Chemical Sensors Research Articles

Phage Biosensor for the Classification of Metastatic Urological Cancers from Urine

Most of the annual 10 million cancer-related deaths are caused by metastatic disease. Survival rates for cancer are strongly dependent on the type of cancer and its stage at detection. Early detection remains a challenge due to the lack of reliable biomarkers and cost-efficient screening methods. Phage biosensors can offer a solution for early detection using non-invasive liquid biopsies. Here, we report the first results of the bifunctional phage biosensor to detect metastatic urological cancers from urine. A dye-sensitized phage library was used to select metastasis-related phage binders. After selection rounds, the most promising phage candidate was used to classify metastatic cancer from controls. Additionally, we applied one chemical sensor (phenoxazine non-fluorescent dye) to classify cancer from urine. A statistical significance (p = 0.0002) was observed between metastatic and non-metastatic cancer, with sensitivity of 70% and specificity of 79%. Furthermore, the chemical sensor demonstrated significance in detecting cancer (p < 0.0001) with a sensitivity of 71% and a specificity of 75%. Our data suggest a new promising field for urine biomarker research, and further evaluation with prospectively collected samples is ongoing. In conclusion, we report, for the first time, the potential of a chemical- and phage-based biosensor method to detect metastatic cancer using urine.

Liquid-Phase Exfoliated Graphene and Polytetrafluoroethylene for Highly Durable and Reusable Chemical Leak Detection Sensors

Graphene-based chemical sensors hold promise across diverse applications owing to their exceptional sensitivity and selectivity. However, achieving their long-term durability and reusability while preserving high sensitivity remains a significant challenge, particularly in harsh environments where exposure to strong chemicals is inevitable. This paper presents a novel approach to address this challenge by synergistically integrating liquid-phase exfoliated graphene (LPEG) with polytetrafluoroethylene (PTFE) within a single sensing strip. Through a comprehensive experimental investigation, we demonstrate the fabrication of highly durable and reusable chemical leak detection sensors by combining LPEG and PTFE. Furthermore, we explore the sensing mechanism, highlighting the roles of LPEG and PTFE in enhancing sensitivity and selectivity, along with durability and reusability. Performance evaluation reveals the sensors’ robustness against mechanical and chemical degradation, coupled with excellent recyclability. This innovative approach holds promise for applications in environmental monitoring, industrial safety, and healthcare, thus advancing the field of graphene-based chemical leak detection sensors.

Tetrazole-functionalized Organoboranes Exhibiting Dynamic Intramolecular N→B-Coordination and Cyanide-selective Anion Binding.

Starting from two different cyano-functionalized organoboranes, we demonstrate that 1,3-dipolar [3+2] azide-nitrile cycloaddition can serve to generate libraries of alkyl-tetrazole-functionalized compounds capable of intramolecular NàB-Lewis adduct formation. Due to the relatively low basicity of tetrazoles, structures can be generated that exhibit weak and labile NàB-coordination. The reaction furnishes 1- and 2-alkylated regio-isomers that exhibit different effective Lewis-acidities at the boron centers, and vary in their optical absorption and fluorescence properties. Indeed, we identified derivatives capable of selectively binding cyanide over fluoride, as confirmed by 11B NMR. This finding demonstrates the potentialities of this synthetic strategy to systematically fine-tune the properties of lead structures that are of interest as chemical sensors.

Development of an innovative colorimetric optical sensor for the detection of silver ions in environmental and biological samples

