Recognition Probe Research Articles

Spectroscopic Study of a Novel Binaphthyl Amine Fluorescent Probe for Chiral Recognition of D/L-Lysine.

Lysine plays a crucial role in promoting development, enhancing immune function, and improving the function of central nervous system tissues. The two configurational isomers of amino acids have significantly different effects. Currently, methods for chiral recognition of lysine have been reported; however, previous detection methods have drawbacks such as expensive equipment and complicated detection processes. Fluorescence analysis, on the other hand, boasts high sensitivity, strong selectivity, and simple operation. In this study, we synthesized four novel Binaphthyl-Amine (BINAM)-based fluorescent probes capable of specifically identifying the L-configuration of lysine among the twenty amino acids that constitute human proteins. The enantiomeric fluorescence enhancement ratio (ef or ΔIL/ΔID) reached up to 15.29, demonstrating high enantioselectivity. In addition, we assessed the probe's recognition capabilities under varying pH levels, reaction times, and metal ion conditions, along with its limit of detection (LOD) and quantum yield. Our results suggest that this probe serves as a highly stable tool for the detection of chiral lysine.

The sensing of circRNA with tetrahedral DNA nanostructure modified microfluidic chip

BackgroundCircular ribonucleic acids (circRNAs) are a type of covalently closed noncoding RNA with disease-relevant expressions, making them promising biomarkers for diagnosis and prognosis. Accurate quantification of circRNA in biological samples is a necessity for their clinical application. So far, methods developed for detecting circRNAs include northern blotting, reverse transcription quantitative polymerase chain reaction (RT-qPCR), microarray analysis, and RNA sequencing. These methods generally suffer from disadvantages such as large sample consumption, cumbersome process, low selectivity, leading to inaccurate quantification of circRNA. It was thought that the above drawbacks could be eliminated by the construction of a microfluidic sensor. ResultsHerein, for the first time, a microfluidic sensor was constructed for circRNA analysis by using tetrahedral DNA nanostructure (TDN) as the skeleton for recognition probes and target-initiated hybridization chain reaction (HCR) as the signal amplification strategy. In the presence of circRNA, the recognition probe targets the circRNA-specific backsplice junction (BSJ). The captured circRNA then triggers the HCR by reacting with two hairpin species whose ends were labeled with 6-FAM, producing long DNA strands with abundant fluorescent labels. By using circ_0061276 as a model circRNA, this method has proven to be able to detect circRNA of attomolar concentration. It also eliminated the interference of linear RNA counterpart, showing high selectivity towards circRNA. The detection process can be implemented isothermally and does not require expensive complicated instruments. Moreover, this biosensor exhibited good performance in analyzing circRNA targets in total RNA extracted from cancer cells. SignificanceThis represents the first microfluidic system for detection of circRNA. The biosensor showed merits such as ease of use, low-cost, small sample consumption, high sensitivity and specificity, and good reliability in complex biological matrix, providing a facile tool for circRNA analysis and related disease diagnosis in point-of care application scenes.

A colorimetric/electrochemical microfluidic biosensor using target-triggered DNA hydrogels for organophosphorus detection

Organophosphorus compounds are widely distributed and highly toxic to the environment and living organisms. The current detection of organophosphorus compounds is based on a single-mode method, which makes it challenging to achieve good portability, accuracy, and sensitivity simultaneously. This study designed a multifunctional microfluidic chip to develop a dual-mode biosensor employing a DNA hydrogel as a carrier and aptamers as recognition probes for the colorimetric/electrochemical detection of malathion, an organophosphorus compound. The biosensor balanced portability and stability by combining a microfluidic chip and target-triggered DNA hydrogel-sensing technologies. Moreover, the biosensor based on target-triggered DNA hydrogel modified microfluidic developed in this study exhibited a dual-mode response to malathion, providing both colorimetric and electrochemical signals. The colorimetric mode enables rapid visualization and qualitative detection and, when combined with a smartphone, allows on-site quantitative analysis with a detection limit of 56 nM. The electrochemical mode offers a broad linear range (0.01–3000 μM) and high sensitivity (a limit of detection of 5 nM). The two modes could validate each other and improve the accuracy of detection. The colorimetric/electrochemical dual-mode biosensor based on target-triggered DNA hydrogel modified microfluidic chip offers a portable, simple, accurate, and sensitive strategy for detecting harmful environmental and food substances.

