650-nm Wavelength Research Articles

Study of Solvent Dependent on Third-Order Nonlinear Optical and Thermo-Optic Coefficient of Malachite Green Dye.

This study reveals the solvent dependent third-order nonlinear optical (NLO) features of malachite green (MG) dye using Z-scan technique. MG dye is dissolved in polar solvents, including DMF, DMSO, ethanol, acetone, methanol, and 1-propanol. The study employs the Z-scan instrument, using a continuous wave (CW) laser as the excitation source, operating at a wavelength of 650nm. The closed aperture (CA) and open aperture (OA) Z-scan techniques are used to assess the nonlinear indices of refraction (n2) and nonlinear coefficient of absorption (β) of MG dye. MG dye demonstrates both saturable absorption (SA) and reverse saturable absorption (RSA) in the OA Z-scan results, due to negative and positive NLO absorption coefficients. MG dye proves a self-defocusing NLO refractive index while operating under low-power conditions. The third-order NLO susceptibility (χ3) of MG dye in various liquids are calculated to be the order of 10-6 esu. Multilinear regression fit is applied here to investigate the various intermolecular interactions between the solute and solvent. MG dye exhibited large thermo-optic coefficient of the order of 10- 3 K- 1 is observed. The results give important new information about the characteristics of MG dye and indicate potential sources of material for NLO applications in future.

Facile and Sustainable Electrostatic Integration of Eosin Y Dye for the Assay of the Atomoxetine Drug Through the Enhancement of the RRS Phenomenon.

The suggested study follows specific protocols to guarantee that the atomoxetine drug analysis approach is environmentally friendly and sustainable. A number of recently created methods were used as prospective evidence for environmental sustainability and applicability, which is an essential point to emphasize. The current study introduces a new and very unique technology using ultrasensitive spectrofluorimetry to identify the atomoxetine (AXT) medication. A one-step, one-pot, direct spectrofluorimetric technique was used in this study's methodology, which was determined to be effective and environmentally sustainable for the drug's evaluation and validation. When AXT and EY reagent were mixed in an acidic setting, a highly resonant Rayleigh scattering product was promptly generated. The application of fluorimetric analysis was built on a novel theory that the augmentation in dye response subsequent to the addition of AXT was directly correlated to the resultant complex's molecular mass, as determined at a wavelength of 365nm. The complexation progression caused a considerable rise in the molecular mass, from 292.82 (AXT+) to 983.68 (AXT-EY) g mol-1. The quantum yield for the coupled product was measured. The linearity was determined to be between 30 and 1500 ng mL-1, while the sensitivity values were found to be between 9.2 and 28.1 ng mL-1. Analyzing AXT-EY complexes allowed us to determine the best values for all of the system's adjustable parameters. The system showed adherence to International Council for Harmonization (ICH) criteria without difficulties. The recommended procedure was then evaluated for environmental friendliness using many current environmental safety metrics. Fortunately, the current analytical technique is also recognized as a white one by the WAC standards, which integrate functional and ecological features using the Green/Red/Blue (RGB 12) design. A novel instrument called BAGI was used to assess the feasibility of the proposed approach in the field of analytical chemistry.

A comparison study of 589 and 650 nm on improving stored whole blood stability by irradiation with a low-power diode pumping solid-state laser.

To assess the effects of diode-pumped solid-state laser irradiation with 589nm and 650nm wavelengths on the stability of stored red blood cells in vitro. This is an intervention study that was conducted from April to July 2021 at the Physiology and Medical Physics Laboratory, College of Medicine, Mustansiriyah University, Baghdad, Iraq, and comprised samples of healthy, adult human blood that were put in tubes with citrate-phosphate dextrose-adenine as an anticoagulant. The blood sample was divided into eight equal aliquots and stored for 21 days at 4ºC. The stability test was done on days 0, 7, 14 and 21 of storage time for non-irradiated and radiated aliquots. For 15 minutes, the irradiated aliquots were subjected to a diode-pumped solid-state laser with a wavelength of 589nm or a laser with a wavelength of 650nm at frequencies of 30, 50 and 70 J/cm². Data was analysed using SPSS 24. Exposure of the whole blood to 589nm and a radiation dose of 70J/cm², 50J/cm² and 30J/cm² was associated with a significant reduction in the percentage of haemolysis that ranged 23-42% throughout the whole storage time. Exposure of the whole blood to 650nm wavelength low-level laser therapy and a radiation dose of 70J/cm², 50J/cm² and 30J/cm² was associated with much less reduction in the percentage of haemolysis that ranged 5-9% throughout the whole storage time. Both 589nm and to some extent 650nm low-level laser irradiation generally reduced haemolysis. The wavelength of 589nm lasers had a more effective influence than the 650nm counterpart in improving the stored red blood cells.

