Publications by authors named "Jiannian Yao"

259 Publications

Photonic skins based on flexible organic microlaser arrays.

Sci Adv 2021 Jul 30;7(31). Epub 2021 Jul 30.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

Flexible photonics is rapidly emerging as a promising platform for artificial smart skins to imitate or extend the capabilities of human skins. Organic material systems provide a promising avenue to directly fabricate large-scale flexible device units; however, the versatile fabrication of all-organic integrated devices with desired photonic functionalities remains a great challenge. Here, we develop an effective technique for the mass processing of organic microlaser arrays, which act as sensing units, on the chip of photonic skins. With a bilayer electron-beam direct writing method, we fabricated flexible mechanical sensor networks composed of coupled-cavity single-mode laser sources on pliable polymer substrates. These microlaser-based mechanical sensor chips were subsequently used to recognize hand gestures, showing great potential for artificial skin applications. This work represents a substantial advance toward scalable construction of high-performance and low-cost flexible photonic chips, thus paving the way for the implementation of smart photonic skins into practical applications.
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http://dx.doi.org/10.1126/sciadv.abh3530DOI Listing
July 2021

Lanthanide MOFs for inducing molecular chirality of achiral stilbazolium with strong circularly polarized luminescence and efficient energy transfer for color tuning.

Chem Sci 2020 Aug 4;11(34):9154-9161. Epub 2020 Aug 4.

Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China

We present herein an innovative host-guest method to achieve induced molecular chirality from an achiral stilbazolium dye (DSM). The host-guest system is exquisitely designed by encapsulating the dye molecule in the molecule-sized chiral channel of homochiral lanthanide metal-organic frameworks (-(+)/-(-)-TbBTC), in which the - or -configuration of the dye is unidirectionally generated a spatial confinement effect of the MOF and solidified by the dangling water molecules in the channel. Induced chirality of DSM is characterized by solid-state circularly polarized luminescence (CPL) and micro-area polarized emission of [email protected], both excited with 514 nm light. A luminescence dissymmetry factor of 10 is obtained and the photoluminescence quantum yield (PLQY) of the encapsulated DSM in [email protected] is ∼10%, which is close to the PLQY value of DSM in dilute dichloromethane. Color-tuning from green to red is achieved, owing to efficient energy transfer (up to 56%) from Ln to the dye. Therefore, this study for the first time exhibits an elegant host-guest system that shows induced strong CPL emission and enables efficient energy transfer from the host chiral Ln-MOF to the achiral guest DSM with the emission color tuned from green to red.
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http://dx.doi.org/10.1039/d0sc02856hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8163402PMC
August 2020

Room temperature exciton-polariton Bose-Einstein condensation in organic single-crystal microribbon cavities.

Nat Commun 2021 Jun 1;12(1):3265. Epub 2021 Jun 1.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.

Exciton-polariton Bose-Einstein condensation (EP BEC) is of crucial importance for the development of coherent light sources and optical logic elements, as it creates a new state of matter with coherent nature and nonlinear behaviors. The demand for room temperature EP BEC has driven the development of organic polaritons because of the large binding energies of Frenkel excitons in organic materials. However, the reliance on external high-finesse microcavities for organic EP BEC results in poor compactness and integrability of devices, which restricts their practical applications in on-chip integration. Here, we demonstrate room temperature EP BEC in organic single-crystal microribbon natural cavities. The regularly shaped microribbons serve as waveguide Fabry-Pérot microcavities, in which efficient strong coupling between Frenkel excitons and photons leads to the generation of EPs at room temperature. The large exciton-photon coupling strength due to high exciton densities facilitates the achievement of EP BEC. Taking advantages of interactions in EP condensates and dimension confinement effects, we demonstrate the realization of controllable output of coherent light from the microribbons. We hope that the results will provide a useful enlightenment for using organic single crystals to construct miniaturized polaritonic devices.
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http://dx.doi.org/10.1038/s41467-021-23524-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8169864PMC
June 2021

High-Lying 3A Dark-State-Mediated Singlet Fission.