Fe(III)-Based Fluorescent Probe for High-Performance Recognition, Test Strip Analysis, and Cell Imaging of Carbon Monoxide.

Fluorescence sensing and imaging techniques are being widely studied for detecting carbon monoxide (CO) in living organisms due to their speed, sensitivity, and ease of use to biological systems. Most fluorescent probes used for this purpose are based on heavy metal ions like Pd, with a few using elements like Ru, Rh, Ir, Os, Tb, and Eu. However, these metals can be expensive and toxic to cells. There is a need for more affordable and biologically safe fluorescent probes for CO detection. Drawing inspiration from the robust affinity exhibited by heme iron toward CO, in this work, a rhodamine derivative called RBF was developed for imaging CO in living cells by binding to Fe(III) and could be used for CO sensing. A Fe(III)-based fluorescent probe for CO imaging in living cells offers advantages of cost effectiveness, low toxicity, and ease of use. The fluorescence detection using the RBF-Fe system showed a direct correlation with increasing levels of CORM-3 (LOD = 146 nM) or the exposure time of CO gas, displaying reduced fluorescence. A CO test paper based on RBF-Fe was created for simple on-site CO detection, where fluorescence would diminish in response to CO exposure, allowing rapid (2 min) visual identification. Imaging of CO in living cells was successfully conducted using the probe system, showing a decrease in fluorescence intensity as CORM-3 concentrations increased, indicating its effectiveness in monitoring CO levels accurately within living cells.

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly mediated cyclic signal amplification strategy for the reliable determination of E. coli O157:H7.

Aratiometric SERS aptasensor based on catalytic hairpin self-assembly (CHA) mediated cyclic signal amplification strategy was developed for the rapid and reliable determination of Escherichia coli O157:H7. The recognition probe was synthesized by modifying magnetic beads with blocked aptamers, and the SERS probe was constructed by functionalizing gold nanoparticles (Au NPs) with hairpin structured DNA and 4-mercaptobenzonitrile (4-MBN). The recognition probe captured E. coli O157:H7 specifically and released the blocker DNA, which activated the CHA reaction on the SERS probe and turned on the SERS signal of 6-carboxyl-x-rhodamine (ROX). Meanwhile, 4-MBN was used as an internal reference to calibrate the matrix interference. Thus, sensitive and reliable determination and quantification of E. coli O157:H7 was established using the ratio of the SERS signal intensities of ROX to 4-MBN. This aptasensor enableddetection of 2.44 × 102 CFU/mL of E. coli O157:H7 in approximately 3h without pre-culture and DNA extraction. In addition, good reliability and excellent reproducibility were observed for the determination of E. coli O157:H7 in spiked water and milk samples. This study offered a new solution for the design of rapid, sensitive, and reliable SERS aptasensors.

Enhancing public health safety: Development and application of a MoS2@CNT-Chit electrochemical DNA biosensor for rapid and accurate detection of S. Typhi

This study introduces an advanced electrochemical biosensor that utilizes MoS2@CNT as an electrode material combined with a specific DNA probe to detect Salmonella Typhi rapidly and accurately. The sensor offers a broad detection range from 1.0 × 10−6 to 1.0 × 10−18 molL−1 and boasts an exceptionally low limit of detection (LOD) of 1.0 × 10−20 molL−1 for the target bacterium. It demonstrates a detection range from 1.0 × 104 to 1.0 × 1011 CFUml−1 in real samples, with a corresponding LOD of 1.0 × 104 CFUml−1. Rigorous testing against base mismatches and various bacterial strains confirms its specificity, ensuring reliable performance. Validated in real samples, the biosensor can accurately identify Salmonella Typhi in water and milk, achieving recoveries ranging from 92.95 % to 99.58 %. The exceptional performance of the biosensor is attributed to the MoS2@CNT electrode material and the specific DNA recognition probe, which enhance electron transfer and reduce steric impedance. These improvements contribute to the sensor's enhanced sensitivity and specificity, making it a significant advancement in public health safety by providing a rapid and accurate tool for detecting Salmonella Typhi in food samples.

