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The COVID-19 pandemic shows significant impacts on credit risk, which is the key concern of corporate bond holders such as insurance companies. Credit risk, quantified by agency credit ratings and credit default swaps (CDS), usually exhibits long-range dependence (LRD) due to potential credit rating persistence. With rescaled range analysis and a novel affine forward intensity model embracing a flexible range of Hurst parameters, our studies on Moody's rating data and CDS prices reveal that default intensities have shifted from the long-range to the short-range dependence regime during the COVID-19 period, implying that the historical credit performance becomes much less relevant for credit prediction during the pandemic. This phenomenon contrasts sharply with previous financial-related crises. Specifically, both the 2008 subprime mortgage and the Eurozone crises did not experience such a great decline in the level of LRD in sovereign CDS. Our work also sheds light on the use of historical series in credit risk prediction for insurers' investment.

RGB-multicolor fluorescent carbon dots from o-phenylenediamine and phenylalanine by changing the solvent type and for white light-emitting diodes.

Given two probability measures on sequential data, we investigate the transport problem with time-inconsistent preferences under a discrete-time setting. Motivating examples are nonlinear objectives, state-dependent costs, and regularized optimal transport with general $f$-divergence. Under the bi-causal constraint, we introduce the concept of equilibrium transport and provide a characterization. We apply our framework to study inertia of two job markets, top-ranking executives and academia. The empirical analysis shows that a job market with stronger inertia is less efficient. The University of California (UC) postdoc job market has the strongest inertia even than that of executives, while there is no evidence of inertia in the UC faculty job market., Comment: 42 pages, 10 figures, 15 tables. Comments are welcome!

This paper studies robust decision problems in a rough environment that is described by Volterra processes. Various alternative dominated models are introduced to reflect decision makers' concerns ...

Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials. Herein, fluorescent CDs excited by visible light emitted red fluorescence with a quantum yield of 32.8% via a facile hydrothermal treatment. In addition to being applied in cell imaging, the as-prepared CDs were also utilized in the detection of ammonia and formaldehyde in aqueous solutions because of their pH-dependent properties, with a low limit of detection of 3.7 nM and 44 μM, respectively. Furthermore, we synthesized flexible and transparent fluorescence films by mixing the as-prepared CDs and PVB powder, which can be utilized to directly detect ammonia gas under visible light according to significant colour changes. Therefore, the as-prepared CDs would have more prominent and influential application in clinical diagnostics and environmental analysis.

Herein we report L-cysteine (Cys)-mediated copper nanoclusters (CuNCs) with assembly-to-monodispersion switching by pH-triggered surface modulation. Aggregated red emissive (R)-CuNCs@Cys at pH = 3 turns to monodispersed blue emissive (B)-CuNCs@Cys at pH = 10, due to the change from weak electrostatic interactions to strong Cu–N bonds that play a decisive role.

With the digitalization of the financial market, dealers are increasingly handling market-making activities by algorithms. Recent antitrust literature raises concerns on collusion caused by artificial intelligence. This paper studies the possibility of cooperation between market makers via independent Q-learning. Market making with inventory risk is formulated as a repeated general-sum game. Under a stag-hunt type payoff, we find that market makers can learn cooperative strategies without communication. In general, high spreads can have the largest probability even when the lowest spread is the unique Nash equilibrium. Moreover, introducing more agents into the game does not necessarily eliminate the presence of supra-competitive spreads.

This paper studies stochastic linear-quadratic control with a time-inconsistent objective and worst-case drift disturbance. We allow the agent to introduce disturbances to reflect her uncertainty about the drift coefficient of the controlled state process. We adopt a two-step equilibrium control approach to characterize the robust time-consistent controls, which can preserve the order of preference. Under a general framework allowing random parameters, we derive a sufficient condition for equilibrium controls using the forward-backward stochastic differential equation approach. We also provide analytical solutions to mean-variance portfolio problems for various settings. Our empirical studies confirm the improvement in portfolio’s performance in terms of out-of-sample Sharpe ratio by incorporating with robustness. Ministry of Education (MOE) Bingyan Han is supported by UIC Start-up Research Fund (Reference No: R72021109). Chi Seng Pun gratefully acknowledges the Ministry of Education (MOE), AcRF Tier 2 Grant (Reference No: MOE2017-T2-1-044) for the funding of this research. Hoi Ying Wong acknowledges the support from the Research Grants Council of Hong Kong via GRF 14303915.