J Am Chem Soc 2021 Apr 12;143(15):5691-5697. Epub 2021 Apr 12.

Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, China.

Singlet fission (SF), the conversion of one high-energy singlet to two low-energy triplets, provides the potential to increase the efficiency of photovoltaic devices. In the SF chromophores with symmetry, exemplified by polyenes, singlet-to-triplet conversion generally involves a low-lying 2A dark state, which serves as either a multiexciton (ME) intermediate to promote the SF process or a parasitic trap state to shunt excited-state populations via internal conversion. This controversial behavior calls for a deep understanding of dark-state-related photophysics involving the higher-lying singlet state. However, the optical "dark" and "transient" nature of these dark states and strong correlation feature of double exciton species make their characterization and interpretation challenging from both experimental and computational perspectives. In the present work combining transient spectroscopy and multireference electronic structure calculations (XDW-CASPT2), we addressed a new photophysical model, i.e., a high-lying 3A dark-state-mediated ultrafast SF process in the benzodipyrrolidone (BDPP) skeleton. Such a 3A dark state with distinctive double excitation character, described as the ME state, could be populated from the initial 1B bright state on an ultrafast time scale given the quasi-degeneracy and intersection of the two electronic states. Furthermore, the suitable optical band gap and triplet energy, high triplet yield, and excellent photostability render BDPP a promising SF candidate for photovoltaic devices. These results not only enrich the arsenal of SF materials but also shed new insights into the understanding of dark-state-related photophysics, which could promote the development of new SF-active materials.
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http://dx.doi.org/10.1021/jacs.0c11681DOI Listing
April 2021

Full-Color and White Circularly Polarized Luminescence of Hydrogen-Bonded Ionic Organic Microcrystals.

Angew Chem Int Ed Engl 2021 Jun 14;60(26):14595-14600. Epub 2021 May 14.

Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.

A simple and general method is presented herein for the in situ preparations of circularly polarized luminescence (CPL)-active microcrystals with a large luminescence dissymmetry factor g , high fluorescence quantum efficiency (Φ ), wide emission color tenability, and well-ordered morphology. The reactions of pyridine-containing achiral molecules 1-7 with chiral camphor sulfonic acid ((±)-CSA) gave crystalline microplates formed by hydrogen bonding interactions between the protonated pyridinium units and the sulfonic anions. The chiral information of CSA are effectively transferred to the microcrystals by hydrogen bonding to afford full-color CPL from deep-blue to red with g in the order of 10 and Φ up to 80 %. Moreover, organic microcrystals with high-performance white CPL (Φ =46 %; |g |=0.025) are achieved via the light-harvesting energy transfer between blue and yellow emitters.
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http://dx.doi.org/10.1002/anie.202103091DOI Listing
June 2021

Superkinetic Growth of Oval Organic Semiconductor Microcrystals for Chaotic Lasing.

Adv Mater 2021 May 30;33(18):e2100484. Epub 2021 Mar 30.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.

Synthesis of novel mesoscopic semiconductor architectures continually generates new photonic knowledge and applications. However, it remains a great challenge to synthesize semiconductor microcrystals with smoothly curved surfaces owing to the crystal growth anisotropy. Here, a superkinetic crystal growth method is developed to synthesize 2D oval organic semiconductor microcrystals. The solid source dispersion induces an exceptionally large molecular supersaturation for vapor deposition, which breaks the crystal growth anisotropy. The synthesized stadium-shaped organic semiconductor microcrystals naturally constitute fully chaotic optical microresonators. They support low-threshold lasing on high-quality-factor scar modes localized near the stadium boundary and directional laser emission assisted by the chaotic modes. These results will reshape the understanding of the crystal growth theory and provide valuable guidance for crystalline photonic materials design.
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http://dx.doi.org/10.1002/adma.202100484DOI Listing
May 2021

A mono-copper doped undeca-gold cluster with up-converted and anti-stokes emissions of fluorescence and phosphorescence.

