Low Detection Limit Research Articles

Tailoring a Two-Dimensional Halide Perovskite Composed of the Secondary Amine Cation for Anisotropic X-ray Responses.

Two-dimensional (2D) metal-halide perovskites have shown broad application prospects in the field of optoelectronic detection. The presence of the natural quantum-well structure results in strong anisotropy of physical properties, while studies on anisotropic X-ray responses remain insufficient. Here, we present an intriguing anisotropy of X-ray-responsive behaviors in a 2D halide perovskite, (t-ACH)2(DMA)Pb2Br7 (1, where t-ACH is trans-4-(aminomethyl)cyclohexanecarboxylate and DMA is dimethylamine), in which the secondary amine DMA+ cation with a large ionic radius locates inside the perovskite cage to form inorganic frameworks. The alternative alignment of inorganic slabs and organic bilayers creates a typical quantum-well architecture, which accounts for the generation of photoelectronic anisotropy. High-quality crystals of 1 exhibit notable semiconducting properties with a large μτ product (1.9 × 10-4 cm2 V-1). Intriguingly, 1 has better X-ray detection sensitivity (∼569.9 μC Gyair-1 cm-2) along the in-plane direction, which is attributed to its excellent charge carrier transport performance in this direction. Conversely, the higher resistance stemming from the organic barrier results in a lower detection limit along the out-of-plane direction (∼78.1 nGyair s-1), much lower than the medical diagnostic criteria (∼5.5 μGyair s-1). This work might open up new possibilities for the creative use of hybrid perovskites in direct X-ray detection.

Evaluation of Cd, Hg, Pb, Zn and Ni in selected cosmetic products: risk assessment for human health

ABSTRACT The ICP-MS method was used to determine the concentrations of five heavy metals: Cadmium (Cd), lead (Pb), zinc (Zn), mercury (Hg), and nickel (Ni). A total of 36 samples of cosmetic products (makeup, eye shadow, and mascara) of various brands were chosen from those available in Riyadh, Saudi Arabia. Several analytical parameters, such as accuracy, precision, linearity, the lower limit of quantification (LOQ), and the lower limit of detection (LOD), were assessed to determine the validity of the proposed method. The determination of Cd, Pb, Zn, Hg, and Ni was verified for accuracy and precision. The results of the determination of studied heavy metals concentration in cosmetic samples reveal that, the concentrations of Cd, Pb, Zn, Hg and Ni ranged from 0.03–0.53, 10.28–107.01, 14.49–867.12, 1.75–6.45 and 4.22–31.36 µg/g, respectively. In all samples of cosmetic products, the concentrations of Cd and Hg were deemed to be within the normal range. However, the concentration of Pb was higher than the recommended value by the World Health Organization (WHO). Nickel concentration was measured with a detection limit lower than the WHO recommended level, but no suggested value for Zn, which is critical for mitochondria, was found. Health risks related to these metal intakes through dermal exposure pathways are assessed using the total hazard quotient (THQs), total hazard index (HI), chronic daily intake (CDI), and hazard quotient (HQ). Despite the low risks of cancer and non-cancer caused by using these cosmetic products, testing results for cancer and non-cancer risks for these products must be regularly examined. Therefore, constant monitoring of cosmetic products, particularly with regard to heavy metal contamination, should be implemented to maintain human safety and security.

Novel ferrofluid based on hydrophobic deep eutectic solvents for separation and analysis of trace estrogens in environmental water and urine samples.

