas-sensing results.

Ultrasensitive Acetone Gas Sensor Based on a K/Sn-Co3O4 Porous Microsphere for Noninvasive Diabetes Diagnosis.

The detection of acetone in human exhaled breath is crucial for the noninvasive diagnosis of diabetes. However, the direct and reliable detection of acetone in exhaled breath with high humidity at the parts per billion level remains a great challenge. Here, an ultrasensitive acetone gas sensor based on a K/Sn-Co3O4 porous microsphere was reported. The sensor demonstrates a detection limit of up to 100 ppb, along with excellent repeatability and selectivity. Remarkably, without the removal of water vapor from exhaled breath, the sensor can accurately distinguish diabetic patients and healthy individuals according to the difference in acetone concentrations, demonstrating its great potential for diabetes diagnosis. The enhanced sensitivity of the sensor is attributed to the increased oxygen adsorption on the material surface due to K/Sn codoping and the stronger coadsorption of Sn-K atoms to acetone molecules. These findings shed light on the mechanisms underlying the sensor's improved performance.

Merging bound states in the continuum-driven ultrahigh sensing figure of merit in all-dielectric metasurfaces.

Radiation-free photonic bound states in the continuum (BIC) in metasurfaces allow ultrahigh quality (Q) factor and strongly confined mode volume, which are extremely advantageous in the development of ultrasensitive microcavity sensors. However, the conventional isolated BICs are susceptible to failure due to symmetry breaking caused by fabrication imperfection and nonzero incident angle. Here, we propose a silicon nitride-based metasurface with multiple BIC merging. The merging of accidental BIC and symmetry-protected BIC can increase the Q-factor near the Brillouin zone Γ point and thus robustly induces a figure of merit (FOM) of refractive index sensing at small incident angles two orders of magnitude higher than that in isolated BIC configuration. Specifically, the FOM in merging BIC reaches 108 at a 2° incident angle. The BIC merging can be universally achieved in square lattices with C4 symmetry, and slower decay of Q-factor and higher FOM can further occur in hexagonal lattices benefiting from higher-order topological charges. The advantage of merging BIC is also maintained when considering in-plane and out-of-plane symmetry breaking. These results offer a unique design path for high-performance metasurface sensors and can be extended to other high-Q applications such as low-threshold lasers, nonlinear frequency conversion, and low-loss waveguides.

Ultrasensitive Room Temperature Formaldehyde Sensors Based on F Doped ZnO Nanostructures Activated by UV Light.

It is urgent to develop an ultrasensitive formaldehyde (HCHO) sensor that can operate at room temperature and has a low detection limit. Metal oxide semiconductors are excellent gas sensitive materials. Therefore, in this paper, we present the synthesis of fluorine (F) doped zinc oxide (ZnO) porous nanomaterials through a straightforward one-pot method with the optimization of F doping levels to achieve the detection of low concentrations of HCHO under UV light at room temperature. Under 375 nm UV light, the sensor exhibits a response value of 386% to 10 ppm of HCHO, which is 2.6 times higher than that of pure ZnO, and its detection limit is as low as 75 ppb. It has excellent selectivity, stability, and moisture resistance, which can meet the requirements of HCHO detection in daily life. Analysis reveals that doping ZnO with F not only increases the material's specific surface area but also introduces active sites. Furthermore, it alters the state of HCHO on the material's surface from physical adsorption to chemical adsorption. The above reasons together enhance the adsorption of HCHO on the gas sensitive material, thereby improving its gas sensitivity performance. Overall, this work demonstrates that F-doped ZnO is a potential material for ultrasensitive HCHO sensors and provides insights into the interpretation of the effect of doping on the gas sensitivity properties of materials.

Modulation of ZrO2-Ag2O-MoO3 nanocomposite into ultrasensitive hydrazine electrochemical sensor for environmental remediation

