And L-ascorbic Acid Research Articles

A novel covalent grafting method between cellulose and ferulic acid through HRP enzyme/acetylacetone/L-Ascorbic acid ternary dual initiator system

In the application of natural dyes, using environmentally and human body harmful metal dyes was still the mainstream dyeing method in the process of cellulose fiber dyeing with natural dyes. This study proposed a new method that can catalyzed the covalent grafting of cellulose materials with Ferulic acid (FA), the ternary system consisting of horseradish peroxidase (HRP), acetylacetone (ACAC) and L-Ascorbic acid (AA). The grafting process of cellulose materials with FA was systematically studied, and the optimal grafting polymerization conditions was determined using orthogonal experimental analysis. In the experiment, it was found that the morphology and structure of cellulose materials significantly affect their grafting polymerization performance with FA, and the change rule of their grafting rate was cotton fabric (3.84%) < cotton yarn (4.54%) < tencel fabric (4.70%) < tencel yarn (53.06%) < cotton cellulose (5.59%) < corn starch (6.70%). The grafted fabrics have excellent color fastness, antibacterial and UV resistance performance. Finally, the structural characteristics of cellulose and its analogues grafted with FA were characterized through FT-IR, 1H NMR, and the possible free radical covalent polymerization mechanism between cellulose materials and FA was analyzed.

A novel biosensor based on tetrahedral DNA nanostructure and terminal deoxynucleotidyl transferase-assisted amplification strategy for fluorescence analysis of uracil-DNA glycosylase activity

Tetrahedral DNA nanostructure (TDN), as a classical bionanomaterial, which not only has excellent structural stability and rigidity, but also possesses high programmability due to strict base-pairs complementation, is widely used in various biosensing and bioanalysis fields. In this study, we first constructed a novel biosensor based on Uracil DNA glycosylase (UDG) -triggered collapse of TDN and terminal deoxynucleotidyl transferase (TDT)-induced insertion of copper nanoparticles (CuNPs) for fluorescence and visual analysis of UDG activity. In the presence of the target enzyme UDG, the uracil base modified on the TDN were specifically identified and removed to produce an abasic site (AP site). Endonuclease IV (Endo.IV) could cleave the AP site, making the TDN collapse and generating 3′-hydroxy (3′-OH), which were then elongated under the assistance of TDT to produce poly (T) sequences. Finally, Copper (II) sulfate (Cu2+) and l-Ascorbic acid (AA) were added to form CuNPs using poly (T) sequences as templates (T-CuNPs), resulting in a strong fluorescence signal. This method exhibited good selectivity and high sensitivity with a detection limit of 8.6 × 10−5 U/mL. Moreover, the strategy has been successfully applied to the screening of UDG inhibitors and the detection of UDG activity in complex cell lysates, which means that it has promising applications in clinical diagnosis and biomedical research.

Different Electrochemical Behavior of Cationic Dopamine from Anionic Ascorbic Acid and DOPAC at CNT Yarn Microelectrodes

Carbon nanotube yarn microelectrodes (CNTYMEs) have micron-scale surface crevices that momentarily trap molecules. CNTYMEs improve selectivity among cationic catecholamines because secondary reactions are enhanced, but no anions have been studied. Here, we compared fast-scan cyclic voltammetry (FSCV) of dopamine and anionic interferents 3,4 dihydroxyphenylacetic acid (DOPAC) and L-ascorbic acid (AA) at CNTYMEs and carbon fiber microelectrodes (CFMEs). At CFMEs, dopamine current decreases with increasing FSCV repetition frequency at pH 7.4, whereas DOPAC and AA have increasing currents with increasing frequency, because of less repulsion at the negative holding potential. Both DOPAC and AA have side reactions after being oxidized, which are enhanced by trapping. At pH 4, the current increases for DOPAC and AA because they are not repelled. In addition, AA has a different oxidation pathway at pH 4, and an extra peak in the CV is enhanced by trapping effects at CNTYMEs. At pH 8.5, co-detection of dopamine in the presence of DOPAC and AA is enhanced at 100 Hz frequency because of differences in secondary peaks. Thus, the trapping effects at CNTYMEs affects anions differently than cations and secondary peaks can be used to identify dopamine in mixture of AA and DOPAC with FSCV.