A novel ferrofluid prepared from ahydrophobic deep eutectic solvent (DES) and Fe3O4@graphite composite materials was introduced as a green microextraction medium for the separation and enrichment of trace estrogens in real samples. It was found that the ferrofluid greatly improved the capacity and selectivity of target analytes, benefiting from the enrichment of both DES and Fe3O4@graphite composite materials. Using a combination of high-performance liquid chromatography-fluorescence detection (HPLC-FLD) and vortex-assisted liquid-liquid microextraction (VALLME), a new method was established for simultaneous rapid processing and accurate determination of three estrogens (estradiol [E2], estriol [E3], and ethinyl estradiol [EE2]) in environmental water and urine samples. Key parameters affecting the extraction efficiency were optimized using a single-factor approach and response surface methodology. Under optimal conditions, this method yielded a low limit of detection (1.01 ng L-1, 3.03 ng L-1, and 25.0 ng L-1 for EE2, E2, and E3, respectively), wide linear range (3-200,000ng L-1), high enrichment factors (9.81-47.2), and satisfactory recovery (73.8-129.0%). Compared with traditional analytical techniques, this method avoids the use of volatile toxic organic extraction solvents and cumbersome phase separation operations.

Two-layer cascaded catalytic hairpin assemblies based on locked nucleic acids for one-step and highly sensitive ctDNA detection.

Enzyme-free signal amplification of catalytic hairpin assembly (CHA) has enabled sensitive detection of circulating tumor DNA (ctDNA) in early clinical diagnosis. Conventional CHA strategies are restrained by the limited amplification efficiency of the single-stage system, and signal leakage from "breathing" influence and nuclease degradation. Here, we introduced two-layer cascaded locked nucleic acid (LNA)-assisted CHA circuits with the intelligent incorporation of LNA in the hairpins and reporter for the highly sensitive one-step detection of scarce ctDNA. The target-triggered upstream CHA reaction continuously generates hybrid products to catalyze the downstream CHA reaction for transducing the primary sensing event, and the released target and the produced hybrid product trigger the next catalytic reaction round at the same time and finally cascade to amplify the target ctDNA fluorescence output signal. Meanwhile, the stronger binding affinity of the LNA-DNA duplex endows the two-layer LNA-assisted CHA system with thermodynamic stability and nuclease resistance, and thus our designed system exhibits an excellent detection performance for target ctDNA in the range from 2 pM to 5 nM with a low detection limit of 0.6 pM. Significantly, the two-layer LNA-assisted CHA circuits have been successfully implemented for the feasible analysis of clinical samples. This two-layer cascaded LNA-assisted CHA strategy provides a promising high sensitivity tool for one-step detection of scarce ctDNA from complex clinical samples and would facilitate the reconfiguration of DNA circuit-based DNA nanotechnology for the precise analysis of other biomarkers in clinical research fields.

Visual Eosin Y-Based Photosensitization Sensing Systems for Ultrasensitive Detection of Diclofenac with Single-Atom Co─N2O2 Site-Immobilized g-C3N4 Nanosheets.

It is highly desired to develop a visual sensing system for ultrasensitive detection of colorless diclofenac (DCF), yet with a significant challenge. Herein, a novel dye-based photosensitization sensing system has been successfully developed for detecting DCF for the first time, in which the used dye eosin Y (DeY) can strongly absorb visible light and then be decolorized obviously by transferring photogenerated electrons to g-C3N4 nanosheets (CN), while the built single-atomic Co─N2O2 sites on CN by boron-oxygen connection can competitively adsorb DCF to impede the photosensitization decoloration of DeY. This system exhibits a broad detection range from 8ngL-1 to 2 mgL-1 with 535nm light, an exceptionally low detection limit (3.5ngL-1), and remarkable selectivity. Through the time-resolved, in situ technologies, and theoretical calculations, the decolorization of DeY is attributed to the disruption of DeY's conjugated structure caused by the triplet excited state electron transfer from DeY to CN, meanwhile, the adsorbed oxygen facilitates the charge transfer process. The preferential adsorption of DCF mainly depends on the strong interactions between the as-constructed single-atom Co and Cl in DCF. This study opens an innovative light-driven sensing system by combining dye and single-atom metal/nanomaterial for visually intuitive detection of environmental pollutants.

Dual-Ligand Europium-Organic Gels as a Highly Efficient Anodic Annihilation Electrochemiluminescence Emitter for Ultrasensitive Detection of MicroRNA.

