The development of two-dimensional (2D) inorganic materials-based quantum dots (QDs) is still in its infancy but is triggering immense enthusiasm due to their high chemical stability, good aqueous ...dispersibility, excellent optical property, good biocompatibility and easy functionalization. This review covers almost all the extant 2D-QDs based on graphene, phosphorene, silicene, carbides, nitrides, transition metal dichalcogenide, transition metal oxides and MXenes,
etc.
Their categories, synthetic routes, properties, functionalization and applications are critically highlighted. In the application section, special emphasis is placed on the progress in bioimaging, cancer therapy, fluorescent sensing and optoelectronics. Meanwhile, the latest advances in 2D QDs-based catalysis and energy since 2015 are addressed. Moreover, 2D nanoclusters, in particular 2D-QDs, are also included. This review provides guidance for 2D-QDs studies to meet the increasing demands in the many diverse applications.
This review critically summarizes recent progress in the categories, synthetic routes, properties, functionalization and applications of 2D materials-based quantum dots (QDs).
Ca2+, a ubiquitous but nuanced modulator of cellular physiology, is meticulously controlled intracellularly. However, intracellular Ca2+ regulation, such as mitochondrial Ca2+ buffering capacity, can ...be disrupted by 1O2. Thus, the intracellular Ca2+ overload, which is recognized as one of the important cell pro‐death factors, can be logically achieved by the synergism of 1O2 with exogenous Ca2+ delivery. Reported herein is a nanoscale covalent organic framework (NCOF)‐based nanoagent, namely CaCO3@COF‐BODIPY‐2I@GAG (4), which is embedded with CaCO3 nanoparticle (NP) and surface‐decorated with BODIPY‐2I as photosensitizer (PS) and glycosaminoglycan (GAG) targeting agent for CD44 receptors on digestive tract tumor cells. Under illumination, the light‐triggered 1O2 not only kills the tumor cells directly, but also leads to their mitochondrial dysfunction and Ca2+ overload. An enhanced antitumor efficiency is achieved via photodynamic therapy (PDT) and Ca2+ overload synergistic therapy.
A multifunctional COF‐based nanoagent, which is equipped with BODIPY‐2I photosensitizer, CaCO3 nanoparticle, and glycosaminoglycan (GAG) targeting agent, can be a highly efficient and selective antitumor nanomedicine for colon tumor via photodynamic therapy (PDT) and Ca2+ overload synergistic therapy.
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Atomically dispersed metal catalysts with well‐defined structures have been the research hotspot in heterogeneous catalysis because of their high atomic utilization efficiency, outstanding activity, ...and selectivity. Dual‐atomic‐site catalysts (DASCs), as an extension of single‐atom catalysts (SACs), have recently drawn surging attention. The DASCs possess higher metal loading, more sophisticated and flexible active sites, offering more chance for achieving better catalytic performance, compared with SACs. In this review, recent advances on how to design new DASCs for enhancing energy catalysis will be highlighted. It will start with the classification of marriage of two kinds of single‐atom active sites, homonuclear DASCs and heteronuclear DASCs according to the configuration of active sites. Then, the state‐of‐the‐art characterization techniques for DASCs will be discussed. Different synthetic methods and catalytic applications of the DASCs in various reactions, including oxygen reduction reaction, carbon dioxide reduction reaction, carbon monoxide oxidation reaction, and others will be followed. Finally, the major challenges and perspectives of DASCs will be provided.
As an extension of single‐atom catalysts, dual‐atomic‐site catalysts (DASCs) with high metal loading, sophisticated and flexible active sites have aroused great interest. The recent development of DASCs in characterization, synthetic methods, and catalytic applications are reviewed.
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Potassium‐ion batteries (KIBs) are receiving increasing interest in grid‐scale energy storage owing to the earth abundant and low cost of potassium resources. However, their development still stays ...at the infancy stage due to the lack of suitable electrode materials with reversible depotassiation/potassiation behavior, resulting in poor rate performance, low capacity, and cycling stability. Herein, the first example of synthesizing single‐crystalline metallic graphene‐like VSe2 nanosheets for greatly boosting the performance of KIBs in term of capacity, rate capability, and cycling stability is reported. Benefiting from the unique 2D nanostructure, high electron/K+‐ion conductivity, and outstanding pseudocapacitance effects, ultrathin VSe2 nanosheets show a very high reversible capacity of 366 mAh g−1 at 100 mA g−1, a high rate capability of 169 mAh g−1 at 2000 mA g−1, and a very low decay of 0.025% per cycle over 500 cycles, which are the best in all the reported anode materials in KIBs. The first‐principles calculations reveal that VSe2 nanosheets have large adsorption energy and low diffusion barriers for the intercalation of K+‐ion. Ex situ X‐ray diffraction analysis indicates that VSe2 nanosheets undertake a reversible phase evolution by initially proceeding with the K+‐ion insertion within VSe2 layers, followed by the conversion reaction mechanism.