This paper solves for the robust time-consistent mean–variance portfolio selection problem on multiple risky assets under a principle component stochastic volatility model. The model uncertainty is introduced to the drifts of the risky assets prices and the stochastic eigenvalues of the covariance matrix of asset returns. Using an extended dynamic programming approach, we manage to derive a semi-closed form solution of the desired portfolio via the solution to a coupled matrix Riccati equation. We provide the conditions, under which we prove the existence and the boundedness of the solution to the coupled matrix Riccati equation and derive the value function of the control problem. Moreover, we conduct numerical and empirical studies to perform sensitivity analyses and examine the losses due to ignoring model uncertainty or volatility information.

Highly ordered metal nanoclusters (NCs) have attracted much attention due to their controllability and regularity. Herein, self-assembled CuNCs with orange-red emission were prepared using m-aminothiophenol (m-AT) within 10 s. The hydrogen bonding interactions of CuNCs@m-AT were controlled precisely by adjusting the pH, and this induced the continuous self-assembly process of monodisperse, nano-spheres, nano-meshes and nano-sheets, and established the relationship between the macrostates and the microstructures of CuNCs@m-AT. For the first time, an organic anion was used to induce the emission of CuNCs@m-AT and to carry out the phase transfer of CuNCs@m-AT from the aqueous phase to the n-butanol phase. In addition, we found that m-AT was more beneficial for the synthesis of CuNCs, compared to o-AT and p-AT. This work provides an example of the structure-dependent CuNCs@m-AT on luminescent properties and showed the potential of –NH2 in the design of superstructures of nanoscale materials with unique functions and properties.

Herein, we directly prepared white fluorescent CDs (W-CDs) using 1,6-dihydroxynaphthalene (1,6-DHN) and l -asparagine ( l -Asn) as carbon sources through a simple solvent-free method. As-prepared W-CDs can be obtained in high yield (95%). A relative pure white LEDs (WLEDs) were fabricated with Commission Internationale de L’Eclairage (CIE) coordinates of (0.32, 0.31). As-prepared W-CDs will have promising future for a wide range of optoelectronic devices.

The color-tunable AuAg nanoclusters (AuAg NCs) are designed by adjusting the location of Ag element, in which β-lactoglobulin (β-Lg) serves as the capping and reducing agent. The mono-metal Au NCs emit red-fluorescent emission (red-Au NCs@β-Lg); however, the stronger metallophilic interaction between Au and Ag facilitate the smaller size, and then the bimetal AuAg NCs@β-Lg present yellow emission (yellow-AuAg NCs@β-Lg). A “Ag+ shell” outside the AuAg NCs@β-Lg cause the emission change to orange (orange-AuAg NCs@β-Lg-Ag+). This is the first time for Ag+ to tune continuously the emission wavelength of AuAg NCs. TEM proves that the size of particle has a close relationship with the fluorescence emissions. l -cysteine (Cys) stabilized the protective effect of β-Lg and shows a “turn on” effect on the fluorescence intensity of yellow-AuAg NCs@β-Lg. In contrary, the strong interaction between Cys and Ag+ destroys the protection of β-Lg to the core of yellow-AuAg NCs@β-Lg and shows a distinct “turn off” effect on the fluorescence intensity of orange-AuAg NCs@β-Lg-Ag+. The above phenomenon has been successfully applied to the detection of Cys in the Hela cells. This location-based color-tunable strategy is expected to open up a new potential to improve the performance of NCs.

