Sensor Surface Research Articles

3D gold dendrite and reduced graphene oxide-chitosan nanocomposite-based immunosensor for carcinoembryonic antigen detection in clinical settings

Electrodeposited metallic nanostructures with tree-like hierarchical morphology, often termed metallic nanodendrites (MNDs), are gradually gaining interest in the development of electrochemical biosensors. Noble metal nanodendrites exhibit exceptional conductive and electrocatalytic activity. In this work, we have reported a robust method of electrodeposition of gold nanodendrites (AuND). In order to achieve this, we first optimized the number of gold nanoparticles (AuNP) as seed molecules on the sensor surface and observed that “less seed” resulted in enhanced growth of AuND. Thereafter, AuNP/AuND was used as an excellent surface in conjugation with reduced graphene oxide (rGO), chitosan (CS), and an Anti-CEA antibody for electrochemical detection of carcinoembryonic antigen (CEA), a clinically established cancer biomarker. The developed immunosensor, glassy carbon electrode/gold nanoparticle/gold nanodendrites/chitosan-reduced graphene oxide/Anti-CEA antibody (GCE/AuNP/AuND/CS-rGO/Anti-CEA), is capable of detecting the biomarker in the linear dynamic range (LDR) of 1 × 10−13 to 1 × 10−8 g/mL, which covers the normal as well as clinical range of CEA in serum with a limit of detection (LOD) of 2.23 (±0.03) x 10−14 g/mL. Real sample analysis was performed in serum with a recovery rate ranging between 90 and 99.20 %, demonstrating the feasibility of the sensors for CEA monitoring.

Three-dimensional surface strain sensor based on PDMS/LIG composite film with adjustable electromechanical performance

Flexible strain sensors play a crucial role in health monitoring, smart wearable devices, and human–machine interaction. Three-dimensional surface evaluation methods for strain sensors offer advantages by being closer to actual strain, featuring a larger working range, and being more suitable for multidirectional strain. In this study, a three-dimensional (3D) surface strain sensor based on polydimethylsiloxane/laser-induced graphene (PDMS/LIG) composite films has been developed. The electromechanical properties of this sensor, encompassing 3D strain range and sensitivity, can be adjusted by manipulating laser parameters and LIG patterns. The key to attaining these specific characteristics lies in the intentional design of crack types and orientations on the sensor's surface. Remarkably, the line-vertical (LV) sensor exhibits outstanding sensitivity with a GF of 211.3. The line-parallel (LP) sensor achieves a GF of 115.1. Additionally, it demonstrates a stretching range of 25% and maintains stable performance over an extensive number of strain/release test cycles (more than 3000 cycles). With these advantages, the 3D strain sensor can not only be applied in human activity monitoring but also monitoring pressure within microchannels in microfluidic chips, suggesting promising applications in the health and medical fields.

Modeling and analysis of discrete particle detection in wide-field surface plasmon resonance microscopy

Wide-field surface plasmon resonance microscopy (WF-SPRM), based on Kretschmann’s configuration, is a powerful technique for detecting nano-objects in solution. In this study, key parameters for building a highly sensitive WF-SPRM are optimized, including laser wavelength, prism refractive index, numerical aperture of the objective, and gold layer thickness. A medium model describes the surface plasmon resonance (SPR) sensor principle, treating molecules bound on the sensor surface as an effective medium with an effective refractive index and thickness. On the other hand, the SPR discrete particle model is introduced to describe the detection principle for discrete particles. Theoretical, numerical, and experimental analyses are conducted, and the calculated intensity profiles of single and double nanoparticles from the discrete particle model describe the experimental profiles well. Furthermore, the influence of coating the gold layer with a dielectric layer on the SPR sensitivity is investigated for varying refractive indices.

Molecularly imprinted electrochemical biosensor for thrombin detection by comparing different monomers.

Aim: Investigating molecularly imprinted polymers (MIPs) in electrochemical biosensors for thrombin detection, an essential protein biomarker. Comparing different monomers to showcase distinct sensitivity, specificity and stability advantages. Materials & methods: Dopamine, thionine and ethanolamine serve as monomers for MIP synthesis. Electrochemical methods and atomic force microscopy characterize sensor surfaces. Performance is evaluated, emphasizing monomer-specific electrochemical responses. Results: Monomer-specific electrochemical responses highlight dopamine's superior signal change and stability over 30days. Notably, a low 5pg/ml limit of detection, a broad linear range (5-200pg/ml) and enhanced selectivity against interferents are observed. Conclusion: Dopamine-based MIPs show promise for high-performance electrochemical thrombin biosensors, suggesting significant applications in clinical diagnostics.

