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Water-soluble fluorescent N-doped carbon quantum dots (N-CQDs) were hydrothermally prepared through a green synthesis route using castor seeds as a single precursor and a hydrothermal method. Several experimental techniques have been used to characterize synthesized N-CQDs to confirm their structure and to verify their applicability in cell imaging and pH sensing. The synthesized N-CQDs were found to have are characterized by amorphous nature with a spherical shape with an average particle size of 6.57 nm as revealed from XRD and TEM measurements. The FTIR results reveal the presence of carboxylic and hydroxyl functional groups on the surface of the CQDs, which was also confirmed by XPS analysis. The fluorescence characterization of the synthesized N-CQDs showed blue emission and excitation dependence with good photostability. It was found that the optimal excitation and emission wavelengths were (λEx = 360) and (λEm = 432) nm, respectively. The fluorescence quantum yield (QY) of about 9.6% at the optimum excitation wavelength 360 nm. Moreover, the fluorescence intensity of N-CQDs showed good linear dependence with the pH values in ranges of 3.5 − 7.5 and 8 − 12 as well as high sensitivity for slight changes of pH values. According to these results, two fluorescent pH sensors were created based on acidic and basic media. The obtained N-CQDs have zeta potential of -21.86 mV and thus have excellent stability in water. Moreover, N-CQDs derived from the castor seeds have antimicrobial activity and exhibits low cytotoxicity to WI-13 cells with IC50 = 394.4 ± 13.8 µg/mL. The results of this study demonstrated that the synthesized N-CQDs derived from castor seeds can be used as pH sensing and antimicrobial materials. On the other hand, they are also promising in applications in cell imaging, thermo-sensing and optoelectronics. [ABSTRACT FROM AUTHOR]

AlphaFold can accurately predict static protein structures but does not account for solvent conditions. Human leucine zipper EF-hand transmembrane protein-1 (LETM1) has one sequence-identifiable EF-hand but how calcium (Ca2+) affects structure and function remains enigmatic. Here, we used highly confident AlphaFold Cα predictions to guide nuclear Overhauser effect (NOE) assignments and structure calculation of the LETM1 EF-hand in the presence of Ca2+. The resultant NMR structure exposes pairing between a partial loop-helix and full helix-loop-helix, forming an unprecedented F-EF-hand with non-canonical Ca2+ coordination but enhanced hydrophobicity for protein interactions compared to calmodulin. The structure also reveals the basis for pH sensing at the link between canonical and partial EF-hands. Functionally, mutations that augmented or weakened Ca2+ binding increased or decreased matrix Ca2+, respectively, establishing F-EF as a two-way mitochondrial Ca2+ regulator. Thus, we show how to synergize AI prediction with NMR data, elucidating a solution-specific and extraordinary LETM1 F-EF-hand. [Display omitted] • An AI-informed NMR structure elucidation method reveals a unique LETM1 F-EF-hand • The Ca2+ bound LETM1 F-EF-hand adopts an open conformation with high hydrophobicity • High affinity LETM1 F-EF-hand Ca2+ binding increases mitochondrial matrix Ca2+ • Abrogated LETM1 F-EF-hand Ca2+ binding decreases mitochondrial matrix Ca2+ AI has revolutionized structural biology but must be applied responsibly. Lin et al. present a method for synergizing AlphaFold predictions with solution NMR data, using the approach to expose an unprecedented F-EF-hand domain in LETM1. This LETM1 F-EF-hand functions as a weak Ca2+ binding sensor that modulates mitochondrial matrix Ca2+. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs), a new member of the nanocarbon family, are revolutionizing a wide range of fields. This new member has been the subject of extensive international research. Its synthesis methods, characteristics, and applications are active research areas. Carbon dots are nanoparticles composed of carbon with a diameter of less than 10 nm. The distinctive structure and size of CDs suggest that their physical, chemical, electrical, and optical properties are modifiable. In addition, they possess properties such as low toxicity, high water solubility, chemical stability, photoluminescence, photostability, electroluminescence, high quantum yield, high surface area, heteroatom doping capability, abundance of surface functional groups, good conductivity, and environmental friendliness. This review attempts to provide an introductory story of carbon dots. From the early beginning of CDs through the myriad of synthesis techniques used to date, the review advances to the properties and applications that have not yet been fully explored. The principal applications covered include fluorescence detection, electrochemical sensing, pH monitoring, fluorescent ink, and metal nanoparticle synthesis. Recent developments, gaps, and obstacles for each of these applications have been discussed. [ABSTRACT FROM AUTHOR]

Anodic Nb–Ti oxide crossbar memristor arrays are successfully produced on Si substrates. Their use as pH sensors is tested by analyzing their current–voltage (I–U) sweeps in Ringer´s solutions with different pH values. A gradual evolution of the memristive hysteretic curve is observed upon pH variation. A sensor calibration showing a linear trend with least square error close to 1 is performed and the performance of the pH sensing is assessed. The limit of detection (LOD), limit of quantification (LOQ), and the sensitivity (S) are determined. The calculated LOD is 0.4 pH, and the LOQ is 1.2 pH. The S is calculated as 0.5 pH corresponding to a concentration of c(OH−) = 3.5 mM. The reproducibility and repeatability of the measurements are calculated as 3.8% and 1.4%, respectively. An X‐ray photoelectron spectroscopy survey allows the study of the oxide composition providing information about its pH‐sensing mechanism. It is found that the OH− species diffused into the mixed anodic oxide are responsible for the pH‐induced high‐ to low‐resistance state changes. A conduction mechanism analysis is carried out and Schottky emission is identified as predominant. [ABSTRACT FROM AUTHOR]

