Temperature-resilient and sustainable Mn-MOF oxidase-like nanozyme (UoZ-4) for total antioxidant capacity sensing in some citrus fruits: Breaking the temperature barrier.

Current nanozyme applications rely heavily on peroxidase-like nanozymes and are limited to a specific temperature range, despite notable advancements in nanozyme development. In this work, we designed novel Mn-based metal organic frameworks (UoZ-4), with excellent oxidase mimic activity towards common substrates. UoZ-4 showed excellent oxidase-like activity (with Km 0.072 mM) in a wide range of temperature, from 10 °C to 100 °C with almost no activity loss, making it a very strong candidate for psychrophilic and thermophilic applications. Ascorbic acid, cysteine, and glutathione could quench the appearance of the blue color of oxTMB, led us to design a visual-based sensing platform for detection of total antioxidant capacity (TAC) in cold, mild and hot conditions. The visual mode successfully assessed TAC in citrus fruits with satisfactory recovery and precisions. Cold/hot adapted and magnetic property will broaden the horizon of nanozyme applications and breaks the notion of the temperature limitation of enzymes.

A novel ratiometric design of microfluidic paper-based analytical device for the simultaneous detection of Cu2+ and Fe3+ in drinking water using a fluorescent MOF@tetracycline nanocomposite.

The regular and on-site monitoring of ions in drinking water is essential for safeguarding public health, ensuring high water quality, and preserving the ecological balance of aquatic ecosystems. Thus, developing a portable analytical device for the rapid, cost-effective, and visual on-site detection of multiple environmental pollutants is notably significant. In the present work, a novel ratiometric microfluidic paper-based analytical device (µPAD) was designed and developed for the simultaneous detection of Fe3+ and Cu2+ ions in water samples taking advantages from built-in masking zone. The µPAD was functionalized with a greenish-yellow fluorescent Zn-based metal-organic framework@tetracycline (FMOF-5@TC) nanocomposite, and the ratiometric design was based on the change in emission color from greenish yellow (FMOF-5@TC) to blue (FMOF-5). The µPAD consisted of one sample zone linked to two detection zones via two channels: the first channel was for the detection of both ions, while the second was intended for detecting only Cu2+ ions and comprised a built-in masking zone to remove Fe3+ ions prior to reaching the detection zone. The corresponding color changes were recorded with the aid of a smartphone and RGB calculations. The linear ranges were 0.1-80 µM for Cu2+ and 0.2-160 µM for Fe3+, with limits of detection of 0.027 and 0.019 µM, respectively. The simple µPAD design enabled the simultaneous detection of Cu2+ and Fe3+ ions in drinking water samples with excellent accuracy and precision, with spike recoveries of 81.28-96.36% and 83.01-102.33% for Cu2+ and Fe3+, respectively.

Dual-spot ratiometric microfluidic paper-based analytical device for accuracy and precision improvement.

Instrumental and environmental fluctuations are common sources of error in smartphone-based optical detection, significantly affecting the accuracy of analytical measurements. In this regard, spotting the sample and reference simultaneously and in close proximity compensates for the fluctuations. This "dual-spot" design is similar to the double-beam technique used in spectrophotometry, which reduces fluctuations in the results. The underlying hypothesis is that any instrumental and/or environmental factors influencing the color intensity in the detection zones will similarly impact the color intensity in the control zone under the same conditions. To test our design, a ratiometric microfluidic paper-based analytical device (µPAD), functionalized with a mixture of green-emissive carbon dots (CDs) and red-emissive ethidium bromide, was developed for the selective detection of ascorbic acid (AA). The green emission of the CDs is quenched by both AA and Fe3+; NaF was thus loaded onto the 3D connector as a masking agent to remove the interference effect of the Fe3+ ions. The color variations were monitored under a UV lamp, using a smartphone to capture the images, and the RGB intensities were processed using the Color Grab application. The proposed double-spot method greatly enhanced the analytical precision and accuracy of the device. A linear working range from 0 to 125 µM was obtained, and the limit of detection was 2.71 µM. The µPAD was successfully used for the detection of AA in human serum, with recoveries from 87.27 to 98.52 %.

Gold single atom-based aptananozyme as an ultrasensitive and selective colorimetric probe for detection of thrombin and C-reactive protein.