Unsteady Compressed Williamson Fluid Flow Behavior under the Influence of a Fixed Magnetic Field (Numerical Study)

A numerical investigation is conducted into a two-dimensional mathematical model of magnetized unsteady incompressible Williamson fluid flow over a sensor surface with fixed thermal conductivity and external squeezing accompanied by viscous dissipation effect. Based on the flow geometry under consideration, the current flow model was created. The momentum equation takes into consideration the magnetic field when describing the impact of Lorentz forces on flow behavior. The energy equation takes varying thermal conductivity into account while calculating heat transmission. The extremely complex nonlinear, unstable governing flow equations for the now under investigation are coupled in nature. Due to the inability of analytical or direct methods, the Runge-Kutta scheme (RK-4) via similarity transformations approach is used to tackle the physical problem under consideration. The physical behavior of various control factors on the flow phenomena is described using graphs and tables. For increasing values of the Weissenberg parameter and the permeable velocity parameter, the temperature boundary layer thickens. As the permeable velocity parameter and squeezed flow index increased, the velocity profile shrank. The velocity profile grows as the magnetic number rises. Squeezed flow magnifying increases the Nusselt number's magnitude. Furthermore, the extremely complex nonlinear complex equations that arise in fluid flow issues are quickly solved by RK-4. The current findings in this article closely align with the findings that have been reported in the literature.

Natural convective and Cattaneo–Christov model for couple stress nanofluid at the middle of the squeezed channel with sensor surface

The aim of this work is to present a natural convective and squeezing flow model of two-dimensional couple stress nanofluid which is flowing on the sensory surface with variable fluid viscosity. The fluid flowing on a microcantilever sensory surface and squeezing is happening at free stream. The sensor is also useful to detect the movement of fluid and the variations in thermal and solutal rates. The Cattaneo–Christov model is adopted along with nanoparticle and chemical reaction to explore the transmission of heat and mass rates. The analysis of heat transmission in non-Newtonian couple stress fluid flowing on squeezed sensory surface by using the Cattaneo–Christov heat conduction model has various industrial and scientific applications including the polymer processing, wastewater treatment, chemical reactors, biomedical flows, cooling and heating processes in industries, heat exchangers, microfluidics, oil and gas industries. All the assumptions are applied in the basic governing laws laws and then we get the model of the partial differential equations. The governing model of equations is transmuted into ordinary differential equations form via the transformations and then the numerical results of these ODE’s are examined with a well-defined numerical technique “Shooting Method”. For higher inputs of couple stress, squeezing index and permeability velocity, the fluid’s internal velocity decreases. Because of the Prandtl number and thermal relaxation coefficient, the heat transfer mechanism slows down. Mass transfer increases for greater inputs of the thermal diffusivity coefficient and decreases due to concentration relaxation. Further, the numerical dependency of emerging parameters on the skin friction is illustrated in tabular form. The parametric effects on the model (velocity, temperature and concentration) are introduced using numerical values shown in the table.

PRACTICAL APPLICATION OF A FRACTIONAL FACTOR EXPERIMENT FOR ASSESSING THE INFLUENCE OF FACTORS ON THE SENSITIVITY OF A CAPACITIVE HUMIDITY SENSOR OF A TWO-LAYER STRUCTURE

