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[Display omitted] • The dual-emission ratiometric fluorescent probe was prepared by a facile hydrothermal synthesis method. • The quantification of Pb2+ was based on the efficient FRET between NCDs and AuNCs. • The sensor has good selectivity and anti-interference ability with satisfactory recovery in real water samples. • A paper-based sensor was fabricated for visual semi-quantitative detection by color change. Ratiometric fluorescent sensors could effectively eliminate the interference of spontaneous fluorescence or instrument fluctuation to improve the analysis sensitivity and accuracy. In this work, a dual-emission nitrogen-doped carbon dots/AuNCs (NCDs-AuNCs) nanohybrid was fabricated under mild conditions by the hydrothermal method, without additional coupling agents, which is facile and environmentally friendly. The prepared nanohybrid was employed for the sensitive detection of Pb2+. The sensor exhibited dual emission peaks at 460 and 625 nm with efficient fluorescence resonance energy transfer under a single excitation wavelength of 360 nm, in which the red fluorescence of AuNCs was enhanced and the blue fluorescence of NCDs was slightly quenched with the presence of Pb2+. The quantitative analysis of Pb2+ was performed upon the change of both fluorescence intensities. The sensor was successfully used for Pb2+ detection in real water samples with satisfactory spiking recoveries in a range of 91.0%–101.3% and low relatively standard deviations (RSDs < 3%), which exhibited good selectivity and anti-interference ability. In addition, a paper-based sensor was fabricated by immobilizing the nanohybrids on filter paper, which enables the visual semi-quantitative determination of Pb2+ by the naked eye through the color transition from blue to pink. The prepared NCDs-AuNCs nanohybrids showed great application potential in environmental water monitoring in an efficient and green way. [ABSTRACT FROM AUTHOR]

The availability of sensitive, reproducible, and broad spectral window range surface enhanced infrared absorption spectroscopy (SEIRAS) substrate is essential to the wide application of SEIRAS technique. Here, a facile method was proposed for the preparation of full mid-infrared range transmission surface-enhanced infrared absorption spectroscopy (T-SEIRAS) substrate, where silver nanoparticles (Ag NPs) was synthesized in situ by immersing copper foam into the silver nitrate solution with the help of hydroxylamine hydrochloride. The T-SEIRAS substrate was characterized with Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). It was found that the spectral window of the substrate was from 600 to 4000 cm−1. The apparent signal enhancement factor of the T-SEIRAS substrate was found to be about 35 times with the utilization of 11-mercaptoundecanoic acid (MUA) as probe molecule. Finally, the T-SEIRAS spectrum of E. coli was successfully obtained. It is expected that this type of T-SEIRAS substrate could be used in inexpensive IR instruments for field sensing applications. • A cost-effective T-SEIRAS substrate for transmission IR analysis was proposed. • The substrate has extraordinary broad spectral window of 600–4000 cm−1. • The apparent signal enhancement of T-SEIRAS for MUA is 35 folds. • The T-SEIRAS spectra of E.coli were obtained. [ABSTRACT FROM AUTHOR]