Changes in the abscisic acid, phenylpropanoids and ascorbic acid metabolism during strawberry fruit growth and ripening

The functional compounds and sensory attributes of strawberries are acquired during ripening; however, the molecular mechanisms regulating this process have not yet been fully elucidated. Therefore, in this study, we aimed to investigate the accumulation of abscisic acid (ABA), phenylpropanoids, and l-ascorbic acid (AsA) as well as their relative gene expression levels during this process. The accumulation of ABA during the fruit growth and ripening stages depends on the upregulation of FaNCED1 and FaNCED2 gene expression, and the downregulation of FaCYP707 expression. Moreover, in the initial stages, the ABA glycosylation pathway is activated as a provision for the ABA levels required for future events. As the ABA levels increase, FaPAL, FaC4H1, and FaC4H4 genes expression are upregulated, aiding in the synthesis of flavonoid precursors, which, in addition to the higher FaUFGT expression, directly reflects an improvement in anthocyanin. AsA content increases during fruit development and ripening and is dependent on the synthesis pathway, due to the upregulation of FaGLDH expression, and on the oxidation and recycling pathways via the regulation of expression levels of FaAPX and FaMR. These results suggest that the activation of FaNCED1 and the inhibition of FaCYP707A1 may contribute to the increase in ABA content, thereby stimulating anthocyanin and AsA synthesis and accumulation.

Green preparation of carbon quantum dots with wolfberry as on-off-on nanosensors for the detection of Fe3+ and l-ascorbic acid

A green and facile hydrothermal synthesis approach is proposed for the preparation of nitrogen-doped carbon quantum dots (N-CQDs) with wolfberry. These N-CQDs were developed as a highly sensitive fluorescent ‘on-off-on’ switch sensor for the sensing of Fe3+ and l-ascorbic acid (AA). The N-CQDs displayed superior fluorescence characteristics of CQDs with a quantum yield up to 22%. The N-CQDs were demonstrated to selectively react with Fe3+, leading to fluorescence quenching effect, which was successfully used for the detection of Fe3+ with a limit of detection at 3 μmoL•L−1. The addition of AA is supposed to repair the surface defects, and result in the fluorescence recovery. Based on this effect, the strategy of ‘on-off-on’ detection of AA was established with a limit of detection at 1.8 μmoL•L−1. Furthermore, the practical application of the detection of Fe3+ lake water and AA in medical tablet was demonstrated, promising an effective and efficient ‘on-off-on’ nanosensor with low-cost, green synthesis for Fe3+ and AA detection.

Kinetic Modeling of Thermal Degradation of Color, Lycopene, and Ascorbic Acid in Crushed Tomato

The kinetics of the thermal degradation of color (L*, a*, and b* coordinates), lycopene (L), and L-ascorbic acid (AA) in crushed tomato were studied over a temperature range of 70 to 100 °C. These results showed that the changes in a*, L, and AA followed a first-order kinetic model (R2 > 0.91), while those for L* and b* did not fit any suitable kinetic models. The temperature effects on degradation rates were adequately compatible with the Arrhenius equation (R2 > 0.96) with the following activation energy values (Ea, kJ mol−1): a* (64.54), L (45.96) and AA (25.69). These Ea values indicated that a* was the most sensitive parameter towards temperature changes, while the reaction rate constants (k) showed that L had the highest degradation rate compared with the other parameters studied. A linear relationship between a* and L content was found, suggesting that a* measured instantaneously by tristimulus colorimeters can be used for the online determination of L degradation in crushed tomatoes during heat treatment. The knowledge gained from this study could be useful for improving the design and optimization of the thermal process of crushed tomato in order to preserve its nutritional value and sensory quality.

Abscisic acid and stress induced by salt: Effect on the phenylpropanoid, L-ascorbic acid and abscisic acid metabolism of strawberry fruits

Strawberry is one of the most popular fruits because of its sensorial and functional properties. However, strawberry crop is sensitive to salt stress conditions. Despite plants have plasticity, high salt concentrations induce molecular, biochemical, and physiological responses in plants. There is evidence that the abscisic acid (ABA) hormone acts as a signaling molecule under stress conditions; however, the molecular mechanisms involved in the synthesis and homeostasis of ABA and in the induction of phytochemical antioxidant compounds under stress conditions remain unclear. In this study, the effect of stress induced by NaCl (salt stress - SS), with or without the simultaneous application of ABA, on the ABA, phenylpropanoids and L-ascorbic acid (AsA) metabolisms were evaluated. The physiological aspects (Na, Cl and proline concentration, photosynthetic variables) were also studied. The results showed that salt stress increases the Na and Cl content in the leaves, affects photosynthetic variables and triggers the production of proline, pelargonidin-3-O-glucoside, total phenolic compounds and AsA content, alongside the upregulation of several genes from the phenylpropanoid and flavonoid pathways. These effects were accompanied by the induction of compounds and transcripts related to ABA biosynthesis, conjugation and catabolism. Otherwise, the exogenous application of ABA in salt stressed plants promotes a shift in gene expression and metabolism to mitigate the stress. Therefore, salt stress affects the metabolism of ABA, phenylpropanoids and AsA in strawberry increasing phytochemical composition which is strongly associated with an ABA-dependent mechanism.

