Qualitative Detection Research Articles

Pathogenic bacteria prevalence in cultured Nile tilapia in Southwest Mexico: A real-time PCR analysis.

The present study investigates molecular-based PCR techniques to estimate the prevalence of fish pathogens in southwest Mexico where recurrent mortality in the tilapia cultures has been observed. Sample of internal organs and lesions of Nile tilapia were taken and analysed in 2018, 2019, 2020 and 2022 to detect bacterial pathogens using PCR. No samples were taken in 2021 due to the COVID-19 pandemic. The real-time PCR conditions were optimized to allow a qualitative reliable detection of the bacteria from fixed fish tissue. A total of 599 pond- and cage-cultured tilapia from the southwestern Mexican Pacific (Guerrero, Oaxaca and Chiapas states) were analysed. In this tropical region, during 2018 and 2019 water temperatures of the tilapia cultures were generally with the optimal range to grow Nile tilapia, although extreme values were recorded on some farms. Most of the tilapia sampled were apparently healthy. No Francisella sp. was detected in any sample, and Staphylococcus sp. was the most prevalent (from 0% to 64%) bacteria from the three states over time. Low prevalence of Aeromonas sp. was found, from 0% to 4.3%, although the fish pathogen Aeromonas dhakensis was not detected. Sterptococcus iniae was only detected in Chiapas in 2019 at a low prevalence (1.4%), while the major tilapia pathogen S. agalactiae was detected at a high prevalence (from 0% to 59%) in the three Mexican states. This is the first detection of these pathogenic bacteria in rural farms using real-time PCR and constitutes a great risk for tilapia aquaculture in Mexico, as well as a potential dispersion of these pathogens to other aquaculture areas.

Fluorescent microsphere immunochromatographic sensor for the detection of total fumonisins B1, B2, and B3 in grain samples

Fumonisin Bs (FBs) are the most common toxic and carcinogenic substances found among naturally occurring contaminants of cereals. A group-specific monoclonal antibody (mAb) 2H7 was prepared that equably recognized fumonisins B1 (FB1), B2 (FB2), and B3 (FB3) with a half-maximal inhibitory concentration (IC50) value for the three forms of 1.52, 2.93, and 3.85 ng/ml, respectively. On this basis, a fluorescent microsphere-based immunochromatographic strip (FM-ICS) was established for the rapid qualitative and quantitative detection of total FBs (FB1, FB2, and FB3) in corn, wheat, and rice. A recovery test showed that the recovery of FM-ICS was 92.8–108.3% with coefficients of variation of 1.2–7.9%. This method has the same reliability as seen with liquid chromatography-tandem mass spectrometry. And the accuracy was further confirmed by certified reference materials. Therefore, it can be used for the detection of FBs in cereal samples.

P504 Prevalence of gastrointestinal infections in ulcerative colitis patients assessed with QIASTAT-DX® GASTROINTESTINAL PANEL 2