Dual emissive Cl, N-codoped carbon dots for highly selective and sensitive detection of amphotericin B in milk and wastewater

Amphotericin B (AmB) is an antifungal drug used in dairy farming. It is significant to monitor AmB in milk and environmental water as AmB is severely toxic. Herein, dual emissive Cl, N-codoped carbon dots (Cl, N-CDs) were facilely synthesized and explored as fluorescent probes for specific recognition of AmB among sixty-eight common substances. The Cl, N-CDs possess long emission wavelengths (650 and 482 nm), large stokes shift (240 nm), and high quantum yield (22.06 %). The fluorescence of Cl, N-CDs can be specifically quenched by AmB with a linear concentration range of 0.1–6 μM, a detection limit of 6.67 nM, and a response time within 1 min. Moreover, the Cl, N-CDs can be applied for the determination of AmB in milk and wastewater with good recoveries (92.00–110.00 %). This work provides a facile method for the preparation of Cl, N-codoped CDs with excellent fluorescence properties, and develops a new approach for fluorescence quantification of AmB in real samples.

A solid-state sensor based on nanosilica/methylcellulose composite and chromoionophore 8-carboxamidoquinoline derivative as an optode pellet for Zinc(II) ion

Zinc is known to play a central role in the immune system that creates a resistance barrier against viral infection. A naked-eye zinc(II) (Zn2+) ion sensor of 2-oxo-2-(quinolin-8-ylamino)acetic acid (OQAA) as a recognition probe was designed and synthesized. By inserting functional groups of amide and carboxylic acid into a conjugated molecule of 8-aminoquinoline, Zn2+ ion (borderline acid) coordinated favorably with aromatic nitrogen atoms (borderline bases) and N-amide. Characterization of OQAA was done by FTIR, 1H NMR, 13C NMR, UV–vis, and ESI-MS. The Zn2+ ion chemosensor was fabricated by immobilizing OQAA chromogenic ionophore onto a nanosilica/methylcellulose (Si/MC) composite pellet to form a solid-state pellet sensor. A distinguishable color change from pale light-yellow to yellowish-brown of the optode pellet was observed in the presence of Zn2+ ions. Optimization of the pellet-based Zn2+ ion sensor was carried out with a fiber optic reflectance spectrophotometer at 0.25 M OQAA in tris buffer (pH 7.4). The optical fiber sensor demonstrated a linear reflectance response between 0.8 M and 2.4 M Zn2+ ion (R²=0.9741) at λmax=635 nm with a limit of detection (LOD) of 3.6 × 10−2 M and response time of 5 min. The reflectance sensor exhibited good selectivity towards Zn2+ ion over other competitive heavy metals e.g., iron(II) (Fe2+), nickel(II) (Ni2+), cobalt(II) (Co2+), copper(II)(Cu2+) and cadmium(Cd2+) ions. Additionally, the proposed Zn2+ ion sensor showed high shelf-life stability of 75 days operational duration with 80.0 % initial optical response remaining. The quick, easy, and uncomplicated preparation of the OQAA-modified Si/MC (OQAA-Si/MC) composite pellet novel material gave a reproducible reflectance signal towards the determination of Zn2+ ion concentration with a low relative standard deviation (RSD) obtained at ∼1.0 % (n=12), and was reusable three times for assay of Zn2+ ion (RSD=1.3 %). The optical chemosensor imparts remarkable color change towards the analysis of Zn2+ ions, and could offer direct and fast in-situ visual inspection of Zn2+ ion levels in complex samples without an instrument.

Quinoxaline-linked N-acyl hydrazine: A “turn-off” fluorescent probe for the selective recognition of Fe3+ in real water samples

Quinoxaline-based novel (E/Z)-2-(12H-benzo[5,6][1,4]thiazino[2,3-b]quinoxalin-12-yl)-N’-(4-fluorobenzylidene)acetohydrazide (BTQAH) based fluorescent probe was synthesised and characterised using FT-IR, mass spectrometry, NMR spectroscopic techniques. The developed probe revealed a “turn-off” response against Fe3+ ion with no interference from other competing ions as revealed from spectral analysis. The probe offers a limit of detection (LOD) as low as 3.39 µM, which is less than that of the guidelines issued by WHO and US-EPA. A binding stoichiometry of 1:1 was observed in a Fe3+:BTQAH complex as revealed by Job’s plot analysis. A binding constant of 1.13 x 106 M−1 was calculated by the Benesi-Hilderbrand equation. The sensing application of the developed probe (BTQAH) was also extended to the real time analysis of Fe3+ ion in environmental samples. The present approach offers several advantages in terms of rapid, precise, and sensitive analysis of Fe3+ ions.