In this study, a novel europium dual-ligand metal-organic gel (Eu-D-MOGs) with high-efficient anodic annihilation electrochemiluminescence (ECL) was synthesized as an ECL emitter to construct a biosensor for ultrasensitive detection of microRNA-221 (miR-221). Impressively, compared to the ECL signal of europium single-ligand metal-organic gels (Eu-S-MOGs), the ECL signal of Eu-D-MOGs was significantly improved since the two organic ligands could jointly replace the H2O and coordinate with Eu3+, which could remarkably reduce the nonradiative vibrational energy transfer caused by the coordination between H2O and Eu3+ with a high coordination demand. In addition, Eu-D-MOGs could be electrochemically oxidized to Eu-D-MOGs•+ at 1.45 V and reduced to Eu-D-MOGs•- at 0.65 V to achieve effective annihilation of ECL, which overcame the side reaction brought by the remaining emitters at negative potential. This benefited from the annihilation ECL performance of the central ion Eu3+ caused by its redox in the electrochemical process. Furthermore, the annihilation ECL signal of Eu3+ could be improved by sensitizing Eu3+ via the antenna effect. In addition, combined with the improved rolling circle amplification-assisted strand displacement amplification strategy (RCA-SDA), a sensitive biosensor was constructed for the sensitive detection of miR-221 with a low detection limit of 5.12 aM and could be successfully applied for the detection of miR-221 in the lysate of cancer cells. This strategy offered a unique approach to synthesizing metal-organic gels as ECL emitters without a coreactant for the construction of ECL biosensing platforms in biomarker detection and disease diagnosis.

Ultrahigh-Speed 3D DNA Walker with Dual Self-Protected DNAzymes for Ultrasensitive Fluorescence Detection and Intracellular Imaging of microRNA.

Herein, a dual self-protected DNAzyme-based 3D DNA walker (dSPD walker), composed of activated dual self-protected walking particles (ac-dSPWPs) and track particles (TPs), was constructed for ultrasensitive and ultrahigh-speed fluorescence detection and imaging of microRNAs (miRNAs) in living cells. Impressively, compared with the defect that "one" target miRNA only initiates "one" walking arm of the conventional single self-protected DNAzyme walker, the dSPD walker benefits from the secondary amplification and spatial confinement effect and could guide "one" target miRNA to generate "n" secondary targets, thereby initiating "n" nearby walking strands immediately, realizing the initial rate over one-magnitude-order faster than that of the conventional one. Moreover, in the process of relative motion between ac-dSPWPs and TPs, the ac-dSPWPs could cleave multiple substrate strands simultaneously to speed up movement and reduce the derailment rate, as well as combine with successive TPs to facilitate a large amount of continuous signal accumulation, achieving an ultrafast detection of miRNA-221 within 10 min in vitro and high sensitivity with a low detection limit of 0.84 pM. In addition, the DNA nanospheres obtained by the rolling circle amplification reaction can capture the Cy5 fluorescence dispersed in liquids, which achieves the high-contrast imaging of miRNA-221, resulting in further ultrasensitive imaging of miRNA-221 in cancer cells. The proposed strategy has made a bold innovation in the rapid and sensitive detection as well as intracellular imaging of low-abundance biomarkers, offering promising application in early diagnosis and relevant research of cancer and tumors.

Serum hydroxycotinine was associated with chronic kidney disease (CKD): a cross-sectional study based on NHANES