In vitro comparison of low-power diode pumping solid-state laser radiation at 589 and 650 nm on red blood cells suspension viscosity, stability, and deformability.

To investigate the effect of diode-pumped solid-state laser irradiation with yellow 589nm and red 650nm wavelengths on rheological parameters in vitro. The comparative study was conducted between November 2021 and April 2022 at the at the Postgraduate Medical Physics Laboratory, Mustansiriyah University, Baghdad, Iraq, and comprised blood samples from healthy adult volunteers. The samples were divided into 4 aliquots. The first was preserved as a control sample, while the other 3 were exposed to a diode-pumped solid-state laser, delivering the beam for 589nm and 650nm wavelengths at radiation dose 15, 22.5, 33.5J/cm2 for 20, 30 and 45 minutes, and with each laser having a 50mW output power and a 4 mm2 spot diameter. Data was analysed using SPSS (version 24). There were 6 subjects aged 18-60 years. There was no significant difference in the viscosity values between laser wavelengths (p>0.05). Compared to the laser wavelength of 650nm, irradiation with a 589nm wavelength at the same dose resulted in a significant reduction (p<0.009) in deformability. The rigidity index of red blood cell suspension was reduced the most at a radiation dose of 22.5J/cm2 for both lasers compared to the control samples. No significant variations were found in suspended erythrocyte viscosity (p>0.05). The wavelength with 589nm lasers showed more effective influence than its 650nm counterpart in improving the rheological parameters of blood viscosity and erythrocytes deformability.

Spatially confined dual-emission nanoprobes assembled from silicon nanoparticles and gold nanoclusters for ratiometric biosensing.

Gold nanoclusters (AuNCs) possess weak intrinsic fluorescence, limiting their sensitivity in biosensing applications. This study addresses these limitations by developing a spatially confined dual-emission nanoprobe composed of silicon nanoparticles (SiNPs) and AuNCs. This amplified and stabilized fluorescence mechanism overcomes the limitations associated with using AuNCs alone, achieving superior sensitivity in the sensing platform. The nanoprobe was successfully employed for ratiometric detection of bleomycin (BLM) in serum samples, operating at an excitation wavelength of 365nm, with emission wavelengths at 480nm and 580nm. The analytical performance of the system is distinguished by a linear detection range of 0-3.5μM, an impressive limit of detection (LOD) of 35.27nM, and exceptional recoveries ranging from 96.80 to 105.9%. This innovative approach significantly enhances the applicability and reliability of AuNC-based biosensing in complex biological media, highlighting its superior analytical capabilities.

Pharmacognostic Studies on Christia obcordata (Poir.) Bakh. f. and Christia vespertilionis (L.f.) Bakh. f