Mixed N,O-donor Directed Blue Emissive Nano-dispersed Mesoporous Mn(II)-MOF: Dual Sensing Probe for Recyclable and Ultrasensitive ppb-Level Recognition of TNP and Cr(VI)-Oxoanions.

A new mesoporous Mn(II)-MOF [Mn2(phen)2(nia)2]∞ with 4-c uninodal net topology and reiterating rectangular channels in its cargo-net like extension was synthesized using π-conjugated phenanthroline (phen) and syn-syn bridging 5-nitroisopthalic acid (nia) linkers. The MOF (1) exhibited phase purity, uniform morphology, photo and thermal stability, and robustness; duly triggered by the exceptional framework rigidity via intermolecular H-bonding and interlayer π-π stacking interactions. The bright-blue luminescence of the MOF nano-dispersion was explored for sensitive, specific and ultrafast detection of trinitrophenol (TNP) with extremely low LOD (90.62 nM), high KSV (18.27×104 M-1) and Kq (4×1014 M-1s-1). The vapor-phase TNP sensing was also accomplished. Additionally, 1 served towards discriminatory, aqueous-phase monitoring of Cr(VI)-oxoanions, depicting LODs: 36.08 and 35.70 ppb; KSV: 3.46×104 and 4.87×104 M-1; Kq: 3.26×1013 M-1s-1 and 4.31×1013 M-1s-1; and response time: 32 and 40s for CrO4 2- and Cr2O7 2- respectively. The quenching mechanisms (i. e., RET, PET, IFE, weak interactions, collisional quenching and π⋅⋅⋅π stacking) was explained from several experimental investigations and theoretical DFT calculations. The recyclable sensing events and quantification from complex environmental matrices with admirable recovery rates and high KSV (13.02-22.44×104; ~6.31-10.98×104 and ~6.60-11.42×104 M-1 for TNP, CrO4 2- and Cr2O7 2-) undoubtedly advocated the consistency of the probe.

K+-Specification with Flavone P0 Probe in a G-Quadruplex DNA.

G-quadruplex (G4) DNA is considered as a prospective therapeutic target due to its potential biological significance. To understand G4 biological roles and function, a G4-specific fluorescent probe is necessary. However, it is difficult for versatile G4 to precisely recognize without perturbing their folding dynamics. Herein, we reported that flavone P0 can be a fluorescent probe for G4 DNA-specific recognition and have developed a highly selective detection of K+ ion by dimeric G4/P0 system. When comparing various nucleic acid structures, including G4, i-motif, ss/ds-DNA, and triplex, an apparent fluorescence enhancement is observed in the presence of G4 DNA for 85-fold, but only 8-fold for non-G4 DNA. Furthermore, based on fluorescent probe of flavone P0 for G4 DNA screening, the noncovalent dimeric G4/P0 system is exploited as a K+ sensor, that selectively responds to K+ with a 513-fold fluorescence enhancement and a detection range for K+ ion concentration from 0 to 500 mM. This K+ sensor also has a remarkably anti-interference ability for other metal cations, especially for a high concentration of Na+. These results have demonstrated that flavone P0 is an efficient tool for monitoring G-quadruplex DNA and endows flavone P0 with bioanalytical and medicinal applications.