Herein, a facile single-step wet chemical approach was executed for the composition of semiconductor ternary metal oxides (TMO) i.e., ZrO2-Ag2O-MoO3 nanocomposite (NC) in an alkaline medium. For structural as well as morphological elucidation, the calcined nanocomposite was characterized through ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), powdered X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) analysis. Later, the glassy carbon electrode (GCE) was modified into a highly responsive as well as selective hydrazine (HDZN) electrochemical probe (ZrO2-Ag2O-MoO3-NC/PEDOT:PSS/GCE) by the fabrication of thin layered ZrO2-Ag2O-MoO3 NC onto GCE facilitated by 5 % PEDOT:PSS as conducting polymer binder. While examining the analytical parameters through novel current–potential (I-V) electrochemical approach, for the first time, the newly designed electrochemical probe, as selective hydrazine sensor, happened to own the low detection limit (LOD; 0.028 pM) with greater sensitivity (33.86 μAμM−1cm−2) and broad linear dynamic range (LDR; 0.1 M–1.0 nM) in addition to coefficient of correlation (r)/r2 square (r = 0.9941, r2 = 0.9882) and low limit of quantification (LOQ; 0.093 pM). Furthermore, reproducibility as well as prolonged stability of this newly proposed probe towards hydrazine were also assessed and found to be reliable in short response time. Hence, this work presents an inaugural report about the sensing of HDZN through the newly designed non reported ZrO2-Ag2O-MoO3-NC/PEDOT:PSS/GCE via an economical as well as novel electrochemical, current–potential (I-V), approach. Additionally, this proposed method is equally responsive towards both environmental and extracted real samples analysis on large scale.

Resonance scattering generated by rotating bodies

Abstract The scattering of rotating bodies to a polarized plane wave, including the dielectric cylinder and sphere, is studied. The resonance caused by rotation is emphasized. Numerical results prove that the resonance scattering caused by rotation can be realized in the optical range. It is sensitive to the rotation dimensionless parameter γ. The internal Mie mode corresponding to the electromagnetic field intensity changes with γ, and the resonant mode appears when the particle rotates at a specific speed. Moreover, the resonant mode changes with γ. It causes resonance scattering to appear in the same particle at different speeds. Inside particles, resonant rings are composed of a series of array points and are determined by γ. Under resonance conditions, the energy near the rotating cylinder is consistent with its rotation direction. In contrast, the direction of energy flow in the rotating sphere model is opposite to the direction of particle rotation. This work provides a novel idea for the design of ultra-sensitive sensors and resonators. It has promising applications in optical communication, optical microscopy, and optical signal processing.

Nano‐Patterned CuO Nanowire Nanogap Hydrogen Gas Sensor with Voids

AbstractHydrogen (H2) is increasingly employed in industrial applications, such as developing hydrogen fuel cells for vehicles and power plants. However, H2 explodes at a concentration limit of 4%, necessitating the development of ultrasensitive hydrogen sensors capable of early‐stage detection of hydrogen leaks. In this study, nano‐patterned polycrystalline cupric oxide (CuO) nanowire array nanogap gas sensors with voids are fabricated using electron‐beam lithography and ex situ oxidization by annealing, which could detect 5 ppb H2 and show response and recovery times of less than 10 s without a baseline shift. Combining a pre‐H2 annealing process in Ar/H2 for Cu nanowires and a low‐rate oxidation process enhances the crystallinity of CuO nanowires, facilitating the preparation of polycrystalline CuO nanowires with voids, which is a significantly practical approach for the improvements of gas sensing properties. Response and recovery times of <10 s can be obtained for a gap separation of ≈30 nm. These improvements are discussed based on a high electric field of ≈1.3 MV cm−1. The relationship between the normalized response and H2 concentration is discussed based on the power law. This paper presents highly reliable and fast H2 sensors without a baseline shift to meet the demands of the hydrogen industry.

Ultrasensitive and Stretchable Strain Sensors Based on Laser-Induced Graphene With ZnO Nanoparticles.

Laser-induced graphene (LIG) has attracted considerable attention for its use in flexible and stretchable sensors, owing to its electrical/mechanical properties and scalable fabrication processes. Although laser scanning facilitates the formation of LIG and its strain sensor, the strain-sensing sensitivity enhancement of LIG remains limited by the material's properties and structural design. In this study, we demonstrate a substantial improvement in sensitivity that was achieved by fabricating a LIG using ZnO nanoparticle (NP)-assisted photothermal enhancement. The results show that ZnO NPs selectively reduce the threshold fluence needed to convert polyimide (PI) into LIG. By transferring the LIG formed on PI to poly(dimethylsiloxane), we fabricate a stretchable strain sensor with ultrahigh sensitivity and a gauge factor of 1214 at 10% strain, which is approximately 60 times higher than the gauge factor without ZnO NPs. Using the selective graphenization properties of LIG, a flexible, dual-sided integrated sensor sheet that is equipped with flexible strain and ultraviolet (UV) sensors is demonstrated. This sheet enables simultaneous monitoring of UV intensity and joint bending angles of sports wearable devices. We validated the developed sensors by attaching them to a runner's body to monitor and simulate forefoot and heel strikes, demonstrating the sensor's ultrahigh sensitivity and long-term stability without the need for a camera. These findings highlight the potential of the proposed method for developing multifunctional sensor applications with ultrahigh sensitivity and stability.