An ultra-efficient biocatalytic peroxidase-like Au-based single-atom nanozyme (Au-SAzymes) has been synthesized from isolated Au atoms on black nitrogen doped carbon (Au-N-C) using a simple complexation-adsorption-pyrolysis method. The atomic structure of AuN4 centers in black carbon was revealed by combined high-resolution transmission electron microscopy/high-angle annular dark-field scanning transmission electron microscopy. The Au-SAzymes showed a remarkable peroxidase activity with 1.7 nM as Michaelis-Menten constant, higher than most previously reported SAzyme activity. Density functional theory and Monte Carlo calculations revealed the adsorption of H2O2 on AuN4 with formation of OH* and O*. Molecular recognition was greatly enhanced via label-free integration of thiol-terminal aptamers on the surface of single Au atoms (Aptamer/Au-SAzyme) to design off-on ultrasensitive aptananozyme-based sensor for detecting thrombin and CRP with 550 pM and 500 pg mL-1 limits of detection, respectively. The Aptamer/Au-SAzyme showed satisfactory accuracy and precision when applied to the serum and plasma of COVID-19 patients. Due to the maximum Au atom utilization, approximately 3636 samples can be run per 1 mg of gold, highlighting the commercialization potential of the developed Aptamer/Au-SAzyme approach.

Dual-state dual emission from precise chemically engineered bi-ligand MOF free from encapsulation and functionalization with self-calibration model for visual detection.

Synthesis of dual-state dual emitting metal-organic frameworks (DSDE-MOFs) is uncommon and challenging. Additionally, DSDE-MOFs can fulfil the expanding need for on-site detection due to their stability and self-reference for a variety of non-analyte variables. In the present work, a novel intrinsic DSDE of chemically engineered bi-ligand Eu-based MOF (UoZ-1) was designed. The prepared UoZ-1 spherical particles were small-sized around 10-12 nm and displayed blue (425 nm) and red fluorescence (620 nm) at both states, dispersed in liquid and in solid state, when excited at 250 nm. A ratiometry platform was developed since the red emission was quenched by the addition of folic acid and the blue emission was almost remained unaffected. In the fluorometric ratiometric-mode, a dynamic linear range was recorded from 10 to 200 µM with LOD about 0.4 µM. Visual-based detection with assistance of smartphone was developed for quantification based on RGB analysis using Color Grab App. In the visual-mode, LOD as small as 2.3 µM was recorded. By utilizing the intrinsic dual-emitting UoZ-1, highly stable, recyclable, sensitive, and selective on-site visual detection of folic acid can be achieved. UoZ-1, a DSDE-MOF with no encapsulation or functionalization requirements, exhibits great potential for diverse applications.

Intrinsic Dual-State Emission Zinc-Based MOF Rodlike Nanostructures with Applications in Smartphone Readout Visual-Based Detection for Tetracycline: MOF-Based Color Tonality.

Dual-state emitters (DSEs) are entities that exhibit fluorescence in both the solution and solid state, which open up a wide range of possibilities for their utilization in various fields. The development of detection platforms using intrinsic luminescent metal-organic frameworks (LMOFs) is highly desirable for a variety of applications. DSE MOFs as a subclass of intrinsic LMOFs are highly attractive due to no need for encapsulation/functionalization by fluorophores and/or using luminescent linkers. Herein, a highly stable intrinsic dual-state blue emission (λem = 425 nm) zinc-based MOF with rodlike nanostructures (denoted as UoZ-2) was synthesized and characterized. To the best of our knowledge, intrinsic DSE of Zn-MOFs with blue emission in the dispersed form in solution and solid-state fluorescence have not been reported yet. When tetracycline (TC) was added, a continuous color evolution from blue to greenish-yellow with dramatic enhancement was observed due to aggregation induced emission (AIE). Thus, a sensitive ratiometry-based visual detection platform, in solution and on paper independently, was designed for detection of TC exploiting the DSE and AIE properties of UoZ-2 alone and UoZ-2:TC. The detection limit was estimated to be 4.5 nM, which is considered to be one of the most sensitive ratiometric fluorescent probes for TC sensing. The ratiometry paper-based UoZ-2 sensor displays a reliable TC quantitative analysis by recognizing RGB values in the on-site TC detection with satisfactory recoveries.

Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review.

Heavy metal contamination of water sources has emerged as a major global environmental concern, threatening both aquatic ecosystems and human health. Heavy metal pollution in the aquatic environment is on the rise due to industrialization, climate change, and urbanization. Sources of pollution include mining waste, landfill leachates, municipal and industrial wastewater, urban runoff, and natural phenomena such as volcanic eruptions, weathering, and rock abrasion. Heavy metal ions are toxic, potentially carcinogenic, and can bioaccumulate in biological systems. Heavy metals can cause harm to various organs, including the neurological system, liver, lungs, kidneys, stomach, skin, and reproductive systems, even at low exposure levels. Efforts to find efficient methods to remove heavy metals from wastewater have increased in recent years. Although some approaches can effectively remove heavy metal contaminants, their high preparation and usage costs may limit their practical applications. Many review articles have been published on the toxicity and treatment methods for removing heavy metals from wastewater. This review focuses on the main sources of heavy metal pollution, their biological and chemical transformation, toxicological impacts on the environment, and harmful effects on the ecosystem. It also examines recent advances in cost-effective and efficient techniques for removing heavy metals from wastewater, such as physicochemical adsorption using biochar and natural zeolite ion exchangers, as well as decomposition of heavy metal complexes through advanced oxidation processes (AOPs). Finally, the advantages, practical applications, and future potential of these techniques are discussed, along with any challenges and limitations that must be considered.

Accuracy improvement via novel ratiometry design in distance-based microfluidic paper based analytical device: instrument-free point of care testing.

Developing accurate, precise, instrument-free, and point-of-need microfluidic paper-based devices is highly significant in clinical diagnosis and biomedical analysis. In the present work, a ratiometric distance-based microfluidic paper-based analytical device (R-DB-µPAD), along with a three-dimensional (3D) multifunctional connector (spacer), was designed to improve the accuracy and detection resolution analyses. Specifically, the novel R-DB-µPAD was used for the accurate and precise detection of ascorbic acid (AA) as a model analyte. In this design, two channels were fabricated as detection zones, with a 3D spacer located between the sampling and detection zones to improve the detection resolution by preventing the reagents mixing from overspreading between these zones. Two probes for AA were used: Fe3+ and 1,10-phenanthroline were deposited in the first channel, and oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) was added to the second channel. Accuracy improvement of this ratiometry-based design was achieved by enhancing the linearity range and reducing the volume dependency of the output signal. Moreover, the 3D connector improved the detection resolution by eliminating the systematic errors. Under the optimal conditions, the ratio of the distances of the color bands in the two channels was used to construct an analytical calibration curve in the range from 0.05 to 1.2 mM, with a limit of detection of 16 µM. The proposed R-DB-µPAD combined with the connector was successfully used for the detection of AA in orange juice and vitamin C tablets with satisfactory accuracy and precision. This work opens the door for multiplex analysis of various analytes in different matrices.

Deep insights to explain the mechanism of carbon dot formation at various reaction times using the hydrothermal technique: FT-IR, 13C-NMR, 1H-NMR, and UV-visible spectroscopic approaches.

A well-explained mechanism for synthesizing carbon dots (CDs) is not yet explored and is still a subject of great debate and challenge. This study used a one-step hydrothermal method to prepare highly efficient, gram-scale, excellent water solubility, and blue fluorescent nitrogen-doped carbon dots (NCDs) with the particle size average distribution of around 5 nm from 4-aminoantipyrine. The effects of varying synthesis reaction times on the structure and mechanism formation of NCDs were investigated using spectroscopic methods, namely FT-IR, 13C-NMR, 1H-NMR, and UV-visible spectroscopies. The spectroscopic results indicated that increasing the reaction time affects the structure of the NCDs. As the hydrothermal synthesis reaction time is extended, the intensity of the peaks in the aromatic region decreases, and new peaks in the aliphatic and carbonyl group regions are generated, which display enhanced intensity. In addition, the photoluminescent quantum yield increases as the reaction time increases. The presence of a benzene ring in 4-aminoantipyrine is thought to contribute to the observed structural changes in NCDs. This is due to the increased noncovalent π-π stacking interactions of the aromatic ring during the carbon dot core formation. Moreover, the hydrolysis of the pyrazole ring in 4-aminoantipyrine results in polar functional groups attached to aliphatic carbons. As the reaction time prolongs, these functional groups progressively cover a larger portion of the surface of the NCDs. After 21 h of the synthesis process, the XRD spectrum of the produced NCDs illustrates a broad peak at 21.1°, indicating an amorphous turbostratic carbon phase. The d-spacing measured from the HR-TEM image is about 0.26 nm, which agrees with the (100) plane lattice of graphite carbon and confirms the purity of the NCD product with a surface covered by polar functional groups. This investigation will lead to a greater understanding of the effect of hydrothermal reaction time on the mechanism and structure of carbon dot synthesis. Moreover, it offers a simple, low-cost, and gram-scale method for creating high-quality NCDs crucial for various applications.