Knowledge of pharmacognostic standardisation is crucial in the field of herbal research. Christia obcordata (Poir.) Bakh.f. and Christia vespertilionis (L.f.) Bakh.f., commonly known as ‘butterfly wing’ are ornamental plants belonging to the family Fabacae. Christia vespertilionis is believed as a promising anti-cancer agent and is consumed by the old folks of Malaysia in the form of decoction. Moreover, these plants have also been used to treat bronchitis, urinary blockage, and improve blood circulation. Despite the listed medicinal properties, there is no evidence in literature of the pharmacognostic standardization on the aerial parts of these plants.Hence, the current study will evaluate the pharmacognostic standardization parameters on the aerial parts of Christia obcordata (Poir.) Bakh.f. and Christia vespertilionis (L.f.) Bakh.f. Standardisation of these plants was carried out using macroscopic studies, microscopic studies, physicochemical parameters, and phytochemical investigation. Macroscopic showed both plants have similar characteristics in the followings, shape, phyllo taxis, margin-entire, leaf type, and powder microscopy results showed the upper cuticle, upper epidermis, palisade cells, vascular bundle, spongy mesophyll, phloem fibers, sclerenchyma, xylem vessels, collenchyma, sclerenchyma, lower epidermis, lower cuticle, parenchyma, stomatal index, vein number, vein islet, and palisade cells are studied as important key differentiating features on the selected plants. Phytochemical screening on the aerial part extracts presence of steroid, flavonoid, tannin, alkaloid, and carbohydrate on both plants. Fluorescence analysis was carried out individually on the four different extracts and was examined under daylight and U.V light at a wavelength of 254nm and 365nm. To conclude, based on this research finding, the study can be a standardization tool for these plants, providing ease in identifying and determining the purity and quality of the investigated plant.

Hydrophilic Photocrosslinkers as a Universal Solution to Endow Water Affinity to a Polymer Photocatalyst for an Enhanced Hydrogen Evolution Rate.

A universal approach for enhancing water affinity in polymer photocatalysts by covalently attaching hydrophilic photocrosslinkers to polymer chains is presented. A series of bisdiazirine photocrosslinkers, each comprising bisdiazirine photophores linked by various aliphatic (CL-R) or ethylene glycol-based bridge chains (CL-TEG), is designed to prevent crosslinked polymer photocatalysts from degradation through a safe and efficient photocrosslinking reaction at a wavelength of 365nm. When employing the hydrophilic CL-TEG as a photocrosslinker with polymer photocatalysts (F8BT), the hydrogen evolution reaction (HER) rate is considerably enhanced by 2.5-fold compared to that obtained using non-crosslinked F8BT photocatalysts, whereas CL-R-based photocatalysts yield HER rates comparable to those of non-crosslinked counterparts. Photophysical analyses including time-resolved photoluminescence and transient absorption measurements reveal that adding CL-TEG accelerates exciton separation, forming long-lived charge carriers. Additionally, the in-depth study using molecular dynamics simulations elucidates the dual role of CL-TEG: it enhances water penetration into the polymer matrix and stabilizes charge carriers after exciton generation against undesirable recombination. Therefore, the strategy highlights endowing a high-permittivity environment within polymer photocatalyst in a controlled manner is crucial for enhancing photocatalytic redox reactivity. Furthermore, this study shows that this hydrophilic crosslinker approach has a broad applicability in general polymer semiconductors and their nanoparticulate photocatalysts.

Artificial Photosynthetic System with Spatial Dual Reduction Site Enabling Enhanced Solar Hydrogen Production.

Although S-scheme artificial photosynthesis shows promise for photocatalytic hydrogen production, traditional methods often overly concentrate on a single reduction site. This limitation results in inadequate redox capability and inefficient charge separation, which hampers the efficiency of the photocatalytic hydrogen evolution reaction. To overcome this limitation, a double S-scheme system is proposed that leverages dual reduction sites, thereby preserving energetic photo-electrons and holes to enhance apparent quantum efficiency. The design features a double S-scheme junction consisting of CdS nanospheres decorated with anatase TiO2 nanoparticles coupled with graphitic C3 N4 . The as-prepared catalyst exhibits a hydrogen evolution rate of 26.84mmolg-1 h-1 and an apparent quantum efficiency of 40.2% at 365 nm. This enhanced photocatalytic hydrogen evolution is ascribed to the efficient charge separation and transport induced by the double S-scheme. Both theoretical calculations and comprehensive spectroscopy tests (both insitu and exsitu) affirm the efficient charge transport across the catalyst interface. Moreover, substituting the reduction-type catalyst CdS with other similar sulfides like ZnIn2 S4 , ZnS, MoS2 and In2 S3 further confirms the feasibility of the proposed double S-scheme configuration. The findings provide a pathway to designing more effective double S-scheme artificial photosynthetic systems, opening up fresh perspectives in enhancing photocatalytic hydrogen evolution performance.