Fluorescent polydopamine nanoparticles as a nanosensor for the sequential detection of mercury ions and l-ascorbic acid based on a coordination effect and redox reaction.

Herein, a novel fluorescence nanosensor using intrinsic fluorescent polydopamine nanoparticles (PDA NPs) as an effective signal reporter has been constructed for the simple, rapid and sequential detection of mercury ions (Hg2+) and l-ascorbic acid (AA) based on a coordination effect and redox reaction. The fluorescence of the PDA NPs could be specifically quenched by Hg2+ through intense coordination effects between the Hg2+ and the groups (catechol, amine, ketone and imine) on the surface of the PDA NPs. However, when AA and Hg2+ coexisted in solution, the fluorescence of the PDA NPs pronouncedly recovered via the redox reaction of Hg2+, with it being reduced to Hg0 by AA. The fluorescence quenching mechanism of Hg2+ towards the PDA NPs and the redox reaction between Hg2+ and AA were also fully investigated. The nanosensor exhibited high sensitivity and desirable selectivity for Hg2+ and AA detection. Moreover, the strategy was successfully explored in real samples (tap water, lake water and human serum samples) with satisfactory recoveries. The developed nanosensor provides new sights and good inspiration for Hg2+ and AA detection under real conditions.

One-step synthesis of amine-functionalized fluorescent silicon nanoparticles for copper(II) ion detection

Amine-functionalized silicon nanoparticles (A-SiNPs) with intense green fluorescence and photostability are synthesized via a one-step, low-cost hydrothermal method under mild conditions using 3-aminopropyl triethoxysilane (APTES) as a silicon source and L-ascorbic acid (AA) as a reducing reagent. The amine-rich surface not only improves water dispersability and stability of the A-SiNPs but also offers a specificcopper(II) ion (Cu2+) coordination capability. The as-prepared A-SiNPs can be directly employed forCu2+ detection in "turn-off" mode, resulting from Cu2+ coordination-induced fluorescence quenching effect. Under optimal conditions, Cu2+ detection was accomplished with a linear range from 1 to 500μM and a limit of detection (LOD) at 0.1μM, which was much lower than the maximum level (~ 20μM) of Cu2+ in drinking water permitted by the US Environmental Protection Agency (EPA). In addition, the A-SiNPs were successfully used to detect Cu2+ in spiked river water, demonstrating its good selectivity and potential application for analysis of surface water samples. Graphical abstract.

A Seedless Method for Gold Nanoparticle Growth inside a Silica Matrix: Fabrication of Materials Capable of Third-Harmonic Generation in the Near-Infrared.

A composite in which gold nanoparticles (AuNPs) approximately 10 nm in size are embedded in amorphous transparent silica matrix has been produced. The synthetic protocol uses HAuCl4 as the Au ion source, tetraethoxysilane (TEOS) as the SiO2 precursor, and l-ascorbic acid (AA) as the reducing agent. AA is employed before the sol-gel process in an amount sufficient only for reduction of Au3+ ions to Au+ . By using a cationic surfactant, benzylcetyldimethylammonium chloride hydrate (BDAC) and/or cetyltrimethylammonium bromide (CTAB), the Au+ ions are encapsulated within metalomicelles, which prevents them from being reduced to Au0 and enables their homogeneous distribution in the gel. Reduction of Au+ to Au0 and the growth of the AuNPs occurs at room temperature during the gelation, and arises from the release of EtOH during the hydrolysis of TEOS. The composites contain 0.027 wt % of Au. They exhibit nonlinear optical behavior characterized by the third-order nonlinear refraction index, n2 , in the range 3.6-5.7×10-16 cm2 W-1 at λ=1.030 μm. The composites are capable of effective third-harmonic generation of ultrashort near-IR (210 fs, 1.030 μm) laser pulse through a direct third-order mechanism.