4D printable and recyclable two-way shape memory butadiene rubber as ultrasensitive, longer-lasting, and lower-cost fire warning sensors

Fire sensors have been widely used for early warning of fire in confined space in buildings. However, the currently used fire sensors cannot achieve high sensitivity, long service life, and low cost at the same time. In this work, 4D printable and recyclable two-way shape memory polymers (2 W-SMPs), which are made of a butadiene rubber (P-80), have been designed for fire warning sensor with ultra-high sensitivity, longer-lasting service life, and lower-cost. The P-80 displays a high reversible actuation with a crystallization-induced elongation (CIE) and a melting-induced contraction (MIC) as large as 99.3 % and 90.4 %, respectively. The designed fire sensor exhibits an average respond time as fast as 0.2 s and can be reused for more than 20 times. The mechanism for the excellent two-way shape memory effect and recyclability of the P-80 has been revealed. The entropy and enthalpy increase is the primary reasons for the large MIC in P-80, which contributes to 76.1 % and 23.9 % of MIC, respectively. The recyclability of the P-80 is caused by the reconstruction of C = C bond via olefin metathesis reaction, resulting in the dynamic topology reformation. This work provides a guideline for development of 4D printable and recyclable 2 W-SMPs.

Tetrahedral DNA nanostructures-assisted electrochemical assay for detecting circulating tumor DNA by combining a masking tactic with 3D-hybridization chain reactions

Circulating tumor DNA (ctDNA) is a remarkable noninvasive tumor marker that plays a crucial role in tumor diagnosis, prognosis and treatment. However, detecting low-abundance ctDNA from a substantial amount of nucleic acids originating from healthy cells is challenging. Herein, we proposed a tetrahedral DNA nanostructures (TDNs)-assisted electrochemical biosensor for ctDNA detection. This biosensor combines a masking tactic with 3D-hybridization chain reactions. Masking hairpins (MHs) were initially introduced to prevent interference from wild-type (WT) DNA. Then, the initiator sequence was transferred to the electrode surface modified with TDNs by the target ctDNA. The initiator sequence triggers the 3D self-assembly of hairpin strands, leading to the formation of DNA networks or even DNA hydrogels (long reaction time). This process generates numerous evenly distributed biotin molecules that can bind to streptavidin peroxidase to considerably amplify the signal. This method exhibits high sensitivity (the minimum concentration for detecting ctDNA is 1 aM, which corresponds to 60 ctDNA molecules in 100 μl sample) and excellent specificity (single mismatch). More importantly, this high-performance sensor can detect ctDNA with other mutation sites and their mixtures by modifying the corresponding capture probes on the TDNs. Furthermore, this ultrasensitive sensor effectively detects target ctDNA (0.001%) at high levels of WT DNA and in complex matrices such as serum. These findings suggest that the sensor has promising potential as a noninvasive tool for early tumor diagnosis.

Interfacially Fabricated Covalent Organic Framework Membranes for Film-Based Fluorescence Humidity Sensors and Moisture Driven Actuators.

Rapid, on-site measurement of ppm-level humidity in real time remains a challenge. In this work, we fabricated a few micrometer thick, β-ketoenamine-linked covalent organic framework (COF) membrane via interfacially confined condensation of 1,3,5-tris-(4-aminophenyl)triazine (TTA) with 1,3,5-tri-formylphloroglucinol (TP). Based on the super-sensitive and reversible response of the COF membrane to water vapor, we developed a high-performance film-based fluorescence humidity sensor, depicting unprecedented detection limit of 0.005 ppm, fast response/recovery (2.2 s/2.0 s), and a detection range from 0.005 to 100 ppm. Remarkably, more than 7,000-time continuous tests showed no observable change in the performance of the sensor. The applicability of the sensor was verified by on-site and real-time monitoring of humidity in a glovebox. The superior performance of the sensor was ascribed to the highly porous structure and unique affinity of the COF membrane to water molecules as they enable fast mass transfer and efficient utilization of the water binding sites. Moreover, based on the remarkable moisture driven deformation of the COF membrane and its composition with the known polyimide films, some conceptual actuators were created. This study brings new ideas to the design of ultra-sensitive film-based fluorescent sensors (FFSs) and high-performance actuators.