A fluorescent probe for specific dual recognition of Ni2+ and pH

Nickel ion (Ni2+) and pH play an important role in environment and living organisms. A fluorescent probe “naphthalimide- s-triazine” (NCNS) for targeted dual detection of Ni2+ and pH was synthesized. As a result, NCNS exhibits excellent optical properties: a much larger Stokes shift (140 nm), eminent changes of fluorescence intensity and significant red-shift both for Ni2+ and pH. As for the detection of Ni2+, the selectivity is high and the anti-interference is strong. NCNS can fluorescently detect Ni2+ in a wider pH range from 4.0 to 10.5. It provides a much lower limit of detection (LOD, 20.03 nM), a rapid response time (150 s) and six times reversibility, showing the high sensitivity. Particularly, NCNS can be applied to fluorescently detect Ni2+ in actual water samples and HA-VSMC imaging. In the detection of pH, the probe generates a ratiometric fluorescence in a wide pH range (3.0 ∼ 12.3). NCNS has been successfully made test paper both for Ni2+ and pH. The mechanisms of the double recognition are verified by the density functional theory (DFT) calculations and the nuclear magnetic resonance (NMR) titration experiments.

A highly selective Cd‐based metal‐organic framework fluorescent probe for rapid recognition of cephalothin in water

Nowadays, the problem of antibiotic pollution in the water environment is becoming more and more serious, which has caused great harm to human health and the circulatory system. Therefore, it is extremely crucial to design an effective and sensitive method for the recognition of antibiotics in water. In this research, 1‐(4‐carboxyphenyl)‐1H‐pyrazole‐3‐carboxylic acid (H2L) was used as a ligand to prepare a luminescent two‐dimensional (2D) metal–organic framework (MOF), CdL·H2O (1). 1 can specifically recognize antibiotic cephalothin (CET) in aqueous environments through a fluorescence‐enhanced response, which demonstrated a favorable linear correlation between the fluorescence intensities of 1 and the concentrations of CET (0–50 μM) with a linear fluorescence enhancement slope KEC value of 5.4750 × 104 M−1 and a limit of detection (LOD) of 165 nM. The fast response, good selectivity, anti‐interference ability, and reusability for CET recognition were also verified. 1 represents the inaugural MOF‐based fluorescent material designed for the recognition of CET. Additionally, the detection mechanism for CET was explored in detail with a view to better understanding the fluorescence sensing process.

A dual-responsive RhB-doped MOF probe for simultaneous recognition of Cu2+ and Fe3+

Based on the dual response of RhB@UiO-67 (1:6) to Cu2+ and Fe3+, a proportional fluorescent probe with (I392/I581) as the output signal was developed to recognize Cu2+ and Fe3+. Developing highly sensitive and selective trace metal ions probes is crucial to human health and ecological sustainability. In this work, a series of ratio fluorescent probes (RhB@UiO-67) were successfully synthesized using a one-pot method to enable fluorescence sensing of Cu2+ and Fe3+ at low concentrations. The proportional fluorescent probe RhB@UiO-67 (1:6) exhibited simultaneous quenching of Cu2+ and Fe3+, which was found to be of interest. Furthermore, the limits of detection (LODs) for Cu2+ and Fe3+ were determined to be 2.76 μM and 0.76 μM, respectively, for RhB@UiO-67 (1:6). These values were significantly superior to those reported for previous sensors, indicating the probe’s effectiveness in detecting Cu2+ and Fe3+ in an ethanol medium. Additionally, RhB@UiO-67 (1:6) demonstrated exceptional immunity and reproducibility towards Cu2+ and Fe3+. The observed fluorescence quenching of Cu2+ and Fe3+ was primarily attributed to the mechanisms of fluorescence resonance energy transfer (FRET), photoinduced electron transfer (PET), and competitive absorption (CA). This work establishes a valuable foundation for the future study and utilization of Cu2+ and Fe3+ sensing technologies.

The Intramolecular Charge Transfer Mechanism by Which Chiral Self-Assembled H8-BINOL Vesicles Enantioselectively Recognize Amino Alcohols.

