Research Article Issue
Luminescence modulation of ultrasmall gold clusters by aromatic ligands
Nano Research 2023, 16 (8): 11366-11374
Published: 22 June 2023

Luminescence is one of the most important properties for metal nanoclusters; however, clearly revealing its origin remains challenging. The different luminescence properties of the two prototypical 8e nanoclusters Au11 and Au13 remain elusive—Au11 is always nonluminescent, whereas Au13 is luminescent. In this work, by using a designed unique aromatic ligand (quinoline-2-thiol), we obtained new atomically precise phosphine-thiolate-protected neutral Au11-SH and cationic Au13-SH. In comparison with the classic phosphine-halide-protected Au11-Cl and Au13-Cl, the Cl-to-thiol alteration triggered room-temperature luminescence of the Au11 core and dramatically modulated that of the Au13 core. Ultrafast ultraviolet/infrared (UV/IR) spectroscopy, which is sensitive to organic aromatic groups, together with ultrafast transient absorption (TA) spectroscopy unprecedently revealed a relaxation process from the ligand to core state affecting the dynamics in excited states and some critical intermediate states favouring efficient room-temperature emission of these nanoclusters. This work provides some new insights into the origin of photoluminescence of metal nanoclusters and opens an avenue to modulate the dynamics of their excited states using aromatic ligands, which would have direct applications in lighting, light harvesting, and photocatalysis.

Research Article Issue
Enhancement of visible-light-driven oxidative amine coupling under aerobic and anaerobic conditions by photocatalyst with spatial separation of photoinduced charge carriers
Nano Research 2023, 16 (4): 4715-4722
Published: 23 November 2022

Spatial separation of oxidation/reduction cocatalyst is an effective means to improve the efficiency of charge separation in photocatalytic reaction systems. Herein, a yolk–shell Pd@NH2-UiO-66@Cu2O heterojunction was designed and synthesized by integration of electron collector Pd and hole collector Cu2O inside and outside of a photoactive metal-organic framework (MOF) NH2-UiO-66, respectively. The obtained Pd@NH2-UiO-66@Cu2O heterojunction effectively inhibits the electron and hole recombination through the photo-induced electrons and holes flow inward and outward of the composite, and promotes the reduction and oxidation abilities for the oxidative coupling of benzylamine to imines. Compared with Pd/NH2-UiO-66@Cu2O, Pd@NH2-UiO-66, and Pd/NH2-UiO-66, Pd@NH2-UiO-66@Cu2O exhibits the highest photocatalytic activity. More importantly, Pd@NH2-UiO-66@Cu2O shows a conversion rate of benzylamine up to 99% either by oxidation under aerobic conditions or by strong adsorption of H atom (Hads) under anaerobic conditions. In addition, the catalyst shows good stability and can be recycled at least ten times. This work provides useful guidance on construction of MOFs-based composites with spatially separated photoinduced charge carriers to realize efficient oxidation coupling of benzylamine in both aerobic and anaerobic conditions.

Communication Issue
Conducting polymer-functionalized mesoporous metal-organic frameworks for high-performance Li-S battery
Nano Research 2023, 16 (4): 4867-4873
Published: 28 October 2022

It was known that mesoporous metal-organic frameworks (MOFs) with hierarchical pores and unsaturated metal sites can effectively inhibit the shuttle effect of lithium polysulfides in lithium-sulfur battery, however, the unsatisfactory structural stability and electrical conductivity limit the application of mesoporous MOFs (MMOFs) in Li-S batteries. Aiming at sensible solutions, the conductive polyaniline (PANI) was incorporated into the MMOF to enhance the discharge capacity and the cycling stability of proposed Li-S batteries, as the stability and the conductivity of the MMOF cathode was improved simultaneously. The activated MMOF-PANI provides physical and chemical adsorption of polysulfides against their shuttle effect. Moreover, the introduction of PANI into the channels of MMOF effectively improves the conductivity of MMOF, thus improving the electrochemical performance of the MMOF-PANI-based batteries. Benefiting from these synergetic effects, the S@MMOF-PANI cathode delivers improved electrochemical performance including excellent rate performance and cycling stability. The battery shows an initial capacity of 777.7 mAh·g−1 at 2.0 C and a low decay rate of 0.06% per cycle in 1,000 cycles and approximately a repeatable rate performance.