Objective Smoking has been suggested as a modifiable and cardiovascular risk factor for chronic kidney disease (CKD). Although long-term smoking has been associated with CKD, the potential relationship between its metabolite hydroxycotinine and CKD has not been clarified. Methods A total of 8,544 participants aged 20 years and above from the National Health and Nutrition Examination Survey (NHANES) 2017 - March 2020 were enrolled in our study. CKD was defined by estimated glomerular filtration rate (eGFR) < 60 mL/(min*1.73 m2). Serum hydroxycotinine was measured by an isotope-dilution high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometric (ID HPLC-APCI MS/MS) method with a lower limit of detections (LLOD) at 0.015 ng/mL. The non-linear relationship was explored with restricted cubic splines (RCS). Pearson’s correlation coefficient and a multivariate logistic regression model were used for correlation analysis. Results Serum hydroxycotinine and eGFR were negatively correlated in both non-CKD group (r= −0.05, p < 0.001) and CKD group (r= −0.04, p < 0.001). After serum hydoxycotinine dichotominzed with LLOD, serum hydroxycotinine ≥ 0.015 ng/mL was negatively correlated with eGFR not only in non-CKD group (r = −0.05, p < 0.001) but also in CKD group (r = −0.09, p < 0.001). After adjusting for comprehensive confounders, results from the multivariate logistic regression analysis showed that participants with serum hydroxycotinine ≥ 0.015 ng/mL had increased odds of CKD (OR = 1.505, p < 0.001). Conclusions Serum hydroxycotinine might be positively associated with CKD. Further study is warranted to find the right concentration of hydroxycotinine to measure the CKD.

Parallel detection of multiple biomarkers in a point-of-care-competent device for the prediction of exacerbations in chronic inflammatory lung disease

Sudden aggravations of chronic inflammatory airway diseases are difficult-to-foresee life-threatening episodes for which advanced prognosis-systems are highly desirable. Here we present an experimental chip-based fluidic system designed for the rapid and sensitive measurement of biomarkers prognostic for potentially imminent asthma or COPD exacerbations. As model biomarkers we chose three cytokines (interleukin-6, interleukin-8, tumor necrosis factor alpha), the bacterial infection marker C-reactive protein and the bacterial pathogen Streptococcus pneumoniae—all relevant factors in exacerbation episodes. Assay protocols established in laboratory environments were adapted to 3D-printed fluidic devices with emphasis on short processing times, low reagent consumption and a low limit of detection in order to enable the fluidic system to be used in point-of-care settings. The final device demonstrator was validated with patient sample material for its capability to detect endogenous as well as exogenous biomarkers in parallel.

Tailoring the Ni-O Microenvironment in Amorphous-Dominated Highly Active and Stable Zn/NiO for Hydrogen Sulfide Detection.

Amorphous metal oxide semiconductor (MOS) materials are endowed with great promise to modulate electronic structures for gas-sensing performance improvement. However, the elevated-temperature requirement of gas sensors severely impedes the application of amorphous materials due to their low thermal stability. Here, a cationic-assisted strategy to tailor the Ni-O microenvironment in an amorphous-dominated Zn/NiO heterogeneous structure with high thermal stability was developed. It was found that 6 mol % Zn incorporation into amorphous NiO can effectively preserve the amorphous-dominated NiO phase even at high temperature. After calcination, the amorphous oxide can only be converted to crystals partly thus leading to the formation of amorphous/crystalline compounds, and the content of the amorphous phase can be adjusted by changing the calcination temperature. This amorphous/crystalline configuration can induce more electron transfer from Ni to Zn species, leading to the formation of active Niδ+ (δ>2) centers. Ex situ XPS and in situ Raman spectroscopy studies proved that the generated Niδ+ species pronouncedly promote the electron transfer during the H2S adsorption process. The amorphous/crystalline-6 mol % Zn/NiO sensor exhibits exceptional hydrogen sulfide response (2 ppm, 3.23), outstanding repeatability (as long as 5 weeks), and low limit of detection (as low as 50 ppb), surpassing most reported nickel-based gas sensors such as the crystal nickel oxide prepared in this work. The response and detection limit of the latter is only (2 ppm, 1.89) and (0.05 ppm) respectively. Our work thus opens up more opportunities for fundamental understanding and modulating of highly active amorphous sensing materials.

