Low Concentration Range Research Articles

Monomer and Excimer Emission in Electrogenerated Chemiluminescence of Pyrene and 2,7-Di-tert-butylpyrene Associated with Electron Transfer Distance.

Electrogenerated chemiluminescence (ECL) is a light emission phenomenon caused by electrochemically generated radical anions (R•-) and cations (R•+), in which the ion annihilation results in the formation of a pair of excited (R*) and ground state (R) of a luminescent molecule. Here, the ECL properties of pyrene (Py) and 2,7-di-tert-butylpyrene (di-t-BuPy) are reported. It was found that at a commonly employed concentration (1 mM), the ECL spectra were time-dependent because of increasing the oligomer emission and increasing the concentration of R near R*, leading to an enhancement of the excimer emission. At a low concentration range (20-30 μM), the shape of the ECL spectra containing the monomer and excimer emission was determined by isolated pairs of R* and R, which were generated through ion annihilation of R•- and R•+. It was found that in the ECL of Py and di-t-BuPy originated from the isolated pairs of R•- and R•+, 58 and 48% of the excited states were the excimer states, respectively. Diffusion equation analysis indicates that the lower excimer formation in the case of di-t-BuPy is because of a farther initial separation distance between R* and R, i.e., a longer electron transfer distance between the radical ions. The Marcus model for the electron transfer kinetics suggests that the farther electron transfer distance is mainly caused by the larger molecular size, which resulted in a smaller reorganization energy of the solvent acetonitrile molecule. Taking advantage of the photophysical and electrochemical properties of Py and di-t-Bu Py, the monomer and excimer emission in ECL is discussed.

Self-assembly method of glucose oxidase in a fully packaged microfluidic glucose biosensor

In this work, a self-assembly approach is proposed to bio-functionalize the fully packaged microfluidic biosensors for catalyzing glucose based on the designed and fabricated microfluidic chip with suspending structure by micro-electro-mechanical system technology. Glucose oxidase is successfully immobilized on the surface of microelectrodes to build composite layers by the proposed self-assembly approach, with cysteamine applied as a functional linker. The biological activity and stability of glucose oxidase is optimized by the electrodeposition of chitosan membrane. Experiments results suggest that the fully packaged microfluidic biosensor integrated with self-assembled glucose oxidase can effectively detect the existence of glucose in sample solution. The detection range of glucose concentration is 0–10 mM. With SNR of 3, the detection limit is 51.2 µM and sensitivity is 23.47 ± 1.36 µA cm−2 mM−1 within low concentration range of 0–0.1 mM, while the detection limit is 497 µM and the sensitivity is 10.63 ± 1.28 µA cm−2 mM−1 among high concentration range of 0.1–10 mM. The proposed study provides a straightforward method to construct a microfluidic biosensor, which is promising in miniaturized clinical medical device.

NO/SO2/HCl emissions from solid waste combustion via oxygen-carrier-aided combustion in rotary kiln

Rotary kiln incineration technology has become an important approach to achieve the harmless, reduced, and resourceful solid waste (SW) due to its wide range of fuel adaptability and high treatment efficiency. SW incineration through oxygen carrier (OC) aided combustion in the rotary kiln shows significant advantages in improving SW conversion and reducing CO emission. However, the impacts of introducing OC into the rotary kiln on the emissions of NO, SO2, and HCl, are still unknown. This research objective was to investigate the effects of OCs on the emission characteristics of NO, SO2, and HCl. Natural manganese and ilmenite ores as OCs, are added to a continuous-feeding rotary kiln during the combustion of biomass SW and hazardous SW. The results show that the introduction of OCs can significantly improve the uniformity of oxygen distribution in the furnace, and promotes the conversion of fuel N to NO. At high temperatures and low oxygen concentrations range, the reduction rate of NO by high-concentration CO or catalytic reduction by char and ash is faster than the oxidation of fuel N by OCs, which decreases NO concentration. Moreover, at high temperatures, when OCs are distributed in the bed of the rotary kiln, the fuel in the oxygen-poor zone can obtain O2 or lattice oxygen from the OCs, which promotes the decomposition and oxidation of S-containing compounds in fuels and increase the SO2 concentration. In addition, OCs in the bed provide more reaction sites for fuel conversion and promote the release of Cl as HCl at high temperatures. Specifically, during the oil sludge combustion at 900 °C, compared with the inert reference case, the addition of ilmenite ore increased the concentrations of NO, SO2, and HCl by 47.44%, 64.87%, and 20.28%, respectively, which is attributed to the better reactivity and redox cycle stability of ilmenite ore. This study highlights the potential of OC-aided combustion in rotary kilns as an approach to regulate SW combustion and offers a foundation for the future related research.