Research Article Issue
Sub-2 nm IrO2/Ir nanoclusters with compressive strain and metal vacancies boost water oxidation in acid
Nano Research 2023, 16 (1): 334-342
Published: 02 September 2022

IrO2 exhibits good stability but limited electrocatalytic activity for oxygen evolution reaction in acid. Defect engineering is an effective strategy to improve the intrinsic ability of electrocatalysts by tailoring their electronic structure. Herein, we have successfully synthesized IrO2/Ir heterophase with compressive strain and metal vacancies via a simple substitution-etching method. In virtue of the solubility of Cr in strong alkali, metal vacancies could be formed at surface after etching Cr-doped IrO2/Ir in alkali, which leaded to modulated electronic structure. Meanwhile, the substitution of Cr with smaller atom radius would induce the formation of compressive strain and the relocated atoms made the d-band center shifted. With the regulated electronic structure and tuned d-band center, the obtained electrocatalyst only needed 285 mV to reach 10 mA·cm−2 in 0.1 M HClO4. Reaction kinetic has been rapidly accelerated as indicated by the smaller Tafel slope and charge transfer resistance. Theoretical calculations revealed that the d-band center and charge density distribution have been regulated with the introduction of defects in IrO2/Ir, which significantly decreased the free energy barrier of rate determining step. This work provides a valuable reference to design effective and defects-rich electrocatalysts.

Research Article Issue
Rational designed isostructural MOF for the charge–discharge behavior study of super capacitors
Nano Research 2022, 15 (7): 6208-6212
Published: 10 May 2022

In recent years, the rapid charge–discharge property of super capacitors based on metal-organic frameworks (MOFs) has seen excellent applications in energy storage equipment. However, the purposeful design of high-performance electrodes for MOF-derived super capacitors is still an urgent problem that needs to be solved. Herein, we rationally design and prepare three MOFs with the same crystal configuration and controllable functional groups. Through the combination of rigorous experiment and calculation, we have verified the effects of the specific surface area of the electrode material as well as the binding energy between the electrode material and the electrolyte ions on the performance of the super capacitor. This work not only extends the application of MOFs, but also provides a model-material platform for the study of charge–discharge behavior of MOF-based super capacitors, creating a way of thinking for the selection and design of MOF materials for energy storage applications.

Research Article Issue
An efficient and versatile biopolishing strategy to construct high performance zinc anode
Nano Research 2022, 15 (6): 5081-5088
Published: 19 March 2022

Conventional strategies for highly reversible Zn anodes usually involve complex and time-consuming production processes of current collectors, expensive and toxic electrolyte additives, or the introduction of inactive materials in protective layer. Here, we develop a fast, facile, and environmentally friendly biopolishing method to prepare dendrite-free Zn anodes, which merely involves the simple immersion of Zn foil in a biocompatible cysteine aqueous solution. The ravine structure formed by sulfhydryl etching for 30 min not only increases the electroactive area of Zn anode but also regulates the distribution of electric field and Zn ions, ensuring the homogeneous deposition and stripping of Zn ions. The biopolished Zn anode can be operated steadily for 2,000 h with a low voltage hysteresis at a current density of 1 mA·cm−2. In addition, Zn anodes with a cycle life of 500 h can be built by soaking for only 5 min, proving the high efficiency of the proposed method. This strategy is generalized to substances with sulfhydryl groups for polishing Zn electrodes with improved performance. The cysteine-polished Zn//activated carbon supercapacitor can stably run for 20,000 cycles without obvious capacity attenuation. The proposed strategy shows potential for producing advanced Zn anodes.