Electronic tongue made of gelatin self-supporting films on printed electrodes to detect lactose

An electronic tongue was developed for the detection of lactose content in commercial foods. This was accomplished by employing optimized detection units comprised of gelatin films and information visualization methods for data analysis. The films incorporating gelatin, tannic acid, and zein, served as the basis for the sensors, whose electrodes were screen printed using carbon black ink. Self-supporting films were produced using various combinations of these materials, some of which had limited solubility in water (from 33% to 36%). They were hydrophobic and yielded reproducible electrical impedance spectra to be used as sensing units. Lactose detection experiments were conducted using various standard concentrations and commercial food samples. Capacitance decreased with lactose concentration at low frequencies, with films lacking a hydrophobic coating showing higher capacitance signals (exceeding 200 nF). Low limits of detection were obtained for the most sensitive films, as low as 2.03 × 10−19 mol/L, comparable to existing biosensors to detect lactose. Combining data from four sensing units in an electronic tongue allowed for the differentiation of lactose concentrations ranging from 1 × 10−20 mol/L to 1 × 10−6 mol/L using the interactive document mapping (IDMAP) projection technique, leading to a silhouette coefficient of 0.716. The discriminatory power of the electronic tongue was validated by distinguishing between lactose-containing and lactose-free food products. These findings highlight the potential of electronic tongues made with sustainable materials for applications in food quality assessment and lactose intolerance management.

Ratiometric luminescent simultaneous sensing of aristolochic acids (I-IV) by a novel metal-organic framework and its nanowire.

Aristolochic acids(AAs), which are a group of nitrophenanthrene carboxylic acids formed by Aristolochia plant, have become an increasing serious threat to humans due to their nephrotoxicity and carcinogenicity. Fast and accurate approaches capable of simultaneous sensing of aristolochic acids (I-IV) are vital to avoid intake of such compounds. In this research, the novel ratiometric fluorescence zinc metal-organic framework and its nanowire have been prepared. The two different coordination modes (tetrahedral configuration and twisted triangular bipyramidal configuration) within zinc metal-organic framework lead to the significant double emissions. The ratiometric fluorescence approach based on nanowire provides a broader concentration range (3.00 × 10-7~1.00 × 10-4 M) and lower limit of detection (3.70 × 10-8 M) than that based on zinc metal-organic framework (1.00 × 10-6~1.00 × 10-4 M, 5.91 × 10-7 M). The RSDs of the results are in the range 1.4-3.5% (nanowire). The density functional theory calculations and UV-Vis absorption verify that the sensing mechanism is due to charge transfer and energy transfer. Excellent spiked recoveries for AAs(I-IV) in soil and water support that nanowire is competent to simultaneously detect these targets in real samples, and the proposed approach has potential as a fluorescence sensing platform for the simultaneous detection of AAs (I-IV) in complex systems.

An electrochemical aptasensor for zearalenone detection based on the Co3O4/MoS2/Au nanocomposites and hybrid chain reaction.

Anelectrochemical aptasensor was used for the fast and sensitive detection of zearalenone (ZEN) based on the combination of Co3O4/MoS2/Au nanocomposites and the hybrid chain reaction (HCR). The glassy carbon electrode was coated with Co3O4/MoS2/Au nanomaterials to immobilize the ZEN-cDNA that had been bound with ZEN-Apt by the principle of base complementary pairing. In the absence of ZEN, the HCR could not be triggered because the ZEN-cDNA could not be exposed. After ZEN was added to the surface of the electrode, a complex structure was produced on the modified electrode by the combination of ZEN and ZEN-Apt. Therefore, the ZEN-cDNA can raise the HCR to produce the long-strand dsDNA structure. Due to the formation of dsDNA, the methylene blue (MB) could be inserted into the superstructure of branched DNA and the peak currents of the MB redox signal dramatically increased. So the concentration of ZEN could be detected by the change of signal intensity. Under optimized conditions, the developed electrochemical biosensing strategy showed an outstanding linear detection range of 1.0×10-10 mol/L to 1.0×10-6 mol/L, a low detection limit (LOD) of 8.5×10-11 mol/L with desirable selectivity and stability. Therefore, the fabricated platform possessed a great application potential in fields of food safety, medical detection, and drug analysis.