The ultrasensitive detection of p-nitrophenol using a simple activated carbon electrode modified with electrodeposited bismuth dendrites

Bismuth dendrites were electrodeposited onto an activated glassy carbon electrode and the resulting modified electrode was employed in the electrochemical detection of para-nitrophenol, an aromatic aquatic pollutant. The carbon electrode was activated by cycling between − 2.0 and 2.0 V vs. SCE to create active sites that can promote the electron transfer reaction. Bismuth dendrites were subsequently deposited at a potential of − 1.0 V vs. SCE for 400 s. A near 5-fold increase in the peak current associated with the conversion of para-nitrophenol (100 μM) to para-hydroxyaminophenol was obtained on activating the glassy carbon electrode. A more impressive 7-fold increase in the peak current was achieved on decorating the activated glassy carbon with bismuth dendrites. Calibration curves with linear regions from 1.6 to 170 μM and between 0.005 and 1.6 μM para-nitrophenol were obtained to give a LOD value of 0.18 nM and a sensitivity of 29.4 μA μM−1 cm−2 for the lower concentration range. Good repeatability, reproducibility and selectivity were achieved, while recovery values between 96.5 and 106.7 % were obtained in water samples. In addition, the bismuth dendrites were easily regenerated through an oxidation step at 0.6 V vs. SCE followed by a 400 s electrodeposition period in 1.0 mM Bi(III).

Interface Engineering-Driven Room-Temperature Ultralow Gas Sensors with Elucidating Sensing Performance of Heterostructure Transition Metal Dichalcogenide Thin Films.

In this report, we investigate the room-temperature gas sensing performance of heterostructure transition metal dichalcogenide (MoSe2/MoS2, WS2/MoS2, and WSe2/MoS2) thin films grown over a silicon substrate using a pulse laser deposition technique. The sensing response of the aforementioned sensors to a low concentration range of NO2, NH3, H2, CO, and H2S gases in air has been assessed at room temperature. The obtained results reveal that the heterojunctions of metal dichalcogenide show a drastic change in gas sensing performance compared to the monolayer thin films at room temperature. Nevertheless, the WSe2/MoS2-based sensor was found to have an excellent selectivity toward NO2 gas with a particularly high sensitivity of 10 ppb. The sensing behavior is explained on the basis of a change in electrical resistance as well as carrier localization prospects. Favorably, by developing a heterojunction of diselenide and disulfide nanomaterials, one may find a simple way of improving the sensing capabilities of gas sensors at room temperature.

Optimization of sample clean-up for the determination of small amounts of MOSH and MOAH in edible oils – method DGF C-VI 22 (20)

Methods for determining MOSH and MOAH in edible oils showed major problems with interlaboratory comparability of analytical results, especially in the lower concentration range below 10 mg/kg. However, a method with improved sensitivity and reproducibility is urgently needed to obtain a valid data basis for minimization efforts. To cope this problem a new method was created in 2020. The method was established as the standard method DGF C-VI 22 (20) of the German Society for Fat Science e.V. (DGF). For the development of this method different sample epoxidation approaches have been performed, evaluated and improved. Additionally, a saponification, a decision tree for sample preparation, an upstream clean-up column and a system suitability test were introduced. The focus was on reliability and interlaboratory comparability over all edible oil matrices up to a LOQ of 1 mg/kg. The optimized method was validated in terms of trueness and precision in a collaborative trail with 11 laboratories. The achieved recovery rates of 89–105% MOSH and 70–105% MOAH met the JRC requirements. Method and validation results were obtained with HorRat values between 1.3 and 1.8 for MOSH and MOAH.