ABSTRACT A recently developed optical chemical sensor for silver assessment relies on polymer inclusion membranes (PIM) and avoids the use of plasticisers. This innovative optical sensor is constructed through a physical immobilisation process known as the encapsulation technique, resulting in an optical chemical membrane. The suggested PIM integrates 2-(2`-hydroxynaphthylazo)benzo-thiazole (HNABT) was used as a colorimetric reagent, polyvinyl chloride (PVC) as the foundational polymer, and dinonyl naphthalene sulphonic acid (DNNS) as an extractant. The created PIM demonstrates heightened responsiveness within the described approach, credited to the sensor membrane, in contrast to the optical sensor without PIM. The achieved results demonstrated that the sensor response was based on some factors such as plasticiser, film thickness, stirring effect, HNABT concentration, DNNS concentration and pH of the aqueous solution. Within the measurement range spanning from 7.5 to 250 ng mL−1 of Ag+ at pH 7.75, the absorbance response exhibits a notable correlation, achieving detection and quantification limits of 2.3 and 7.3 ng mL−1, respectively. The λmax for the PIM-based sensor registers at 577 nm. Additionally, the reproducibility and repeatability of the system are characterised by RSD of 2.25% and 1.13%, respectively, with a swift response time of approximately 3.0 min. The optode membrane’s selectivity is scrutinised in pH-buffered solutions concerning Ag+ ions. The proposed sensor is effectively applied for Ag+ assessment in food, water, environmental, and biological samples. The obtained results are corroborated by the FAAS procedure.

Efficient fabrication of high quality SU-8 photoresist based microsphere lasers via emulsion

Abstract SU-8 photoresist is a highly important material in the field of microfabrication and photonics owing to its low cost, excellent chemical and mechanical durability, high refractive index and transparency in the visible range. As a result, SU-8 photoresist has been employed as a cavity matrix for microsphere lasers. However, the current fabrication technique of SU-8 based microsphere lasers is complex and time-consuming. Here, we demonstrate a novel, cost-effective fabrication method for dye-doped SU-8 microspheres with diameters ranging from about 15 to 100 µm. These microspheres exhibit efficient lasing emission under optical pulse excitation. Lasing thresholds of 20 to 30 µJ·mm-2 and quality factors ranging from 1500 to 3000 are achieved. The size dependence of lasing characteristics indicates that the lasing mechanism is due to whispering gallery mode. Interestingly, these microsphere lasers can work in water, presenting promising application prospects in the fields of biological and chemical sensors.

High Q/V single-mode nanobeam-grating resonator, functional in the ultra-high sensitive label-free lab-on-a-chip chemical sensor

High Q/V single-mode nanobeam-grating resonator, functional in the ultra-high sensitive label-free lab-on-a-chip chemical sensor

Synthesis of silica inverse opal and evaluation of its potential as an optical chemical sensor for detection of metal salts

In this paper, SiO2 inverse opal photonic crystals, made by the co-assembly of SiO2 and polymethylmethacrylate (PMMA) microspheres, were used to detect 20 different metal salts with a concentration of 0.002 mol/L. Surprisingly, two different behaviors were observed. Some metal salts caused a redshift in photonic bandgap (PBG) while the others led to a PBG’s blueshift. The observed different behaviors of salts are due to their distinct influence on the lattice constant of the inverse structures which was precisely investigated by analyzing the field emission scanning electron microscopy (FESEM) images and ultraviolet–visible (UV–Vis) spectroscopy. It has been revealed that the competition between the hydrophilicity of SiO2 and the hygroscopicity of metal salts led to a shift of PBG toward blue or red. The maximum shift in the PBG range was observed for mercury (II) nitrate salt (19 nm), which indicates a sensitivity of 9.5 nm per concentration unit (mM). Furthermore, the lowest displacement of the PBG was observed for the sodium nitrate salt (5 nm), which represents a sensitivity of 2.5 nm/mM. The lowest and highest values of the detection limit (LOD) for mercury (II) nitrate salt and sodium nitrate salt equal 0.193 mmol/L and 0.887 mmol/L, respectively. In addition, according to the calibration curve, with a regression coefficient of R2 > 0.95, there is a linear relationship between the salt concentration and the displacement of the PBG of the structure. Based on the results illustrating the sensitivity of the synthesized inverse opal to the type and concentration of the salts, inverse opal can be regarded as a promising structure to create a new perspective in the field of chemical sensing.