MXene@MnIn2S4‐Gated Organic Photoelectrochemical Transistors with Nanozyme‐Mediated Multiple Quenching Effects for Ultrasensitive Detection of Okadaic Acid

AbstractOrganic optoelectronics have attracted widespread interdisciplinary research interest but lags far behind in the application in marine environmental detection. The organic photoelectrochemical transistor (OPECT) shows promise as a powerful tool for comprehensive monitoring and early warning of marine conditions, which can be further enhanced by the valuable signal amplification strategy of nanozyme‐mediated catalytic precipitation. Herein, OPECT technology is integrated with nanozyme‐mediated catalytic precipitation for the first time, establishing an ultrasensitive detection platform for okadaic acid (OA). Specifically, MXene@MnIn2S4 (MXMnIS) hybrid composed of Schottky‐junction is synthesized via a hydrothermal method, which can efficiently modulate the device with high current gain. Linking with a sandwich immunoassay, the Ru‐C3N4 nanozyme with peroxidase‐mimicking activity can catalyze the oxidation of 4‐chloro‐1‐naphthol (4‐CN) to form an insoluble precipitate on the electrode surface, resulting in a decrease in the photocurrent and altering the transistor response. Importantly, the proposed OPECT biosensor presented an excellent sensitivity and a low detection limit (32.5 pM), fully satisfying the fundamental requirements for the quantitative detection of intracellular and extracellular OA in the practical culture media of Prorocentrum lima at different growth stages. This OPECT platform based on the nanozyme‐mediated quenching effect is significant for effectively monitoring the safety of the marine ecological environment and food safety.

Electrochemical sensor based on reduced graphene oxide paste electrode for detection of gemcitabine as a chemotherapy drug in breast cancer

The development of a precise and sensitive electrochemical sensor is essential in the field of medical diagnostics in order to identify gemcitabine, a chemotherapy drug that is commonly used to treat breast cancer. This work presents a novel electrochemical sensor based on a reduced graphene oxide (rGO) nanocomposite and a zirconium-based metal-organic framework (Zr-MOF) with terephthalic acid as a ligand. Gemcitabine (GEM), a chemotherapy medication used to treat breast cancer, is detected with remarkable sensitivity and selectivity by the Zr-MOF-rGO modified graphene paste electrode (GrPE) sensor. By combining the strong structure and active sites of Zr-MOF with the large surface area and electrical conductivity of rGO, the sensor's design maximizes electron transfer rates and GEM adsorption capacity. The sensor outperforms current GEM sensors with its wide linear detection range (0.5–490 μM) and low detection limit (0.008 μM). The sensor's long-term analytical applicability is confirmed by stability and reusability studies, which produced accuracy rates surpassing 94 % and RSD values below 4.21 % in recovery trials using spiked human blood serum and urine samples. Overall, the results of this investigation show that the Zr-MOF-rGO/GrPE electrode has the potential to be a useful platform for the detection of gemcitabine in patients with breast cancer.

Design of a two-dimensional photonic crystal biosensor to identify blood cholesterol in humans

The cholesterol detection of human blood using a two-dimensional photonic crystal biosensor has been studied in this paper. The structure calculations are done using Plane Wave Expansion (PWE) and Finite Difference Time Domain (FDTD). Photonic crystals can be used to detect biological components by utilizing a two-dimensional structure and resonator nano ring. These nano rings cause waveguide and resonator coupling. The cylinders around the sensing region have investigated the improvement structure output. The quality factor and figure of merit (FOM) for this sensor are 4988 and 57.14 RIU−1, respectively, and the low detection limit (DL) is 0.001(RIU), with a sensitivity of 32 (nm/RIU).