The work uses a fractional factorial experiment in order to reduce the number of experiments. Capacitive humidity sensors of a two-layer structure made on a sitall substrate served as experimental samples. Hygroscopic salt NaCl was used to create a moisture-sensitive layer that would perform the function of a dielectric. Solutions of this salt with concentrations of 0,89 mol/l and 5,33 mol/l were applied by spraying on the surface of capacitive humidity sensors with thicknesses of 5,0 μm and 10.0 μm. In order to prevent the drop of the dew point, a protective layer was created − it is a moisture-absorbing polymethyl methacrylate film with thicknesses of 40 μm and 80 μm. According to the Cochrane’s test, it is proved that the fractional factorial experiment is reproducible. Using regression analysis, a quantitative assessment of the influence of factors on the sensitivity of the capacitive humidity sensor of the two-layer structure was carried out. Based on the developed regression equation, it was established that the concentration of the NaCl salt solution significantly affects the sensitivity of the capacitive humidity sensor of the two-layer structure. Significant coefficients of the regression equation were determined using the Student's test. Adequacy of the adjusted regression equation to the results of the factorial experiment was proved using Fisher's test. Based on the regression equation on the scale of real factors, which contributes to the optimization of the humidity sensor manufacturing parameters, it was established that the sensitivity of the capacitive humidity sensor of the two-layer structure depends on such factors as the thickness of the protective layer and the concentration of the NaCl salt solution. However, the sensitivity of the capacitive humidity sensor of the two-layer structure is significantly affected by the concentration of the hygroscopic NaCl salt solution. The highest sensitivity of 2,46 nF/% is provided with the following optimal parameters of the manufacturing process of the capacitive humidity sensor of the two-layer structure: the concentration of the hygroscopic NaCl salt solution is 5,33 mol/l, the thickness of the protective layer is 80 μm. Considering that the thickness of the moisture-sensitive layer does not significantly affect the sensitivity of the capacitive humidity sensor, the thickness of this layer can be taken in the range from 5,0 μm to 10,0 μm.

Novel Approach for the Immobilization of Cellobiose Dehydrogenase in PEDOT:PSS Conductive Layer on Planar Gold Electrodes

Third-generation biosensors use enzymes capable of direct electron transfer (DET) to the sensor surface. They are of interest for continuous glucose monitoring in blood or interstitial fluid, but they are rarely investigated. One reason is the hindered DET of the enzymes to the metallic electrodes. In this publication, a novel method for the immobilization of cellobiose dehydrogenase (CDH) DET enzymes employing conductive poly(3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) inks and a protective polyethylene glycol dimethacrylate (PEG-DMA) hydrogel layer on gold electrodes is reported. This layer stack showed a glucose-specific current response for voltages between −0.2 and 0.4 V in physiological PBS buffer, and enabled interference-less sensing in a solution of acetaminophen, ascorbic acid, dopamine, and uric acid at 0 V. A Michaelis–Menten fit led to a maximum current density (Imax) of 257 ± 7.9 nA/mm2 and a Michaelis–Menten constant (Km) of 28.4 ± 2.2 mM, with a dynamic range of 0.1–20 mM glucose and a limit of detection of 0.1 mM. After 16 h of continuous measurement of 20 mM glucose, the signal decreased to 60% of its initial value. Storage stability was successfully verified until up to 10 days. In summary, this paper shows a simplified approach for the fabrication of third-generation biosensors using CDH-PEDOT:PSS and PEG-DMA hydrogel inks.

ZnO/RuO2 nanocomposite modified glassy carbon electrode as sensor for determination of exercise-induced myoglobin biomarkers

A novel ZnO/RuO2 nanocomposite modified electrochemical sensor was developed for the rapid and ultrasensitive quantification of Mb biomarkers related to exercise-induced muscle injury. The sensor demonstrated a wide linear range from 0.1 to 100 nM along with an ultra-low detection limit down to 30 pM Mb under optimal conditions. A rapid response time below 10 s was achieved. The sensor surface showed excellent electrocatalytic activities towards Mb oxidation, attributing to the synergistic properties of the mixed transition metal oxide interface. Systematic investigations revealed reversible electrochemical behavior and diffusion controlled electron transfer kinetics governing the oxidation process. Negligible interferences were observed against potentially co-existing species. Spike-recovery experiments using real human serum samples yielded excellent recovery rates between 97.3% and 103.1%. Significantly enhanced post-exercise Mb levels up to 8.2 nM were successfully detected in clinical specimens, confirming the sensor's ability to sensitively monitor muscular trauma via minimally invasive blood tests. The sensor provided tangible analytical advantages over previous Mb detectors and immunoassays in terms of detection limit, sensitivity, simplicity and cost-effectiveness. Findings validate the feasible adoption of the sensor technology to facilitate prompt diagnosis of exercise-induced myoglobinemia in sports medicine clinics.