Biosynthetic amyloid fibril CsgA-Fe3O4 composites for sustainable removal of heavy metals from water

Removal of heavy metals from water has been a hot topic. However, few studies have been conducted for the tricky low concentration range. Experimental designs often have heavy metal concentrations much higher than the actual environmental loading, which leads to poor practical results of adsorbent materials. This study showed that amyloid fiber CsgA-Fe3O4 composites are ideal for the removal of heavy metals from water, especially at low concentrations. We constructed CsgA-Fe3O4 composites by fusing short functional peptides that specifically bind to Fe3O4 magnetic nanoparticles. The CsgA-Fe3O4 composites achieved 98.73 %, 98.43 %, and 93.00 % removal of 1 mg/L Cu2+, Cd2+, and Pb2+, respectively. Moreover, the adsorption rate remained above 80 % after six repeated adsorptions, indicating that CsgA-Fe3O4 was highly reusable. Meanwhile, the high removal rate (>90 %) of heavy metals in the simulated wastewater demonstrated the excellent environmental stability of CsgA-Fe3O4. Finally, by FT-IR and XPS characterization, we found that the adsorption mechanism of CsgA-Fe3O4 is mainly the complexation of surface oxygen-containing functional groups and heavy metal ions. In general, the CsgA-Fe3O4 composite is an efficient, inexpensive, and sustainable adsorption material for mitigating low concentrations of difficult-to-treat heavy metal pollution in water bodies.

AirQuality Lab-on-a-Drone: A Low-Cost 3D-Printed Analytical IoT Platform for Vertical Monitoring of Gaseous H2S.

The measurement of gaseous compounds in the atmosphere is a multichallenging task due to their low concentration range, long and latitudinal concentration variations, and the presence of sample interferents. Herein, we present a quadcopter drone deployed with a fully integrated 3D-printed analytical laboratory for H2S monitoring. Also, the analytical system makes part of the Internet of Things approach. The analytical method applied was based on the reaction between fluorescein mercuric acetate and H2S that led to fluorescence quenching. A 5 V micropump at a constant airflow of 50 mL min-1 was employed to deliver constant air into a flask containing 800 μL of the reagent. The analytical signal was obtained using a light-emitting diode and a miniaturized digital light detector. The method enabled the detection of H2S in the range from 15 to 200 ppbv, with a reproducibility of 5% for a sampling time of 10 min and an limit of detection of 9 ppbv. All devices were controlled using an Arduino powered by a small power bank, and the results were transmitted to a smartphone via Bluetooth. The proposed device resulted in a weight of 300 g and an overall cost of ∼50 USD. The platform was used to monitor the concentration of H2S in different intervals next to a wastewater treatment plant at ground and vertical levels. The ability to perform all analytical steps in the same device, the low-energy requirements, the low weight, and the attachment of data transmission modules offer new possibilities for drone-based analytical systems for air pollution monitoring.

Hybridization chain reaction circuit controller: CRISPR/Cas12a conversion amplifier for miRNA-21 sensitive detection

MicroRNA (miRNA) is crucial to the diagnose of various diseases. However, the accurate detection of miRNA has been challenging due to its short length and low abundance. Here, we designed a hybridization chain reaction (HCR) circuit controller to initiate the CRISPR/Cas12a conversion amplifier (HCR-Cas12a controller) for sensitive detection of miRNA-21 (miR-21). In the HCR, pre-crRNA was encapsulated in a hairpin structure until the miR-21 was present. Afterward, Cas12a fully exerted its RNase activity to self-mature pre-crRNA. Then, the trans-cleavage activity of Cas12a was initiated by activator. This results in the conversion of biological signals to fluorescent signal. During HCR-Cas12a controller, the circuit formed quickly, while the Cas12a system worked in a short time. The miR-21 was ultra-sensitively detected with the wide detection range of 1 fM - 100 nM, and the calculated limit of detection was 75.4 aM. The sensitivity was an order of magnitude lower than the standard method. The formation of HCR at room temperature does not require a thermal cycler. Additionally, Cas12a can work without the need for precise or expensive instruments. Therefore, our proposed method was suitable for low-resource settings, and provided a technical basis for sensitive detection of miRNA in low concentration range.