Efficient inner filter effect sensors based on CdTeS quantum dots and Ag nanoparticles for sensitive detection of l-cysteine

In the design of new fluorescence sensors, exploration of new sensors with excellent performances and smart designs for the detection of ions and biomolecules is of continuing interest. Therefore, we designed an inner filter effect (IFE) based sensor by effectively combining between CdTeS quantum dots (QDs) and Ag nanoparticles (NPs). Ternary alloyed CdTeS QDs were synthesized by two steps and using 3-mercaptopropionic acid (MPA) as stabilizer, polyvinylpyrrolidone (PVP) stabilized Ag NPs were prepared by crystal-seed. The emission peak of CdTeS QDs and the absorption peak of Ag NPs could availably overlap by changing the Te/S molar ratios and l-ascorbic acid (AA) concentrations. The CdTeS QDs/Ag NPs (QNs) with an obviously emission at 580 nm were used as IFE-based sensors for l-cysteine (L-Cys). The QNs fluorescence was increasing with addition of l-Cysteine (L-Cys), the fluorescence (PL) intensity (F/F0) was linearly proportional to the L-Cys concentrations ranging from 20 μM to 400 μM with the correlation coefficient (R2) of 0.9942 and the detection limit was calculated to be 0.025 μM (S/N = 3), where F and F0 were the PL intensity in the presence and absence of L-Cys at 580 nm, respectively. Moreover, there was no interference to some potential interfering substances, which showed high sensitivity and selectivity for L-Cys.

Sodium ascorbate (SA) and l-ascorbic acid (AA) as modifiers of burn affected skin – A comparative analysis

Proper functioning of living organisms requires controlling the factors which govern the level of oxidative stress in the system, that is presence of free radicals at a given, rather low, level and preventing their excess. In this work it is shown that SA and AA active antioxidants, governing the oxidative stress in the wound, modify standard serum solution as well as burn affected necrotic eschar at the molecular structure level. In the case of incubation of skin fragments in SA and AA, the following findings were reported: modification of serum, that is appearance of low molecular weight oligomer bands in AA and recreation of native serum bands in SA. In frozen serum solutions modified by AA FTIR 1759 and 1420-1053 cm-1 bands are observed, whereas in SA FTIR 1603, 1411-1054 and 536 cm-1 bands appear. In the case of modification of the burn affected necrotic eschar in SA and AA - frequency shifts in the fingerprint region 1780-1000 cm-1 can be biomarkers indicating tissue regeneration process under the influence of antioxidants. 1780-1580 cm-1 and 1418-1250 cm-1 regions on the Raman spectra are particularly rich in spectral information. Modification of samples of skin burnt with AA activates the regions of the β-sheet aggregates whereas treatment of the samples with SA ascorbate demonstrates changes which testify to reconstruction of α-helix structure (SAXS studies).

Rapid and continuous parametric screening for the synthesis of gold nanocrystals with different morphologies using a microfluidic device

Metal nanocrystals of various shapes and sizes show great potential for applications in biomedicine because of their unique optical, thermal, and electrical properties. However, it is technically challenging to achieve delicate control over reaction conditions to successfully prepare nanocrystals with desired shapes. With the advent of microfluidic technology, sufficient mixing and precise parameter control can be achieved in nanoparticle synthesis to ensure high reproducibility, uniformity, and stability in nanosynthesis. Additionally, a multi-step reaction can be implemented using a microfluidic chip to simplify the synthetic process. Here, we present a microfluidic platform that allows the reaction parameters to be varied in a continuous fashion to screen for conditions that enable the synthesis of gold nanocrystals with a high aspect ratio. By changing the relative flow rates among AgNO3, gold seeds, and L-ascorbic acid (AA), various reactant concentrations were tested for the nanosynthesis. After only several minutes of on-chip nanosynthesis, spherical nanocrystals ranging in size from 13 to 40 nm and nanorods with aspect ratios ranging from 1.4 to 4.3 were prepared with high reproducibility. Compared with conventional off-chip batch synthesis, which requires hours to complete, the microfluidic platform offers the advantages of high efficiency, precise parameter control, low reagent consumption, minimal human intervention, and multi-step synthesis. This on-chip synthesis platform is expected to have broad prospects in both chemistry and biomedicine.