Exploring Optically Stable Reddish-Orange Fluorescent Magnetic Pigment (0.90)Y2O3:(0.10-x)Eu3+:(x)Bi3+ for Anti-counterfeiting Applications.

The (0.90)Y2O3:(0.10-x)Eu3+:(x)Bi3+ nanophosphors (0.00 ≤ x ≤ 0.06) are synthesised using chemical combustion citrate route and characterized via X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV- visible and photoluminescence spectroscopy. The scanning electron micrographs indicate that the grain size of the phosphors ranges between 40 to 50nm. The photoluminescence (PL) spectra, acquired under the excitation wavelength of 365nm of ultraviolet light, show emission peaks at wavelengths 580nm, 586-598nm, 610nm, 629-661nm and 686-695nm corresponding to the 5D0 → 7FJ electronic transitions of the Eu3+ ion with J = 0, 1, 2, 3 and 4, respectively. The most intense PL spectra at 611nm (5D0 → 7F2), showcasing reddish-orange emission, indicate a higher concentration of Eu3+ ions in asymmetric sites within the Y2O3 host matrix. The presence of the distinct electronic transitions of Eu3+ in PL spectra acclaims that Bi3+ ions transfer their energy efficiently to Eu3+ ions in the matrix. Physical and chemical tests are being conducted on nanophosphors with Bi3+ substitutional doping of x = 0.02 and x = 0.04, both demonstrating intense PL emission. Magnetisation measurements suggest the soft magnetic nature of the nanophosphors, attributing it to the presence of Eu3+ ions in the 7F2 state. The highest PL intensity is seen in the nanophosphor (x = 0.04) with substitutional doping of 6% of Eu3+ and 4% of Bi3+ in Y2O3. This nanophosphor also demonstrates excellent optical stability in the investigated conditions and exhibits soft magnetic behaviour, positioning it as a promising material for incorporation as a fluorescent magnetic pigment in security ink applications. These features serve to prevent counterfeiting of secured documents both optically and magnetically.

Non-destructive prediction of TVB-N using color-texture features of UV-induced fluorescence image for freeze-thaw treated frozen-whole-round tilapia.

The investigation of UV-induced fluorescence imaging coupled with machine learning was conducted to non-destructively detect the total volatile basic nitrogen (TVB-N) of frozen-whole-round tilapia (FWRT) during freezing and thawing. The UV-induced fluorescence images of FWRT at the wavelength of 365 nm were acquired by self-developed fluorescence image acquisition system. In total, 169 color and texture features based on RGB, hue-saturation-intensity and L*a*b* color spaces and gray level co-occurrence matrix were extracted, respectively. Successive projections algorithm (SPA) was employed to select the optimal 16 features to achieve feature dimension reduction modeling. With full and extracted features as input, the models of partial least squares regression (PLSR), least-squares support vector machine (LSSVM) and convolutional neural network (CNN) were established for TVB-N prediction. Results indicated that the full features-based CNN performed better than SPA based prediction models (SPA-PLSR and SPA-LSSVM). The CNN model was determined to be the optimal with an RP2 value of 0.9779, RMSEP value of 1.1502 × 10-2 g N kg-1 and RPD value of 6.721 for TVB-N content predictiin. The CNN method based on UV fluorescence imaging technology has potential for quality and safety detection of FWRT. © 2023 Society of Chemical Industry.

Fiber Optical Network Damage Detection Passive Splitter 1:8 in ODC uses IOT Technology as a means of Real Time Reporting

Fiber optic networks currently have a lot of interest, so a network monitoring system is needed that guarantees quality and speed of repair if mass disruption occurs. in research [1] regarding fiber network damage detection using IoT with the use of a 1:4 splitter and the use of a detector that can work at a wavelength of 650nm so that it can detect damaged cables with output in the software. So in connection with this, the author wants to develop the results of this research by using a 1:8 splitter and carrying out detection using the LDR sensor and NodeMCU ESP32 using IoT (Internet of Things) technology. The ESP32 NodeMCU will receive data in the form of light intensity values ??at each ODC from the LDR sensor. And then sent to a database that is connected directly to the Android application. The cable identification process occurs in three states: normal, warning, and error. The test and analysis results show that the hardware device can work well, with attenuation in the passive splitter cable of 10.28 dB and a light source with a wavelength of 650 nm. Cable detected as damaged is indicated by an output in the software with a delay of 4.56 s.

