Li Zhang’s research while affiliated with Nanchang University and other places

An imidazolyl hydrogen-bonded organic framework (HOF-T) with outstanding thermal and water stability was constructed by C-H…N hydrogen bonding and C-H…π interaction. UO22+ can be selectively captured by the imidazole group...

As large numbers of people are suffering from gout, an accurate, rapid, and sensitive method for the detection of gout biomarker, uric acid, is important for its effective control, diagnosis, and therapy. Although colorimetric detection methods based on uricase have been considered, they still have limitations as they produce toxic H 2 O 2 and are expensive and not stable. Here, a novel uricase‐free colorimetric method was developed for the sensitive and selective detection of uric acid based on the light‐induced oxidase‐mimicking activity of a new photosensitized covalent organic framework (COF) (2,4,6‐trimethylpyridine‐3,5‐dicarbonitrile–4‐[2‐(4‐formylphenyl)ethynyl]benzaldehyde COF [DCTP–EDA COF]). DCTP–EDA COF has a strong ability to harvest visible light, and it could catalyze the oxidation of 1,4‐dioxane, 3,3′,5,5′‐tetramethylbenzidine under visible light irradiation to produce obvious color changes. With the addition of uric acid, however, the significant inhibition of the oxidase‐mimicking activity of DCTP–EDA COF remarkably faded the color, and thus uric acid could be colorimetrically detected in the range of 2.0–150 μM with a limit of detection of 0.62 μM (3 σ /K). Moreover, the present colorimetric method exhibited high selectivity; uric acid level in serum samples was successfully determined, and the recoveries ranged from 96.5% to 105.64%, suggesting the high accuracy of the present colorimetric method, which demonstrates great promise in clinical analysis.

Carbon dots (CDs) as an emerging carbon nanomaterial have attracted considerable attention and have been widely used in numerous fields. When compared with semiconductor quantum dots and organic dyes, CDs are a very friendly optical probe with low toxicity, good biocompatibility and good anti-photobleaching. These qualities give them the potential to be greener than other types of quantum dots and organic dyes. Covering several common synthesis strategies, including biomass synthesis, large-scale synthesis and sustainable synthesis technology, this book focuses on the green synthesis of CDs and their applications in the fields of bioanalytical, catalytic, biomedical, and environmental sciences. It is a useful reference for anyone working in green chemistry, analytical chemistry, biomedical or environmental science.

Nanomaterials with enzyme mimetic activity have attracted extensive attention, especially in the regulation of their catalytic activities by biomolecules or other polymers. Here, a covalent organic framework (Tph‐BT COF) with excellent photocatalytic activity is constructed by Schiff base reaction, and its mimetic oxidase activity and peroxidase activity is inversely regulated via single‐stranded DNA (ssDNA). Under light‐emitting diode (LED) light irradiation, Tph‐BT exhibited outstanding oxidase activity, which efficiently catalyzed oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) to produce blue oxTMB, and ssDNA, especially those with poly‐thymidine (T) sequences, can significantly inhibit its oxidase activity. On the contrary, Tph‐BT showed weak peroxidase activity, and the presence of ssDNA, particularly poly‐cytosine (C) sequences, can remarkably enhance the peroxidase activity. The influence of base type, base length, and other factors on the activities of two enzymes is also studied, and the results reveal that the adsorption of ssDNA on the surface of Tph‐BT prevented intersystem crossing (ISC) and energy transfer processes to reduce ¹O2 generation, while the electrostatic interaction between ssDNA and TMB enhanced Tph‐BT's affinity for TMB to facilitate the electron transfer from TMB to •OH. This study investigates multitype mimetic enzyme activities of nonmetallic D‐A conjugated COFs and demonstrates their feasibility of regulation by ssDNA.

To ensure the long-term sustainable development of nuclear energy as well as the prevention and control of uranium pollution, new materials that can simultaneously detect and separate uranium are still urgently needed. Herein, a new fluorescent covalent organic polymer (COP), namely HT-COP-AO, was synthesized and employed as both the fluorescent probe and absorbent for simultaneous uranium detection and separation considering its excellent fluorescence property and strong uranium coordination ability. The results showed that the fluorescence of HT-COP-AO was quickly quenched by uranium within 2 minutes, and the limit of detection was 0.23 µM (3σ/K). Further studies implied that uranium was coordinated with the amidoxime groups of HT-COP-AO through U-N and O=U=O bonds, which resulted in electron transfer from uranium to HT-COP-AO and quenching the fluorescence of HT-COP-AO consequently. Meanwhile, HT-COP-AO exhibited excellent absorption ability towards uranium, and the maximum absorption capacity (qmax = 401.3 mg/g) was higher than most reported amidoxime modified materials. The HT-COP-AO also showed high selectivity for both uranium detection and separation which makes it a great promising for uranium monitoring in real water samples.