Functionalised carbon nano spheres modified electrode for simultaneous determination of dopamine and uric acid

In this paper we report the interaction of functionalised carbon nano spheres (FCNSs) with dopamine (DA), Uric acid (UA) and l-ascorbic acid (AA). FCNSs were characterised using SEM, AFM, spectroscopic and electrochemical measurements. Functionalised carbon nano spheres paste electrode (FCNSPE) has shown excellent preconcentration property of DA over its surface. UA also has also shown good electrochemical activity over the modified electrode. Parameters were optimised for the enhanced oxidation signal of DA in connection with simultaneous determination of DA and UA. An analytical method was developed for the simultaneous determination of DA and UA using the simple method of fabrication of electrode with detection limits (S/N of 3) of 10nM and 42nM for DA and UA respectively. Electrochemical oxidation signals of DA and UA were interference free from the oxidation of AA and other commonly occurring interfering agents. The method was applied for the determination of DA in spiked blood serum sample and for UA in real blood serum samples.

Effect of insulin-transferrin-selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation on in vitro bovine embryo development.

The aim of this study was to evaluate the effect of adding a combination of insulin, transferrin and selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation (IVM) and in vitro culture (IVC) on in vitro embryo production. To verify the effect of the supplements, cleavage and blastocyst rates, embryo size and total cell number were performed. Embryonic development data, embryo size categorization and kinetics of maturation were analyzed by chi-squared test, while the total cell number was analyzed by a Kruskal-Wallis test (P < 0.05). When ITS was present during IVM, IVC or the entire culture, all treatments had a cleavage and blastocyst rates and embryo quality, similar to those of the control group (P < 0.05). Supplementation of IVM medium with ITS and AA for 12 h or 24 h showed that the last 12 h increased embryo production (51.6%; n = 220) on D7 compared with the control (39.5%; n = 213). However, no improvement was observed in blastocyst rate when less competent oocytes, obtained from 1-3 mm follicles, were exposed to ITS + AA for the last 12 h of IVM, with a blastocyst rate of 14.9% (n = 47) compared with 61.0% (n = 141) in the control group. The results suggest that the addition of ITS alone did not affect embryo production; however, when combined with AA in the last 12 h of maturation, there was improvement in the quantity and quality of embryos produced. Furthermore, the use of ITS and AA during IVM did not improve the competence of oocytes obtained from small follicles.

The Effect of Chelating Agents on Enhancement of 1,1,1-Trichloroethane and Trichloroethylene Degradation by Z-nZVI-Catalyzed Percarbonate Process

This study primarily focused on the performance of 1,1,1-trichloroethane (1,1,1-TCA) and trichloroethylene (TCE) degradation involving redox reactions in zeolite-supported nanozerovalent iron composite (Z-nZVI)-catalyzed sodium percarbonate (SPC) system in aqueous solution with five different chelating agents (CAs) including oxalic acid (OA), citric acid monohydrate (CAM), glutamic acid (GA), ethylenediaminetetraacetic acid (EDTA), and L-ascorbic acid (ASC). The experimental results showed that the addition of OA achieved almost 100 % degradation of 1,1,1-TCA and TCE. The addition of CAM and GA also significantly increased the contaminant degradation, while excessive addition of them inhibited the degradation. In contrast, EDTA and ASC showed negative impacts on 1,1,1-TCA and TCE degradation, which might be due to the strong reactivity with iron and OH● scavenging characteristics. The efficiency with CA addition on 1,1,1-TCA and TCE degradation decreased in the order of OA > CAM > GA > no CAs > EDTA > ASC. The extensive investigations using probe compound tests and scavenger tests revealed that both contaminants degraded primarily by OH● and O2 –● in chelated Z-nZVI-catalyzed SPC system. The significant improvement in 1,1,1-TCA and TCE degradation efficiency was accredited due to the (i) increase in concentration of Fe2+ and (ii) continuous generation of OH● radicals and maintenance of its quantity, ensuring more stability in the aqueous solution. Finally, the complete mineralization of 1,1,1-TCA and TCE in the OA-chelated, Z-nZVI-catalyzed SPC system was confirmed without any chlorinated intermediate by-products detected, demonstrating a great potential of this technique in the application of groundwater remediation.

Levels of l-ascorbic acid and cadmium in the saphenous vein of patients with coronary artery disease are negatively correlated

BackgroundThe aim of this study was the simultaneous determination of levels of cadmium and l-ascorbic Acid (AA) in human saphenous vein (SV) used in coronary artery bypass grafting (CABG) and check whether there is a relationship between these levels. MethodsHuman SV were collected from 40 patients (20 men and 20 women; age, 40–75 years) at the time of routine coronary artery surgical revascularization. The concentration of cadmium in the tissue was determined according to the GF AAS—atomic absorption method. The concentration of AA was assayed in supernatant by FIA method with spectrophotometric detection. ResultsAA concentration (mean±SD); men: 98,7±13,18μg/g tissue, women: 96,06±11,98μg/g tissue. Cadmium concentration(mean±SD); men: 309±103,71ng/g tissue, women: 348,5±255,71ng/g tissue. Correlations among concentrations of AA and cadmium were insignificant negative in the group of men (Pearson r=−0,1504, p=0,5269) and in the group women (Pearson r=−0339, p=0144). ConclusionsNegative correlations among concentrations of AA and cadmium in human SV obtained in our study may indicate a protective effect of this vitamin in relation to toxic cadmium.