Utilizing fab fragment-conjugated surface plasmon resonance-based biosensor for detection of Salmonella Enteritidis.

Although antibodies, a key element of biorecognition, are frequently used as biosensor probes, the use of these large molecules can lead to adverse effects. Fab fragments can be reduced to allow proper antigen-binding orientation via thiol groups containing Fab sites that can directly penetrate Au sites chemically. In this study, the ability of the surface plasmon resonance (SPR) sensor to detect Salmonella was studied. Tris(2-carboxyethyl)phosphine was used as a reducing agent to obtain half antibody fragments. Sensor surface was immobilized with antibody, and bacteria suspensions were injected from low to high concentrations. Response units were changed by binding first reduced antibody fragments, then bacteria. The biosensor was able to determine the bacterial concentrations between 103 and 108 CFU/mL. Based on these results, the half antibody fragmentation method can be generalized for faster, label-free, sensitive, and selective detection of other bacteria species.

Ultrasensitive, Label-Free Voltammetric Detection of Dibutyl Phthalate Based on Poly-l-lysine/poly(3,4-ethylenedioxythiophene)-porous Graphene Nanocomposite and Molecularly Imprinted Polymers.

Development of an efficient technique for accurate and sensitive dibutyl phthalate (DBP) determination is crucial for food safety and environment protection. An ultrasensitive molecularly imprinted polymers (MIP) voltammetric sensor was herein engineered for the specific determination of DBP using poly-l-lysine/poly(3,4-ethylenedioxythiophene)/porous graphene nanocomposite (PLL/PEDOT-PG) and poly(o-phenylenediamine)-imprinted film as a label-free and sensing platform. Fabrication of PEDOT-PG nanocomposites was achieved through a simple liquid-liquid interfacial polymerization. Subsequently, poly-l-lysine (PLL) functionalization was employed to enhance the dispersibility and stability of the prepared PEDOT-PG, as well as promote its adhesion on the sensor surface. In the presence of DBP, the imprinted poly(o-phenylenediamine) film was formed on the surface of PLL/PEDOT-PG. Investigation of the physical properties and electrochemical behavior of the MIP/PLL/PEDOT-PG indicates that the incorporation of PG into PEDOT, with PLL uniformly wrapping its surface, significantly enhanced conductivity, carrier mobility, stability, and provided a larger surface area for specific recognition sites. Under optimal experimental conditions, the electrochemical response exhibited a linear relationship with a logarithm of DBP concentration within the range of 1 fM to 5 µM, with the detection limit as low as 0.88 fM. The method demonstrated exceptional stability and repeatability and has been successfully applied to quantify DBP in plastic packaging materials.

Core-Shell Nanocables Decorated with Carbon Spherical Shells and Silver Nanoparticles for Sensing Ethinylestradiol Hormone in Water Sources and Pills.

The selective, rapid detection of low levels of hormones in drinking water and foodstuffs requires materials suitable for inexpensive sensing platforms. We report on core-shell Ag@C nanocables (NCs) decorated with carbon spherical shells (CSSs) and silver nanoparticles (AgNPs) by using a hydrothermal green approach. Sensors were fabricated with homogeneous, porous films on screen-printed electrodes, which comprised a 115 nm silver core covered by a 122 nm thick carbon layer and CSSs with 168 nm in diameter. NCs and CSSs were also decorated with 10-25 nm AgNPs. The NC/CSS/AgNP sensor was used to detect ethinylestradiol using square wave voltammetry in 0.1 M phosphate buffer (pH 7.0) over the 1.0-10.0 μM linear range with a detection limit of 0.76 μM. The sensor was then applied to detect ethinylestradiol in tap water samples and a contraceptive pill with recovery percentages between 93 and 101%. The high performance in terms of sensitivity and selectivity for hormones is attributed to the synergy between the carbon nanomaterials and AgNPs, which not only increased the sensor surface area and provided sites for electron exchange but also imparted an increased surface area.