We present for the first time a SERS based microbial sensor for assessing acute freshwater toxicity. The assay is based on indole, which is synthesized in many Gram-positive and Gram-negative bacteria by L-tryptophan via tryptophanase (TnaA). In the presence of external toxic substances in the microbial growth environment, microorganisms' respiratory and metabolic functions are inhibited at varying degrees, leading to a decrease in indole production. We used SERS to monitor the conversion of L-tryptophan to indole and thus assess the toxic effects of toxic chemicals on E. coli. Two other factors affecting bacterial metabolism were also explored: L-tryptophan concentration and its incubation time with E coli. Copper was chosen as a simulated toxicant to assess the method's effectiveness for acute toxicity in freshwater. The IC 50 of Cu2+ was found to be 2.028 mg/L, which showed a significant improvement in sensitivity compared to other methods. [Display omitted] • A SERS based biosensor method for water acute toxicity evaluation was firstly proposed. • The method is based on the indole producing capability of E coli bacteria. • Acute toxicity assessed using indole concentration change upon introducing toxic chemical. • The toxicity of model ion Cu2+ was determined with an IC 50 of 2.028 mg/L. The substances emerging in environmental water bodies are becoming increasingly complex, causing severe ecotoxicological problems. In addition, the intricate interaction among various chemicals in a water body makes it difficult to accurately evaluate the water quality by simply determining the specie and concentration of the chemicals. Thus, acute toxicity evaluation of water body presents significant importance in environmental monitoring, especially in emergency response. This work proposes a SERS approach for evaluating acute toxicity of fresh water for the first time, where indole, an interspecies signal molecule produced by E. coli strains during regulated spore formation, could be affected by toxic substances, was used as indicator. Several key factors that may affect the evaluation of acute toxicity in water were explored, including the concentration of exogenous L-tryptophan and the incubation time of E. coli with L-tryptophan. Finally, the established system was applied to the acute toxicity evaluation of model chemical Cu2+. The IC 50 was determined to be 2.028 mg L-1, better than the results reported in the literature. This study demonstrates the feasibility of using SERS-based microbial sensors to assess acute toxicity in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly efficient sensing strategy for TNBP was reported. • The CL mechanism for signal amplification of Ce4+/SO 3 2- system was investigated. • TNBP molecules induce the enhanced generation of HSO 3 • - radicals and amplified CL emission. Tributyl phosphate (TNBP) with remarkable biological neurotoxicity and genotoxicity is a typical organophosphate flame retardant (OPFR) emerging contaminant, which has been found frequently in water, atmosphere, and solid, etc. It is important to explore efficient sensing strategies for TNBP. Herein, a direct Ce4+/SO 3 2- chemiluminescence (CL) system for efficiently and sensitively detecting TNBP flame retardant has been developed. The CL mechanism was uncovered by exploring reactive oxygen species (ROS), the emitting species, and reaction products. The results demonstrate that TNBP molecules induce the enhanced generation of HSO 3 • - radicals in Ce4+/SO 3 2- system, and a large amount of SO 2 * are subsequently generated, which account for the amplified CL emission. In view of this, a novel CL sensor for TNBP is established, which shows the advantages of fast determination, great selectivity, wide linear range (50–10000 ng mL−1), low limit of detection (13.61 ng mL−1), and good precision (RSD < 4.67%, n = 13). This work further provides an interesting perspective for direct CL behavior of OPFRs, and paves the way for the real-time monitoring of emerging pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-mode pyrene-based Zr-MOF was constructed to realize fluorescence "turn-on" in alkaline, and "turn-off" in acidic conditions. • The pyrene-based Zr-MOF fluorescence detection of alkaline pH liquid was established. • Detection method of pH film sensor by embedding the MOF particles into the PVA substrate was developed using smartphone detector. Rapid detection of on-the-spot water sample pH has become an urgent problem to resolve, and developing a method with the characters of fast, convenient and low-cost is significant. In this study, an amino functionalized pyrene-based Zr-MOF (NU-1000-NH 2) was synthesized by solvent-assisted ligand incorporation (SALI) method, in which the Zr 6 metal cluster, fluorescent pyrene-based H 4 TBAPy and p -aminobenzoic acid were acted as node, linker and modulator, respectively. The as-synthesized NU-1000-NH 2 possessed the pH-dependent fluorescence enhancement property at 450 nm emission under alkaline condition, thus a convenient fluorescence "turn-on" pH sensor was fabricated. Upon introduction of OH–, the carboxylate groups in NU-1000-NH 2 could react with it, and the deprotonation and gradual collapse of the NU-1000-NH 2 crystal were occurred, resulting in the release of the fluorescent H 4 TBAPy ligand and fluorescence enhancement. Moreover, to solve the difficulties of on-the-spot pH detection, the solid-phase pH film sensor was successfully constructed by embedding the NU-1000-NH 2 particles into the polyvinyl alcohol (PVA), combining with the RGB model and smartphone detector. The proposed fluorescent MOF-based pH sensor with dual-mode detection is expected to achieve on-the-spot pH monitoring in the field of environmental monitoring. [ABSTRACT FROM AUTHOR]

[Display omitted] • A UV-induced CL sensing platform based on PMS and luminol was established. • CL inhibition mechanism triggered by competitive consumption of ROS was proposed. • This CL sensor demonstrated excellent analytical performance with rapid determination, high selectivity and sensitivity. Organophosphate flame retardants (OPFRs) are emerging contaminants that cause great concern, and triphenyl phosphate (TPHP) with an extremely serious biotoxicity is a representative harmful OPFR. It remains a great challenge to develop real-time sensing strategy for TPHP. Herein, a UV-induced chemiluminescence (CL) sensing platform with potassium monopersulfate (PMS) as the source of reactive oxygen species (ROS) is established. Extraordinary CL emission can be generated due to the oxidation of luminol by ROS (e.g., SO 4 − and OH) from the UV-activated PMS. More importantly, the CL emission is greatly inhibited with the introduction of TPHP. Mechanism investigation for CL inhibition effect shows that, TPHP reacts with these ROS, leading to the obvious competitive consumption of ROS, and thus the oxidation degree of luminol is significantly impaired. Based on this, a new CL platform for the sensing of TPHP is fabricated, which demonstrates the advantages of simple operation, rapid determination, miniaturization potential, high selectivity and sensitivity, and grants the limit of detection down to 42.3 ng/L. This interesting work paves the way for the fast discrimination of emerging contaminants, and exhibits great prospects in real-time environmental monitoring. [ABSTRACT FROM AUTHOR]