CdTe@ZnS quantum dots for rapid detection of organophosphorus pesticide in agricultural products

Organophosphorus pesticides (OPPs) constitute the most widely employed class of pesticides. However, the prevalent use of OPPs, while advantageous, raises concerns due to their toxicity, posing serious threats to food safety. Chemical sensors utilizing quantum dots (QDs) demonstrate promising applications in rapidly detecting OPPs residues, thereby facilitating efficient inspection of agricultural products. In this study, we employ an aqueous synthesis approach to prepare low toxic CdTe@ZnS QDs with stable fluorescence properties. To mitigate the risk of imprecise measurements stemming from the inherent susceptibility of fluorescence to quenching, we have adopted the principle of fluorescence resonance energy transfer (FRET) for the construction of the turn-on quantum dot sensor. With a detection limit for chlorpyrifos as low as 10 ppb (10 μg/L), the QDs sensor exhibits notable resistance to interference from various pesticides. Application of this system to detect organophosphorothioate pesticides in apples produced results consistent with those obtained from high-performance liquid chromatography (HPLC) detection, affirming the promising application prospects of this sensing system for the rapid detection of OPPs residues.

Design a Friendly Nanoscale Chemical Sensor Based on Gold Nanoclusters for Detecting Thiocyanate Ions in Food Industry Applications

The surfactant cetyltrimethylammonium bromide (CTAB) induces the aggregation of gold nanoclusters (GNCs), leading to the development of a proposed fluorometric technique for detecting thiocyanate (SCN−) ions based on an anti-aggregation mechanism. This approach is straightforward to execute, highly sensitive, and selective. A significant quenching effect occurs in fluorescence upon using the aggregation agent CTAB in GNCs synthesis, resulting in a transition from intense red fluorescence to dim red. The decrease in fluorescence intensity of GNCs in the presence of CTAB is caused by the mechanism of fluorescence quenching mediated by aggregation. As the levels of SCN− rise, the fluorescence of CTAB-GNCs increases; this may be detected using spectrofluorometry or by visually inspecting under UV irradiation. The recovery of red fluorescence of CTAB-GNCs in the presence of SCN− enables the precise and discerning identification of SCN− within the concentration range of 2.86–140 nM. The minimum detectable concentration of the SCN− ions was 1 nM. The selectivity of CTAB-GNCs towards SCN− ions was investigated compared to other ions, and it was demonstrated that CTAB-GNCs exhibit exceptional selectivity. Furthermore, we believe that CTAB-GNCs have novel possibilities as favorable sensor candidates for various industrial applications. Our detection technique was validated by analyzing SCN− ions in milk samples, which yielded promising results.

Role of Silica, Carbon, and ZnO Nanomaterials in the Fabrication of Electrochemical Sensors for the Detection of Water Contaminants and Food Dye

AbstractSilica‐based nanomaterials have attracted huge attention for maximizing their safety and efficacy due to their nontoxicity, chemical and thermal stability, size tunability, and versatile functionality. Nanosilica with ZnO or carbon in a composite has excellent usage as an electrochemical sensor. Recent technological progression in nanotechnology and nanoscience has seen a number of applications of zinc oxide (ZnO) nanomaterials ranging from electronics, and sensing to environmental, and biomedical applications because of its various applications, multifunction, high specific surface area, stability, biocompatibility, nontoxicity, electrochemical activities, and so on. Carbon also has various advantageous properties like renewability, low ohmic resistance, and very stable response due to which carbon paste electrodes have attracted attention in the fabrication of electrochemical sensors. Electrochemical sensors are inexpensive, portable, and have excellent ability in detecting water contaminants, pesticides, disinfectants, pathogens, and different molecules. Artificial dyes are usually mixed with vegetable sauces, drinks, and other food items, which can cause cancer in human body. Voltametric methods with electrochemical sensors can be used to detect them in food samples. In this review, the present applications of ZnO and carbon nanomaterial‐based chemical sensors are meticulously studied to detect water contaminants and food dyes where nanosilica plays an important role as a sensor modifier.