The Investigating of the Effect of Magnetic Field on a Flint Glass for Optical Isolators Applications

In this study, the effect of a magnetic field on a Flint Glass for optical isolator applications has been reported. A flint glass and a laser light source with a wavelength of 650nm were used as a medium and a light source, respectively. The magnetic field was produced by applying a current through a coil. The linearly polarized light was passed through the medium in the presence of a magnetic field, and the angle of rotation was measured. The angle of rotation was plotted versus magnetic field strength and fitted linearly. The experimental results showed that the flint glass becomes optically active in the presence of a magnetic field because it rotates the plane of linearly polarized light, and this rotation increases with respect to the magnetic field linearly. The Verdet constant was calculated for 650nm, which is a large coefficient for the rotation of the plane of polarized light.

Fluorescent and Biocompatible Nitrogen and Sulfur Co-Doped Carbon Nanodot as an Ocular Fundus Angiography Imaging Agent.

The florescence characteristics and the toxicities of carbon nanodots (CDs) are directly related to their elemental compositions. Fluorescent and non-toxic agent for imaging of biological systems was aimed. Sulfur and nitrogen co-doped CDs (S/N-CDs) was hydrothermally produced in an average size of 8nm. S/N-CDs showed blue fluorescence under UV-light with an excitation wavelength of 365nm. After 24h, S/N-CDs was non-cytotoxic in HUVEC and L929 cells. S/N-CDs have a great potential to act as an alternative material for commercial fluorescent materials with its 85.5% of quantum yield. S/N-CDs was approved in vitro as an imaging agent for an ocular fundus angiography of rats.

Low-cost, portable, on-site fluorescent detection of As(III) by a paper-based microfluidic device based on aptamer and smartphone imaging.

A turn-on fluorescent aptasensor based on a paper-based microfluidic chip was developed to detect arsenite via aptamer competition strategy and smartphone imaging. The chip was prepared by wax-printing hydrophilic channels on filter paper. It is portable, low-cost, and environmentally friendly. Double-stranded DNA consisting of aptamer and fluorescence-labeled complementary strands was immobilized on the reaction zone of the paper chip. Due to the specific strong binding between aptamer and arsenite, the fluorescent complementary strand was squeezed out and driven by capillary force to the detection area of the paper chip, so that the fluorescent signal arose in the detection area under the excitation wavelength of 488nm. Arsenite can be quantified by using smartphone imaging and RGB image analysis. Under the optimal conditions, the paper-based microfluidic aptasensor exhibited excellent linear response over a wide range of 1 to 1000nM, with a detection limit as low as 0.96nM (3σ).

Green synthesized TiO2 nanoparticles: Structural characterization and photoinduced antifungal activity against P. steckii

This study synthesized titanium dioxide (TiO2 ) nanoparticles (NPs) from mango leaf extract and investigated the features and antibacterial capabilities of three different. The microscopic morphological observation, scanning electron microscopy, and transmission electron microscopy results showed that all three NPs showed agglomeration phenomenon, and the TN-1 sample existed as large agglomerates, whereas the agglomeration phenomenon of TN-3 sample was improved by the modified, without large agglomerates. The biosynthetic TN-2 and TN-3 NPs were spherical and uniform in size, whereas those of the TN-3 sample was the smallest, ranging from 10 to 30nm. X-ray diffraction and Raman spectroscopy results exhibited that these were highly pure anatase NPs. The result of ultraviolet (UV)-visible-near-infrared spectral analysis showed that the TN-2 and TN-3 samples displayed higher UV absorption properties than the TN-1 samples and were highest in the modified NPs, which was more suitable for preparing chitosan-based nanocomposite material in future experiments and studies. The colony diameters of the TN-1, TN-2, and TN-3 treatment groups were 7.99, 7.80, and 6.86mm, respectively, after 120min of UV light induction at a wavelength of 365nm. Significant differences were evident between the TN-3 and the other two groups (p<0.05), indicating that the TN-3 sample more effectively inhibited Penicillium steckii than the other TiO2 NPs. PRACTICAL APPLICATION: Nanomaterials coated film preservation is widely used in fruit and vegetable preservation. In this paper, TiO2 nanomaterials will be green synthesized using mango leaf and structurally characterized, whereas antibacterial tests will be conducted against the mango fruit-specific bacterium Penicillium steckii, which will provide a theoretical basis for the storage and preservation of mango.