Abstract Background In inflammatory bowel disease (IBD), an acute clinical flare may be due to either disease exacerbation or an enteric infection. Thus, it is recommended to exclude infections before escalating IBD therapy. In this setting, conventional tests identify only a minimal proportion of infections (i.e. 10%). Whether nucleic acid multiplex tests can expand the range of detected pathogens and increase the overall prevalence is still a matter of debate. Methods We performed a single-center transversal prospective study at Fondazione IRCCS Policlinico Ca’ Granda. Stool samples from consecutive ulcerative colitis (UC) patients experiencing a disease flare and a group of patients in clinical remission were enrolled between February and October 2023 and tested with QIAstat-Dx Gastrointestinal Panel 2 (Qiagen GmbH, Hilden, Germany) for simultaneous qualitative detection and identification of nucleic acids from multiple viruses, bacteria, and parasites. Clinically active disease was defined as a Partial Mayo Score (PMS) of ≥2. Results Overall, 85 UC patients were enrolled. Demographics and clinical features are displayed in Table 1. Median age was 42 (18-79), 52% were males. The two most common treatment regimens were mesalamine (54%) and biologic/small molecule treatment (35%). 66 (78%) patients were clinically active, while 19 (22%) were in remission. In the active group, median bowel movements were 5 (3-15), 58 (88%) patients had loose stool, 32 (49%) reported abdominal pain, 40 (61%) urgency, 10 (15%) overnight symptoms, 6 (9%) fever. Median PMS was 5 (2-8). Median hemoglobin was 13.8 (8.2-16.4) g/dL, fecal calprotectin 508 (<5-4980) ug/g. Prevalence of gastrointestinal infections with QIAstat-Dx was 30 vs. 10% (p=0.13) in active vs. remission group, respectively. The most common infections were: C.Difficile infection (CDI) (4 cases), Cytomegalovirus (CMV) (4 cases) and enteropathogenic E.Coli (EPEC) (4 cases). Regarding viral and E. Coli infections, clinical remission (PMS <2) occurred spontaneously. As for CMV, Campylobacter spp., and CDI, all patients except one achieved remission following specific antimicrobial treatment. In one patient CMV infection led to hospital admission (circulating CMV DNA 35,395 IU/mL). The remaining patient did not receive specific antiviral therapy since sigmoidoscopy only detected isolated CMV+ cells, and remission was achieved with UC treatment escalation. Conclusion In UC patients experiencing a clinical flare, prevalence of gastrointestinal infections with QIAstat-Dx® Gastrointestinal Panel 2 is numerically higher than patients in remission. Further studies are needed to investigate whether increased detection could influence the clinical outcomes of IBD patients and time and costs for the healthcare system.

A Single Set of Well-Designed Aptamer Probes for Reliable On-site Qualitative and Ultra-Sensitive Quantitative Detection.

Aptamer-based probes are pivotal components in various sensing strategies, owing to their exceptional specificity and versatile programmable structure. Nevertheless, numerous aptamer-based probes usually offer only a single function, limiting their capacity to meet the diverse requirements of multi-faceted sensing systems. Here, we introduced supersandwich DNA probes (SSW-DNA), designed and modified on the outer surface of nanochannels with hydrophobic inner walls, enabling dual functionality: qualitative detection for on-site analysis and quantitative detection for precise analysis. The fragmented DNAs resulting from the target recognition, are subsequently identified through lateral flow assays, enabling robust on-site qualitative detection of microcystin-LR with an impressively low limit of detection (LOD) at 0.01 μg/L. Meanwhile, the nanochannels enable highly sensitive quantification of microcystin-LR through the current analysis, achieving an exceptionally low LOD at 2.5×10-7 μg/L, with a broad dynamic range spanning from 1×10-6 to 1×102 μg/L. Furthermore, the process of target recognition introduces just a single potential error propagation, which reduces the overall risk of errors during the entire qualitative and quantitative detection process. This sensing strategy broadens the scope of applications for aptamer-based composite probes, holding promising implications across diverse fields, such as medical diagnosis, food safety, and environmental protection.

A Single Set of Well‐Designed Aptamer Probes for Reliable On‐site Qualitative and Ultra‐Sensitive Quantitative Detection

AbstractAptamer‐based probes are pivotal components in various sensing strategies, owing to their exceptional specificity and versatile programmable structure. Nevertheless, numerous aptamer‐based probes usually offer only a single function, limiting their capacity to meet the diverse requirements of multi‐faceted sensing systems. Here, we introduced supersandwich DNA probes (SSW‐DNA), designed and modified on the outer surface of nanochannels with hydrophobic inner walls, enabling dual functionality: qualitative detection for on‐site analysis and quantitative detection for precise analysis. The fragmented DNAs resulting from the target recognition, are subsequently identified through lateral flow assays, enabling robust on‐site qualitative detection of microcystin‐LR with an impressively low limit of detection (LOD) at 0.01 μg/L. Meanwhile, the nanochannels enable highly sensitive quantification of microcystin‐LR through the current analysis, achieving an exceptionally low LOD at 2.5×10−7 μg/L, with a broad dynamic range spanning from 1×10−6 to 1×102 μg/L. Furthermore, the process of target recognition introduces just a single potential error propagation, which reduces the overall risk of errors during the entire qualitative and quantitative detection process. This sensing strategy broadens the scope of applications for aptamer‐based composite probes, holding promising implications across diverse fields, such as medical diagnosis, food safety, and environmental protection.