This paper studies a class of robust mean–variance portfolio selection problems with state-dependent risk aversion. Model uncertainty, in the sense of considering alternative dominated models, is introduced to the problem to reflect the investor’s uncertainty-averse preference. To characterise the robust portfolios, we consider closed-loop equilibrium control and spike variation approaches. Moreover, we show that a closed-loop equilibrium strategy exists and is unique under some technical conditions. This partially addresses open problems left in Björk et al. (Finance Stoch. 21:331–360, 2017) and Pun (Automatica 94:249–257, 2018). By using a necessary and sufficient condition for the equilibrium, we manage to derive the analytical form of the equilibrium strategy via the unique solution to a nonlinear ordinary differential equation system. To validate the proposed closed-loop control framework, we show that when there is no uncertainty, our equilibrium strategy is reduced to the strategy in Björk et al. (Math. Finance 24:1–24, 2014), which cannot be deduced under the open-loop control framework. Ministry of Education (MOE) Submitted/Accepted version Bingyan Han is supported by UIC Start-up Research Fund (Reference No: R72021109). Chi Seng Pun gratefully acknowledges the Ministry of Education (MOE), AcRF Tier 2 grant (Reference No: MOE2017-T2-1-044) for the funding of this research. Hoi Ying Wong acknowledges the support from the Research Grants Council of Hong Kong via GRF 14303915.

In this paper, polyethyleneimine (PEI) was applied as a carbon source for synthesizing fluorescent carbon dots (CDs) through a facile and one-step hydrothermal route. Both the N-doping and the amino-functionalization of CDs were accomplished simultaneously. The CDs exhibited strong blue fluorescence and good dispersion in aqueous solution. A large number of amino groups on the surface of CDs greatly simplified the subsequent modification steps. Through an amide reaction, glutathione-functionalized CDs were successfully applied to the selective detection of Co2+, in the linear range from 2.0 × 10−5 to 1.0 × 10−4 mol L−1.

Metal ion-doping has been paid little attention for improving the fluorescence intensity of carbon dots (CDs) compared with nonmetallic-element doping. Herein, for the first time, Fe2+-doped CDs were facilely synthesized at 80 °C instead of by a hydrothermal method. Fe2+ was confirmed to be the only definitive common metal ion to synthesize highly fluorescent CDs with proline (Pro) as a carbon resource. The as-synthesized Fe2+-doped CDs showed bright blue fluorescence at 455 nm and exhibited favorable anti-ion, pH, and time stability. The blue cysteine-functional-Fe2+-doped CDs were combined with red gold nanoclusters (Au NCs) to construct a nanohybrid by electrostatic interaction for the ratiometric fluorescence sensing of Zn2+ and histidine (His), in which the CDs acted as a reference signal and the Au NCs as an analyte-responsive unit. The detection of Zn2+ and histidine (His) was shown by two distinct blue-pink and pink-blue-pink fluorescence color changes, respectively. Both of them showed excellent selectivity and sensitivity. Dual-emission fluorescent probes avoid the shortcomings of single fluorescence signals, which are susceptible to experimental conditions, and have a bright future being utilized for the visual detection of Zn2+ and His in practical analysis.

The encapsulation of Cu nanoclusters (Cu NCs) in metal-organic frameworks (MOFs) would improve the properties of Cu NCs. So far, these composites were reported by a two-step synthesis process. In this work, a facile one-pot synthesis of hybridization of glutathione (GSH) protected Cu NCs (Cu NCs@GSH) and MOF-5 (Cu NCs@GSH/MOFs) composites was reported for the first time. The results of UV-vis, TEM, XPS and SEM proved Cu NCs@GSH were distributed homogeneously over the entire MOF structure. The fluorescence intensity of Cu NCs encapsulated in MOF-5 was enhanced about 35-fold owing to the confining scaffold of the MOF and the stability was extended from 3 days to 3 months. Cu NCs@GSH/MOFs composites exhibited strong orange fluorescence and the emissions could change between blue, orange and red as they were partially reversible in different pH environments. This one-pot synthetic strategy could be extended for the encapsulation of fluorescent Ag NCs in MOFs as well. As-prepared Cu NCs@GSH/MOF-5 composites had high stability, and were easily recycled by centrifugation in aqueous solution, therefore, it would be utilized to develop a reusable sensor for detection of metal ions in the future.