This article describes the process of fabricating an integrated all-solid electrode (IASE) by integrating thin films of titanium dioxide (TiO2) and silver/silver chloride (Ag/AgCl) onto an indium tin oxide (ITO) substrate. The fabrication of a pH sensing electrode (SE) involved utilizing a spin-coated thin film composed of TiO2. Thermally produced thin films of Ag/AgCl were used to develop solid reference electrodes (RE). The present work examined the impact of the drying process on the pH sensitivity and linearity of the lowtemperature deposited IASE. The drying procedure was carried out within a temperature range from room temperature to 100°C. The investigation involved the examination of crystallinity, surface morphology, and thin film composition through the utilization of field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX) methods. In addition, a comparison was made between the pH sensing performance of the IASE and a commercially available Ag/AgCl RE. The findings of this research demonstrate that the IASE sample, which underwent a drying process at a temperature of 100°C, exhibited remarkable sensitivity and linearity values of 66.7 mV/pH and 0.9827, separately, when compared to the commercially available RE. [ABSTRACT FROM AUTHOR]

The research introduces a revolutionary Internet of Things (IoT)-based system for fish farming, designed to significantly enhance efficiency and cost-effectiveness. By integrating the NodeMcu12E ESP8266 microcontroller, this system automates the management of critical water quality parameters such as pH, temperature, and oxygen levels, essential for fostering optimal fish growth conditions and minimizing mortality rates. The core of this innovation lies in its intelligent monitoring and control mechanism, which not only supports accelerated fish development but also ensures the robustness of the farming process through automated adjustments whenever the monitored parameters deviate from desired thresholds. This smart fish farming solution features an Arduino IoT cloud-based framework, offering a user-friendly web interface that enables fish farmers to remotely monitor and manage their operations from any global location. This aspect of the system emphasizes the importance of efficient information management and the transformation of sensor data into actionable insights, thereby reducing the need for constant human oversight and significantly increasing operational reliability. The autonomous functionality of the system is a key highlight, designed to persist in adjusting the environmental conditions within the fish farm until the optimal parameters are restored. This capability greatly diminishes the risks associated with manual monitoring and adjustments, allowing even those with limited expertise in aquaculture to achieve high levels of production efficiency and sustainability. By leveraging data-driven technologies and IoT innovations, this study not only addresses the immediate needs of the fish farming industry but also contributes to solving the broader global challenge of protein production. It presents a scalable and accessible approach to modern aquaculture, empowering stakeholders to maximize output and minimize risks associated with fish farming, thereby paving the way for a more sustainable and efficient future in the global food supply. [ABSTRACT FROM AUTHOR]

We implemented an ion-sensitive field effect transistor (ISFET) array chip comprising n-ISFET and p-ISFET for sensor application using 0.18 μ m CMOS technology. N-channel metal-oxide semiconductor (NMOS) and P-channel metal-oxide semiconductor (PMOS) ISFETs are fabricated in regular dimensions (< 8 μ m) compatible with the standard CMOS process. We implemented n-ISFET cells and p-ISFET cells of different dimensions for characterization and to observe the possible effect of scalability. Each cell also has two identical NMOS and PMOS ISFETs of standard dimension, unlike very large dimensions (> 200 μ m). We are using metals 1–6 and via together on the gate area to make it an extended or floating gate for the electrochemical sensing of ISFET. These metals are electrically floating with an intermediate dielectric. These different-size floating gate ISFETs provide different sensing areas, and the passivation Si3N4 layer is used for pH sensing without any extra post-processing measures. We observe the ISFET sensitivity and performance with the 0.18 μ m technology submicron effect. The measured results propose ISFET as a promising sensor device for portable applications. The ISFET chip dimension is 1179 μ m × 1185 μ m. [ABSTRACT FROM AUTHOR]

A light-addressable potentiometric sensor (LAPS) is a semiconductor-based sensor platform for sensing and imaging of various chemical species. Being a potentiometric sensor, no faradaic current flows through its sensing surface, and no electrochemical reaction takes place in the course of LAPS measurement. In this study, a four-electrode system is proposed, in which a LAPS is combined with the conventional three-electrode electrochemical system. A LAPS is included as the fourth electrode for potentiometric sensing and imaging of the target analyte in the course of an electrochemical reaction taking place on the surface of the working electrode. The integrated system will be useful for analyzing dynamic processes, where both the electrochemical process on the electrode surface and the ion distribution in the solution need to be simultaneously investigated. Different grounding modes of control circuits that can simultaneously conduct potentiostatic/galvanostatic polarization and LAPS measurement are designed, and their functionalities are tested. The interference between polarization and LAPS measurement will also be discussed. [ABSTRACT FROM AUTHOR]

The development of a fluorescent pH sensor and the treatment of wastewater with nanoparticles are both critical topics. Variations in pH impact the morphology and subsequent properties of nanoparticles, affecting their utilization in various fields, while using nanoparticles offers an improved approach for treating industrial waste. The present study examines the effects of these variables on biologically produced nitrogen-doped carbon quantum dots (NCQDs). The synthesis was achieved through a hydrothermal process using Rubus niveus leaf extract as a precursor. UV-Vis spectroscopy analysis revealed absorption spectra over a wide range from 200 nm to 800 nm, with prominent peaks at 236 nm and 392 nm. Additionally, the direct energy band gap of the NCQDs was found to be 3.65 eV. SEM imaging displayed flower-shaped particles, and FT-IR analysis indicated the presence of amide, CHO, N-H, and C-N functional groups. The XRD pattern revealed that the surface morphology of NCQDs is amorphous in nature. A significant response in fluorescence intensity with varying pH values was observed, confirming the potential of NCQDs as pH sensors. The reaction kinetics of Rhodamine-B (Rh-B) dye was analyzed to assess the potential of NCQDs for dye degradation, revealing pseudo-first-order kinetics with a correlation coefficient of 0.80. [ABSTRACT FROM AUTHOR]