Thermal Degradation and Isomerization of β-Carotene in Oil-in-Water Nanoemulsions Supplemented with Natural Antioxidants.

The goal of this study was to see the impact on the retention and isomerization of encapsulated β-carotene (BC) in nanoemulsions fortified with natural antioxidants (α-tocopherol (AT) and l-ascorbic acid (AA)). The physical stability of nanoemulsion, oxidative stability, and isomerization of all-trans-β-carotene (BC) in oil-in-water (O/W) nanoemulsions were determined in the presence or absence of natural antioxidants at 25 and 50 °C at certain intervals of time by high-performance liquid chromatography (HPLC). Sodium caseinate was used as the emulsifier, and corn oil (CO) was more protective than medium-chain triglycerides (MCT) and used for isomerization studies. Mean diameters of control (without antioxidants) and AA- and AT-fortified particles were similar. Mean particle diameter of nanoemulsions increased from 10 to 25 nm at 25 °C and from 40 to 50 nm at 50 °C during 30 days of storage. The isomerization from all-trans-BC to cis-BC isomers was inhibited by antioxidants. The isomerization rates were in the following order: 13-cis-BC > 15-cis-BC > 9-cis-BC. AT had better antioxidant activities than AA in inhibiting BC degradation in O/W nanoemulsions. The results indicated that BC encapsulated in nanoemulsions supplemented with antioxidants could significantly improve BC's chemical stability.

Interference-blind microfluidic sensor for ascorbic acid determination by UV/vis spectroscopy

A microfluidic sensor is developed and targeted at specific ingredients determination in drug/food/beverage matrices. The surface of a serpentine polydimethylsiloxane (PDMS) microchannel is modified by enzyme via physisorption. When solutions containing target ingredients pass through the microfluidic channel, enzyme-catalyzed reaction occurs and only converts the target molecules to its products. The whole process is monitored by an end-channel UV/vis spectroscopic detection. Ascorbate oxidase and l-ascorbic acid (AA) are taken as enzyme-substrate model in this study to investigate the feasibility of using the developed strategy for direct quantification of AA in standard solutions and complex matrices. A dietary supplement product, Vitamin C tablet, is chosen as a model matrix to test the microfluidic bio-sensor in real-sample analysis. The results illustrate that the established microfluidic bio-sensor exhibits good reproducibility, stability, and anti-interference property. Technically, it is easy to realize, depends on low investment in chip fabrication, and simple instrumental procedure, where only UV/vis spectrophotometer is required. To sum up, the developed strategy is economical, specific, and accurate, and can be potentially used for fast quantification of ingredient in samples with complex matrix background. It is promising to be widely spread in food industry and quality control department.

Dumbbell-shaped carbon quantum dots/AuNCs nanohybrid as an efficient ratiometric fluorescent probe for sensing cadmium (II) ions and l-ascorbic acid

In this work, for the first time, an efficient carbon quantum dots/gold nanoclusters (CQDs/AuNCs) nanohybrid based ratiometric fluorescent probe for sensitive and selective sensing of cadmium (II) ions and l-ascorbic acid (AA) has been established. The blue emissive CQDs, prepared by a one-step hydrothermal treatment with alanine and histidine, play the role of reference fluorophore. The red emissive AuNCs, capped by 11-mercaptoundecanoic acid (MUA), serve as a specific recognition element. Different from MUA-capped AuNCs, the proposed CQDs/AuNCs nanohybrid exhibits high selectivity and sensitivity to cadmium (II) ions with a detection limit of 32.5 nM, which is attributed to the static quenching and the inner filter effect (IFE) of Cd2+ to CQDs/AuNCs nanohybrid. Unbelievable, in the presence of AA, the above-quenched sensor is recovered gradually. The proposed fluorescence sensor displays an enhanced performance for AA determination in the range from 0.15 to 15 μM (R = 0.995) with a detection limit down to 0.105 μM. More importantly, this fluorescent “on–off–on” method also offers the excellent performance to Cd2+ and AA detection in lake water and in human serum, respectively.