A novel fluorescence turn-off sensing strategy for I− ions detection was developed based on the internal filtering effect between CDs and iodide-induced aggregation His-AuNCs. [Display omitted] • An ultrasensitive sensing strategy for iodide detection was proposed. • His-AuNCs and iodide form ground-state complexes that block the CDs' fluorescence. • A new insight into I− ions determination with CDs/His-AuNCs is presented. In this work, a novel fluorescence turn-off sensing strategy for I− ions detection was developed. The fluorescence of CDs/His-AuNCs hybrid probes was effectively turned off by I− ions. It was attributed to the internal filtration effect between the fluorescence emission peak of CDs and the absorption spectrum of His-AuNCs enhanced by I− ions. Quantitative analysis of I− ions can be achieved by analyzing the fluorescence quenching degree of CDs/His-AuNCs. Under the optimal experimental conditions, it exhibited good linearity in two concentration ranges of I− ions: 0.1–5.0 μM and 5.0–60.0 μM (low detection limit = 34 nM). The established sensing platform has been successfully exploited for the detection of I− ions in practical water samples. This work provided new insight into the determination of anions using fluorescent nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface modification of SERS nanomaterials can modulate the spectra of analytes and bring richer information. • Combining the modulated SERS spectra with multivariate analysis, structure similar fluoroquinolones antibiotics can be discriminated. • The SCA outperforms PCA in terms of spectral differentiation and identification. Surface-enhanced Raman spectroscopy (SERS) stands out in chemical analysis due to its rich molecular information, fast analysis speed, and high sensitivity. However, the differentiation of structural-similar chemicals is still challenging due to their similar SERS profiles. In this work, multivariate analysis (PCA and SCA) was combined with SERS for the differentiation and identification of highly similar chemicals using surface-modified SERS nanomaterials (MUO@Ag NPs), where three structural similar fluoroquinolone antibiotics (Norfloxacin, Ofloxacin, and Ciproflxacin) were used as examples. Due to their close molecular structure, the three chemicals showed very similar SERS spectra, with main feature located at 1394 cm−1. Introducing surface modification of the SERS substrate (MUO@Ag NPs) brought richer spectral information than the pristine ones. The performance of the two chemometric methods (PCA and SCA)was then compared using the MUO@Ag NPs as SERS substrate. SCA was found superior in identifying and differentiating these chemicals compared with widely adopted PCA analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Cu-NCDs exhibited stronger fluorescence emission peaks benefiting from the Cu doping. • Selective and sensitive detection of Fe3+ and TC were achieved based on Cu-NCDs. • The total Fe in the detection system was realized by adding H 2 O 2 into the Cu-NCDs. • The Cu-NCDs were applied in the detection of Fe3+ and TC in real water samples. This paper synthesized carbon dots (Cu-NCDs) doped with nitrogen and copper, which could be used as a sensor for measurement of Fe3+ and tetracycline (TC). The average particle sizes of CDs and Cu-NCDs were determined as 3.9 nm and 4.8 nm, respectively. The presence of carbon, oxygen, nitrogen and Cu atoms was confirmed in the structure of Cu-NCDs. Both CDs and Cu-NCDs exhibited a strong fluorescence (FL) emission peak at 450 nm, but the doping of Cu and N makes the surface of Cu-NCDs positively charged, which enhances the fluorescence intensity. The carbon dots doped with copper had more significant optical effects than those doped with other metals, and the relative quantum yield (QY) of the Cu-NCDs was as high as 53.6%. Cu-NCDs can be used as multi-functional fluorescent probes to selectively detect Fe3+ and TC based on fluorescence quenching. The limit of detection of Fe3+ and TC separately was found as 1.189 µM and 0.416 µM. This probe is also suitable for the indirect determination of Fe2+ because the Fe2+ is oxidated to Fe3+ by H 2 O 2. The mechanisms of the quenching process for Fe3+ and TC were explored that is the complex process of dynamic quenching and static quenching based on internal filtration effect (IFE), respectively. The fabricated sensors were successfully applied to determine Fe3+ and TC in tap and lake water samples, suggesting a promising application in environment analysis. [ABSTRACT FROM AUTHOR]