During chronic wound healing, the inflammatory phase can endure for extended periods, heavily impeding or halting the process. Regular inspections and dressing changes are crucial. Modern dressings like hydrogels, hydrocolloids, and foam provide protection and an optimal healing environment. However, they have limitations in offering real-time wound bed status and healing rate. Evaluation relies heavily on direct observation, and passive dressings fail to identify subtle healing differences, preventing adaptive adjustments in biological factors and drug concentrations. In recent years, the clinical field recognizes the value of integrating intelligent diagnostic tools into wound dressings. By monitoring biomarkers linked to chronic wounds' inflammatory state, real-time data can be captured, reducing medical interventions and enabling more effective treatment plans. This fosters innovation in chronic wound care. Researchers have developed smart dressings with sensing, active drug delivery, and self-adjustment capabilities. These dressings detect inflammatory markers like temperature, pH, and oxygen content, enhancing drug bioavailability on the wound surface. As wound healing technology evolves, these smart dressings hold immense potential in chronic wound care and treatment. This comprehensive review updates our understanding on the role and mechanism of action of the smart dressings in chronic refractory wounds by summarizing and discussing the latest research progresses, including the intelligent monitoring of wound oxygen content, temperature, humidity, pH, infection, and enzyme kinetics; intelligent drug delivery triggered by temperature, pH, near-infrared, and electricity; as well as the intelligent self-adjustment of pressure and shape. The review also delves into the constraints and future perspectives of smart dressings in clinical settings, thereby advancing the development of smart wound dressings for chronic wound healing and their practical application in clinical practice. [ABSTRACT FROM AUTHOR]

Sustainability in packaging materials is important now with a world overwhelmed by plastic pollution. In this study, anthocyanins extracted from banana bracts were incorporated into a biodegradable polyvinyl alcohol (PVA)/starch matrix to prepare a colorimetric pH-responsive film for intelligent food packaging applications. Anthocyanins are a class of natural dyes that are used to detect pH changes due to the presence of phenolic or conjugated groups. PVA/starch films with varying concentrations of anthocyanin (1.5–3%) were made by the solution casting method. FTIR, TGA, SEM, WVTR, and moisture absorption were used to characterize the films. Anthocyanin extract added to the PVA/starch film boosted the percentage elongation at break but lowered the elastic modulus and tensile strength. pH sensing ability was established by the degrees of lightness (L), redness (+a) or greenness (−a), and yellowness (+b) or blueness (−b) values of the prepared films. A test for food spoilage was conducted using pasteurized milk. This research proposed a novel technique for fabricating films that are suitable for use in food packaging and as a biodegradable substitute for existing packaging materials. [ABSTRACT FROM AUTHOR]

Abstract Water-soluble fluorescent N-doped carbon quantum dots (N-CQDs) were hydrothermally prepared through a green synthesis route using castor seeds as a single precursor and a hydrothermal method. Several experimental techniques have been used to characterize synthesized N-CQDs to confirm their structure and to verify their applicability in cell imaging and pH sensing. The synthesized N-CQDs were found to have are characterized by amorphous nature with a spherical shape with an average particle size of 6.57 nm as revealed from XRD and TEM measurements. The FTIR results reveal the presence of carboxylic and hydroxyl functional groups on the surface of the CQDs, which was also confirmed by XPS analysis. The fluorescence characterization of the synthesized N-CQDs showed blue emission and excitation dependence with good photostability. It was found that the optimal excitation and emission wavelengths were (λEx = 360) and (λEm = 432) nm, respectively. The fluorescence quantum yield (QY) of about 9.6% at the optimum excitation wavelength 360 nm. Moreover, the fluorescence intensity of N-CQDs showed good linear dependence with the pH values in ranges of 3.5 − 7.5 and 8 − 12 as well as high sensitivity for slight changes of pH values. According to these results, two fluorescent pH sensors were created based on acidic and basic media. The obtained N-CQDs have zeta potential of -21.86 mV and thus have excellent stability in water. Moreover, N-CQDs derived from the castor seeds have antimicrobial activity and exhibits low cytotoxicity to WI-13 cells with IC50 = 394.4 ± 13.8 µg/mL. The results of this study demonstrated that the synthesized N-CQDs derived from castor seeds can be used as pH sensing and antimicrobial materials. On the other hand, they are also promising in applications in cell imaging, thermo-sensing and optoelectronics.

Vannamei shrimp is a high-value, economically important brackish water aquaculture commodity that is easy to cultivate. Optimal growth of Vannamei shrimp can be achieved by monitoring water quality parameters such as pH and turbidity. The pH levels can be measured using a pH sensor, with a pH meter as a reference. Turbidity levels are measured with a turbidity sensor in NTU units, with a turbidity stick serving as a reference. Testing of these sensors was conducted from morning to noon over three days in the brackish water ponds of IBAP Banjar Kemuning, Sidoarjo, recording 100 data samples. The performance of both sensors fluctuated due to disturbances around the pond, prompting the use of the Moving Average (MA) filter method to improve accuracy. Applying MA with varying window sizes (wz) resulted in a performance increase of 0.24% in the morning and 0.1% at noon. Additionally, turbidity sensor testing indicated that the pond conditions were consistent with the turbidity measurements obtained using the turbidity stick.