Fluorescence has been extensively employed for visual detection; however, it is inconvenient for people to distinguish single-color fluorescence changes. Herein, a dual-signal ratiometric fluorescent probe of a carbon quantum dot/gold nanocluster (CQD/Au NC) nanosystem for sensitive and selective detection of Ag+ and L-cysteine (Cys) was established. The CQDs with blue fluorescence at 472 nm served as a reference signal and Au NCs with orange fluorescence at 605 nm functioned as a reporter. From zeta potential measurements and TEM images, there was no indication of interaction between the two materials due to electrostatic repulsion. Upon adjusting the proportion of the CQDs and Au NCs, the nanosystem emitted a gray-orange emission at a single excitation wavelength. Ag+ enhanced the orange colour of Au NCs, but Cys could quench it completely with the high affinity of the coordination interaction between Cys and Ag+, while the blue fluorescence of CQDs was not affected. Therefore, the fluorescence of the nanosystem showed gray orange to light orange colour for determination of Ag+, and light orange to blue colour for determination of Cys. Moreover, paper-based visual detection was successfully carried out, which showed a more distinguishable color difference than that in aqueous solution. Our method has bright potential for application in the real-time and online visual detection of Ag+ and Cys in the future.

Rich-thymine (T) single- or double-strand DNAs have been identified as efficient templates favoring the formation of fluorescent copper nanoparticles (Cu NPs). In this work, we confirmed single base T could be a template to synthesize water-soluble copper nanoclusters (Cu NCs@T) for the first time. Our work provided basic evidence of the benefit of using T-rich DNA strands for the synthesis of fluorescent Cu NPs. Transmission electron microscopy demonstrated that Cu NCs@T had a diameter of 2.8 ± 0.5 nm, which is much smaller than Cu NPs templated by single- or double-strand DNAs. X-ray photoelectron spectroscopy confirmed the valence state of the Cu in Cu NCs@T most likely lies between 0 and +1. The as-prepared Cu NCs@T exhibited yellow photoluminescence and the maximum excitation and emission peaks were at 354 nm and 561 nm, respectively. In addition, we also showed that the as-prepared Cu NCs@T can be developed into a practical sensor for “turn-on” luminescence with the emission red-shifted detection of Mn2+ in aqueous solution with a high selectivity. The limit of detection for Mn2+ was determined to be 10 μM and the linear response with the Mn2+ concentrations range from 100 μM to 250 μM.

A turn-on fluorescence analysis method was established for detection of Pb2+ based on aggregation-induced emission. Glutathione-protected non-noble metal copper nanoclusters (Cu NCs@GSH) showed nearly no fluorescence. However, the fluorescence intensity of Cu NCs@GSH was remarkably improved in the presence of Pb2+ and showed bright orange fluorescence. A fluorescence method for detection of Pb2+ was established based on this principle. The fluorescence change of the Cu NCs@GSH solution showed a linear relationship with Pb2+ concentration within the range of 200–700 μM. The limit of detection was 106 μM (S/N = 3). This method is simple, rapid and highly selective, and can be used for the visual qualitative detection of Pb2+ under ultraviolet (UV) lamp.

Bimetal nanoclusters (BNCs) have attracted great attention due to their cooperative electronic, optical, and catalytic properties. In this study, the highly luminescent Cu/Ag BNCs were prepared based on the weakly luminescent glutathione (GSH)-capped Cu NCs for the first time. After the introduction of a certain amount of Ag+, a 9-fold enhancement of the luminescence intensity was obtained from GSH-protected Cu/Ag BNCs. The luminescence emission peak was blue shifted from 620 nm (red emission) to 604 nm (orange-yellow emission). The Cu/Ag BNCs exhibited an average size of around 1.4 ± 0.2 nm, as observed from a thorough analysis of transmission electron microscopy data. The as-prepared Cu/Ag BNCs exhibited excellent anti-interference performance against various metal ions. In addition to the intrinsic optical properties, the Cu/Ag BNCs were employed as a temperature sensor by virtue of the luminescence intensity of Cu/Ag BNCs responding sensitively to temperature fluctuating in the range of 4–55 °C.

Herein, we introduced a kind of physical method using acetone to directly extract fluorescent carbon quantum dots (CQDs) from ordinary carbon black in one step. The as-extracted CQDs exhibited an excitation-dependent emission behavior and a high quantum yield of up to 19.01%. Moreover, we find that the polarity of the solvent will affect the size of CQDs for the first time.