The chiral H8-BINOL derivatives R-1 and R-2 were efficiently synthesized via a Suzuki coupling reaction, and they can be used as novel dialdehyde fluorescent probes for the enantioselective recognition of R/S-2-amino-1-phenylethanol. In addition, R-1 is much more effective than R-2. Scanning electron microscope images and X-ray analyses show that R-1 can form supramolecular vesicles through the self-assembly effect of the π-π force and strong hydrogen bonding. As determined via analysis, the fluorescence of the probe was significantly enhanced by mixing a small amount of S-2-amino-1-phenylethanol into R-1, with a redshift of 38 nm, whereas no significant fluorescence response was observed in R-2-amino-1-phenylethanol. The enantioselective identification of S-2-amino-1-phenylethanol by the probe R-1 was further investigated through nuclear magnetic titration and fluorescence kinetic experiments and DFT calculations. The results showed that this mechanism was not only a simple reactive probe but also realized object recognition through an ICT mechanism. As the intramolecular hydrogen bond activated the carbonyl group on the probe R-1, the carbonyl carbon atom became positively charged. As a strong nucleophile, the amino group of S-2-amino-1-phenylethanol first transferred the amino electrons to a carbonyl carbocation, resulting in a significantly enhanced fluorescence of the probe R-1 and a 38 nm redshift. Similarly, S-2-amino-1-phenylethanol alone caused severe damage to the self-assembled vesicle structure of the probe molecule itself due to its spatial structure, which made R-1 highly enantioselective towards it.

Organic small molecule catalytic PET-RAFT electrochemical signal amplification strategy for miRNA-21 detection

Quantitative detection of the cancer-associated biomarker miRNA-21 is essential for the prevention and treatment of early-stage cancer patients. In the early diagnosis of cancer, due to the low concentration of miRNA in the organism, it is necessary to develop a fast, simple, highly sensitive and specific method using signal amplification techniques. Herein, a photo-induced electron/energy transfer reversible addition-fragmentation chain transfer polymerization signal amplification electrochemical biosensor was developed. Peptide nucleic acid was used as the recognition probe for miRNA-21 and the chain transfer agent (4-cyano-4-(dodecylsulfonylsulfanylthiocarbonyl)sulfonylpentanoic acid) bearing a carboxylic acid group was successfully conjugated with a phosphate group in the presence of ZrOCl2 to form the phosphate-Zr(IV)-carboxylic acid complex. Subsequently, the polymerization of the monomer (ferrocenylmethyl methacrylate) was achieved by blue light irradiation in the presence of erythrosin B (higher triple quantum yield) and triethanolamine (increases electron transfer rate). With this sophisticated signal amplification biosensing platform, low detection limit of 12.4 aM was achieved for miRNA-21. The biosensor reduces costs and simplifies experimentation while ensuring high sensitivity and selectivity. Meanwhile, the biosensor exhibits excellent anti-interference ability in serum samples and has great potential for practical applications in the early prevention of cancer.

Highly sensitive and novel dual-emission fluorescence nanosensor utilizing hybrid carbon dots-quantum dots for ratiometric determination of chlorpromazine.

Herein, a ratiometric fluorimetric nanosensor is introduced for the sensitive and selective analysis of chlorpromazine (CPZ) via employing blue-emitting B-doped carbon dots (B-CDs) as the reference fluorophore and green-emitting CdTe capped thioglycolic acid (TGA) quantum dots (TGA-CdTe-QDs) as the specific recognition probe. The sensor exhibits dual emission centered at 440 and 560nm, under a single excitation wavelength of 340nm. Upon the addition of ultra-trace amount of CPZ, the fluorescence signal of TGA-CdTe-QDs declines due to electron transfer process from excited TGA-CdTe-QDs to CPZ molecules, whereas the fluorescence peak of B-CDs is unaffected. Therefore, a new fluorimetric platform was prepared for the assay of CPZ in the range of 2.2 × 10-10 to 5.0 × 10-9M with a detection limit of 1.3 × 10-10M. Moreover, the practicability of the designed strategy was investigated for the detection of CPZ in biological samples and the results demonstrate that it possesses considerable potential to be utilized in practical applications.