Abstract Industrialization and urbanization contribute significantly to environmental pollution, particularly in water bodies. The consequences of this pollution are dire, impacting both the environment and public health. A serious hazard to life on Earth, contaminated water can cause food poisoning, diarrhea, respiratory diseases, and skin ailments, among other health problems. In countries like Bangladesh, where industrial activities, particularly in the garment sector, are prevalent, waste dumping into rivers and canals has reached alarming levels. This has resulted in a drastic decline in water quality, endangering aquatic life and ecosystems. To solve this important issue, we built an innovative real-time water quality monitoring system using the Internet of Things (IoT). Our system operates at three levels, collecting data from different layers of wastewater. Key parameters, including temperature, turbidity, total dissolved solids (TDS), and pH, are continuously monitored to assess water quality. The analysis revealed that wastewater temperature varied between 25 and 37 °C across different sites, with higher temperatures observed in industrial zones, indicating potential thermal pollution. Total dissolved solids (TDS) levels exhibited substantial variations, ranging from 170 to 360 ppm, surpassing standard thresholds and posing a threat to aquatic ecosystems. Turbidity readings ranged from 1.30 to 12.89 NTU, with higher turbidity observed in areas receiving industrial discharge, highlighting the impact of suspended solids on water clarity. pH values exceeded 7.0 across all sites, ranging from 9.5 to 10.32, indicating alkaline wastewater, particularly in regions with dyeing and textile industries. By integrating these specific metrics into our monitoring system, we provide valuable insights into industrial wastewater quality and its environmental implications. These findings underscore the urgent need for real-time monitoring and targeted interventions to address water pollution. Implementing sustainable water management strategies in industrial contexts is critical to protecting public health and preserving ecosystems for future generations.

pH regulation in human biofluids is a crucial step for disease diagnosis and health monitoring. Traditional pH sensors are limited by their bulky size in wearable systems, and fragile glass tips require frequent calibration, thus limiting their use in continuous monitoring. Flexible sensors, particularly those utilizing microwires and thread-based substrates, present advantages for small sample analysis, including natural breathability and suitability for bandage or textile integration. This study examines iridium oxide and silver–silver chloride coated on thin gold wires, fabricated using sol–gel and dip-coating processes known for their simplicity. The flexible microwires demonstrated promising pH performance from a study of their pH characteristics, sensitivity, hysteresis, and potential drift. Electrodes tested in microwells allowed for small sample volumes and localized pH measurement in a controlled environment. Additional integration into fabrics for sweat sensing in wearables highlighted their potential for continuous, real-time health monitoring applications. [ABSTRACT FROM AUTHOR]

A high-sensitivity pH sensor based on an AlGaN/GaN high-electron mobility transistor (HEMT) with a 10 nm thick Au-gated sensing membrane was investigated. The Au nanolayer as a sensing membrane was deposited by electron-beam evaporation and patterned onto the GaN cap layer, which provides more surface-active sites and a more robust adsorption capacity for hydrogen ions (H+) and hydroxide ions (OH−) and thus the sensitivity of the sensor can be significantly enhanced. A quasi-reference electrode was used to minimize the sensing system for the measurement of the microliter solution. The measurement and analysis results demonstrate that the fabricated sensor exhibits a high potential sensitivity of 58.59 mV/pH, which is very close to the Nernstian limit. The current sensitivity is as high as 372.37 μA/pH in the pH range from 4.0 to 9.18, under a 3.5 V drain-source voltage and a 0 V reference-source voltage. Comparison experiments show that the current sensitivity of the Au-gated sensor can reach 3.9 times that of the SiO2-gated sensor. Dynamic titration experiments reveal the pH sensor's ability to promptly respond to immediate pH variations. These findings indicate that this pH sensor can meet most application requirements for advanced medical and chemical analysis. [ABSTRACT FROM AUTHOR]

Industrialization and urbanization contribute significantly to environmental pollution, particularly in water bodies. The consequences of this pollution are dire, impacting both the environment and public health. A serious hazard to life on Earth, contaminated water can cause food poisoning, diarrhea, respiratory diseases, and skin ailments, among other health problems. In countries like Bangladesh, where industrial activities, particularly in the garment sector, are prevalent, waste dumping into rivers and canals has reached alarming levels. This has resulted in a drastic decline in water quality, endangering aquatic life and ecosystems. To solve this important issue, we built an innovative real-time water quality monitoring system using the Internet of Things (IoT). Our system operates at three levels, collecting data from different layers of wastewater. Key parameters, including temperature, turbidity, total dissolved solids (TDS), and pH, are continuously monitored to assess water quality. The analysis revealed that wastewater temperature varied between 25 and 37 °C across different sites, with higher temperatures observed in industrial zones, indicating potential thermal pollution. Total dissolved solids (TDS) levels exhibited substantial variations, ranging from 170 to 360 ppm, surpassing standard thresholds and posing a threat to aquatic ecosystems. Turbidity readings ranged from 1.30 to 12.89 NTU, with higher turbidity observed in areas receiving industrial discharge, highlighting the impact of suspended solids on water clarity. pH values exceeded 7.0 across all sites, ranging from 9.5 to 10.32, indicating alkaline wastewater, particularly in regions with dyeing and textile industries. By integrating these specific metrics into our monitoring system, we provide valuable insights into industrial wastewater quality and its environmental implications. These findings underscore the urgent need for real-time monitoring and targeted interventions to address water pollution. Implementing sustainable water management strategies in industrial contexts is critical to protecting public health and preserving ecosystems for future generations. [ABSTRACT FROM AUTHOR]