Efficient detection of 45 ppb ammonia at room temperature using Ni-doped CeO2 octahedral nanostructures

To meet the requirements in air quality monitors for the public and industrial safety, sensors are required that can selectively detect the concentration of gaseous pollutants down to the parts per million (ppm) and ppb (parts per billion) levels. Herein, we report a remarkable NH3 sensor using Ni-doped CeO2 octahedral nanostructure which efficiently detects NH3 as low as 45 ppb at room temperature. The Ni-doped CeO2 sensor exhibits the maximum response of 42 towards 225 ppm NH3, which is ten-fold higher than pure CeO2. The improved sensing performance is caused by the enhancement of oxygen vacancy, bandgap narrowing, and redox property of CeO2 caused by Ni doping. Density functional theory confirms that O vacancy with Ni at Ce site (VONiCe) augments the sensing capabilities. The Bader charge analysis predicts the amount of charge transfer (0.04 e) between the Ni-CeO2 surface and the NH3 molecule. As well, the high negative adsorption energy (≈750 meV) and lowest distance (1.40 Å) of the NH3 molecule from the sensor surface lowers the detection limit. The present work enlightens the fabrication of sensing elements through defect engineering for ultra-trace detection of NH3 to be useful further in the field of sensor applications.

The effect of probe density coverage on the detection of oenological tannins in Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) experiments.

Polyphenols are a group of compounds found in grapes, musts, and wines. Their levels are crucial for grape ripening, proper must fermentation, and final wine characteristics. Standard chemical analysis is commonly used to detect these compounds, but it is costly, time-consuming, and requires specialized laboratories and operators. To address this, this study explores a functionalized acoustic sensor for detecting oenological polyphenols. The method involves utilizing a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) to detect the target analyte by using a gelatin-based probe layer. The sensor is functionalized by optimizing the probe coverage density to maximize its performance. This is achieved by using 12-mercaptododecanoic acid (12-MCA) to immobilize the probe onto the gold sensor surface, and dithiothreitol (DTT) as a reducing and competitive binding agent. The concentration of 12-MCA and DTT in the solutions is varied to control the probe density. QCM-D measurements demonstrates that the probe density can be effectively adjusted using this approach, ranging from 0.2×1013 molecules cm-2 to 2×1013 molecules cm-2 . This study also investigates the interaction between the probe and tannins, confirming the sensor ability to detect them. Interestingly, the lower probe coverage achieves higher detection signals when normalized to probe immobilization signals. Moreover, significant changes in mechanical properties of the functionalization layer are observed after the interaction with samples. The combination of QCM-D with gelatin functionalization holds great promise for future applications in the wine industry. It offers real-time monitoring capabilities, requires minimal sample preparation, and provides high sensitivity for quality control purposes. This article is protected by copyright. All rights reserved.

