Carbon dots (CDs) are known as the rising star of carbon-based nanomaterials and, by virtue of their unique structure and fascinating properties, they have attracted considerable interest in ...different fields such as biological sensing, drug delivery, photodynamic therapy, photocatalysis, and solar cells in recent years. Particularly, the outstanding electronic and optical properties of the CDs have attracted increasing attention in biomedical and photocatalytic applications owing to their low toxicity, biocompatibility, excellent photostability, tunable fluorescence, outstanding efficient up-converted photoluminescence behavior, and photo-induced electron transfer ability. This article reviews recent progress on the synthesis routes and optical properties of CDs as well as biomedical and photocatalytic applications. Furthermore, we discuss an outlook on future and potential development of the CDs based biosensor, biological dye, biological vehicle, and photocatalysts in this booming research field.
Two excited state proton transfer mechanisms of 3-hydroxyisoquinoline (3HIQ) in cyclohexane and acetic acid (ACID) were investigated based on the time-dependent density functional theory (TDDFT), ...suggesting a different double-proton transfer mechanism from the one proposed previously (
J. Phys. Chem. B
, 1998,
102
, 1053). Instead of the formation of keto-enol complexes for 3HIQ self-association in cyclohexane, our theoretical results predicted that 3HIQ self-association exists in two forms: the normal form (enol/enol) and the tautomer form (keto/keto) in cyclohexane. A high barrier (37.023 kcal mol
−1
) between the 3HIQ enol monomer and 3HIQ keto monomer form indicated that the 3HIQ keto monomer in the ground state should not exist. In addition, the constructed potential energy surfaces of the ground state and excited state have been used to explain the proton transfer process. Upon optical excitation, the enol/enol form is excited to the first excited state, then transfers one proton, in turn, transition to the ground state to transfer another proton. A relatively low barrier (8.98 kcal mol
−1
) demonstrates two stable structures in the ground state. In view of the acetic acid solvent effect, two protons of 3HIQ/ACID transfer along the dihydrogen bonds in the first excited state, which is a different transfer mechanism to 3HIQ self-association. In addition, the proton transfer process provides a possible explanation for the fluorescence quenching observed.
Two excited state proton transfer mechanisms of 3-hydroxyisoquinoline (3HIQ) in cyclohexane and acetic acid (ACID) were investigated.
A new sensor for determination of Ag
+
ion (Ag
+
) by surface-enhanced Raman scattering (SERS) is reported. Gold nanoparticles (AuNPs) and 4-aminodiphenyl disulfide (APDS) were chosen as the SERS ...substrate and probe molecule, respectively. With the addition of Ag
+
, three new peaks (1141, 1392, and 1435 cm
−1
) appeared in the SERS spectrum, indicating that the conversion of APDS to
p
,
p
′-dimercaptoazobenzene (DMAB) was achieved. As the concentration of Ag
+
increased, the conversion of APDS to DMAB also increased and showed a good linear relationship (
R
2
= 0.9746) in the range of 10 to 100 μM of Ag
+
. The limit of detection (LOD) was 7 μM. Compared with the traditional determination method, the SERS method is convenient and fast and requires no complicated preprocessing.
Graphical abstract
A highly stable electrochemical biosensor for pesticide detection was developed. For the first time polymeric ionic liquids (PILs) were introduced to construct an acetylcholinesterase (AChE) ...biosensor . AChE was entrapped in PILs microspheres through an emulsion polymerization reaction, where negatively charged Au nanoparticles (Au NPs) can be immobilized by the positively charged PILs, leading to improved catalytic performance. The results suggest that the positively charged PILs not only provide a biocompatible microenvironment around the enzyme molecule, stabilizing its biological activity and preventing its leakage, but also act as a modifiable interface allowing other components with electron transport properties to be loaded onto the polymer substrate, thus providing an efficient electron transport channel for the entrapped enzyme. More notably, when AChE was immobilized in a positively charged environment, the active site is closer to the electrode, promoting faster electron transfer. The detection limits of the constructed electrochemical biosensor AChE@PILs@Au NPs/GCE toward carbaryl and dichlorvos (DDVP) were 5.0 × 10
−2
ng ml
−1
and 3.9 × 10
−2
ng ml
−1
, in a wide linear range of 6.3 × 10
−2
–8.8 × 10
2
ng ml
−1
and 1.3 × 10
−1
–1.4 × 10
3
ng ml
−1
, respectively. More importantly, the biosensor has high thermal and storage stability, which facilitates rapid field analysis of fruits and vegetables in a variety of climates. In addition, the biosensor reported has good repeatability and selectivity and has high accuracy in the analysis of peaches, tap water, and other types of samples.
Graphical abstract
Formal regiodivergent C-H alkynylation of 1-aryl-5-pyrazolones has been realized under the catalysis of Rh(iii) and Au(i) complexes by using a hypervalent iodine reagent as the alkyne source. ...Mechanistic studies indicate that the regioselectivity is ascribed to not only the choice of the catalyst but also the nature of the substrate. The substrate scope and functional group compatibility have been fully examined.
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•A series of acidic catalysts based on rGO were designed for desulfurization.•Different acidic anions could be sequentially ‘written in’ and ‘erased’ on rGO.•Screening of catalysts ...could be achieved via the rewriteable cycle.•The interfacial desulfurization mechanism of acidic rGO was investigated.•PolyViEtImPW12O40-rGO exhibits excellent catalytic performance and reusability.