An aggregation-induced emission copper nanoclusters fluorescence probe (TA-CuNCs@CTAB) was designed for the detection of tetracycline (TC) based on the turn-off fluorescence intensity. [Display omitted] • An aggregation-induced emission copper nanoclusters fluorescence probe (TA-CuNCs@CTAB) was designed. • TA-CuNCs@CTAB fluorescence probe can detect TC in environment samples with high accuracy and good selectivity. • The detection mechanism is the internal filtration effect (IFE) of TA-CuNCs@CTAB induced by TC. Copper nanoclusters (CuNCs) is a promising fluorescent material for water detection with unique fluorescence characteristics and low cost. To boost the fluorescence characteristics of CuNCs, cetyltrimethylammonium bromide (CTAB) modified material has the ability to improve the sensitivity, selectivity and sensing performance of the probe. Herein, fluorescence-enhanced copper nanoclusters (TA-CuNCs@CTAB) based on the tannic acid templated is designed due to the electrostatic interaction between CTAB and TA-CuNCs, the addition of CTAB induced the aggregation of TA-CuNCs, and the enhancement of fluorescence signal was achieved using the aggregation-induced emission (AIE) mechanism. As a new fluorescent probe (TA-CuNCs@CTAB) for tetracycline (TC) turn-off detection, it has satisfactory linearity in the two ranges of 5–50 μM and 50–130 μM, with a detection limit of 65 nM. The detection mechanism is that the internal filtration effect (IFE) of TA-CuNCs@CTAB induced by TC leads to a significant fluorescence quenching. Therefore, this method is used to detect TC in actual water samples, which is more convenient to operate, has high accuracy and good selectivity, and has a good application prospect in detecting TC. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly sensitive FRET sensor for the detection of 2019-nCoV mAb was proposed. • FRET between GQDs and Ag@Au NPs led to the fluorescence quenching of the former. • The FRET efficiency declined due to the binding of 2019-nCoV mAb on Ag@Au NPs-NCP. • A fluorescence immunosensor for dedetection of 2019-nCoV mAb was developed. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has dramatically changed the world, is a highly contagious virus. The timely and accurate diagnosis of SARS-CoV-2 infections is vital for disease control and prevention. Here in this work, a fluorescence immunoassay was developed to detect 2019 Novel Coronavirus antibodies (2019-nCoV mAb). Fluorescent graphene quantum dots (GQDs) and Ag@Au nanoparticles (Ag@AuNPs) were successfully synthesized and characterized. Fluorescence resonance energy transfer (FRET) enables effective quenching of GQDs fluorescence by Ag@AuNPs. With the presence of 2019-nCoV mAb, a steric hindrance was observed between the Ag@AuNPs-NCP (2019-nCoV antigen) complex and GQDs, which reduced the FRET efficiency and restored the fluorescence of GQDs. The fluorescence enhancement efficiency has a satisfactory linear relationship with the logarithm of the 2019-nCoV mAb in a concentration range of 0.1 pg mL−1–10 ng mL−1, and the limit of detection was 50 fg mL−1. The method has good selectivity. When the serum sample was spiked with 2019-nCoV mAb, the recovery rate was between 90.8% and 103.3%. The fluorescence immunosensor demonstrates the potential to complement the existing serological assays for COVID-19 diagnosis. [ABSTRACT FROM AUTHOR]

• The "on-off-on" S, N-CDs probe was prepared by the ultra-fast one-pot method. • The S,N-CDs/PVA film sensor with stable fluorescenceare was synthesized. • The fluorescence recognition of Cr(VI) and AA in liquid/solid media were realized. In this work, an "on-off-on" fluorescent sensor of sulfur and nitrogen co-doped carbon dots (S, N-CDs) was explored for the identification of Cr (VI) and ascorbic acid (AA), which showed a good selectivity and anti-interfere ability to more than 30 interfering substances. The fluorescence recognition was realized in liquid and solid media under optimal conditions based on the internal filtration effect (IFE). In the liquid medium, the linear dynamic range of Cr (VI) was 0.03–50 μM and the limit of detection (LOD) was 21.14 nM. The linear detection range and the LOD of AA were 1–1000 μM and 0.28 μM, respectively. For solid-phase detection, we embed S, N-CDs into polyvinyl alcohol (PVA) to synthesize a visual fluorescent film sensor, which was irradiated by 365 nm ultraviolet light, for easily and accurately detecting Cr (VI) and AA on-site. The ranges of linearity were 0.1–50 μM and 10–500 μM, respectively, and the LODs were 92.48 nM and 6.99 μM, respectively. This is of great significance such as low cost, user-friendliness, and fast response for the analysis of environmental water samples. [ABSTRACT FROM AUTHOR]