In this paper, we consider equilibrium strategies under Volterra processes and time-inconsistent preferences embracing mean-variance portfolio selection (MVP). Using a functional It\^o calculus approach, we overcome the non-Markovian and non-semimartingale difficulty in Volterra processes. The equilibrium strategy is then characterized by an extended path-dependent Hamilton-Jacobi-Bellman equation system under a game-theoretic framework. A verification theorem is provided. We derive explicit solutions to three problems, including MVP with constant risk aversion, MVP for log returns, and a mean-variance objective with a linear controlled Volterra process. We also thoroughly examine the effect of volatility roughness on equilibrium strategies. Numerical experiments demonstrate that trading rules with rough volatility outperform the classic counterparts., Comment: An earlier version of this paper was circulated and cited under the title "Time-consistent feedback strategies with Volterra processes"

Motivated by empirical evidence for rough volatility models, this paper investigates continuous-time mean-variance (MV) portfolio selection under the Volterra Heston model. Due to the non-Markovian and non-semimartingale nature of the model, classic stochastic optimal control frameworks are not directly applicable to the associated optimization problem. By constructing an auxiliary stochastic process, we obtain the optimal investment strategy, which depends on the solution to a Riccati-Volterra equation. The MV efficient frontier is shown to maintain a quadratic curve. Numerical studies show that both roughness and volatility of volatility materially affect the optimal strategy., Comment: Final version, 22 pages, 5 figures, to appear in Applied Mathematics & Optimization

This paper investigates Merton’s portfolio problem in a rough stochastic environment described by Volterra Heston model. The model has a non-Markovian and non-semimartingale structure. By considering an auxiliary random process, we solve the portfolio optimization problem with the martingale optimality principle. Optimal strategies for power and exponential utilities are derived in semi-closed form solutions depending on the respective Riccati-Volterra equations. We numerically examine the relationship between investment demand and volatility roughness.

This paper studies a class of robust mean--variance portfolio selection problems with state-dependent risk aversion. Model uncertainty, in the sense of considering alternative dominated models, is introduced to the problem to reflect the investor's uncertainty-averse preference. To characterise the robust portfolios, we consider closed-loop equilibrium control and spike variation approaches. Moreover, we show that a closed-loop equilibrium strategy exists and is unique under some technical conditions. This partially addresses open problems left in Bjork et al. (Finance Stoch. 21:331--360, 2017) and Pun (Automatica 94:249--257, 2018). By using a necessary and sufficient condition for the equilibrium, we manage to derive the analytical form of the equilibrium strategy via the unique solution to a nonlinear ordinary differential equation system. To validate the proposed closed-loop control framework, we show that when there is no uncertainty, our equilibrium strategy is reduced to the strategy in Bjork et al. (Math. Finance 24:1--24, 2014), which cannot be deduced under the open-loop control framework.

This paper studies stochastic linear-quadratic control problems for an ambiguity-adverse agent with a time-inconsistent objective. We allow the agent to incorporate disturbances into the state's drift or choose an alternative model among a set of models equivalent to the reference model, to reflect her ambiguity aversion on the drift coefficient of the state process. We adopt an innovative two-step equilibrium control approach to characterize the robust time-consistent controls and simultaneously preserve the preference order. Under a general framework allowing random parameters, we derive a sufficient condition for equilibrium controls using the forward-backward stochastic differential equation approach. We also provide analytical solutions to mean-variance portfolio problems for various settings. Our empirical studies confirm the improvement in the portfolio's performance in terms of Sharpe ratio by incorporating robustness.

A sensitive capillary electrophoresis-electrochemiluminescence (CE-ECL) assay with an ionic liquid (IL) was developed for the determination of arecoline in areca nut. The IL, 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF(4) ), was an effective additive improved not only the separation selectivity but also the detection sensitivity of the analyte. BMImBF(4) in the separation electrolyte made the resistance of the separation buffer much lower than that of the sample solution, which resulted in an enhanced field amplified electrokinetic injection CE. ECL intensity of arecoline is about two times higher than that of the analyte with phosphate-IL buffer system. Resolution between arecoline and other unknown compounds in real samples was improved. Under the optimized conditions (ECL detection at 1.2 V, 16 kV separation voltage, 20 mmol/L phosphate with 10 mmol/L BMImBF(4) buffer at pH 7.50, 5 mmol/L Ru(bpy)(3)(2+) and 50 mmol/L phosphate buffer in the detection reservoir), a detection limit of 5 × 10(-9) mol/L for arecoline was obtained. Relative standard deviations of the ECL intensity and the migration time were 4.51% and 0.72% for arecoline. This method was successfully applied to determination of the amount of arecoline in areca nut within 450 s.