Integrated imaging and proteomics sensors detect proteome aggregation induced by platinum-based chemotherapy drugs in living cells and mice model

Proteome aggregation is challenging to analyze given its loss of defined 3-D structures to develop chemo- and bio-sensors. Herein, we present integrated chemical sensors to image the occurrence of proteome aggregation and dissect its proteomic composition. Via these combinative sensors, we systematically reveal for the first time platinum-based drugs can deteriorate proteome stability, compromise protein homeostasis (proteostasis) network, and consequently cause proteome aggregation. Fluorescent protein aggregation imaging sensors (AggStain and AggRetina) not only confirms these drugs generally induce intracellular proteome aggregation but also quantifies the compactness (polarity) heterogeneity inside these aggregates. Chemical proteomics sensor (AggLink) further captures and profiles the composition of aggregated proteome, which uncovers the fluctuations of proteostasis network and metabolic pathways. In mice model, proteome aggregation and oxidative stress are imaged in multi-organs with platinum enrichment. Together, we integrate imaging and proteomics sensors to provide an alternative mechanism-of-action for platinum-based drugs’ anti-cancer function in addition to their common DNA intercalation mechanism.

Boron-nitride nanostructures for the detection of harmful gases (CO, CO2, H2S, N2O, and SO2)

Boron-nitride (BN) structures are considered materials with several applications, including sensing platforms. Through density functional theory calculations based on the PBE-D3/6-311G(d,p) level of theory, we propose the boron-nitride nanosheet, armchair nanotube (5,5), and fullerene as possible sensors for the harmful gases CO, CO2, H2S, N2O, and SO2. According to our results, the systems exhibit adsorption energies of −0.10 eV to −1.26 eV, and remarkable electronic parameters such as chemical potential, energy gap, and HOMO and LUMO energies, ideal for serving as chemical sensors of such pollutant gases. The nanostructures can be selective to sense a particular gas, mainly CO, N2O, and SO2. Additionally, we note a dramatic change in the electrical conductivity up to 2.14 eV, and low recovery time from 15 μs to 6.2 s. Finally, the BNNS-SO2, BNNT-N2O, BNNT-SO2, and BNF-CO are the more promissory systems to be used as chemical sensors of SO2, N2O, and CO.

Feasibility study of coffee husk char-derived carbon dots to enhance solar photovoltaic-thermal applications

Coffee is one of the most traded commodities in the world. Coffee husk makes up the majority of the solid debris generated during the dry processing of coffee, which is between 30% and 50%. Pyrolysis is a reliable and feasible technology to valorise the coffee husk. The present study proposes and investigates a novel method for producing carbon dots from coffee husk char through pyrolysis. Nanomaterials are becoming more popular to improve the thermal and optical properties of working fluids used in solar photovoltaic and thermal conversion systems. The coffee husk-char derived carbon dot (CHC-CD) nanofluids are prepared with different char concentrations (1%, 2%, 3% and 4%). The chemical and optical properties of the nanofluid produced from coffee husk char (CHC-CD nanofluid) are investigated. The morphology, size and particle size distribution of the CHC-CD particles were studied using field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The particles were found to have an average size of 5.38 nm. The CHC-CD nanofluid had a basic pH and negative zeta potential, which was found to decrease with an increase in the char concentration and pH. The nanofluid prepared with 2% char was found to have a zeta potential of −61.4 mV. It was evident from the UV–vis transmittance spectra that the CHC-CD nanofluid prepared with a char concentration of 2% had very limited transmittance in the UV region and good transmittance above 735 nm. This transmittance range is found to be favourable for the smooth and efficient operation of silicon-based solar PV cells. The CHC-CD nanofluid also showed a maximum intensity emission wavelength of 522 nm at an excitation wavelength of 450 nm. Characterisation of the carbon phase, surface functional groups, and surface defects was also done using XRD, FTIR, and Raman spectroscopy, respectively. The optical and chemical properties indicate that the developed CHC-CD nanofluid can find application not only in solar photovoltaic and thermal systems but also in applications in biomedical and chemical sensor applications.