Green nanocomposite: fabrication, characterization, and photocatalytic application of vitamin C adduct-conjugated ZnO nanoparticles.

Recently, the conjugation of metal oxide nanoparticles with organic moieties has attracted the attention of many researchers for various applications. In this research, the green and biodegradable vitamin C was employed in a facile and inexpensive procedure to synthesize the vitamin C adduct (3), which was then blended with green ZnONPs to fabricate a new composite category (ZnONPs@vitamin C adduct). The morphology and structural composition of the prepared ZnONPs and their composites were confirmed by several techniques: Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), UV-vis differential reflectance spectroscopy (DRS), energy dispersive X-ray (EDX) analysis, elemental mapping, X-ray diffraction (XRD) analysis, photoluminescence (PL) spectroscopy, and zeta potential measurements. The structural composition and conjugation strategies between the ZnONPs and vitamin C adduct were revealed by FT-IR spectroscopy. The experimental results for the ZnONPs showed that they possessed a nanocrystalline wurtzite structure with quasi-spherical particles with a polydisperse size ranging from 23 to 50 nm, while the particle size appeared greater in the FE-SEM images (band gap energy of 3.22 eV); after loading with the l-ascorbic acid adduct (3), the band gap energy dropped to 3.06 eV. Later, under solar light irradiation, the photocatalytic activities of both the synthesized ZnONPs@vitamin C adduct (4) and ZnONPs, including the stability, regeneration and reusability, catalyst amount, initial dye concentration, pH effect, and light source studies, were investigated in detail in the degradation of Congo red dye (CR). Furthermore, an extensive comparison between the fabricated ZnONPs, composite (4), and ZnONPs from previous studies was performed to gain insights to commercialize the catalyst (4). Under optimum conditions, the photodegradation of CR after 180 min was 54% for ZnONPs and 95% for the ZnONPs@l-ascorbic acid adduct. Moreover, the PL study confirmed the photocatalytic enhancement of the ZnONPs. The photocatalytic degradation fate was determined by LC-MS spectrometry.

Enhanced Peroxidase-Mimic Catalytic Activity via Cerium Doping of Strontium-Based Metal-Organic Frameworks with Design of a Smartphone-Based Sensor for On-Site Salivary Total Antioxidant Capacity Detection in Lung Cancer Patients.

The development of artificial nanozymes with superior catalytic performance and excellent stability has been a long-standing objective for chemists. The total antioxidant capacity (TAC) is one of the most important bioanalytical measures of oxidative stress in the body. The present work aims to develop a smartphone-assisted visual detection sensor using cerium-doped strontium-based metal-organic frameworks (Ce-SrMOFs) as peroxidase-like nanozymes for the rapid, low-cost, on-site detection of TAC. The pristine SrMOF functioned as a peroxidase nanozyme, and its enzymatic activity was enhanced after doping it with Ce(IV) ions because of the multivalent nature and synergistic impact of the heteroatoms. The Ce-SrMOFs were sensitive to the single electron transfer and hydrogen atom transfer processes, which implies that the Ce-SrMOFs can serve as an ideal nanozyme candidate for TAC analysis. The investigated mechanism revealed that •OH is the most active oxygen species for the peroxidase-like activity. The Ce-SrMOFs exhibited a strong affinity for 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, with Km values of 0.082 and 0.427 mM, which are 5.29- and 8.67-fold lower than those of horseradish peroxidase (HRP), respectively. The Ce-SrMOFs were used for the detection of ascorbic acid, cysteine, and glutathione, with limits of detection of 44, 53, and 512 nM, respectively. The proposed method proved effective in measuring the TAC in saliva samples from lung cancer patients, thereby yielding results with satisfactory precision and accuracy.