An interpretative review of the wastewater-based surveillance of the SARS-CoV-2: where do we stand on its presence and concern?

Wastewater-based epidemiology (WBE) has been used for monitoring infectious diseases like polio, hepatitis, etc. since the 1940s. It is also being used for tracking the SARS-CoV-2 at the population level. This article aims to compile and assess the information for the qualitative and quantitative detection of the SARS-CoV-2 in wastewater. Based on the globally published studies, we highlight the importance of monitoring SARS-CoV-2 presence/detection in the wastewater and concurrently emphasize the development of early surveillance techniques. SARS-CoV-2 RNA sheds in the human feces, saliva, sputum and mucus that ultimately reaches to the wastewater and brings viral RNA into it. For the detection of the virus in the wastewater, different detection techniques have been optimized and are in use. These are based on serological, biosensor, targeted PCR, and next generation sequencing for whole genome sequencing or targeted amplicon sequencing. The presence of the SARS-CoV-2 RNA in wastewater could be used as a potential tool for early detection and devising the strategies for eradication of the virus before it is spread in the community. Additionally, with the right and timely understanding of viral behavior in the environment, an accurate and instructive model that leverages WBE-derived data may be created. This might help with the creation of technological tools and doable plans of action to lessen the negative effects of current viral epidemics or future potential outbreaks on public health and the economy. Further work toward whether presence of viral load correlates with its ability to induce infection, still needs evidence. The current increasing incidences of JN.1 variant is a case in point for continued early detection and surveillance, including wastewater.

Silver dendrite metasurface SERS substrates prepared by photoreduction method for perfluorooctanoic acid detection

Perfluorooctanoic acid (PFOA), a novel organic pollutant, has been shown to be toxic, persistent, bioaccumulative, long-range transportable, and globally prevalent. This article is based on surface enhanced Raman scattering (SERS) spectroscopy analysis technology. The monolayer of SiO2 was prepared by chemical reduction etching self-assembly method and silver dendrites were grown on it, thus forming the SERS substrate with silver dendrite Metasurface structure with Raman detection enhancement factor up to 2.32 × 105. The prepared silver dendrite Metasurface SERS substrate was applied to the qualitative and quantitative detection of PFOA, with a quantitative detection limit of 15.89 ppb. The results of this paper provide a new, simple, and quick method for the detection of PFOA in the environment.

Machine learning assisted dual-functional nanophotonic sensor for organic pollutant detection and degradation in water

This study presents a dual-functional thin film, known as Ag nanoparticles decorated, ZnO nanorods coated silica nanofibers (AgNP-ZnONR-SNF), which demonstrates remarkable capabilities in both water purification and organic pollutants sensing. The 3D fibrous structure of ZnONR-SNF provides a large surface-area-to-volume ratio for piezo- and photo-catalytic degradation of organic pollutants under UV irradiation, achieving over 98% efficiency. Ag nanoparticles decorated on ZnONR-SNF form “hot-spot” that significantly enhance the surface-enhanced Raman spectroscopy (SERS) signal, resulting in an enhancement factor of 1056 and an experimental detection limit of 1 pg mL−1. Furthermore, a machine learning algorithm is developed for the qualitative and quantitative detection of multiple contaminants, achieving high accuracy (92.3%) and specificity (89.3%) without the need for preliminary processing of Raman spectra. This work provides a promising nanoengineering solution for water purification and sensing with improved detection accuracy, purification efficiency, and cost-effectiveness.

Fully Reversible and Super-Fast Photo-Induced Morphological Transformation of Nanofilms for High-Performance UV Detection and Light-Driven Actuators.