Nanoscale 2021 Mar;13(10):5300-5306

Beijing National Laboratory for Molecular Sciences (BNLMS) and State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100090, China.

We have synthesized single crystals of a highly stable Cu-doped undeca-gold cluster protected by both triphenylphosphine (PPh3) and 2-pyridinethiol (-SPy) ligands, formulated as [Au11Cu1(PPh3)7(SPy)3]+. This cluster (Au11Cu1 NCs for short) has a metallic core of C3v [email protected] with the Cu atom capped on one of the nine triangular facets and it is triply-coordinated to three N atoms of the SPy ligands of which the sulfur atom simultaneously binds to three adjacent Au atoms via singly-coordinated S-Au bonds, respectively. The other seven gold atoms form a crown structure by a link of three orthogons with common sides and are protected by seven PPh3 ligands. Besides the well-organized coordination, this Au11Cu1 nanocluster is demonstrated to exhibit superatom stability of the metallic core within 8 valence electrons (assuming that the 3 electrophilic-SPy ligands capture 3 electrons from the metal center). More interestingly, this Au11Cu1 nanocluster shows interesting emissions in both ultraviolet visible (UV-Vis) and near infrared (NIR) regions, and the emissions display novel anti-Stokes up-conversion lasing characteristics. TD-DFT calculated UV-vis and emission spectra well reproduce the experimental results, shedding light on the nature of excitation states and underlying mechanism of electronic transitions between diverse energy levels of such a monolayer-protected bimetallic cluster.
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http://dx.doi.org/10.1039/d0nr07624dDOI Listing
March 2021

Wavelength-Tunable Single-Mode Microlasers Based on Photoresponsive Pitch Modulation of Liquid Crystals for Information Encryption.

Research (Wash D C) 2020 2;2020:6539431. Epub 2020 Dec 2.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

Information encryption and decryption have attracted particular attention; however, the applications are frequently restricted by limited coding capacity due to the indistinguishable broad photoluminescence band of conventional stimuli-responsive fluorescent materials. Here, we present a concept of confidential information encryption with photoresponsive liquid crystal (LC) lasing materials, which were used to fabricate ordered microlaser arrays through a microtemplate-assisted inkjet printing method. LC microlasers exhibit narrow-bandwidth single-mode emissions, and the wavelength of LC microlasers was reversibly modulated based on the optical isomerization of the chiral dopant in LCs. On this basis, we demonstrate phototunable information authentication on LC microlaser arrays using the wavelength of LC microlasers as primary codes. These results provide enlightenment for the implementation of microlaser-based cryptographic primitives for information encryption and anticounterfeiting applications.
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http://dx.doi.org/10.34133/2020/6539431DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7877376PMC
December 2020

Nontrivial band geometry in an optically active system.

Nat Commun 2021 Jan 29;12(1):689. Epub 2021 Jan 29.

Institut Pascal, PHOTON-N2, Université Clermont Auvergne, CNRS, SIGMA Clermont, F-63000, Clermont-Ferrand, France.

Optical activity, also called circular birefringence, is known for two hundred years, but its applications for topological photonics remain unexplored. Unlike the Faraday effect, the optical activity provokes rotation of the linear polarization of light without magnetic effects, thus preserving the time-reversal symmetry. In this work, we report a direct measurement of the Berry curvature and quantum metric of the photonic modes of a planar cavity, containing a birefringent organic microcrystal (perylene) and exhibiting emergent optical activity. This experiment, performed at room temperature and at visible wavelength, establishes the potential of organic materials for implementing non-magnetic and low-cost topological photonic devices.
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http://dx.doi.org/10.1038/s41467-020-20845-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7846789PMC
January 2021

Singlet Fission in a -Azaquinodimethane-Based Quinoidal Conjugated Polymer.