Efficient photo-Fenton catalysis using magnetic iron nanoparticles decorated boron nitride quantum dots: theoretical and experimental investigations.

To achieve the efficient removal of pharmaceutical wastes, novel photo-Fenton catalysts, iron-decorated boron nitride quantum dots (Fe@BNQDs) were prepared. Fe@BNQDs were characterized using XRD, SEM-EDX, FTIR, and UV-Vis spectrophotometry. The decoration of Fe on the surface of BNQDs enhanced the catalytic efficiency due to the photo-Fenton process. Photo-Fenton catalytic degradation of folic acid was investigated under UV and visible light. The influence of H2O2, catalyst dose, and temperature on the degradation yield of folic acid was investigated using Response Surface Methodology. Moreover, the efficiency of the photocatalysts and kinetics was investigated. Radical trapping experiments revealed that holes were the main dominant species in the photo-Fenton degradation mechanism and BNQDs played active roles because of their hole extraction ability. Additionally, active species such as e- and O2 -˙ have a medium effect. The computational simulation was utilized to provide insights into this fundamental process, and for this purpose, electronic and optical properties were calculated.

Dual-template molecularly surface imprinted polymer on fluorescent metal-organic frameworks functionalized with carbon dots for ascorbic acid and uric acid detection.

In this work, dual-template molecularly imprinted polymer surfaces imprinted on blue fluorescent Cr-based MOF (Cr-MOF) functionalized with yellow emissive carbon dots (Y-CDs) were prepared using l-ascorbic acid (AA) and uric acid (UA) as templates for simultaneous selective recognition of AA and UA. The as-prepared nanocomposite probe (Y-CDs/Cr-MOF@MIP) contains two recognition site cavities and emits a dual well-resolved fluorescence spectra when excited at 390 nm; blue emission (λem 450 nm) is due to Cr-MOF, and yellow emission (λem 560 nm) is due to Y-CDs. The yellow fluorescence emission of Y-CDs was quenched upon the addition of ascorbic acid, while Cr-MOF's emission remained unaffected. In the same way, the blue fluorescence emission of the Cr-MOFs was quenched in the presence of uric acid, while the yellow emission remained constant. Both emissions were quenched in a sample containing both AA and UA. This can be exploited to design a dual-template biosensor to detect UA and AA simultaneously. The Y-CDs/Cr-MOF@MIP sensor displayed a dynamic linear response for AA in the range 25.0 µM - 425.0 µM with a detection limit of 1.30 µM, and for UA in the range 25.0 µM - 425.0 µM with a detection limit of 1.10 µM. The dual-target probe Y-CDs/Cr-MOF@MIP was highly selective and sensitive for the detection of UA and AA in human urine samples due to the selectivity of the two recognition sites.

Ultra-small highly fluorescent zinc-based metal organic framework nanodots for ratiometric visual sensing of tetracycline based on aggregation induced emission.

Color tonality by intrinsic fluorescent metal-organic frameworks (MOFs) is highly desirable in bioanalytical applications due to its stability, low-cost and robustness with no need for functionalization and/or encapsulation of fluorophores. In the present work, ultra-small and higly fluorescent zinc-based MOFs (FMOF-5) were synthesized. The prepared FMOFs were around 5 nm in size, and gave strong blue emission at 440 nm when excited at 350 nm. Interestingly, tetracycline (TC) selectively tuned the blue emission of FMOF-5 to greenish-yellow emission (520 nm) with dramatic enhancement through aggregation induced emission (AIE). The fluorimetric analysis of TC was carried out through the ratiometric peak intensities of F520/F440, with detection limit (LOD) of 5 nM. To realize quantitative point-of-care based on color tonality, a smartphone integrated with the ratiometric visual platform was thereby design. Hence, TC was visually detected with LOD of 10 nM. The prepared FMOF-5-based probe showed high stability (3 months) and reusability (∼10 times). The developed visual-based platform presents great promise for practical point of care testing due to its low-cost, robustness, ruggedness, simple operation, and excellent selectivity and repeatability.