Flexible and highly ultraviolet (UV) sensitive materials garner considerable attention in wearable devices, adaptive sensors, and light-driven actuators. Herein, a type of nanofilms with unprecedented fully reversible UV responsiveness are successfully constructed. Building upon this discovery, a new system for ultra-fast, sensitive, and reliable UV detection is developed. The system operates by monitoring the displacement of photoinduced macroscopic motions of the nanofilms based composite membranes. The system exhibits exceptional responsiveness to UV light at 375nm, achieving remarkable response and recovery times of < 0.3s. Furthermore, it boasts a wide detection range from 2.85µWcm-2 to 8.30mWcm-2, along with robust durability. Qualitative UV sensing is accomplished by observing the shape changes of the composite membranes. Moreover, the composite membrane can serve as sunlight-responsive actuators for artificial flowers and smart switches in practical scenarios. The photo-induced motion is ascribed to the cis-trans isomerization of the acylhydrazone bonds, and the rapid and fully reversible shape transformation is supposed to be a synergistic result of the instability of the cis-isomers acylhydrazone bonds and the rebounding property of the networked nanofilms. These findings present a novel strategy for both quantitative and qualitative UV detection.

Development of a high-throughput DNA isolation method for livestock and poultry meat based on mesoporous metal-organic framework-coated solid-phase microextraction device

A rapid, portable, simple, low-cost, and high-throughput DNA isolation method was developed for the quantitative identification of meat adulteration based on mesoporous UiO-66 coated solid phase microextraction (SPME) devices. The high-throughput DNA extraction system consists of 96 UiO-66 SPME devices and a polyformaldehyde plate, which can extract DNA from 96 livestock and poultry meat samples simultaneously. At the same time, several parameters of the high throughput DNA isolation method were optimized, including lysis buffer volume, elution buffer volume, lysis time and elution time, etc. Compared with the single DNA isolation device, the 96-SPME high-throughput extraction system maintains the original good universality, reproducibility, chemical stability, and reusability. On this basis, it obtained higher DNA concentration (80 ± 34 ng μL−1), satisfactory DNA purity (A260/A280=2.4) and shorter extraction time (less than 7.2 s per sample), which are much more convenient and efficient than the conventional kit method and the single SPME DNA isolation method. In addition, the conventional multiplex polymerase chain reaction and real-time polymerase chain reaction techniques were used for the qualitative and quantitative detection of meat adulteration. The DNA obtained from this extraction method is highly reproducible and sensitive for the identification of duck ingredients in beef, with a detection range of 1–100 % and a minimum detection limit of 1 % (w/w).

Rapid and sensitive detection of nucleic acids using an RAA-CRISPR/Cas12b one-pot detection assay (Rcod)

Rapid, sensitive and specific methods are crucial for nucleic acid detection. CRISPR/Cas12b has recently been widely used in nucleic acid detection. However, due to its thermophagic property, DNA isothermal recombinase-aided amplification (RAA) and subsequent CRISPR/Cas12b detection require two separate reactions, which is cumbersome and inconvenient and may cause aerosol pollution. In this study, we propose an RAA-CRISPR/Cas12b one-pot detection assay (Rcod) for Bordetella pertussis detection without additional amplification product transfer steps. The time from sample processing to response time was less than 30 min using nucleic acid extraction-free method, and the sensitivity reached 0.2 copies/μL. In this system, Alicyclobacillus acidoterrestris Cas12b protein (AacCas12b) exhibited strong and specific trans-cleavage activity at a constant temperature of 37 °C, while the cis-cleavage activity was weak. This characteristic reduces the interference of AacCas12b with nucleic acids in the system. Compared with real-time PCR, our Rcod system detected B. pertussis in 221 clinical samples with a sensitivity and specificity of 97.96 % and 99.19 %, respectively, with nucleic acid extraction-free method. The rapid, sensitive and specific Rcod system provides ideas for the establishment of CRISPR-based one-step nucleic acid detection and may aid the development of reliable point-of-care nucleic acid tests. ImportancePertussis is an acute respiratory infection caused by B. pertussis that is highly contagious and potentially fatal, and early diagnosis is essential for the treatment of whooping cough. In this study, we found that AacCas12b has high and strongly specific trans-cleavage activity at lower temperatures. A RAA-CRISPR/Cas12b one-step detection platform (Rcod) without interference with amplification was developed. In addition, the combination of Rcod and nucleic acid extraction-free method can quickly and accurately detect the qualitative detection of B. pertussis, and the detection results are visualized, which makes the pathogen nucleic acid detection and analysis process simpler, and provides a new method for the rapid clinical diagnosis of B. pertussis.