Allyl-isothiocyanate against colorectal cancer via the mutual dependent regulation of p21 and Nrf2

Allyl-isothiocyanate (AITC) is a common Isothiocyanates (ITC) and its chemo-preventive and anti-tumor effects are believed to be related to the activation of NF-E2 p45-related Factor 2 (Nrf2). However, its anti-tumor effects on colorectal cancer (CRC) are not well elucidated. Here, we investigated the therapeutic in vitro and/or in vivo effects and mechanisms of action (MOA) for AITC on CRC cell line HCT116 (human) and MC38 (mouse). AITC treatment in a low concentration range (1 mg/kg in vivo) significantly inhibited the tumor cell growth and increased the expression of p21 and Nrf2. The AITC-mediated induction of p21 was dependent on Nrf2 but independent on p53 in vitro and in vivo at low dose. In contrast, the high dose of AITC (5 mg/kg in vivo) failed to increase substantial levels of p21/MdmX, and impaired the total antioxidant capacity of tumors and subsequent anti-tumor effect in vivo. These results suggest that an optimal dose of AITC is important and required for the proper Nrf2 activation and its anti-CRC effects and thus, providing insights into the potential applications of AITC for the prevention and treatment of CRC.

In-house validation of an LC-MS method for the multiplexed quantitative determination of total allergenic food in chocolate.

Mass spectrometry has been widely accepted as a confirmatory tool for the sensitive detection of undeclared presence of allergenic ingredients. Multiple methods have been developed so far, achieving different levels of sensitivity and robustness, still lacking harmonization of the analytical validation and impairing comparability of results. In this investigation, a quantitative method has been validated in-house for the determination of six allergenic ingredients (cow's milk, hen's egg, peanut, soybean, hazelnut, and almond) in a chocolate-based matrix. The latter has been produced in a food pilot plant to provide a real and well-characterized matrix for proper assessment of method performance characteristics according to official guidelines. In particular, recent considerations issued by the European Committee for Standardization have been followed to guide a rigorous single-laboratory validation and to feature the main method performance, such as selectivity, linearity, and sensitivity. Synthetic surrogates of the peptide markers have been used both in native and labelled forms in matrix-matched calibration curves as external calibrants and internal standards, respectively. A two-order of magnitude range was investigated, focusing on the low concentration range for proper assessment of the detection and quantification limits (LOD and LOQ) by rigorous calibration approach. Conversion factors for all six allergenic ingredients have been determined for the first time to report the final quantitative information as fraction of total allergenic food protein (TAFP) per mass of food (µgTAFP/gfood), since such areporting unit isexploitable in allergenic risk assessment plans. The method achieved good sensitivity with LOD values ranging between 0.08 and 0.2 µgTAFP/gfood, for all ingredients besides egg and soybean, whose quantitative markers reported a slightly higher limit (1.1 and 1.2 µgTAFP/gfood, respectively). Different samples of chocolate bar incurred at four defined concentration levels close to the currently available threshold doses have been analyzed to test the quantitative performance of the analytical method, with a proper estimate of the measurement uncertainty from different sources of variability. The sensitivity achieved resulted in compliance with the various threshold doses issued or recommended worldwide.

Novel and Simple Method for Quantification of 2,4,6-Trichlorophenol with Microbial Conversion to 2,4,6-Trichloroanisole.

Contamination with 2,4,6-trichloroanisole (TCA) often causes taste and odor (T&O) problems in drinking water due to its low odor threshold concentration. Microbial O-methylation of the precursor 2,4,6-trichlorophenol (TCP) would be the dominant mechanism for TCA formation. Simple and rapid measurement of TCP in the low concentration range is necessary to control the problems induced by TCA. In this study, the combination of microbial conversion and instrumental analysis was proposed as a method of TCP quantification. Fungi and bacteria were isolated from various water samples and examined for their ability to produce TCA from TCP. As a result, a strain exhibiting quantitative TCA production and a high growth rate was obtained and named Mycolicibacterium sp. CB14. The conversion rate of TCP to TCA by this strain was found to be high and stable (85.9 ± 5.3%), regardless of the applied TCP concentration, although within the range of 0.1-10 µg/L. The limits of detection and quantification for TCP by this proposed method were determined to be 5.2 ng/L and 17.3 ng/L, respectively. By improving the methods, Mycolicibacterium sp. CB14 could be used for the quantification of TCP at very low concentration levels, which is sufficient to manage the T&O problem caused by TCA.