Reverse transcription loop‐mediated isothermal amplification (RT‐LAMP) is a molecular amplification method that can detect SARS‐CoV‐2 in a shorter time than the current gold‐standard molecular diagnostic reverse transcription‐polymerase chain reaction (RT‐PCR). However, previously developed RT‐LAMP assays have mostly relied on highly subjective visual colorimetric interpretation. In this study, an RT‐LAMP assay was developed with quantitative measurement of reaction pH using a novel portable pH biosensor compared to qualitative colorimetric interpretation and gel electrophoresis, with 57 clinical COVID‐19 samples used for validation of the test. The LoD of the assay is 103 copies/μL. The highest sensitivity was found in the qualitative methods (93.75%), while the highest specificity and likelihood ratio was found in the pH sensor (87.5% and 6.72). On the sensor measurement, a significant difference (p < 0.0001) was observed between the average pH of the RT‐PCR (+) COVID‐19 (6.15 ± 0.27), while the average pH of the RT‐PCR (−) samples (6.72 ± 0.22). Correlation analysis revealed a strong correlation (r = 0.78, p < 0.0001) between the Ct values obtained from RT‐PCR with the biosensor pH readout. RT‐LAMP with the quantitative pH sensor readout method has the potential to be further developed as an objective molecular assay for rapid and simple detection of SARS‐CoV‐2. [ABSTRACT FROM AUTHOR]

An ultra-high sensitivity pH sensor based on vertical organic electrochemical transistors (vOECT) with extended gate was proposed. The vOECT, which exhibited high transconductance (gm), was for the first time used in the preparation of a pH sensor. The extended gate was modified by electrochemical deposition of polyaniline (PANI) using the cyclic voltammetry (CV) technique. Open circuit potential (OCP) measurements were used to optimize the scan rate, showing a super-Nernstian sensitivity at all scan rates. The pH sensor based on vOECT with extended gate was investigated at different pH levels, and it exhibited an ultra-high sensitivity of 3363.6 µA/pH in the pH range 5–9, which was about 36 times greater than the maximum current sensitivity (91 µA/pH) of other transistor-based pH sensors, to the best of our knowledge. This pH sensor performed excellently in terms of reversibility, long-term stability, and selectivity. To confirm the reliability of the pH sensor, we conducted measurements on real samples using this pH sensor and compared the results with those obtained from a standard pH meter. The ultra-high sensitivity pH sensor based on vOECT with extended gate offers a sensitive and promising alternative in environmental monitoring, food safety, chemistry, clinical diagnostics, and bio-sensing applications. [ABSTRACT FROM AUTHOR]

River water is essential for people's lives and environmental health. There is a need to manage river water to maintain river water quality. This research aims to develop a river water quality analysis system that is practical, easy, and capable of storage and processing using several sensors connected to a computer system. The tools used in this research are Arduino UNO R3 board and sensors. River water samples with various characteristics were taken from four spots of the Cikapundung River. The results showed that river water quality analysis can be done using sensor-based Arduino UNO R3. The temperature at the four spots ranges from 27-32oC and is included in the safe category for sanitation use. Judging from the turbidity factor, the turbidity value of river water is in the high category, namely 49.2-58.1 NTU, which is unsuitable for sanitary use. Regarding the TDS factor, the TDS range in river water is 150-222 ppm, indicating that river water is not polluted. Meanwhile, the pH value shows that the pH range of river water is alkaline and can be used for sanitation with a range of 7.93-8.16. This indicates that the water quality in the Cikapundung River that needs attention is the turbidity factor. It takes awareness of the surrounding community and government agencies to work together to improve the river's environmental health sustainably. [ABSTRACT FROM AUTHOR]

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Salivary pH is one of the crucial biomarkers used for non-invasive diagnosis of intraoral diseases, as well as general health conditions. However, standard pH sensors are usually too bulky, expensive, and impractical for routine use outside laboratory settings. Herein, a miniature hydrogel sensor, which enables quick and simple colorimetric detection of pH level, is shown. The sensor structure was manufactured from non-toxic hydrogel ink and patterned in the form of a matrix with 5 mm × 5 mm × 1 mm individual sensing pads using a 3D printing technique (bioplotting). The authors' ink composition, which contains sodium alginate, polyvinylpyrrolidone, and bromothymol blue indicator, enables repeatable and stable color response to different pH levels. The developed analysis software with an easy-to-use graphical user interface extracts the R(ed), G(reen), and B(lue) components of the color image of the hydrogel pads, and evaluates the pH value in a second. A calibration curve used for the analysis was obtained in a pH range of 3.5 to 9.0 using a laboratory pH meter as a reference. Validation of the sensor was performed on samples of artificial saliva for medical use and its mixtures with beverages of different pH values (lemon juice, coffee, black and green tea, bottled and tap water), and correct responses to acidic and alkaline solutions were observed. The matrix of square sensing pads used in this study provided multiple parallel responses for parametric tests, but the applied 3D printing method and ink composition enable easy adjustment of the shape of the sensing layer to other desired patterns and sizes. Additional mechanical tests of the hydrogel layers confirmed the relatively high quality and durability of the sensor structure. The solution presented here, comprising 3D printed hydrogel sensor pads, simple colorimetric detection, and graphical software for signal processing, opens the way to development of miniature and biocompatible diagnostic devices in the form of flexible, wearable, or intraoral sensors for prospective application in personalized medicine and point-of-care diagnosis. [ABSTRACT FROM AUTHOR]