A simple indicator displacement assay ensemble for rapid and selective determination and naked-eye detection of Cu2+ and citrate through a novel diazo-based colorimetric chemosensor

ABSTRACT Citrate as a naturally occurring ion with important biological roles, especially in metabolic cycles, and as an important biomarker in the early diagnosis of many diseases, including prostate cancer, has received special attention. In the present study, a novel, sensitive, fast and simple colorimetric bisazo-based chemosensor was developed for sequential determination and naked-eye detection of Cu2+ and citrate. UV-Vis spectroscopic studies showed that Reactive Red 141 (RR141) exhibits high selectivity and sensitivity towards Cu2+ in the presence of many other cations in deionised water (10 mmol L−1 MES(2-(N-morpholino)ethanesulfonic acid)/NaOH buffer solution, pH 6.0) and complex real samples as well. The obvious colorimetric response while interaction with copper and citrate is due to complexation between RR141 and Cu2+, and then the citrate detection occurred through metal transfer from the RR141-Cu2+ towards the citrate anion releasing RR141 via an indicator displacement route. The mechanism of detection has been carefully investigated using the semi-empirical calculation method of MM2 molecular mechanics. The proposed detection method for citrate ion has a detection limit of 0.15 µmol L−1 and a satisfactory linear range of 1.92–45.96 µmol L−1, which is consistent with the desired average diagnostic concentration in prostate cancer (less than 2 mmol L−1). Our studies’ results indicate the high capability of the developed chemical sensor for quantitative and qualitative citrate detection in various complex media, including biological and clinical real samples.

SARS-CoV-2 IgG antibody status in unvaccinated and 2-dose vaccinated Indonesians by AstraZeneca.

Indonesia began deploying a COVID-19 vaccine in January 2021, prioritising vaccination for high-risk groups such as healthcare workers, the elderly and those with comorbidities, and ending with the general public due to limited vaccine availability. Our study aimed to evaluate antibody response in Indonesians who had received two doses of the vaccine vs. those who had not. The study design was a cohort study involving 46 unvaccinated people and 23 people who had received the second dose of the AstraZeneca vaccine in three months. Methods used for the qualitative and quantitative detection of IgG antibodies included rapid RI-GHA and ELISA tests. Findings showed that positive IgG antibodies qualitatively detected by the rapid RI-GHA test were significantly higher in those vaccinated (60.9%) than in unvaccinated people (26.1%). Using the ELISA assay, all vaccinated individuals qualitatively showed positive antibodies (cut-off ≥4.33 BAU/ml), and the average quantitative titer of anti-SARS-CoV-2 s-RBD IgG was significantly higher in vaccinated (157.06±238.68 BAU/ml) than in unvaccinated (51.90±87.60 BAU/ml) individuals. Some unvaccinated individuals with no history of infection were found to have anti-SARS-CoV-2 antibodies that may have been previously asymptomatic, although their mean antibody titers were certainly lower than those in the 2-dose group. Approximately 56% of vaccinated individuals had antibody titers above 60 BAU/ml as a cut-off for protective threshold, a significantly higher proportion than unvaccinated individuals. In conclusion, vaccination with two doses AstraZeneca increased anti-SARS-CoV-2 antibodies which resulted in enhanced immunity against symptomatic COVID-19.

Development of Dual Diagnostic-Therapeutic Nanoformulation Effective Against Pancreatic Cancer in Animal Model.