Inductance coil high-frequency contactless chemical sensor: Systematic study of its cationic sensitivity

Contactless sensors for chemical analysis, based on inexpensive and widely available electronic components, are a promising alternative to existing routine laboratory methods. We have proposed a novel type of a contactless sensor, composed of three simple components: an alternate current generator, an inductance coil, and a receiver. The sample, placed into the coil as a core of the inductor, modifies the current passing through the coil. Previously, we have demonstrated that this contactless sensor may have numerous applications for chemical analysis. In this work, we have explored the performance of the coil-based measuring platform further and performed the first systematic study of the response of inductance coil sensor to metal cations in aqueous solutions. Sixteen metal cations with different charge and radii were studied. Linear response ranges, sensitivity values and the comparison between univariate and multivariate regression modeling are presented. The largest linear response range was observed for transition metal cations Ni2+, Cu2+, Pb2+ and Nd3+ (10-3 – 10-1 M), the narrowest – for Li+ and Gd3+ (10-2 – 3.2x10-1 M) with R2 values larger than 0.94. The dependence of the response on the radius and the charge of the cation are discussed. The analytical characteristics of the device show its potential in contactless and low-cost chemical analysis and set the ground for the future research.

Aerosol-Synthesized Surfactant-Free Single-Walled Carbon Nanotube-Based NO2 Sensors: Unprecedentedly High Sensitivity and Fast Recovery.

This study pioneers a chemical sensor based on surfactant-free aerosol-synthesized single-walled carbon nanotube (SWCNT) films for detecting nitrogen dioxide (NO2). Unlike conventional CNTs, the SWCNTs used in this study exhibit one of the highest surface-to-volume ratios. They show minimal bundling without the need for surfactants and have the lowest number of defects among reported CNTs. Furthermore, the dry-transferrable and facile one-step lamination resultsin promising industrial viability. When applied to devices, the sensor shows excellent sensitivity (41.6% at 500ppb), rapid response/recovery time (14.2/120.8s), a remarkably low limit of detection (below ≈0.161ppb), minimal noise, repeatability for more than 50 cycles without fluctuation, and long-term stability for longer than 6months. This is the best performance reported for a pure CNT-based sensor. In addition, the aerosol SWCNTs demonstrate consistent gas-sensing performance even after 5000 bending cycles, indicating their suitability for wearable applications. Based on experimental and theoretical analyses, the proposed aerosol CNTs are expected to overcome the limitations associated with conventional CNT-based sensors, thereby offering a promising avenue for various sensor applications.

MEMS Resonant Beam with Outstanding Uniformity of Sensitivity and Temperature Distribution for Accurate Gas Sensing and On-Chip TGA.

Micromechanical resonators have aroused growing interest as biological and chemical sensors, and microcantilever beams are the main research focus. Recently, a resonant microcantilever with an integrated heater has been applied in on-chip thermogravimetric analysis (TGA). However, there is a strong relationship between the mass sensitivity of a resonant microcantilever and the location of adsorbed masses. Different sampling positions will cause sensitivity differences, which will result in an inaccurate calculation of mass change. Herein, an integrated H-shaped resonant beam with uniform mass sensitivity and temperature distribution is proposed and developed to improve the accuracy of bio/chemical sensing and TGA applications. Experiments verified that the presented resonant beam possesses much better uniformity of sensitivity and temperature distribution compared with resonant microcantilevers. Gas-sensing and TGA experiments utilizing the integrated resonant beam were also carried out and exhibited good measurement accuracy.

All‐Printed Electrically Driven Lighting via Electrochemiluminescence

AbstractElectrochemiluminescence (ECL) has attracted significant attention as a promising light‐emitting technology owing to its simple configuration and solution processability. ECL has wide applications in biological and chemical sensors, lighting, and displays. ECL lighting devices are fabricated as sandwiched structures with a transparent electrode on top, which limits their widespread adoption. Intricate structures with high precision and customizable designs can be directly fabricated using 3D printing. However, 3D printing of ECL devices is challenging because of poor printability and structural integrity of ECL luminophore inks. Here, all‐printed electrically driven lighting is demonstrated using the direct ink writing method. The ECL reactive layer and electrodes are directly printed using a side‐by‐side electrode configuration. A 3D printable ECL ink is developed by incorporating silica nanoparticles as rheological modifiers to realize well‐defined patterns with high structural integrity. Graphene is introduced on Ag multilayer electrodes to embrace both the electrical conductivity and electrochemical stability for efficient ECL operation. This all‐printing approach allows the fabrication of ECL devices with complex designs, such as combs and spirals. Moreover, it facilitates seamless printing on various substrate materials, making this technology an asset in the fields of biology, chemistry, and electronics.