Recently, various kinds of micro- and nanofluidic functional devices have been proposed, where a large surface-to-volume ratio often plays an important role in nanoscale ion transport phenomena. Ionic current analysis methods for ions, molecules, nanoparticles, and biological cells have attracted significant attention. In this study, focusing on ionic current rectification (ICR) caused by the separation of cation and anion transport in nanochannels, we successfully induce electrodiffusioosmosis with concentration differences between protons separated by nanochannels. The proton concentration in sample solutions is quantitatively evaluated in the range from pH 1.68 to 10.01 with a slope of 243 mV/pH at a galvanostatic current of 3 nA. Herein, three types of micro- and nanochannels are proposed to improve the stability and measurement accuracy of the current–voltage characteristics, and the ICR effects on pH analysis are evaluated. It is found that a nanochannel filled with polyethylene glycol exhibits increased impedance and an improved ICR ratio. The present principle is expected to be applicable to various types of ions. [ABSTRACT FROM AUTHOR]

Electrochemical pH sensors have a wide range of industrial applications such as in medicine due to their fast response and high sensitivity to pH changes. This work focuses on the preparation of samples based on the nanostructure of TiO2 with potentiostatically deposited particles of iridium and its oxides (IrO2), using a Ti-6Al-4V alloy as the base material, and subsequent surface characterization. Transmission electron microscopy and secondary ion mass spectroscopy showed Ir particles distributed in the nanotubes. Using a potentiostatic method, a stable pH sensor was prepared. By monitoring the open circuit potential, it was shown that this sensor is usable even without being kept in a storage medium and does not react to changes in the redox potential of the solution. [ABSTRACT FROM AUTHOR]

Abstract The correlation between altered extracellular pH and various pathological conditions, including cancer, inflammation and metabolic disorders, is well known. Bulk pH measurements cannot report the extracellular pH value at the cell surface. However, there is a limited number of suitable tools for measuring the extracellular pH of cells with high spatial resolution, and none of them are commonly used in laboratories around the world. In this study, a versatile ratiometric nanosensor for the measurement of extracellular pH was developed. The nanosensor consists of biocompatible polystyrene nanoparticles loaded with the pH-inert reference dye Nile red and is surface functionalized with a pH-responsive fluorescein dye. Equipped with a targeting moiety, the nanosensor can adhere to cell membranes, allowing direct measurement of extracellular pH at the cell surface. The nanosensor exhibits a sensitive ratiometric pH response within the range of 5.5–9.0, with a calculated pKa of 7.47. This range optimally covers the extracellular pH (pHe) of most healthy cells and cells in which the pHe is abnormal, such as cancer cells. In combination with the nanosensors ability to target cell membranes, its high robustness, reversibility and its biocompatibility, the pHe nanosensor proves to be well suited for in-situ measurement of extracellular pH, even over extended time periods. This pH nanosensor has the potential to advance biomedical research by improving our understanding of cellular microenvironments, where extracellular pH plays an important role.

Glass pH sensors are unsuitable for in vivo biomedical, clinical, or food applications because of brittleness of glass, the difficulty in measurement of small volumes and complex matrices, and the need for calibration. Herein, a novel enamel reference electrode for pH sensors is developed using a binary xAg2O·(100–x)TeO2 glass/stainless steel (SUS) electrode. Subsequently, the effects of Ag2O content on the precipitated crystalline phases and pH sensitivity of Ag2O–TeO2 glass/SUS electrodes are examined. The results indicate that the xAg2O·(100–x)TeO2 glass/SUS samples exhibit relatively low pH sensitivity. The pH sensitivities of the samples can be classified into two distinct groups. The first group, comprising samples with an Ag2O content of 25 mol% or more, exhibits a pH sensitivity higher than 10 %. The second group, comprising samples with an Ag2O content of 22 mol% or less, exhibits a pH sensitivity of less than 10 %. The pH sensitivity tends to decrease with increase in stutzite fraction in Ag–Te alloys. Results of X-ray diffraction measurements and transmission electron microscopy observations indicate that the hessite and stutzite Ag–Te alloys, which are minor and conductive, are the primary contributors to the low pH sensitivity observed. Moreover, the pH sensitivity of xAg2O·(100–x)TeO2/SUS is observed to be between those of the Ag–Te alloy and the Ag2O–TeO2 glass matrix. We propose occurrence of an electrical shunt should occur between the Ag–Te alloy and the Ag+-ion conductive Ag2O–TeO2 glass matrix. Regarding xAg2O·(100–x)TeO2 glass/SUS, the 20Ag2O·80TeO2 glass/SUS to 21Ag2O·79TeO2 glass/SUS compositions represent promising candidates as for KCl-leakage-free reference electrodes for pH sensors.

Effective and continuous monitoring of bioprocesses requires the parallel screening of multiple key parameters to enhance the processes and ultimately improve the quality of the end products. In this work, the development and characterization of only few square millimeters microfabricated multi-sensor array chip for analysis of yeast fermentation is described. We originally integrated platinum nanostructures (nano-Pt) on the microelectrodes by a simple, CMOS compatible, and scalable electrodeposition procedure. This step was proven to be pivotal to obtain highly sensitive and selective microsensors with minimal cross-talk and measurement variability. Nano-Pt enables reliable sensing at lower applied potentials, offering a promising solution to mitigate electrical cross-talk in closely integrated sensor configurations. The multi-sensor features potentiometric parallel-plate nanostructured electrodes for measuring pH, interdigitated nano-Pt electrodes for indirectly measuring microbial growth and activity by measuring the electrolyte conductivity, and microelectrodes based on nano-Pt for measuring dissolved oxygen (DO) and glucose via amperometry. Importantly, all-solid-state on-chip reference electrodes for potentiometric and amperometric sensors of this chip have been developed and characterized to enable standalone measurements and achieve true miniaturization, avoiding the need for external conventional reference electrodes. The chip includes a meander thin-film resistance temperature detector for temperature monitoring as well. Our platform represents the first step towards viable in-situ monitoring of lab-scale yeast fermentation and to control the homogeneity of process parameters in large scale bioreactors.