Erythrocytes and fibroblasts in the pancreatic cancer tumor microenvironment promote tumor cell growth and invasion by providing nutrients and promoting immunosuppression. Additionally, they form a barrier against the penetration of chemotherapeutic drugs. Therefore, the search for diversified tumor-targeting materials plays an essential role in solving the above problems. Physicochemical characterization of Graphene fluorescent nanoparticles (GFNPs) and nanomedicines were analyzed by transmission electron microscopy (TEM), elemental analyzers and ultraviolet fluorescence (UV/FL) spectrophotometer. Localization of GFNPs in cell and tissue sections imaged with laser confocal microscope, fluorescence scanner and small animal in vivo imager. Qualitative detection and quantitative detection of GFNPs and GFNPs-GEM were performed using High performance liquid chromatography (HPLC). Based on the 3 nm average dimensions, GFNPs penetrate vascular endothelial cells and smooth muscle cells, achieve up to label 30% tumor cells and 60% cancer-associated fibroblasts (CAFs) cells, and accurately label mature red blood cells in the tumor microenvironment. In orthotopic transplanted pancreatic cancer models, the fluorescence intensity of GFNPs in tumors showed a positive correlation with the cycle size of tumor development. The differential spatial distribution of GFNPs in three typical clinical pancreatic cancer samples demonstrated their diagnostic potential. To mediate the excellent targeting properties of GFNPs, we synthesized a series of nanomedicines using popular chemotherapeutic drugs, in which complex of GFNPs and gemcitabine (GFNPs-GEM) possessed stability in vivo and exhibited effective reduction of tumor volume and fewer side effects. GFNPs with multiple targeting tumor microenvironments in pancreatic cancer possess diagnostic efficiency and therapeutic potential.

Qualitative and quantitative rapid detection of VOCs differentially released by VAP-associated bacteria using PTR-MS and FGC-PTR-MS.

Ventilator-associated pneumonia (VAP) is a prevalent disease caused by microbial infection, resulting in significant morbidity and mortality within the intensive care unit (ICU). The rapid and accurate identification of pathogenic bacteria causing VAP can assist clinicians in formulating timely treatment plans. In this study, we attempted to differentiate bacterial species in VAP by utilizing the volatile organic compounds (VOCs) released by pathogens. We cultured 6 common bacteria in VAP in vitro, including Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Staphylococcus aureus, which covered most cases of VAP infection in clinic. After the VOCs released by bacteria were collected in sampling bags, they were quantitatively detected by a proton transfer reaction-mass spectrometry (PTR-MS), and the characteristic ions were qualitatively analyzed through a fast gas chromatography-proton transfer reaction-mass spectrometry (FGC-PTR-MS). After conducting principal component analysis (PCA) and analysis of similarities (ANOSIM), we discovered that the VOCs released by 6 bacteria exhibited differentiation following 3 h of quantitative cultivation in vitro. Additionally, we further investigated the variations in the types and concentrations of bacterial VOCs. The results showed that by utilizing the differences in types of VOCs, 6 bacteria could be classified into 5 sets, except for A. baumannii and E. cloacae which were indistinguishable. Furthermore, we observed significant variations in the concentration ratio of acetaldehyde and methyl mercaptan released by A. baumannii and E. cloacae. In conclusion, the VOCs released by bacteria could effectively differentiate the 6 pathogens commonly associated with VAP, which was expected to assist doctors in formulating treatment plans in time and improve the survival rate of patients.

Quantitative analysis of microplastics in seawater based on SERS internal standard method.

Microplastics can enter the human body through the food chain and can cause cardiovascular or cerebrovascular diseases; thus, it is essential to detect microplastics sensitively and accurately. Traditional methods have some drawbacks, such as a low sensitivity and complicated experimental procedures, so it is difficult to detect microplastics less than 1 μm. While surface enhanced Raman scattering technology can compensate for these shortcomings, there are fewer reports on the quantitative detection of microplastics using SERS technology. In this study, SERS and an internal standard method were utilized to detect microplastics qualitatively and quantitatively. The electric field enhancement effect of common gold, silver, and copper substrates were simulated by the finite element method, and the influence rule of structural parameters on the enhancement factor was obtained to optimize structural parameters. Subsequently, a gold nanopyramid array substrate was prepared using the colloidal sphere template method. Finally, the prepared substrate was applied to detect polystyrene microplastics with a diameter of 500 nm, and the detection of limit is 1.8 × 10-4 mg mL-1 in the quantitative range of 2-2 × 10-4 mg mL-1, and the correlation coefficient of the linear regression equation is 0.9918. The experimental results showed that this proposal has a lower detection limit and a wider quantitative range and expands ideas for the qualitative and quantitative detection of microplastics in seawater.

High performance electrochemical CO2 reduction over Pd decorated cobalt containing nitrogen doped carbon.