A new type of graphene-based catalyst with rewriteable function was designed and synthesized based on poly(1-vinyl-3-ethylimidazolium bromide) modified and reduced graphene oxide (denoted as polyViEtImBr-rGO). The modified polymeric ionic liquid polyViEtImBr not only acted as interlink between the polar catalytic anion and the non-polar graphene substrate, but also endowed the favorable dispersibility of polyViEtImBr-rGO in ionic liquid, leading to the adequate exposure of immobilized catalytic sites during the process of desulfurization. Moreover, due to the reversible anion-exchange property of the modified polyViEtImBr, various anions of Brønsted acids or heteropolyacids could be sequentially ‘written in’ or ‘erased’ on the nanosheets of rGO for desulfurization, thus establishing a green model for screening suitable catalysts based only on the limits of the same carrier. Such a rewriteable cycle was confirmed and monitored by characterization of TEM, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). Based on this catalyst screening process of a rewriteable cycle, polyViEtImPW12O40-rGO, a heteropolyanoin modified rGO, was selected as the optimized catalyst. Benefiting from the synergistic effects between rGO and acidic anions, together with the large surface area and open two-dimensional structure of rGO, polyViEtImPW12O40-rGO was found to exhibit an excellent catalytic performance toward various sulfur-containing compounds. Furthermore, the outstanding reusability of polyViEtImPW12O40-rGO was also displayed owing to its structural stability. It was found that the sulfur removal efficiency of DBT could still reach 98.0% after the catalyst polyViEtImPW12O40-rGO had even been recycled eight times.
A new type of catalyst was synthesized by immobilizing heteropolyacid on ionic liquid-modified mesostructured cellular silica foam (denoted as MCF) and applied to the oxidative desulfurization of ...fuel. The surface morphology and structure of the catalyst were characterized by XRD, TEM, N
adsorption-desorption, FT-IR, EDS and XPS analysis. The catalyst exhibited good stability and desulfurization for various sulfur-containing compounds in oxidative desulfurization. Heteropolyacid ionic liquid-based MCF solved the shortage of the amount of ionic liquid and difficult separation in the process of oxidative desulfurization. Meanwhile, MCF had a special three-dimensional structure that was not only highly conducive to mass transfer but also greatly increased catalytic active sites and significantly improved catalytic efficiency. Accordingly, the prepared catalyst of 1-butyl-3-methyl imidazolium phosphomolybdic acid-based MCF (denoted as BMIM
PMo
O
-based MCF) exhibited high desulfurization activity in an oxidative desulfurization system. The removal of dibenzothiophene could achieve levels of 100% in 90 min. Additionally, four sulfur-containing compounds could be removed completely under mild conditions. Due to the stability of the structure, sulfur removal efficiency still reached 99.8% after the catalyst was recycled six times.
Photoelectrochemical (PEC) water splitting is a promising method for the conversion and storage of solar energy. A combination of catalysts with photoelectrodes is generally required for the ...development of active photoanodes in PEC devices. In this work, we present two BiVO4 photoanodes modified with cobalt salophen (Co(salophen)) complexes for PEC water oxidation. The resulting photoanodes show significantly enhanced PEC performance. Under simulated sunlight illumination (AM 1.5G, 100 mW cm−2), high photocurrents of 3.89 mA cm−2 and 4.27 mA cm−2 were obtained for Co1/BiVO4 and Co2/BiVO4, respectively at 1.23 V (vs. the reversible hydrogen electrode (RHE)) in a neutral solution, an almost three-fold enhancement over that of the unmodified BiVO4. Intensity-modulated photocurrent spectroscopy (IMPS) analysis shows that the Co(salophen) complexes not only accelerate the water oxidation reaction but also reduce the surface recombination. The half-cell solar energy conversion efficiencies for Co1/BiVO4 and Co2/BiVO4 were 1.09% and 1.18% at 0.7 V, respectively. Due to their hydrophobic nature, the Co(salophen) complexes can bind strongly to the surface of BiVO4. When the Co2 complex featuring four hydrophobic tert-butyl groups in a salophen ligand was anchored to BiVO4, an extremely stable photocurrent of more than 3.5 mA cm−2 at 1.23 V vs. RHE is sustained for at least 3 h without decay. Such a stable and robust photoanode based on a molecular WOC surpasses those attained by most of the state-of-the-art heterogeneous catalysts.
Heavy metals have been widely applied in industry, agriculture, and other fields because of their outstanding physics and chemistry properties. However, heavy metal pollution is inevitable in the ...process of mass production and emission. Heavy metal ions will cause irreversible harm to the human body and other organisms due to their nondegradable nature even at low concentrations of exposure and ingestion. Therefore, it is of great significance for human health and ecological environment to develop high accuracy and sensitivity as well as stable techniques for detecting heavy metal ions. In recent years, surface-enhanced Raman scattering (SERS) spectroscopy has been regarded as a promising new technique for the determination of trace heavy metal ions on account of its special fingerprint identification capability, high sensitivity, rapid detection ability, and simple operation. This review summarized in detail the basic principles and strategies for detecting mercury ions, copper ions, arsenic ions, zinc ions, cadmium ions, lead ions, and chromium (VI) ions as well as the current challenges and future trends for the determination of heavy metal ions based on SERS technology.
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