Study on the lower limit of gas detection based on snapshot infrared multispectral imaging system

Study on the lower limit of gas detection based on snapshot infrared multispectral imaging system

Porous Prussian blue nanolayers formed in situ on Fe-MOFs-modified electrode surfaces by electrochemically triggered dual-templating effect for ultrasensitive detection of lead ions and Staphylococcus aureus

In this study, introducing Fe-MOFs as reactants to the electrode surface creates a novel mode for modulating interface performance that can lead to rapid enrichment of reactants in the proximity of electrodes by electrochemical-induced confinement effect. A facile, controllable, and room temperature electrochemical approach utilizes Fe-MOFs as nanotemplates to produce porous Prussian blue (PB) nanolayers on the electrode surfaces. Unlike conventional chemical conversion that needs a supply of exogenous acid regents, the electrochemical method creates a solid acidic condition in the oxygen evolution reaction cycle to release Fe3+ from the Fe-MOFs, improving conversion efficiency and electrochemical activity of PB. Furthermore, small oxygen bubbles generated by splitting H2O near the electrodes are also good templates, promoting the formation of porous structures that can increase effective surface area and mass-transfer efficiency. As a conceptional application, using Fe-MOFs as self-sacrificial tags, an ultrasensitive electrochemical platform with triple amplification is developed to detect Pb2+ and S. aureus based on DNAzyme-CHA cascade reaction. The designed platform shows low detection limits of 8.5 fM and 1 CFU/mL for Pb2+ and S. aureus, respectively. Moreover, the platform has high selectivity, stability and reproducibility, and also shows satisfactory recovery rates when validated using actual samples.

Dion‐Jacobson 2D Perovskite 2AMPPbBr4 with Type II Band Alignment for Highly Sensitive X‐Ray Detection

Abstract2D hybrid perovskites have emerged as a promising alternative material to address the environmental stability and the ion‐migration of the 3D perovskites for direct X‐ray detector applications. Nevertheless, the X‐ray detection performance of the 2D hybrid perovskites still lags because of its low X‐ray attenuation ability and limited solubility for thick film deposition. Here, a high‐performance X‐ray detector in Dion‐Jacobson 2D hybrid perovskite, 2(aminomethyl) pyridinium lead bromide (2AMPPbBr4), is studied. 2AMPPbBr4 exhibits an ultra‐short interlayer distance of 3.43 Å, leading to high X‐ray attenuation ability. Furthermore, DFT results indicate that 2AMPPbBr4 exhibits type II band alignment between 2AMP2+ ligand and the [PbI6]4− layers, facilitating effective spatial separation of photo‐generated carriers. The X‐ray detector made of 2AMPPbBr4 with an average thickness of 200 µm is realized via an improved drop‐casting method. An improved X‐ray sensitivity of 3933.88 µC Gy−1 cm−2 and a low detection limit of 4.17 nGy s−1 is achieved. This work paves the way for high‐performance X‐ray detectors based on the emerging 2D perovskite materials.

Construction of phosphatase-like COF-OMe@Valine-CeO2 nanozymes for ultrasensitive electrochemical detection of organophosphorus pesticides

Construction of highly-active artificial nanozymes for pesticides detection has great significance of human health and ecological systems. Herein, we have successfully designed a two-step approach to synthesize the TAPB-DMTP-COF (hereafter denoted as COF-OMe, TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde; COF, covalent organic framework)@Valine integrated cerium oxide nanozymes (COF-OMe@Valine-CeO2) with phosphatase-like activities, which can cleave phosphate bonds (PO) of organophosphorus pesticides (OPs) for the formation of electroactive p-nitrophenol (p-NP). In detail, the Ce (IV)/Ce (III) species serve as the active sites to polarize and hydrolyze PO bond in OPs, and the excellent adsorption performance of porous COF-OMe toward OPs could promote the hydrolysis process of PO. Moreover, the efficient charge transfer at the covalent interface of COF-OMe@Valine-CeO2 also contributed to this excellent catalytic process. By virtue of those advantages, the COF-OMe@Valine-CeO2 electrochemical platform was successfully applied in methyl-paraoxon (MP) detection. The resulting electrochemical sensors displayed high sensitivity, a wide linear response range of 0.034–76 μmol/L, and low detection limits of 0.011 μmol/L for MP. The research not only provides a preparation method for COF with excellent nanozyme activity, but broadens some new insights for the design of highly efficient nanozymes for on-time detection for OPs.