Efficient electrocatalytic CO2 reduction reaction (eCO2RR) to various products, such as carbon monoxide (CO), is crucial for mitigating greenhouse gas emissions and enabling renewable energy storage. In this article, we introduce Pd nanoparticles which are deposited over in-house synthesized nitrogen doped tubular carbon (NC) whose ends are blocked with cobalt oxide (CoOx). This composite material is denoted as Pd@CoOx/NC. Among the series of synthesized electrocatalysts, the optimum ratio (Pd@CoOx/NC1) within this category exhibits exceptional performance, manifesting an 81% faradaic efficiency (FE) for CO generation which was quantitatively measured using a gas chromatograph. This remarkable efficiency can be attributed to several scientific factors. Firstly, the presence of Pd nanoparticles provides active sites for CO2 reduction. Secondly, the NC offer enhanced electrical conductivity and facilitate charge transfer during the reaction. Thirdly, the CoOx capping at the ends of the NC serves to stabilize the catalyst, favoring the formation of CO. The remarkable selectivity of the catalyst is further confirmed by the qualitative CO detection method using PdCl2 strips. Pd@CoOx/NC1 exhibits a high current density of 55 mA cm-2 and a low overpotential of 251 mV, outperforming Pd decorated multiwalled carbon nanotubes (Pd@MWCNTs) which shows a higher overpotential of 481 mV. Pd@CoOx/NC1 shows long-term stability at different potentials and rapid reaction kinetics. These findings highlight Pd@CoOx/NC1 as promising CO2 reduction catalysts, with implications for sustainable energy conversion techniques.

Recent advances in the fluorimetric and colorimetric detection of cobalt ions.

Cobalt is an essential metal to maintain several functions in the human body and is present in functional materials for numerous applications. Thus, to monitor these functions, it is necessary to develop suitable probes for the detection of cobalt. Presently, researchers are focused on designing different chemosensors for the qualitative and quantitative detection of the metal ions. Among the numerous methods devised for the identification of cobalt ions, colorimetric and fluorimetric techniques are considered the best choice due to their user-friendly nature, sensitivity, accuracy, linearity and robustness. In these techniques, the interaction of the analyte with the chemosensor leads to structural changes in the molecule, causing the emission and excitation intensities (bathochromic, hyperchromic, hypochromic, and hypsochromic) to change with a change in the concentration of the analyte. In this review, the recent advancements in the fluorimetric and colorimetric detection of cobalt ions are systematically summarized, and it is concluded that the development of chemosensors having distinctive colour changes when interacting with cobalt ions has been targeted for on-site detection. The chemosensors are grouped in various categories and their comparison and the discussion of computational studies will enable readers to have a quick overview and help in designing effective and efficient probes for the detection of cobalt in the field of chemo-sensing.

Constructing graphene oxide/Au nanoparticle cellulose membranes for SERS detection of mixed pesticide residues in edible chrysanthemum.

Edible chrysanthemum is widely cultivated and used as an important ingredient of medicine, tea and multifunctional food. During the planting of chrysanthemum, pesticides are extensively used for preventing plant diseases and insect pests. To ensure the food safety of edible chrysanthemum, rapid detection methods are urgently needed for on-site inspection. In this study, a graphene oxide/Au nanoparticle (GO/Au NP) cellulose substrate was prepared through layer-by-layer assembly of GO and Au NPs on a mixed cellulose ester membrane. Surface-enhanced Raman spectroscopy (SERS) detection of four types of organophosphorus and organosulfur pesticides was achieved by filtering the extracting solution through the substrate and analysing SERS spectra. Qualitative and semi-quantitative detection of fenthion, phoxim, isocarbophos and thiram was accomplished with the detection limits of 38.01, 8.13, 48.97 and 8.74 ng mL-1, respectively. A spiking experiment further demonstrated the feasibility of this method for rapid and on-site detection of mixed pesticides in chrysanthemum. This study provides a new approach for rapid detection of multiple hazardous substances in flowering and herbal plants.

Rapid Qualitative and Quantitative Detection of Warfarin Sodium Based on Terahertz Spectroscopy

Rapid Qualitative and Quantitative Detection of Warfarin Sodium Based on Terahertz Spectroscopy