Research Article Issue
Layer-by-layer alloying of NIR-II emissive M50 (Au/Ag/Cu) superatomic nanocluster
Nano Research 2022, 15 (6): 5569-5574
Published: 10 March 2022

The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters. However, the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters (NCs) has long been a challenging pursuit. In this work, two novel alloy nanoclusters [PPh4]4[Ag32Cu18(PFBT)36] ((AgCu)50) and [PPh4]4[Au12Ag20Cu18(PFBT)36] (Au12(AgCu)38), where PFBT is pentafluorobenzenethiolate, with shell-by-shell configuration of M12@Ag20@Cu18(PFBT)36 (M = Ag/Au) were synthesized by a facile one-pot co-reduction method. Notably, a fingerprint library of [Ag50−xCux(PFBT)36]4− (x = 0 to 50) from Ag50 to Cu50 has been successfully established as revealed by electrospray ionization mass spectrometry. Single-crystal X-ray diffraction analysis of trimetallic Au12(AgCu)38 confirmed the layer-by-layer alloying under reducing conditions. What is more, (AgCu)50 and Au12(AgCu)38 both show broad photoluminescence (PL) peak in the second near-infrared (NIR-II) window, and the Au doping in the innermost shell considerably enhances the photoluminescence intensity. This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.

Research Article Issue
Evolution of all-carboxylate-protected superatomic Ag clusters confined in Ti-organic cages
Nano Research 2021, 14 (7): 2309-2313
Published: 05 July 2021

In this study, the size of the titanium organic cage was controlled to achieve the restricted growth from a single Ag(I) atom (Ag@Ti5) to rare all-carboxylate-protected superatomic Ag cluster (Ag6@Ti6). The classical octahedral Ag64+ cluster with two delocalized electrons (2e) has been encapsulated in a Ti6 organic cage, which shows high stability in air and dimethyformamide (DMF). Furthermore, larger 2e nested double-tetrahedra Ag clusters (Ag86+ and Ag97+) protected using a tetrahedral hollow metalloligand framework (Ag8@Ti4 and Ag9@Ti4) were obtained. Electrospray ionization mass spectrometry (ESI-MS) and density functional theory (DFT) calculations confirmed that there are two delocalized electrons on these small Ag clusters. This study provides a new form of protection for superatomic Ag clusters and provides a feasible strategy for the development of stable Ag clusters.

Research Article Issue
Intercluster aurophilicity-driven aggregation lighting circularly polarized luminescence of chiral gold clusters
Nano Research 2020, 13 (12): 3248-3252
Published: 25 August 2020

Herein, we prepared two novel pairs of enantiomeric gold cluster complexes, Au4PL4/Au4PD4 and (Au4L4)n/(Au4D4)n with atomic precision. In Au4PL4/Au4PD4, the discrete chiral Au4-based aggregation-induced emission (AIE) luminogens are separated by bulky substitutes. The corresponding aggregates are cyan-emitting with a photoluminescence quantum yield (PLQY) of 14.4%. Upon decreasing the size of the substituents, these chiral Au4 clusters are strung together by inter-cluster Au-Au interactions, which cause a low-energy green emission from the aggregated (Au4L4)n/(Au4D4)n with a much higher PLQY of 41.4% and more intense circularly polarised photoluminescence (CPL) with a dissymmetry factor |gPL| of 7.0 × 10-3. Using (Au4L4)n/(Au4D4)n, circularly polarised organic light-emitting diodes (CP-OLEDs) were for the first time fabricated with |gEL| = |gPL|. These findings signify that inter-cluster metallophilic interactions are a new and important type of driving force for AIE and crystallization-induced emission (CIE), suggesting great potential of CPL-active metal clusters in CP-OLEDs.

total 9