A Review of Development of Chemical Sensors

A comprehensive summary of the most recentre search concentrating on chemical sensors utilizing nano tubes,Nano rods,Nano belts, and nano wiresis given in this article. The experimental principle, sensor device design,sensor mechanism, and multiple significant conclusionsreceivethevastmajorityofourattention.Thefollowingfoursectionsprovide additional information on the creation of chemical sensors based on nanostructured materials: nanotube sensors, Nano rod sensors, Nano belt sensors and Nano wire sensors. Weconcludethisreviewwithpersonalperspectivesonthedirectionstowardswhichfuture research on nanostructured sensors might be directed. At ambient temperature, the nanotube sensors show a far faster response time and a significantly higher sensitivity than the current solid-state sensors. Reversibility of the sensor can be obtained by heating it to a high temperature or by slowly recovering under ambient conditions. Over the past decade, synthesized nanomaterial’s, such as carbon nanotube, nanoparticle, quantum dot, and nanowire, have already made breakthroughs in various fields, including biomedical sensors. Enormous surface area-to-volume ratio of the Nano materials increases sensitivity dramatically compared with macro-sized material. Herein we present a comprehensive review about the working principle and fabrication process of nanowire sensors. Then anotube sensor sex hibit a fast response and asubstantially higher sensitivity than thatofexistingsolid-statesensorsatroomtemperature.Sensorreversibilityisachievedbyslow recovery under ambient conditions or by heating to high temperatures.Synthesized Nano materials, including carbon nanotubes, nanoparticles, quantum dots, and nanowires, have already achieved significant advances in a number of sectors, including biological sensors, during the last ten years. When compared to macro-sized material, the nanoparticles' enormous surface area-to-volume ratio significantly boosts sensitivity. We provide a thorough overview of the fabrication process and operating principle of the nanowire sensor here. Recent advances including self-powering, reusability, sensitivity in high ionic strength solvent,andlong-term stabilityaresurveyedandhighlightedas well.Nanowire isexpectedtolead significant improvement of biomedical sensor in the near future.Advantages and disadvantages of the sensors are provided along with brief descriptions. An electrical device that monitors changes in a quantity, such as voltage, temperature, pressure, or humidity, is called a sensor. As a result, classification is done according to the attribute that a sensor measures. A temperature sensor detects even the smallest variations in its environment or shifts in temperature, such as hot or cold weather. Microelectronic manufacturing techniques have been used to manufacture chemical and electrochemical sensors.Thedevelopment ofchemical sensors has been spurred forward by the recentadvancesinmicromachingtechnology.Chemicalsensorresearchhasadvancedthanksto micro machining methods like sacrificiallayers, plasmaetching, andchemicalanisotropicetching. These methods enable the creation of low mass, low power driven devices as well as controlled working conditions and temperature. Researchersbecameinterestedinthesecarefullychoseninvitronanostructureswhentheywere combined with nanomaterials because the improved properties of these nanostructures led to advances inthe analytical performance of chemical and biosensors. Thisstudycoversthe latest advancements in recognition elements that are integrated in to chemical sensors and bio sensors used in the food, medical, and environmental domains. These elements include both traditional ones like enzymes and antibodies as well as more modern ones like aptomers and phages.Cyclic voltammetry and electron microscopy are frequently used in the characterization of chemically modified sensors and biosensors because they enable the confirmation of electrode mechanisms and surface morphologies. X-ray photoelectron spectroscopy (XPS), among other methods, is a special tool for obtaining information on the sensor surface that is qualitative, quantitative/semi-quantitative, and speciation-related. However, XPS is still not widely applied in this industry. The purpose of this work is to review a few selected studies that demonstrate how wellXPSperformswhencharacterizingthetopsurfacelayersofbiosensorsandchemically Modified sensors. The reader is provided with the necessary background information in a brief introduction to X-ray photoelectron spectroscopy. The use of XPS to characterize sensors appropriate for environmental and food analysis is highlighted.

Setups for eliminating static charge of the ATLAS18 strip sensors

Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration to beable to track charged particles produced at the High-Luminosity LHC, started in 2020 and is expected tocontinue till 2028. The ITk detector will include 18,000 highly segmented and radiation hard n+-in-psilicon strip sensors (ATLAS18), which are being manufactured by Hamamatsu Photonics. Mechanical and electrical characteristics of produced sensors are measured upon their delivery at several institutes participating in a complex Quality Control (QC) program. The QC tests performed on each individual sensor check the overall integrity and quality of the sensor.During the QC testing of ATLAS18 strip sensors, an increased number of sensors thatfailed the electrical tests was observed. In particular, IV measurements indicated an early breakdown,while large areas containing several tens or hundreds of neighbouring strips with low interstrip isolationwere identified by the Full strip tests, and leakage current instabilities were measured in a long-term leakage current stability setup. Moreover, a high surface electrostatic charge reaching a level of several hundreds of volts per inch was measured on a large number of sensors and on the plastic sheets, whichmechanically protect these sensors in their paper envelopes. Accumulated data indicates a clearcorrelation between observed electrical failures and the sensor charge-up.To mitigate the above-described issues, the QC testing sites significantly modified the sensor handlingprocedures and introduced sensor recovery techniques based on irradiation of the sensor surface with UVlight or application of intensive flows of ionized gas. In this presentation, we will describe the setupsimplemented by the QC testing sites to treat silicon strip sensors affected by static charge andevaluate the effectiveness of these setups in terms of improvement of the sensor performance.