• A new fluorescence method was developed for the MPD determination. • The proposed method had a wide linear range of 10–600 μg L−1. • A low detection limit of 4 μg L−1 was obtained. • The method was successfully applied for detecting MPD in real samples. This work presented a new fluorescence method for the determination of m-phenylenediamine (MPD) based on the reaction between MPD and acetylacetone. The formed compound Hacac-MPD exhibited strong blue fluorescence emission under 365 nm excitation. Its fluorescence intensity had an excellent correlation with the MPD concentration Under the optimal conditions, the developed method gave a linear range of 10–600 μg L−1 with a low detection limit of 4 μg L−1. Furthermore, the coexistence of common inorganic ions and other aromatic amines had hardly influence on the determination of MPD, demonstrating high selectivity. Additionally, the MPD in spiked water samples and hair dye samples was successfully detected by the developed method, and the recoveries were 97.5%-101.6% and 98.3%-98.9%, respectively. The established method exhibited a good application prospect for the determination of MPD in environment and daily necessities. [ABSTRACT FROM AUTHOR]

• A self-supporting liquid film SERS method was proposed for the sensitive detection of berberine. • Berberine in urine was successfully analyzed and showed great consistency with HPLC. • The average excretion rates of berberine after oral administration in patients were monitored. Though surface-enhanced Raman scattering (SERS) has been widely used in the biomedical field, pharmacokinetic monitoring remains a challenge due to its inherent poor reproducibility. Here in this work, a novel and reproducible SERS platform based on the self-supporting liquid film (SLF) was proposed for the pharmacokinetic monitoring of berberine hydrochloride (BB) in human urine. Briefly, the KBr-modified silver nanoparticles (Ag NPs) suspension was mixed with the analyte. Then the mixture was placed in a customized template to form the SLF platform. In the optimized condition, the results showed that the limit of detection (LOD) of BB was 0.55 ppb. The relative standard deviation (RSD) of the SERS measurements was stable below 10%, and a wide linear range from 1 to 100 ppb (R2 = 0.997) and 100 to 500 ppb (R2 = 0.994). The averaged recovery was determined from 94% to 104% for spiked urine samples. Side-by-side comparison for urine sample analysis was performed between the proposed SLF method and high-performance liquid chromatography (HPLC), where good agreement was achieved. Moreover, the average excretion rates of BB after oral administration in six patients were satisfactorily monitored. The SLF SERS platform can realize rapid and reliable quantitative drug analysis and has potential applications in point-of-care testing. [ABSTRACT FROM AUTHOR]

• MIPs-SPE platform was proposed for the selective screening of the risk categories in food. • MIPs-PVA hydrogel was used as the sampling and sensing platform. • The screening method shows a high selectivity without sample pretreatment. • The whole screening analysis in food could be accomplished within 5 min. In fluorescence measurement, one pressing concern today is to construct sensors that can withstand various disturbances for highly selective and sensitive detection of trace analytes in complicated samples. Molecularly imprinted polymers (MIPs) with tailored binding sites are preferred to be recognition elements in sensors for effective target detection. Here, MIPs combined with solid-phase extraction (SPE), followed by direct fluorescence detection on the same extraction medium, was proposed for rapid onsite selective screening for risk categories in food safety without sample pretreatment. A novel surface solid-phase fluorescence substrate with special adsorption property for rhodamine B (RhB) or sulfamethoxazole (SMX) was synthesized by wrapping the MIPs in the deformable hydrogel prepared by polyvinyl alcohol (PVA). Parameters that affected the extraction capacity of the analytes were explored. MIPs-PVA hydrogel showed a good selectivity (imprinting factor α = 2.95 with RhB-MIPs-PVA hydrogel), reproducibility (RSD ≤ 16.5% with 5 ppm RhB) and sensitivity (0.1 ppm to RhB) with a short analysis time of less than 5 min including sampling. The proposed method is very promising as a rapid, onsite screening protocol for food safety. [ABSTRACT FROM AUTHOR]