The pH monitoring is significantly important in chemical industry, biological process, and pollution treatment. However, it remains a great challenge to measure pH in extreme alkalinity conditions. Herein, we employ an electrolyte-gated field-effect-transistor (FET) strategy using non-stoichiometric SrCoOx with rich oxygen-vacancy defects as channel materials for detecting extreme alkalinity. The corresponding channel can provide effective oxygen-ion-migration sites for reversible transformation of OH- ↔ O2- + H+ driven by electric field. The resultant electrolyte-gated FET sensor exhibits a sensitive linear response to high concentrations of alkaline solution, 1–20 M. Significantly, the sensor has the ability to directly indicate the pH values ranging from 14.0 to 17.0 in consideration of ion-activity coefficient data. This work offers a great possibility for directly detecting base concentration as well as pH values in extreme alkaline solutions. [ABSTRACT FROM AUTHOR]

An optical fiber pH sensor based on a long-period fiber grating (LPFG) is reported. Two oppositely charged polymers, polyethylenimine (PEI) and polyacrylic acid (PAA), were alternately deposited on the sensing structure through a layer-by-layer (LbL) electrostatic self-assembly technique. Since the polymers are pH sensitive, their refractive index (RI) varies when the pH of the solution changes due to swelling/deswelling phenomena. The fabricated multilayer coating retained a similar property, enabling its use in pH-sensing applications. The pH of the PAA dipping solution was tuned so that a coated LPFG achieved a pH sensitivity of (6.3 ± 0.2) nm/pH in the 5.92–9.23 pH range. Only two bilayers of PEI/PAA were used as an overlay, which reduces the fabrication time and increases the reproducibility of the sensor, and its reversibility and repeatability were demonstrated by tracking the resonance band position throughout multiple cycles between different pH solutions. With simulation work and experimental results from a low-finesse Fabry–Perot (FP) cavity on a fiber tip, the coating properties were estimated. When saturated at low pH, it has a thickness of 200 nm and 1.53 ± 0.01 RI, expanding up to 310 nm with a 1.35 ± 0.01 RI at higher pH values, mostly due to the structural changes in the PAA. [ABSTRACT FROM AUTHOR]

In recent years, research in the field of sensors has been rapidly advancing. As a result, this study proposes a pH sensor based on a magnesium oxide (MgO) thin film. The MgO sensing layer of the pH sensor was deposited onto the electroless nickel immersion gold (ENIG) electrode using a radio frequency (RF) sputtering system, where the ENIG electrode is integrated as the working electrode and reference electrode on a Flexible Printed Circuit Board (FPCB). FPCB offers advantages such as flexibility, acid resistance, heat resistance, and low cost. Furthermore, the performance of the pH sensor is enhanced by modifying the sensing layer with Nafion and (3-Aminopropyl)triethoxysilane (APTES). This study utilized the potentiometric method to measure and analyze the performance of the pH sensor, and the measurement range of the pH sensor is from pH 3 to pH 11 with an average sensitivity of 46.48 mV/pH and linearity can reach 0.996. In terms of material analysis, this research utilizes atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX) to analyze the surface morphology and elemental composition of the sensing layer to verify MgO film.

The research introduces a revolutionary Internet of Things (IoT)-based system for fish farming, designed to significantly enhance efficiency and cost-effectiveness. By integrating the NodeMcu12E ESP8266 microcontroller, this system automates the management of critical water quality parameters such as pH, temperature, and oxygen levels, essential for fostering optimal fish growth conditions and minimizing mortality rates. The core of this innovation lies in its intelligent monitoring and control mechanism, which not only supports accelerated fish development but also ensures the robustness of the farming process through automated adjustments whenever the monitored parameters deviate from desired thresholds. This smart fish farming solution features an Arduino IoT cloud-based framework, offering a user-friendly web interface that enables fish farmers to remotely monitor and manage their operations from any global location. This aspect of the system emphasizes the importance of efficient information management and the transformation of sensor data into actionable insights, thereby reducing the need for constant human oversight and significantly increasing operational reliability. The autonomous functionality of the system is a key highlight, designed to persist in adjusting the environmental conditions within the fish farm until the optimal parameters are restored. This capability greatly diminishes the risks associated with manual monitoring and adjustments, allowing even those with limited expertise in aquaculture to achieve high levels of production efficiency and sustainability. By leveraging data-driven technologies and IoT innovations, this study not only addresses the immediate needs of the fish farming industry but also contributes to solving the broader global challenge of protein production. It presents a scalable and accessible approach to modern aquaculture, empowering stakeholders to maximize output and minimize risks associated with fish farming, thereby paving the way for a more sustainable and efficient future in the global food supply.