Poly(N,N-dimethylacrylamide)-stabilized gold nanoparticles as nanozymes with enhancement of catalytic activity for detection of lomefloxacin.

Recently, polymer-protected gold nanoparticles (AuNPs) have attracted extensive attention due to their good catalytic activities. However, how to regulate their catalytic activities by changing the polymer chain morphologies or the interactions between the ligands and the analytes through externalstimuli is still a great challenge. This study describes a simple synthesis of AuNPs capped by thermo-responsive poly(N,N-dimethylacrylamide) (PDMAM). In comparison with three kinds of PDMAMs@AuNPs, PDMAM-2@AuNPs exhibited better peroxidase-mimic ability via the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2) to generate oxidized TMB (oxTMB). Interestingly, its catalytic activity could be regulated by changing environmental temperature. Importantly, the addition of the antibiotic lomefloxacin endowed the PDMAM-2@AuNPs with enhancement in catalytic efficiency due to electrostatic interactions and the increased levels of reactive oxygen species. Based on this principle, a protocol for highly selective and sensitive monitoring of lomefloxacin has been constructed with the color change from pale blue to deep blue. The ultraviolet-visible absorbance of oxTMB at the wavelength of 650nm showed a good linear relationship with antibiotic concentration in the range of 0.25-10.0µM (R2 = 0.990). The limit of detection was 0.1µM. The practical application of the proposed protocol with the promoted peroxidase-mimic activity for the measurement of lomefloxacin in capsules was realized.

Photobiomodulation Therapy Affects the Elastic Modulus, Cytoskeletal Rearrangement and Migration Capability of Human Osteosarcoma Cells.

Photobiomodulation (PBM) therapy utilizes low-power lasers to modulate the viability of living human cells and leads to changes in proliferation, differentiation, adhesion and gene expression, even though the rearrangement of cytoskeleton was not previously studied. The present study aims to evaluate the photobiological effects on the elastic behavior of human osteosarcoma cells (MG-63) and their morphological changes. Fluorescence staining, confocal imaging and atomic force microscopy (AFM) topography were performed to study the effects of PBM therapy with the exposure of 532nm-25mW, 650nm-3mW, 650nm-150mW and 780nm-70mW beams following the 5-min continuous irradiation. The area of each beam was 3.14cm2 with a source-surface distance of 20cm. Besides the cell proliferation assessment, the migratory potential of MG-63 was determined with the wound healing technique. The results indicated an increase in stiffness and shape index of radiation-induced cells 24h after exposure along with the obvious F-actins changes. But, cell stiffening was not observed 72h after 532nm laser irradiation. Also, a decrease in the migration rate was seen in all of the groups after 72h of irradiation except cells treated with 532nm wavelength. However, 532nm laser beams increase the migratory potential 24h after exposure. Within 72h after irradiation, the cell proliferation was only affected by applying 532nm and 650nm-150mW laser beams. It was concluded that applying photobiomodulation with wavelengths of 650nm (at both utilized powers) and 780nm alters the migration capability and provides a quantitative description of cytoskeletal changes. Moreover, membrane stiffening can be considered as the biological marker of PBM treatments.