The elimination of anion is of great importance from radioactive nuclear waste containing ⁹⁹TcO4⁻ by rationally designing anion-scavenging materials with high density of charge and more accessible adsorption sites. Herein, a tailor-made cationic organic polymer with donor-acceptor (D-A) structure, namely TrDCPN, was successfully synthesized by rationally modifying the benzimidazole unit for efficient trapping the perrhenate (ReO4⁻) as a ⁹⁹Tc surrogate. Systematic control of the skeleton affect enables the material to integrate a variety of features, surmounting the long-term challenge of ⁹⁹TcO4⁻/ReO4⁻ remediation under extreme conditions of high acid/base and high ionic strength. Furthermore, the TrDCPN shows excellent affinity toward ReO4⁻ in the existence of large excess of competitive anions (SO4²⁻, NO3⁻ and PO4³⁻ etc.) as well as promising reusability for trapping ReO4⁻. The excellent stability and separation were derived from the introduction of large conjugated modules, triazine core and hydrophobic. More importantly, the synthetic cationic organic polymer with D-A feature was first proved that the introduction of halogen can effectively enhance the backbone charge, and increase the adsorption capacity by synergy of ion exchange, electrostatic interaction and δ hole-anion interaction. The adsorption capacity of TrDCPN can be up to 420.3 mg/g and reach equilibrium within 20 min. It is noteworthy that TrDCPN successfully immobilizes ReO4⁻ from simulated Hanford waste with a high separation efficiency of 93%, providing a new paradigm for material design to dispose of the problem of radioactive pollutants in the environment.

Tc is one of the most problematic nuclear fuel products due to its long half-life and high environmental mobility. Direct removal of TcO4⁻ from the highly alkaline solution of nuclear fuel is a serious and challenging environmental issue. In this work, the first efficient synthetic approach introducing halogens into a two-dimensional metal–organic framework, named Mn-MOF, is established using MnCl2·4H2O coordinating with neutral nitrogen-donor ligand, showing ultrahigh stability in alkaline aqueous even under 1 M NaOH. The luxuriant Mn-Cl bonds and ordered hydrophobic pore channels enable the Mn-MOF to have an efficient adsorption capacity for ReO4⁻ with a large capacity (403 mg g⁻¹), which is higher than most MOF adsorbents. More importantly, the Mn-MOF shows an excellent selectivity toward ReO4⁻ in high-density competitive anions, such as NO3⁻ and SO4²⁻. Moreover, the outstanding performance of Mn-MOF in removing ReO4⁻ endowed it successfully separated ReO4⁻ from the simulated Savannah River Site (SRS) high-level waste (HLW) stream with high removal of 66.84% at the phase ratio of 10. The adsorption mechanism is further demonstrated by FT-IR, XPS analysis, and DFT calculation, showing that the ReO4⁻ can selectively interact with Mn-Cl bonds and imidazole groups, forming unique halogen bonds Cl-O-Re, and a series of hydrogen bonds, respectively. This work suggests a new approach to the removal of TcO4⁻ from nuclear fuel. Graphical abstract

Graphene quantum dots (GQDs) have generated enormous excitement because of their superiority in facile preparation, good biocompatibility, and excellent optical properties. Besides their unique luminescence emission comparable to carbon dots (CDs) and other quantum dots (QDs), GQDs consist of a single atomic layer of nanosized graphite and demonstrate similar surface structure and crystal configuration to graphene favorable for their wide applications. This chapter summarizes recent progress on the strategies for preparation and structure tuning of GQDs, then discusses the main sensing mechanisms, and finally highlights new insights into their optical applications in chemosensing, biosensing, and bioimaging. Meanwhile, the challenges and future potential developments on GQDs are discussed and speculated.

Light-activated mimic oxidase is a promising alternative of natural enzyme, in which oxygen molecule is decomposed with the catalysis of mimic oxidases under light radiation and the corresponding substrates are oxidized without H2O2. However, most of the reported light activated nanozymes are metal oxides and carbon-based nanomaterials, and there is still much room for exploration of new kinds of light activated nanozymes and improvement in light absorption capacity and substrate selectivity to extent their applications. Covalent organic frameworks (COFs) are porous crystalline polymers and have been widely applied in photocatalysis due to the versatile chemical stability and extended π-conjugated framework. Herein, a new nitrogen-rich triazine-containing COF (TTA-Tp COF) was illustrated to exhibit light activated oxidase mimic activity. Under white LED irradiation, the oxidase-mimic activity of TTA-Tp COF was dramatically enhanced and the colorless solution visibly changed to blue within 10 minutes using 3, 3’, 5, 5’-tetramethylbenzydine (TMB) as substrate. Further study demonstrated that the enhanced oxidase-mimic activity might be accounted for the increased π-electron communication and light harvest efficiency ascribing from the fully conjugated feature of TTA-Tp COF, and thus TTA-Tp COF could be easily excited under visible light to generate reactive oxygen species (ROS) in the presence of dissolved oxygen which oxidized TMB to its oxidized blue product. As a mimic oxidase, TTA-Tp COF has the advantages of easy light control, excellent catalytic oxidation ability and good stability. Moreover, the light activated oxidase mimic activity of TTA-Tp COF was applied to visually detect captopril, and the linear range is 1.0 to 100.0 μM (R² = 0.992) with a detection limit of 0.78 μM (3σ/K). The TTA-Tp COF based colorimetric method also had a good selectivity, and the measured captopril concentration in captopril tablet was identical to that obtained by the standard method. Moreover, the spiked experiments for tablet samples and 100 folds diluted human serum samples received recoveries ranging from 91.9 to 105.6%, suggesting a high accuracy of the present TTA-Tp COF based colorimetric method.