How low can we (reliably) go? A method comparison of thyroid-stimulating hormone assays with a focus on low concentrations.

International guidelines concerning subclinical hyperthyroidism and thyroid cancer advice absolute cut-off values for aiding clinical decisions in the low range of thyroid-stimulating hormone (TSH) concentrations. As TSH assays are known to be poorly standardized in the normal to high range, we performed a TSH assay method comparison focusing on the low range. Sixty samples, selected to cover a wide range of TSH concentrations (<0.01 to 120 mIU/L) with oversampling in the lower range (<0.4 mIU/L), were used for the method comparison between three TSH immunoassays (Cobas, Alinity and Atellica). In addition, 20 samples were used to assess the coefficient of variation from duplicate measurements in these three methods. The TSH immunoassays showed standardization differences with a bias of 7-16% for the total range and 1-14% for the low range. This could lead to a different classification of 1.5% of all measured TSH concentrations <0.40 mIU/L measured in our laboratory over the last 6 months, regarding the clinically important cut-off value of TSH = 0.1 mIU/L. As the imprecision of the immunoassays varied from 1.6-5.5%, this could lead to a similar reclassification as the bias between immunoassays. We established the standardization differences of frequently used TSH assays for the total and low concentration ranges. Based on the proportional bias and the imprecision, this effect seems to have limited clinical consequences for the low TSH concentration range. Nevertheless, as guidelines mention absolute TSH values to guide clinical decision-making, caution must be applied when interpreting values close to these cut-offs.

Changes in Ozone Pollution Trend Characteristics and Sensitivity in Jinan from 2015 to 2020

The surface ozone (O3) spatiotemporal distribution, variations, and its causes in Ji'nan from 2015 to 2020 were revealed based on the air quality monitoring network data and satellite retrievals from the Ozone Monitoring Instrument (OMI). The results showed that the ozone concentration in Ji'nan gradually increased from 2015 to 2020. The annual 90th percentile of the daily maximum 8-h average (MDA8) O3(namely the annual evaluation value) and the MDA8 O3(April-September) increased by 4.8 μg·(m3·a)-1 and 3.8 μg·(m3·a)-1, respectively. The trend of the ozone levels in the high-concentration range increased faster than that in the low-concentration range. The MDA8 in June increased by 7.4 μg·(m3·a)-1, and the rate range of increases was 2.6-3.9 μg·(m3·a)-1 in the cool seasons (December-February); thus, the O3 control in winter cannot be ignored. It is apparent from the diurnal variations in ozone from 2015 to 2020 in April-September that the average ozone levels have risen in recent years. The growth rate in the daytime was higher than that at night. The capacity of photochemical production has been increasing, especially in recent years. Additionally, it is noteworthy that the peak time for ozone levels occurred approximately 1-2 h earlier. The disparity of ozone concentrations among different stations gradually decreased in recent years. Compared with that in 2015, the range of areas with high O3 concentrations in 2019-2020 was further expanded. The significant positive trends in MDA8-90th and MDA8 (April-September) were observed in 16.1% and 22.6% of the monitoring sites in Ji'nan (P<0.05), most of which were located in urban areas and the suburbs close to urban areas. The temporal and spatial changes in ozone in Jinan had been affected by the changes in VOCs and NOx emissions since 2015. Satellite remote sensing data from 2015 to 2020 revealed that the NO2 tropospheric columns (April-September) showed reductions of 20.6%, with a decreasing rate of 0.3×1015 mole·(cm2·a)-1, especially in the urban areas and suburbs. The detected variation trends of tropospheric HCHO were weak and insignificant, which suggested that the decrease in NOx emissions was much greater than the decrease in VOCs emissions, and the gap had become more obvious in the urban areas. With responses to precursor emissions, the chemical sensitivity of O3 formation had been changing. The VOCs-limited regimes continuously decreased, and the mixed NOx/VOCs-sensitive regimes and NOx-limited regimes increased. In general, such an extremely inappropriate control ratio of ozone precursor NOx/VOCs led to an overall trend of slow increasing fluctuations of O3 in Ji'nan. The findings clearly indicate that the reduction of VOCs in Ji'nan was far from sufficient, and strengthening the current control of VOCs emissions is an effective measure to control the growth trend of O3 pollution in Ji'nan in the near future, especially in urban and surrounding suburban areas.