The first example of synthesizing single‐crystalline metallic graphene‐like VSe2 ultrathin nanosheets for greatly boosting the performance of potassium‐ion batteries in term of capacity, rate capability, and cycling stability is reported.
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Noble metal single atoms coordinated with highly electronegative atoms, especially N and O, often suffer from an electron‐deficient state or poor stability, greatly limiting their wide application in ...the field of catalysis. Herein we demonstrate a new PH3‐promoted strategy for the effective transformation of noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) at a low temperature (400 °C) into a class of thermally stabilized phosphorus‐coordinated metal single atoms (MPSAs) on g‐C3N4 nanosheets via the strong Lewis acid–base interaction between PH3 and the noble metal. Experimental work along with theoretical simulations confirm that the obtained Pd single atoms supported on g‐C3N4 nanosheets exist in the form of PdP2 with a novel electron‐rich feature, conceptionally different from the well‐known single atoms with an electron‐deficient state. As a result of this new electronic property, PdP2‐loaded g‐C3N4 nanosheets exhibit 4 times higher photocatalytic H2 production activity than the state‐of‐art N‐coordinated PdSAs supported on g‐C3N4 nanosheets. This enhanced photocatalytic activity of phosphorus‐coordinated metal single atoms with an electron‐rich state was quite general, and also observed for other active noble metal single atom catalysts, such as Ru and Rh.
Noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) on g‐C3N4 nanosheets can be transformed by reaction with PH3 into supported thermally stabilized phosphorus‐coordinated metal single atoms (MPSAs, M=Ru, Rh, Pd) at 400 °C. For Pd, the single‐atom catalytic sites exist as PdP2 with exceptional activity for the hydrogen evolution reaction.
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Iron–nitrogen–carbon (Fe–N–C) is hitherto considered as one of the most satisfactory alternatives to platinum for the oxygen reduction reaction (ORR). Major efforts currently are devoted to the ...identification and maximization of carbon‐enclosed FeN4 moieties, which act as catalytically active centers. However, fine‐tuning of their intrinsic ORR activity remains a huge challenge. Herein, a twofold activity improvement of pristine Fe–N–C through introducing Ti3C2Tx MXene as a support is realized. A series of spectroscopy and magnetic measurements reveal that the marriage of FeN4 moiety and MXene can induce remarkable Fe 3d electron delocalization and spin‐state transition of Fe(II) ions. The lower local electron density and higher spin state of the Fe(II) centers greatly favor the Fe dz2 electron transfer, and lead to an easier oxygen adsorption and reduction on active FeN4 sites, and thus an enhanced ORR activity. The optimized catalyst shows a two‐ and fivefold higher specific ORR activity than those of pristine catalyst and Pt/C, respectively, even exceeding most Fe–N–C catalysts ever reported. This work opens up a new pathway in the rational design of Fe–N–C catalysts, and reflects the critical influence of Fe 3d electron states in FeN4 moiety supported on MXene in ORR catalysis.
The marriage of the FeN4 moiety and MXene can induce remarkable Fe 3d electron delocalization and spin‐state transition of Fe(II) ions. Less local electron density and higher spin state of Fe(II) centers greatly favor the Fe dz2 electron transfer, and lead to an easier oxygen adsorption and reduction on active FeN4 sites, and thus an enhanced oxygen reduction reaction activity.
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Fiber‐shaped supercapacitors with improved specific capacitance and high rate capability are a promising candidate as power supply for smart textiles. However, the synergistic interaction between ...conductive filaments and active nanomaterials remains a crucial challenge, especially when hydrothermal or electrochemical deposition is used to produce a core (fiber)–shell (active materials) fibrous structure. On the other hand, although 2D pseudocapacitive materials, e.g., Ti3C2T
x
(MXene), have demonstrated high volumetric capacitance, high electrical conductivity, and hydrophilic characteristics, MXene‐based electrodes normally suffer from poor rate capability owing to the sheet restacking especially when the loading level is high and solid‐state gel is used as electrolyte. Herein, by hosting MXene nanosheets (Ti3C2T
x
) in the corridor of a scrolled carbon nanotube (CNT) scaffold, a MXene/CNT fiber with helical structure is successfully fabricated. These features offer open spaces for rapid ion diffusion and guarantee fast electron transport. The solid‐state supercapacitor based on such hybrid fibers with gel electrolyte coating exhibits a volumetric capacitance of 22.7 F cm−3 at 0.1 A cm−3 with capacitance retention of 84% at current density of 1.0 A cm−3 (19.1 F cm−3), improved volumetric energy density of 2.55 mWh cm−3 at the power density of 45.9 mW cm−3, and excellent mechanical robustness.
A host–guest hybrid fiber with helical structure is successfully fabricated by incorporating MXene nanosheets (Ti3C2T
x
) in the corridor of a scrolled carbon nanotube scaffold. A solid‐state supercapacitor based on such hybrid fibers with gel electrolyte coating exhibits improved volumetric capacitance with superior rate capability, improved volumetric energy density, and excellent mechanical robustness.