Design of optical emission system in 3D shape detection with oblique laser triangulation probe

In 3D laser scanning measurement system, the measurement accuracy of the whole system is determined by the optical system of the laser triangulation probe. This paper studies the optical transmitting system of oblique laser probe to solve this problem in 3D shape detection, based on the analysis of the principle of oblique laser triangulation. In order to reduce the influence of stray light and reduce the geometric distortion of 3D laser scanning measurement system, this paper selected a laser with a wavelength of 650nm as the light source to improve the distribution uniformity of image plane illumination. The design of optical transmitting system of the laser probe applies the beam splitter and normal coaxial layout under the premise of reducing the number of lenses and ensuring imaging quality. Finally, the results are analysed for radial transfer function curve, spot diagram and relative distortion.

Ratiometric fluorescent 3D DNA walker and catalyzed hairpin assembly for determination of microRNA.

Using6-carboxyfluorescein (FAM) and tetramethyl rhodamine (TAMRA) as fluorescent signals a ratiometric fluorescent three-dimensional (3D) DNA walker based on a catalytic hairpin assembly (CHA) reaction for microRNA-122 detectionwas constructed. This method uses CHA reaction triggered indirectly by the target to mediate the 3D DNA walker operation to amplify the signal. Thedual emission ratio fluorescent signal with a single excitation wavelength was usedas the signal output. This strategy combines DNA walker with CHA reaction and proportional fluorescence signal output methods, which can effectively reduce the background fluorescence signal and the risk of generating false-positive signals. Thus, the impact of environmental factors on the experimentis reduced, thereby obtaining reliable and stable experimental results. It uses the fluorescence excitation wavelength of 488nm and the maximum fluorescence emission wavelength of 520nm and 580nm, respectively. It has a good linear response at a microRNA concentration range of 156.0pM ~ 7.00nM and a detection limit of 42.94pM. This strategy has been successfully appliedto detect microRNAs in spiked serum samples. Graphical abstract Schematic representation of three-dimensional (3D) DNA walker constructed using catalytic hairpin self-assembly reaction (CHA)-assisted amplification and ratiometric fluorescence signal output for the detection of miRNA-122 closely related to hepatitis.

A nanoplatform based on metal-organic frameworks and coupled exonuclease reaction for the fluorimetric determination of T4 polynucleotide kinase activity and inhibition.

A nanoplatform based on metal-organic frameworks (MOFs) and lambda exonuclease (λ exo) for the fluorimetric determination of T4 polynucleotide kinase (T4 PNK) activity and inhibition is described. Fe-MIL-88 was selected as the nanomaterial because of its significant preferential binding ability to single-stranded DNA (ssDNA) over double-stranded DNA (dsDNA) and its quenching property. The synthesized Fe-MIL-88 was characterized by transmission electron microscope, scanning electron microscope, andX-ray photoelectron spectroscopy. In the presence of T4 PNK, FAM-labeled dsDNA (FAM-dsDNA) is phosphorylated on its 5'-terminal. λ exo then recognizes and cleaves the phosphorylated strand yielding FAM-labeled ssDNA (FAM-ssDNA). The fluorescence of the produced FAM-ssDNA is quenched due to Fe-MIL-88's absorbing on FAM-ssDNA. On the contrary, in the absence of T4 PNK, the phosphorylation and cleavage processes cannot take place. Therefore, the fluorescence of FAM-dsDNA still remains. The fluorescence intensity is detected at themaximum emission wavelength of 524nm using the maximum excitation wavelength of 488nm. The assay of T4 PNK based on the fluorescence quenching of FAM-ssDNA achieves a linear relationship in the range 0.01-5.0UmL-1 with a detection limit of 0.0089UmL-1 in buffer. The assay exhibits excellent performance for T4 PNK activity determination in a complex biological matrix. The results also reveal the ability of the assay forT4 PNK inhibitor screening. Graphical abstract Schematic presentation of a nanoplatform based on Fe-MIL-88 and coupled exonuclease reaction for the fluorimetric determination of T4 polynucleotide kinase activity. FAM-ssDNA, FAM-labeled single-stranded DNA; cDNA, complementary DNA; λ exo, lambda exonuclease;T4 PNK, T4 polynucleotide kinase.