Promising optical chemical sensor for detecting Al(III) ions in water based on organic fluorophore

In the present work, an optical sensing scheme was designed to detect the Al(III) ions based on a fluorescent probe. The synthesized probe N-(3-chloro)-salicylaldimine CSI receptor was developed using turn-on fluorescence enhancement. During the treatment process of Al(III) ions, the emission of the CSI probe was increased at 545 nm due to the formation of a 1:1 complex between the chemosensor and the Al(III) ions at room temperature. The gradual addition of Al(III) ions to the studied solution gradually enhanced the CSI emission. The other metal ions, including alkali, alkaline metal ions, and some transition metal ions, had no noticeable impact on the fluorescent intensity. The limit of detection (LOD) and (LOQ) were determined as 0.427 nM and 1.28 nM, respectively. The detection limit for this sensor is very low, demonstrating its remarkable selectivity and ultra-sensitivity. These impressive characteristics allow the detection of Al(III) ions at concentrations as low as 1.28 × 10−3 to 1 μM while highly selective even in the presence of other metal ions. EDTA solution at a concentration of 1 µM was used to make the sensor reversible. We also provide the fact that the CSI probe can be a promising optical chemical for detecting Al(III) ions in real samples.

Controlled Synthesis of Preferential Facet-Exposed Fe-MOFs for Ultrasensitive Detection of Peroxides.

Exposing different facets on metal-organic frameworks (MOFs) is highly desirable to enhance the performance for various applications, however, exploiting a concise and effective approach to achieve facet-controlled synthesis of MOFs remains challenging. Here, by modulating the ratio of metal precursors to ligands, the facet-engineered iron-based MOFs (Fe-MOFs) exhibits enhanced catalytic activity for Fenton reaction are explored, and the mechanism of facet-dependent performance is revealed in detail. Fully exposed (101) and (100) facets on spindle-shaped Fe-MOFs enable rapid oxidation of colorless o-phenylenediamine (OPD) to colored products, thereby establishing a dual-mode platform for the detection of hydrogen peroxide (H2O2) and triacetone triperoxide (TATP). Thus, a detection limit as low as 2.06nm is achieved, and robust selectivity against a wide range of common substances (>16 types) is obtained, which is further improved by incorporating a deep learning architecture with an SE-VGG16 network model, enabling precise differentiation of oxidizing agents from captured images. The present strategy is expected will shine light on both the rational synthesis of nanomaterials with modulated morphologies and the exploitation of high-performance trace chemical sensors.

Silicon flow stop frame for encapsulation of CMOS microsensor chips by wet anisotropic etching in KOH

Bulk micromachining in silicon is governed by the etching process where anisotropic (wet) etching in KOH can yield complex structures beyond that achievable with isotropic (dry) etching techniques. One example is the miniaturised frame reported herein with an area of 2.9 to 7.5 mm2, walls that are 1/10 mm thick, a height of 525 μm equipped with sloping walls that takes advantage of the 54.7° angle of the (111) planes to the horizontal (100) top surface of the wafer. Convex corners liable to damage are protected by sacrificial bridge structures which are etched thin to a point where the frame can be easily removed from the bulk substrate material. Frames made from isotropic (dry) etching processes have been made for comparison. Although the frame structure has different applications in microfabrication, the intended use is a flow stop barrier preventing liquid resins from entering the active area of a CMOS chemical sensor chip during encapsulation for use in aqueous or gaseous media. Beyond this specific proof-of-concept, the strategy is expected to be of general interest for all who treasures KOH etching and wants to explore new avenues based on this process.