In-line gas purging exploiting a novel converging flow-on paper optosensing device for the determination of total ammonia-nitrogen in water samples

A novel, inexpensive, and sensitive microanalytical system for the determination of total ammonia-nitrogen (ammonia-N) in water was developed. The system was designed to detect ammonia using an in-line purging system coupled with a newly designed gas converging flow cell incorporating in-line paper-based colorimetric detection. The gas converging flow cell served as a gas chamber, a paper-based device holder, and a color detection cell. The paper-based device was impregnated with butterfly pea extract (a natural acid-base indicator), the color of which changed on the basis of the generated ammonia gas. Analytical parameters such as concentration of natural indicator and purging time were studied and optimized. The color image could be captured by an integrated endoscope camera or smartphone and analyzed by ImageJ software in RGB mode. Under optimal conditions, two linear dynamic ranges were observed. By using 1:2 (v/v) diluted 2% (w/v) butterfly pea extract in Milli-Q water, a low linear concentration range of 0.05–0.9 mg L−1 with a limit of detection (LOD) of 0.02 mg L−1 and limit of quantification (LOQ) of 0.05 mg L−1 was achieved. By using a non-diluted 2% (w/v) butterfly pea extract, a high linear concentration range of 0.5–4 mg L−1 with an LOD of 0.1 mg L−1 and LOQ of 0.3 mg L−1 was obtained. Finally, the optimized method was leveraged to determine ammonia-N in various water samples from shrimp farming.

Identification of compounds that preferentially suppress the growth of T-cell acute lymphoblastic leukemia-derived cells.

T-cell acute lymphoblastic leukemia (T-ALL) is one of the most frequently occurring cancers in children and is associated with a poor prognosis. Here, we performed large-scale screening of natural compound libraries to identify potential drugs against T-ALL. We identified three low-molecular-weight compounds (auxarconjugatin-B, rumbrin, and lavendamycin) that inhibited the proliferation of the T-ALL cell line CCRF-CEM, but not that of the B lymphoma cell line Raji in a low concentration range. Among them, auxarconjugatin-B and rumbrin commonly contained a polyenyl 3-chloropyrrol in their chemical structure, therefore we chose auxarconjugatin-B for further analyses. Auxarconjugatin-B suppressed the in vitro growth of five human T-ALL cell lines and two T-ALL patient-derived cells, but not that of adult T-cell leukemia patient-derived cells. Cultured normal T cells were several-fold resistant to auxarconjugatin-B. Auxarconjugatin-B and its synthetic analogue Ra#37 depolarized the mitochondrial membrane potential of CCRF-CEM cells within 3 h of treatment. These compounds are promising seeds for developing novel anti-T-ALL drugs.

Electrochemical bulk and film-type oxygen sensors: Strategies for detecting extremely low concentration in hydrogen environments

Potentiometric oxygen sensors with excellent sensitivity in a low oxygen concentration range are designed based on intrinsic logarithmic response characteristics, and an asymmetric electrode structure, differentiated from conventional oxygen sensors with reference oxygen gases or parts exposed to air, is implemented. Electrolytes and electrode materials that formulate oxygen sensor devices are evaluated by comprehensively considering their reactivity to trace oxygen, oxygen ion formation, and ease of movement. The sensor using an yttria-stabilized zirconia bulk ceramic electrolyte measures the oxygen concentration in an oxygen-hydrogen mixture down to 0.5%, with a response time of 7.8 s. The sensor with a Nafion proton conductor film and a polyimide gas separation membrane allows room-temperature sensing and measures the oxygen concentration to a minimum of 2%.

A Low-cost Creatinine Biosensor by Differential Optical Signal Readout for the Whole Blood Analysis.