In this study, indium zinc oxide (IZO) thin films were deposited at different pressures by RF sputtering. The IZO thin films were examined using X-ray diffraction (XRD), SEM, and AFM instruments. The observed crystal orientations [(100), (101), and (008)] were obtained near 31°. The experimental results also reveal slight height variations on the surfaces of the IZO thin films, with average roughness (Ra) values of 2.431, 3.873, and 5.682 nm for sputtering pressures of 10, 20, and 30 mTorr, respectively. In addition, the IZO/Si sensor head and reference electrode were immersed in buffer solutions with various pH values (1, 3, 5, 7, 9, and 11) to measure pH sensitivity. A series of current-voltage (I-V) characteristic curves were obtained using a semiconductor parameter analysis instrument. The pH sensitivity of the IZO extended-gate field-effect transistor (EGFET) was calculated to be approximately 58.9, 56.4, and 52.3 mV/pH for 10, 20, and 30 mTorr sputtering pressures, respectively. The IZO pH-EGFET showed superior pH sensitivity and linear response and has great potential as a disposable pH sensor. [ABSTRACT FROM AUTHOR]

Silicon nanowires (SiNWs) are emerging as versatile components in the fabrication of sensors for implantable medical devices because of their exceptional electrical, optical, and mechanical properties. This paper presents a novel top-down fabrication method for vertically stacked SiNWs, eliminating the need for wet oxidation, wet etching, and nanolithography. The integration of these SiNWs into body channel communication (BCC) circuits was also explored. The fabricated SiNWs were confirmed to be capable of forming arrays with multiple layers and rows. The SiNW-based pH sensors demonstrated a robust response to pH changes, and when tested with BCC circuits, they showed that it was possible to quantize based on pH when transmitting data through the human body. This study successfully developed a novel method for SiNW fabrication and integration into BCC circuits, which could lead to improvements in the reliability and efficiency of implantable medical sensors. The findings demonstrate significant potential for bioelectronic applications and real-time biochemical monitoring. [ABSTRACT FROM AUTHOR]

Cell models are one of the most widely used basic models in biological research, and a variety of in vitro cell culture techniques and models have been developed recently to simulate the physiological microenvironment in vivo. However, regardless of the technique or model, cell culture is the most fundamental but crucial component. As a result, we have developed a cell culture monitoring system to assess the functional status of cells within a biochip. This article focuses on a mini-microscope made from a readily available camera for in situ continuous observation of cell growth within a biochip and a pH sensor based on optoelectronic sensing for measuring pH. With the aid of this monitoring system, scientists can keep an eye on cell growth in real time and learn how the pH of the culture medium affects it. This study offers a new approach for tracking cells on biochips and serves as a valuable resource for enhancing cell culture conditions. [ABSTRACT FROM AUTHOR]

In a world grappling with the dire consequences of poor sanitation and inadequate water conditions, there is an urgent need for a comprehensive solution. The staggering statistics of over 400 million affected cases and 15–25 million lives lost worldwide underscore the gravity of the situation. This paper addresses this critical issue by introducing a novel approach to water quality monitoring that leverages wireless sensor networks. Traditional monitoring techniques have proven inefficient in combating the proactive contamination of water sources. These methods often involve the cumbersome grouping of various points within the distribution network, resulting in delayed outcomes, labour-intensive processes and a lack of real-time data. To overcome these limitations, this study presents a paradigm shift by employing wireless sensor networks as a viable alternative. Our proposed system boosts capability to measure a range of physicochemical parameters linked to water quality, including reductions in potential, conductivity, pH level, temperature and flow rate. By scrutinising these parameters, our sensors effectively detect water contaminants, enabling a proactive response to potential threats. To achieve this, we have meticulously designed and implemented sensors equipped with signal conditioning circuits. These sensors are seamlessly integrated into a network, with each node connected to a microcontroller responsible for data analysis and processing. This integration ensures real-time monitoring, the rapid detection of water quality deviations and swift response mechanisms. [ABSTRACT FROM AUTHOR]

A dual-mode pH sensor based on nitrogen-doped carbon dots (N-CDs) with the source of o-phenylenediamine and tryptophan has been constructed. Under the stimulation of pH, the N-CDs exhibited prominent both color and fluorescence changes, leading to the rarely discovered colorimetric and fluorescent dual-readouts for the evaluation of pH. The mathematic relationship was established between pH and fluorescence intensity of N-CDs, and between pH and the UV–Vis absorbance ratio at 630 nm and 488 nm of N-CDs, respectively, over a quite broad pH range of 2.2 to 12.0. Multiple techniques are used to explore the dual-mode pH-responsive mechanism, and the preliminary explanation is put forward. The experimental results show that the N-CDs have visualized pH sensing applicability for actual samples, including various water samples and HeLa cell. Furthermore, the N-CD ink is developed for successful information encryption and anti-counterfeiting. This work might provide valuable insights into the sensing mechanism of CDs, and the application potential of CDs in broader fields. [ABSTRACT FROM AUTHOR]

Electrostatic spray deposition was applied to prepare pH sensing with spinel ZnCO2O4 thin films based on the measurement of extended-gate field-effect transistors (EGFET). The influence of annealing temperatures on the characteristics of the prepared films was analyzed. The structural and morphological properties of the annealed ZnCo2O4 films were assessed by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and contact angle measurement. The effect of the ZnCo2O4 annealing temperature on the characteristics of pH sensing for the prepared ZnCo2O4 films in EGFET measurement were examined with pH buffer solutions in a pH range of 2–12 at room temperature. The sensing films annealed at 550°C demonstrated a high voltage and current sensitivity at 67.6 mV/pH and 1.033 (µA)½/pH, with linearity values of 0.9968 and 0.9991, respectively. Moreover, the annealed 550°C ZnCo2O4 film exhibited low hysteresis at 4.99 mV and high retention stability. The results revealed that the pH sensing of the ZnCo2O4 EGFET device showed a super-Nernstian sensitivity, which indicated the influence of the surface properties of the annealed film. Therefore, the ZnCo2O4 film should be considered a potential option for the pH sensing layer in EGFET applications. [ABSTRACT FROM AUTHOR]