Paper-based optical nanosensors - A review.

Paper-based analytical devices (PADs) have shown great promise for point-of-care testing and on-site detection of analytes with chemical, biochemical, and environmental importance owing to their low cost, convenience, scalability, portability, and biocompatibility. The World Health Organization stated that sensors should meet the ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverable). Paper-based optical sensors meet most of these criteria, making them in high demand and applicable in remote areas. Optical PADs outputs are obtained by different means, such as dyes, nanostructures, redox agents, and pH indicators. The outstanding physical and chemical characteristics of nanostructures, their intense signals, and tunable optical properties make them ideal for many sensing platforms, including paper-based ones. This review focuses primarily on paper-based nanosensors using various nanostructures to fabricate and produce optical signals for visualization. We describe the fundamentals and state of the art of PADs and comprehensively explain the following topics: paper types as the substrate of PADs, PAD fabrication approaches, nanostructure stabilization on PADs, signal acquisition, data handling, interpretation of results, sensing mechanisms, and application areas. We also discuss future trends and strategies to enable PADs to reach their full potential and increase their commercialization opportunities.

Enhancing of detection resolution via designing of a multi-functional 3D connector between sampling and detection zones in distance-based microfluidic paper-based analytical device: multi-channel design for multiplex analysis.

One of the problems in the distance-based microfluidic paper-based analytical device (DB-µPAD) that limits the detection resolution is the mixing of reagents from the detection to the sampling zone or vice versa due to spreading by capillary action. In the present paper, to overcome mixing of the reagents in the zones, a multi-functional connector using a three-dimensional (3D) design has been developed externally to connect the two zones. Using such a novel design, it is acertained that there is no any mixing due to the dispersion of the reagents in the two zones. Interestingly, the simple 3D connector has other functions, such as its potential to be used as a masking zone and/or reaction zone whenever is needed. Based on this proposed 3D connector-based DB-µPAD, three parallel microchannels were built as detection zones with one sampling zone for multiplex analysis for the detection of Fe2+, Ni2+, and hardness of water. In the Ni2+ channel, the connector piece worked as both masking part and connection part. In the Fe2+ line, the connector served as the connector and reducing pad (Fe3+ to Fe2+ ions). While in the third channel, the connector has connection function only. Satisfactory limit of detection (LoD), accuracy, and precision were obtained using this design. The LODs obtained with the proposed design were 1.13, 0.62, and 1.87 mg.L-1 for total hardness, Fe2+, and Ni2+, respectively.

Nanozyme and Stimulated Fluorescent Cu-Based Metal-Organic Frameworks (Cu-MOFs) Functionalized with Engineered Aptamers as a Molecular Recognition Element for Thrombin Detection in the Plasma of COVID-19 Patients.

An essential tool in the management and control of the COVID-19 pandemic is the development of a fast, selective, sensitive, and inexpensive COVID-19 biomarkers detection method. Herein, an ultrasensitive and label-free biosensing strategy was described for the colorimetric and fluorimetric detection of thrombin. A dual-mode aptasensing method based on integrating engineered ssDNA with a stimulated fluorescent enzyme-mimetic copper-based metal-organic framework (Cu-MOF) as a molecular recognition element for thrombin was investigated. Cu-MOFs displayed stimulated fluorescence and enzyme-mimetic peroxidase activities that oxidize the chromogenic colorless substance TMB to blue-colored oxTMB. The thrombin-based aptamer (ssDNA) can be immobilized on the Cu-MOF surface to form a functionalized composite, ssDNA/MOF, and quench the stimulated fluorescence emission and the enzymatic activity of the Cu-MOF. Later, addition of thrombin recovers the fluorescence and enzymatic activity of the MOF. Thus, a turn-on colorimetry/fluorimetry aptasensing probe was designed for the detection of thrombin. Based on colorimetric assay, 350 pM was recorded as the lower limit of detection (LOD), while based on the fluorescence mode, 110 fM was recorded as the LOD (when S/N = 3). The label-free aptasensing probe was used successfully for the detection of thrombin in COVID-19 patients with satisfactory recoveries, 95-98%. Since the detection time of our aptasensor is relatively rapid (45 min) and due to the low-cost precursors and easy-to-operate characteristics, we believe that it has great potential to be used in point-of-care testing (POCT).