RuSe2/CuO nanohybrids coupled with ALP-assisted for MMP-9 photoelectrochemical assay

A photoelectrochemical (PEC) assay strategy for the detection of matrix metalloproteinase-9 (MMP-9) was fabricated. RuSe2/CuO nanohybrids were first prepared by hydrothermal method. As a transition metal element semiconductor, RuSe2 has excellent optical and electrical properties. By combining the excellent conductivity and adjustable bandgap of CuO, a binary heterojunction nanoflower with high photoelectric response was obtained. The combination of RuSe2 and CuO reduces the electron hole recombination rate; the RuSe2/CuO nanohybrids exhibits a higher photocurrent response. In the MMP-9 PEC strategy determination, the magnetic beads (MB)-peptide-alkaline phosphatase (ALP) recognition probe was formed by modifying C-terminal of the peptide chain with biotin and binding to ALP, and the N-terminal was connected to carboxylated MB. When the target MMP-9 exists, the recognition probe, MB-Peptide-ALP, was recognized by MMP-9 to cut the substrate area and coding area and release ALP, catalyzing the hydrolysis of O-phosphonoxyphenol (OPP) to produce benzene-1,2-diol in situ, the photocurrent response was generated. This strategy provides lower background PEC noise for detecting MMP-9, with the advantage of simplicity and the sensitivity than conventional ELISA. The results showed that the recognition peptide probe PEC method achieved ultra-high sensitivity detection of target MMP-9, with a linear detection range of 1 pg/mL–100 ng/mL and a detection limit of 0.3 pg/mL (S/N = 3). The results of PEC assay strategy in human serum sample give the recoveries rate of 94.3 % to 108.1 % and relative standard deviation of 0.45–5.87 %.

Engineering MOF-derived 2D NPC-TiO2 nanotablet/3D marigold-like ZnIn2S4/CdS nanoparticles dual Z-scheme heterojunction with excellent photoelectric performance: A novel material for sensitive and facile photoelectrochemical sensing detection of mercury ions in aqueous environments by ion-exchange sensing strategy

Herein, a new NH2-MIL-125-derived 2D nitrogen-doped porous carbon-titanium dioxide (NPC-TiO2) nanotablet/3D marigold-like ZnIn2S4/CdS nanoparticles (NPs) dual Z-scheme heterojunction was first exploited for photoelectrochemical (PEC) measurement of mercury ions (Hg2+). Taking NH2-MIL-125 as precursor, the 2D NPC-TiO2 nanotablet was prepared by calcination. The 3D marigold-like ZnIn2S4 and CdS NPs were synthesized by hydrothermal method and aqueous synthesis way, respectively. The acquired NPC-TiO2, ZnIn2S4 and CdS were sequentially modified on the indium tin oxide (ITO) electrode to form the PEC sensing interface by layer-by-layer assembly. Due to the matched band-edge levels, and strong light-harvesting ability, the given heterostructure on ITO electrode generated a large photocurrent. Importantly, it was found that 2D NPC-TiO2 nanotablet/3D marigold-like ZnIn2S4/CdS NPs dual Z-scheme heterojunction could show specifically increased photocurrent signal towards to Hg2+ by employing CdS NPs as Hg2+-recognition probe with selective Cd-to-Hg ion-exchange, resulting from the in-situ formation of the new quaternary NPC-TiO2/ZnIn2S4/CdS/HgS heterostructure to further facilitate the spatial transmission and separation of charges. As a result, Hg2+ was highly sensitively detected with a low detection limit of 20 fM. This PEC sensor was also verified by evaluating Hg2+ in tap water, river water and lake water, demonstrating great application prospect for environment pollutant measurement.

Detecting Moisture in Building Materials and Commercial Food adducts by 2-Hydroxy-naphthaldehyde Derived Chromo-Fluorogenic Chemosensor.

A great deal of effort has been put into developing a novel and cost-effective molecular probe for selective and sensitive recognition of trace amounts of water in organic solvents due to their tremendous advantages in industrial, pharmaceutical, and laboratory-scale chemistry. Herein, a cost-effective chemosensor L has been designed and studied for the detection of trace amounts of water. The addition of water to the DMSO solution of L exhibited an enhancement of fluorescence emission at 460nm along with a color change from green to colorless. The spectral and color changes occurred due to the self-aggregation of L. The interaction between water and L was performed by dynamic light scattering (DLS), scanning electron microscope (SEM) and finally complemented by quantum mechanical calculation. The detection limit was found to be 0.0093 wt% in DMSO. The L also exhibits a fast visual response and is effectively applied to detect trace amounts of moisture in various food materials (salt, sugar, wheat and honey) and building materials (cement, fly ash, limestone and sand).