• Nitro-explosives (NEs) sensor based on cotton swab was fabricated via a one-step method. • The formation mechanisms of amino-2,2′,4,4′,6,6′-hexanitrostilbene complexes were first explored. • The sensor was first used for NEs detection on surfaces via the naked eye-based visual method. • The sensor could detect NEs residues at tens of nanograms within 1 min. Rapid on-site detection of nitro-explosives (NEs) residues on surfaces is of great importance for security screening, especially at the public transit checkpoints. Past practices to recognize NEs generally rely on bulky and expensive instruments. Herein, the rapid on-site detection of 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) on surfaces has been firstly reported together with 2,4,6-trinitrotoluene (TNT) via the naked eye-based visual method, in which a dual functional (sampling and sensing) cotton swab sensor was proposed. The flexible sensor (amino-swab) was prepared through a one-step soaking method. –NH 2 was found to react with the NEs to form different amino-NEs complexes. Unlike TNT, there were two kinds of complexes in the amino-HNS system, and the reaction mechanism of that was explored for the first time. The above orange-like complexes could be identified by the naked eye. The lowest detectable amounts for HNS and TNT on the glass surface were ~89 and ~45 ng (contaminated area: ~1.76 cm2), respectively, while the whole analysis took less than 1 min. The sensor was successfully utilized for NEs detection on luggage and travel bag, suggesting good adaptability. Swab might be a potential sensor for NEs screening due to the merits of cost-effectiveness and versatility. [ABSTRACT FROM AUTHOR]

• SERS has shown a high promise in microenvironmental pH sensing. • Evaluation of response range, resistance ability, accuracy and stability of four pH probes was performed. • 4-Mpy showed the best performance in pH detection with real biological samples. • 2-ABT has been found not suitable for SERS pH application due to the inadequate pH response. Surface-enhanced Raman spectroscopy (SERS) has shown a high promise in microenvironmental pH sensing in recent years, which is significant for understanding various biological processes and multiphase chemical reactions. Generally, the pH sensing capability of the SERS substrate is realized by the surface functionalization of the substrate with a pH sensitive molecule (pH probe). However, to the best of our knowledge, there is no systematic evaluation of mainstream SERS pH probes reported in literatures on the pH response range, resistance to co-present ions, accuracy and stability. Here a systematic analysis of common pH probes, including 4-mercaptobenzoic acid (4-MBA), 4-mercaptopyridine (4-Mpy), 2-aminobenzenethiol (2-ABT), and 4-aminothiophenol (4-ATP) has been carried out with a series of performance assessments. Density functional theory (DFT) calculation was carried out to investigate the vibration mode in SERS spectra. Moreover, the practical application comparison was conducted with urine samples. Overall, 4-MBA showed an excellent sensing performance in the neutral and alkaline area, and meanwhile, the pH response of 4-Mpy and 4-ATP was inclined to the acidic and neutral range. The pH probe 2-ABT is not recommend because of the poor performance. [ABSTRACT FROM AUTHOR]

• A UV image detection system was designed for rapid visual detection of UV absorption gas. • It consisted of a high quantum efficiency UV camera, multiple different wavelength filters and gas regulators. • The UV images of SO 2 were obtained at different concentrations and temperatures. • The detection limit for SO 2 was as low as 4 ppb. We demonstrate a multi-wavelength ultraviolet (UV) imaging detection system for gaseous pollutants with absorption characteristics in the UV band. As a proof of concept, the detection of sulfur dioxide (SO 2) was used as an example to develop a method based on UV imaging. The critical component of the system is a highly sensitive CCD array (1024 × 1024 pixels) UV camera with high quantum efficiency (QE) in the UV range (>30% transmission at 200–240 nm, >50% transmission at 240–400 nm), multiple different wavelength bandpass filters (270 nm, 280 nm, 300 nm, and 310 nm for SO 2), environmental condition controller (temperature range 278–318 K, relative humidity range 35–85%), and a compact and robust design (362 mL of the gas absorption cell with a 4.2 m optical path length). The advantages of this system are convenient, fast, and can realize visualization. The system was applied for detecting SO 2 in various conditions (different concentrations, temperatures, and humidity). After optimization, the detection limit for SO 2 detection is 4 ppb, and the uncertainty of concentration measurement is only about 2.7%. [ABSTRACT FROM AUTHOR]