Silver-Loaded Carbon and Phosphorous Co-Doped Boron Nitride Quantum Dots (Ag@CP-BNQDs) for Efficient Organic Waste Removal: Theoretical and Experimental Investigations.

In this paper, silver-loaded phosphorous and carbon co-doped boron nitride quantum dot (Ag@CP-BNQD) nanocomposites were synthesized using a co-precipitation method followed by a hydrothermal approach. The nanocomposites of Ag@CP-BNQDs were characterized by scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and ultraviolet-visible spectrophotometry. The as-prepared Ag@CP-BNQDs were used for photocatalytic degradation of 10 common organic pollutants, including dyes, pharmaceuticals, and pesticides in aqueous solution under visible light irradiation. The high-performance photocatalysis of Ag@CP-BNQDs proved that Ag@CP-BNQDs is plasmonic and the n-p junction photocatalyst. Theoretical calculations were done to measure the crystals and electronic structures of Ag@CP-BNQDs. Theoretical results showed that loading of Ag behaves as plasmonic sensitizers and co-catalysts and provides extra bands, which make electron movement easier between valance and conduction bands. The mechanism of the charge separation enhancement was postulated. Our findings might deepen our understanding of how sensitizer surface modification works in photodegradation applications.

Ultrasensitive aptamer-functionalized Cu-MOF fluorescent nanozyme as an optical biosensor for detection of C-reactive protein.

In the present work, an aptasensing method based on integration of RNA on Cu-MOF was developed for detection of C-Reactive Protein (CRP). Cu-MOF showed stimulated fluorescence and mimetic peroxidase enzymatic activity at the time and can be used as dual-signal transduction. CRP binding RNA was used as a highly selective recognition element and immobilized on the Cu-MOF. The immobilized RNA can block the peroxidase activity and fluorescence of the signal traducer probe. Adding CRP to the RNA/Cu-MOF will release RNA from the surface of Cu-MOF and recover both the stimulated fluorescence and peroxidase activity. A biosensor was built for detection of CRP using the two modes of transduction, either colorimetry or fluorometry. A dynamic linear range was obtained from 0.1 to 50 ng mL -1with a limit of detection (LOD) as small as 40 pg mL -1was calculated in fluorescence mode and 240 pg mL -1 as LOD in colorimetry mode. The LODs are lower than the LOD of nephelometric techniques used in clinical practice and is comparable to the normal clinical cutoff value in high-sensitivity CRP assays (1 µg/mL). The aptasensor was successfully applied for detection of CRP in Covid-19 patients with spike recoveries between 84 and 102% and RSD from 0.94% to 2.05%.

Enhancing enzymatic activity of Mn@Co3O4 nanosheets as mimetic nanozyme for colorimetric assay of ascorbic acid.

In nanozyme-based assays, increasing enzymatic activity is very desirable for enhancing sensitivity and lowering the detection limit. In this study, novel Mn doped cobalt oxide nanosheets (Mn@Co3O4 NSs) were synthesized by hydrothermal process. The obtained Mn@Co3O4 possessed enhanced dual-enzyme mimetic, oxidase and peroxidase, and can catalytically oxidize of 3, 3', 5, 5'-tetramethylbenzidine (TMB), to a blue product of oxidized TMB. The enzyme kinetics were well-described mathematically using a common Michaelis-Menten and Lineweaver Burk model. The enzyme kinetics constant (Km) was found to be 0.15 mM, which is relatively low comparing with pure Co3O4 nanosheets (0.35 mM) and natural enzyme HRP (0.434 mM). Therefore, the efficient colorimetric method was achieved for determination of H2O2 and ascorbic acid. The limit of detection (LOD) of H2O2 was 8.0 µM and the linear range was 20-200 µM based on direct turn on of the peroxidase-like activity of Mn@Co3O4. While, for ascorbic acid detection based on turn-off approach, the linearity range for the ascorbic acid was 1-8 µM with LOD of 0.4 µM. Moreover, the colorimetric system exhibited good stability and selectivity toward the detection of ascorbic acid effectively in real samples (vitamin C tablets) with satisfactorily accuracy and precision.