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Abstract
Organic-inorganic lead halide perovskites are a new class of semiconductor materials with great potential in photocatalytic hydrogen production, however, their development is greatly plagued ...by their low photocatalytic activity, instability of organic component and lead toxicity in particular. Herein, we report an anti-dissolution environmentally friendly Cs
2
SnI
6
perovskite anchored with a new class of atomically dispersed Pt-I
3
species (PtSA/Cs
2
SnI
6
) for achieving the highly efficient photocatalytic hydrogen production in HI aqueous solution at room temperature. Particularly, we discover that Cs
2
SnI
6
in PtSA/Cs
2
SnI
6
has a greatly enhanced tolerance towards HI aqueous solution, which is very important for achieving excellent photocatalytic stability in perovskite-based HI splitting system. Remarkably, the PtSA/Cs
2
SnI
6
catalyst shows a superb photocatalytic activity for hydrogen production with a record turnover frequency of 70.6 h
−1
per
Pt, about 176.5 times greater than that of Pt nanoparticles supported Cs
2
SnI
6
perovskite, along with superior cycling durability. Charge-carrier dynamics studies in combination with theory calculations reveal that the dramatically boosted photocatalytic performance on PtSA/Cs
2
SnI
6
originates from both unique coordination structure and electronic property of Pt-I
3
sites, and strong metal-support interaction effect that can not only greatly promote the charge separation and transfer, but also substantially reduce the energy barrier for hydrogen production. This work opens a new way for stimulating more research on perovskite composite materials for efficient hydrogen production.
Despite various 2H-MoS
2
/carbon hybrid nanostructures have been constructed and committed to improve the performance for sodium-ion batteries (SIBs), they still show the limited cycle stability due ...to the relatively large volumetric expansion during the charge–discharge process. Herein, we report the construction of cobalt-doped few-layered 1T-MoS
2
nanosheets embedded in N, S-doped carbon (CMS/NSC) nanobowls derived from metal-organic framework (MOF) precursor via a simple
in situ
sulfurization process. This unique hierarchical structure enables the uniformly dispersed Co-doped 1T-MoS
2
nanosheets intimately couple with the highly conductive carbon nanobowls, thus efficiently preventing the aggregation. In particular, the Co-doping plays a crucial role in maintaining the integrity of structure for MoS
2
during cycling tests, confirmed by first-principles calculations. Compared with pristine MoS
2
, the volume deformation of Co-doped MoS
2
can be shrunk by a prominent value of 52% during cycling. Furthermore, the few-layered MoS
2
nanosheets with 1T metallic phase endow higher conductivity, and thus can surpass its counterpart 2H semiconducting phase in battery performance. By virtue of the synergistic effect of stable structure, appropriate doping and high conductivity, the resulting CMS/NSC hybrid shows superior rate capability and cycle stability. The capacity of CMS/NSC can still be 235.9 mAh·g
−1
even at 25 A·g
−1
, which is 51.3% of the capacity at 0.2 A·g
−1
. Moreover, the capacity can still remain 218.6 mAh·g
−1
even over 8,240 cycles at 5 A·g
−1
with a low decay of 0.0044% per cycle, one of the best performances among the reported MoS
2
-based anode materials for SIBs.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The development of highly efficient photocatalytic systems with rapid photogenerated charge separation and high surface catalytic activity is highly desirable for the storage and conversion of solar ...energy, yet remains a grand challenge. Herein, a conceptionally new form of atomically dispersed Co–P3 species on CdS nanorods (CoPSA‐CdS) is designed and synthesized for achieving unprecedented photocatalytic activity for the dehydrogenation of formic acid (FA) to hydrogen. X‐ray absorption near edge structure, X‐ray photoelectron spectroscopy, and time‐resolved photoluminescence results confirm that the Co–P3 species have a unique electron‐rich feature, greatly improving the efficiency of photogenerated charge separation through an interface charge effect. The in situ attenuated total reflection infrared spectra reveal that the Co–P3 species can achieve much better dissociation adsorption of FA and activation of CH bonds than traditional sulfur‐coordinated Co single atom‐loaded CdS nanorods (CoSSA‐CdS). These two new features make CoPSA‐CdS exhibit the unprecedented 50‐fold higher activity in the photocatalytic dehydrogenation of FA than CoSSA‐CdS, and also much better activity than the Ru‐, Rh‐, Pd‐, or Pt‐loaded CdS. Besides, CoPSA‐CdS also shows the highest mass activity (34309 mmol gCo−1 h−1) of Co reported to date. First‐principles simulation reveals that the Co–P3 species herein can form an active PHCOO intermediate for enhancing the rate‐determining dissociation adsorption of FA.
Atomically dispersed Co–P3 species with electron‐rich feature loaded on CdS nanorods exhibit an unprecedented photocatalytic dehydrogenation activity (102.9 mmol gcatal−1 h−1) of formic acid (FA) through the effective dissociation adsorption of FA and activation of the CH bond in the CoP site, much better than noble metal Ru, Rh, Pd, or Pt nanoparticles.
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