Novel CdS nanomaterials were synthesized by a simple “one-pot” hydrothermal biomolecule-assisted method using glutathione (GSH) as the sulfur source and structure-directing reagent. Various morphologies of CdS photocatalysts, such as solid nanospheres (s-CdS), hollow nanospheres (h-CdS) and nanorods (r-CdS), were obtained by controlling only the hydrothermal temperatures. The X-ray diffraction patterns confirmed that all of the samples were typical hexagonal wurtzite CdS. It was found that the absorption edge of s-CdS was at 465 nm with a greater blue shift compared to that of h-CdS and r-CdS. The photocatalytic activity of s-CdS was superior to that of h-CdS and r-CdS under visible light. Photoluminescence measurements revealed their different photogenerated electron/hole recombination ability, which was in accordance with the order of s-CdS

In this work, we reported a simple and sensitive method to detect biothiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), using fluorescent silver nanoclusters (Ag NCs) stabilized by single-stranded DNA (DNA-Ag NCs) as probes. The photoluminescence intensity of DNA-Ag NCs was found to be quenched effectively with the increase of biothiols concentration due to the formed nonfluorescent coordination complex between DNA-Ag NCs and biothiols, resulting in the shift-to-red of emission wavelength. But the fluorescence of DNA-Ag NCs was not changed in the presence of other amino acids at 10-fold higher concentration. Satisfactory detection limits and linear relationships of Cys, GSH and Hcy were obtained, respectively. The resulted plots exhibited good linear relationships in the range from 8.0×10(-9) to 1.0×10(-7) mol L(-1) (R(2)=0.984) for Cys, 8.0×10(-9) to 1.0×10(-7) mol L(-1) (R(2)=0.983) for GSH, and 2.0×10(-6) to 6.0×10(-7) mol L(-1) (R(2)=0.999) for Hcy, respectively; the detection limits of Cys, GSH and Hcy were 4.0 nmol L(-1), 4.0 nmol L(-1), and 0.2 μmol L(-1), respectively. The method was successfully used for the detection of biothiols in human plasma samples.

Water-soluble and ultra-stable L-proline-protected copper nanoclusters (Cu NCs) are reported, which overcome the bottleneck that Cu NCs are easily oxidized. The average size of Cu NCs is found to be 1.88 ± 0.17 nm. The as-prepared Cu NCs exhibit an excellent stability over the physiologically relevant pH range, long storage time, high ionic strength, high concentration of hydrogen peroxide and various common metal ions. The fluorescence intensity of Cu NCs maintains no change after 5 months stored in the refrigerator. Interestingly, the Cu NCs show a pH-dependent fluorescence behavior between 9 and 13, and the reversible process can be repeated for 8 consecutive cycles with the excellent reversibility of the fluorescence intensity. Moreover, the as-prepared Cu NCs display the solvent-dependent properties in the dimethyl sulfoxide and ethylenediamine, where the emission color turn to be green and yellow from blue, respectively. This unique fluorescence property of Cu NCs will make them serve as good probes in analytical applications.

The CdS/TiO2 composites were synthesized using titanate nanotubes (TiO2NTs) with different pore diameters as the precursor by simple ion change and followed by sulfurization process at a moderate temperature. Some of results obtained from XRD, TEM, BET, UV–vis and PL analysis confirmed that cadmium sulfide nanoparticles (CdSNPs) incorporated into the titanium dioxide nanotubes. The photocatalytic production of H2 was remarkably enhanced when CdS nanoparticles was incorporated into TiO2NTs. The apparent quantum yield for hydrogen production reached about 43.4% under visible light around λ = 420 nm. The high activity might be attributed to the following reasons: (1) the quantum size effect and homogeneous distribution of CdSNPs; (2) the synergetic effects between CdS particles and TiO2NTs, viz., the potential gradient at the interface between CdSNPs and TiO2NTs.