Development of a Composite Cu(II)-Selective Potentiometric Sensor Based on a Thiourea Derivative Symmetric Schiff Base

Abstract. In the present study, initially, a thiourea derivative symmetric Schiff base, (1E,3E)-1,3-bis(5-bromo-2-hydroxybenzylidene)thiourea, was synthesized and characterized by FTIR and SEM-EDX analysis. In addition, an all-solid-state composite Cu(II)-selective potentiometric sensor based on this synthesized compound as an electroactive substance was constructed. Optimization studies indicated that the composition of the optimum sensing composite exhibiting the best potentiometric characteristics was 3.0% Schiff base, 5.0 % multi-walled carbon nanotube (MWCNT), 20.0 % paraffin oil and 72.0% graphite by mass. The proposed sensor displayed a linear response in the concentration range of 5.0×10-6-1.0×10-1 M with a slope of 31.1 mV/decade and a detection limit of 5.0×10-7 M. The proposed sensor exhibited a fairly selective, stable (potential drift: 1.85 mV/h), and rapid (<10 s) response towards Cu(II) ions. Because of the magnitude of its potential drift, the sensor should be recalibrated along the analysis time at least half an hour apart. The sensor can employed safely in the samples with pHs in the range of 2.0-6.5. The lifetime of the fresh sensor surface was determined as 2 weeks. The most important advantage of the sensor is that the sensing composite surface is renewable (at least 10 times) and thus the sensor can be used many times for a long period of time. The analytical applications of the sensor were executed successfully by using the electrode in the potentiometric titration of Cu(II) ions with EDTA as an indicator electrode, in the direct determination of Cu(II) contents of spiked water samples, and in the determination of (w/w) Cu% content of a Turkish coin.

Surface Plasmon Resonance Application for Bacteria Pathogen Detection: A Minireview

Detection of pathogenic bacteria requires a fast and accurate process so technological developments related to the sensitivity and selectivity of a sensor are very concerned. Surface Plasmon Resonance (SPR) technology has great potential to detect pathogenic bacteria that are not only used for medical diagnostics, but food safety surveillance and environmental monitoring are also applications of SPR. The success of SPR has proven the advantages of real-time detection without the need for fluorescent markers or additional dyes. The development of sensor surface systems of SPR with nanomaterials is one of the discussions in this paper. The recent development of SPR in recent years is summarized by linking future prospective applications.

Disposable Point-of-Care Electrochemical Sensor for Uric Acid Determination in Human Urine Utilizing a Pencil Graphite Electrode Modified with Polydopamine/Gold Nanoparticles

Point-of-care testing (POCT) is an essential approach in clinical analysis due to its rapidity. In the current research and for the first time, we have developed an electrochemical POC sensor for uric acid (UA) determination using pencil graphite electrode (PGE) substrate modified via a facile self-polymerization of dopamine (DA). Alkaline conditions were used to produce polydopamine (PDA) which inspired from mussel adhesive protein. The PDA-modified electrode was further decorated by electrodeposition of gold nanoparticles (Au-NPs). Sensor surface characterization was conducted using surface characterization techniques like X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) imaging. In addition electrochemical characterization methods were performed utilizing electrochemical impedance spectroscopy (EIS) as well as cyclic voltammetry (CV). The sensor yielded a precise voltammetric response upon using differential pulse voltammetry (DPV) (linearity range: 5.0 × 10−5 mol l−1 − 5.0 × 10−4 mol l−1 of UA with 1.57 × 10–5 mol l−1 limit of detection). The developed sensor’s benefits include decreased manufacturing cost and selectivity. Accurate and satisfactory results were obtained upon application to human urine sample analysis.

A Multidisciplinary Approach toward CMOS Capacitive Sensor Array for Droplet Analysis.

This paper introduces an innovative method for the analysis of alcohol-water droplets on a CMOS capacitive sensor, leveraging the controlled thermal behavior of the droplets. Using this sensing method, the capacitive sensor measures the total time of evaporation (ToE), which can be influenced by the droplet volume, temperature, and chemical composition. We explored this sensing method by introducing binary mixtures of water and ethanol or methanol across a range of concentrations (0-100%, with 10% increments). The experimental results indicate that while the capacitive sensor is effective in measuring both the total ToE and dielectric properties, a higher dynamic range and resolution are observed in the former. Additionally, an array of sensing electrodes successfully monitors the droplet-sensor surface interaction. However practical considerations such as the creation of parasitic capacitance due to mismatch, arise from the large sensing area in the proposed capacitive sensors and other similar devices. In this paper, we discuss this non-ideality and propose a solution. Also, this paper showcases the benefits of utilizing a CMOS capacitive sensing method for accurately measuring ToE.