This study developed a low-cost paper-based biosensor for point-of-care (POC) detection of blood creatinine by using differential optical signal readout. Dual-channel photochemical paper-based test strips were fabricated with stackable multilayer films containing pre-immobilized enzymes and reagents for the identification and conversion of creatinine and creatine. Enzyme-linked reactions generated hydrogen peroxide (H2O2), which formed a blue oxidized condensate with aniline derivatives. The color depth was quantified via the differential optical signal of the two channels and positively correlated with the concentration of the analyte. This method was first proposed to address the issue of endogenous interferences in the enzymatic assay of creatinine, greatly improving the detection accuracy. The proposed biosensor was calibrated with spiked blood samples, and achieved a wide detection range of 31-1483 μmol/L, showing superior detection performance to general enzymatic methods, especially in the low concentration range. Creatine interference testing demonstrated that the biosensor could resist the interference of ≤ 300 μmol/L endogenous creatine. It is believed that the proposed optical differential biosensor for blood creatinine could enable to pave the way for a daily monitoring system for renal diseases.Clinical Relevance- This stackable multilayer paper-based biosensor provides an enzymatic colorimetric assay of creatinine in whole blood, which can be read out by the differential optical signal to exclude interference from endogenous creatine.

Self-referencing photothermal digital holographic microscope for characterization of low-loss liquids

Measurement of absorption coefficients of transparent samples is important for their characterization and identification; however, it is challenging to measure low values, e.g., 10−3–10−4 cm−1 with high accuracy. Here, we report a compact photothermal lateral shearing digital holographic device. It is based on the thermal lens effect and a common-path, self-referencing digital holographic microscope comprising a glass plate, probe beam, and a CMOS camera. The change in phase distribution caused by the temperature change due to light absorption is measured from the recorded holograms to extract the sample's absorbance and absorption coefficient. The feasibility of the proposed configuration is validated by the experimental results obtained with different concentrations of gold nanoparticles (AuNPs) in an aqueous solution. Determination of AuNPs concentration in the nM range is performed, and the obtained limits of detection and quantitation are 0.04 nM and 0.13, respectively. The calibration curve is linear at a low concentration range of 0.06–0.95 nM with 1% reproducibility. In addition, the method's versatility is demonstrated by measuring the absorption coefficient of low-loss solvents, such as ethanol and water. The determined absorption coefficients agree with the reported values, confirming that this method provides good spectrometric capabilities, such as high sensitivity and accuracy.

Synergy between UV light and trichloroisocyanuric acid on methylisothiazolinone degradation: Performance, kinetics and degradation pathway.

Methylisothiazolinone (MIT) is widely used in daily chemicals, fungicides, and other fields and its toxicity has posed a threat to water system and human health. In this study, ultraviolet (UV)/trichloroisocyanuric acid (TCCA), which belongs to advanced oxidation processes (AOP), was adopted to degrade MIT. Total chlorine attenuation detection proved that TCCA has medium UV absorption and a strong quantum yield (0.49 mol E−1). At a pH of 7.0, 93.5% of MIT had been decontaminated after 60 min in UV/TCCA system (kobs = 4.4 × 10−2 min−1, R2 = 0.978), which was much higher than that in the UV alone system and TCCA alone system, at 65% (1.7 × 10−2 min−1, R2 = 0.995) and 10% (1.8 × 10−3 s−1, R2 = 0.915), respectively. This system also behaved well in degrading other five kinds of contaminants. Tert-butanol (TBA) and carbonate (CO32−) were separately used in quenching experiments, and the degradation efficiency of MIT decreased by 39.5% and 46.5% respectively, which confirmed that HO• and reactive chlorine species (RCS) were dominant oxidants in UV/TCCA system. With TCCA dosage increasing in a relatively low concentration range (0.02–0.2 mM) and pH decreasing, the effectiveness of this AOP system would be strengthened. The influences of coexisting substances (Cl−, SO42−, CO32−, NO2− and NO3−) were explored. MIT degradation pathways were proposed and sulfur atom oxidation and carboxylation were considered as the dominant removal mechanisms of MIT. Frontier orbital theory and Fukui indexes of MIT were employed to further explore the degradation mechanism.