CE/Ru(bpy)32+ electrochemiluminescence (ECL) system with the assistance of ionic liquids (ILs) was successfully established for sensitive determination of verticine and verticinone in Bulbus Fritillariae for the first time. Migration behavior of alkaloid largely relies on the hydrogen bonding interactions between alkyl imidazolium cations in ILs and the alkaloids. Running buffer containing 40 mmol/L 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) IL–8 mmol/L phosphate resulted in significant changes in separation selectivity for alkaloids with similar structures. The highest sensitivity of the detection was obtained by maintaining the detection potential at 1.2 V. Under the optimized conditions, relative standard derivations of the ECL intensity and the migration time were 3.27 and 2.84% for verticine and 4.42 and 1.69% for verticinone, respectively. The standard curves were linear between 1 × 10−8 and 1 × 10−6 mol/L for verticine and between 5 × 10−8 and 1 × 10−6 mol/L for verticinone, respectively. Detection limits of 1.25 × 10−10 mol/L for verticine and 1 × 10−10 mol/L for verticinone were obtained (S/N = 3). Developed method was successfully applied to determine the amounts of alkaloids in Bulbus Fritillariae.

In this paper, we described a simple and rapid method, capillary electrophoresis with electrochemiluminescence (CE–ECL) detection using tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+), to simultaneously detect pethidine and methadone. Analytes were injected to separation capillary of 67.5 cm length (25 μm i.d., 360 μm o.d.) by electrokinetic injection for 10 s at 10 kV. Under the optimized conditions: ECL detection at 1.20 V, 30 mM sodium phosphate (pH 6.0) as running buffer, separation voltage at 14.0 kV, 5 mM Ru(bpy)32+ with 50 mM sodium phosphate (pH 6.5) in the detection cell, the linear range from 2.0 × 10− 6 to 2.0 × 10− 5 M for pethidine and 5.0 × 10− 6 to 2.0 × 10− 4 M for methadone and detection limits of 0.5 μM for both of them were achieved (S/N = 3). Relative standard derivations of the ECL intensity were 2.09% and 6.59% for pethidine and methadone, respectively.

Herein, we report a facile one-pot method for the synthesis of orange/red-emitting fluorescent copper nanoclusters (Cu NCs), in which bovine serum albumin (BSA) served as the capping scaffold (Cu NCs@BSA) and hydroxylamine hydrochloride (NH2OH[Formula: see text][Formula: see text][Formula: see text]HCl) as the reducing agent. To the best of our knowledge, this is the first time to adopt this mild reductant to synthesize fluorescent Cu NCs. The as-prepared Cu NCs@BSA exhibits strong orange or red fluorescence at room temperature depending on the synthesis process, and the maximum excitation and emission peaks were at 355[Formula: see text]nm and 615[Formula: see text]nm, 395[Formula: see text]nm and 645[Formula: see text]nm, respectively. Synthesis conditions including the amounts of NH2OH[Formula: see text][Formula: see text][Formula: see text]HCl, the selection of reducing agent, the molar ratio of BSA/Cu(NO3)2, the pH value, the reaction temperature, the reaction time, and various kinds of Cu sources have been systematically studied. Importantly, these Cu NCs exhibit excellent stability for at least 2 months when stored at 4[Formula: see text]C in the dark, and they also show strong oxidation resistance toward H2O2. Moreover, the prepared Cu NCs have been successfully applied to sensitively and selectively sensing Hg[Formula: see text] without suffering any interference from other metal ions and anions.

A novel 3D metal–organic framework (MOF) {[Zn3(bpdc)3 (p-4-bpmb)](DMF)2}n ( 1) (H[Formula: see text]-4,4′-dicarboxylic acid; p-4-[Formula: see text],4-bis(pyridine-4-ylmethoxy)benzene) has been solvothermally synthesized and structurally characterized. Compound 1 exhibits a 3D pillar-layered framework based on the trinuclear {Zn3} building blocks, consisting of Zn-dicarboxylate layers and bipyridyl-derivative pillars. Furthermore, it features three-fold interpenetrating 8-connected hex-type topology. In addition, its thermal stability and luminescent property have also been investigated.