J Am Chem Soc 2020 Oct 12;142(42):17892-17896. Epub 2020 Oct 12.

Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, China.

The exploitation of singlet fission (SF) in photovoltaic devices is restricted by the limited number of SF materials available and the conflicting requirement of intermolecular interactions to satisfy both efficient SF and subsequent triplet extraction. Intramolecular SF (iSF) represents an emerging alternative and may prove simpler to implement in devices. On account of the excellent chemical structure tunability and solution processability, conjugated polymers have emerged as promising candidates for iSF materials despite being largely underexplored. It remains a significant challenge to develop SF-capable conjugated polymers and achieve efficient dissociation of the formed triplet pairs simultaneously. In this contribution, we present a new iSF material in a -azaquinodimethane-based quinoidal conjugated polymer. Using transient optical techniques, we show that an ultrafast iSF process dominates the deactivation of the excited state in such polymer, featuring ultrafast population (<1 ps) and stepwise dissociation of triplet pairs. Notably, these multiexciton states could further diffuse apart to produce long-lived free triplets (tens of μs) in strongly coupled aggregates in solid thin film. Such findings not only introduce a new iSF-active conjugated polymer to the rare SF material family but also shed unique insight into interchain interaction-promoted triplet pair dissociation in aggregates of conjugated polymers, thus openning new avenues for developing next-generation SF-based photovoltaic materials.
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http://dx.doi.org/10.1021/jacs.0c06604DOI Listing
October 2020

Efficient Bosonic Condensation of Exciton Polaritons in an H-Aggregate Organic Single-Crystal Microcavity.

Nano Lett 2020 Oct 2;20(10):7550-7557. Epub 2020 Oct 2.

Institute of Molecular Plus, School of Chemical Engineering and Technology, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, People's Republic of China.

Although organic polariton condensation has been recently demonstrated, they only utilize the photon part of polaritons and ignore the excitonic contribution because the polariton-polariton and polariton-reservoir interactions are weak in organic microcavities owing to the absence of Coulomb exchange-interactions between Frenkel excitons. We demonstrate highly efficient and strongly polarization-dependent polariton condensates in a microcavity consisting of an H-aggregate organic single-crystalline microbelt sandwiched between two silver reflectors. Benefitting from the advantages of vibronic coupling in H-aggregates and heavy exciton-like polaritons, both macroscopic coherent polariton ground-state population and high-energy quantized-modes are observed. The measurements are qualitatively reproduced based on simulations of the spatiotemporal polariton dynamics. The observation of low threshold polariton lasing, the ease of fabrication, and the potential for efficient electronic charge injection make microcrystals of organic semiconductors attractive candidates for continuous wave and electrically pumped functional photonic polariton circuits and organic polariton lasers, operating at room temperature.
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http://dx.doi.org/10.1021/acs.nanolett.0c03009DOI Listing
October 2020

Breaking Kasha's Rule as a Mechanism for Solution-Phase Room-Temperature Phosphorescence from High-Lying Triplet Excited State.

J Phys Chem Lett 2020 Oct 17;11(19):8246-8251. Epub 2020 Sep 17.

Institute of Molecule Plus, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China.

Organic room-temperature phosphorescence (ORTP) has been demonstrated successfully in solids. In contrast, solution-phase ORTP is rarely achieved, because the T → S phosphorescence is too slow to compete against nonradiative decay and the oxygen-quenching effect. Here, we reported that suppression of Kasha's rule is a strategy to achieve solution-phase ORTP from the high-lying T state by spatially separating T and T on different parts of the molecule (CzCbDBT) composed of carbonyl (Cb), dibenzothiophene (DBT), and carbazole moiety (Cz). On one hand, intersystem crossing (ISC) is much faster from S to T than that to T, owing to the small energy-gap Δ and large spin-orbital coupling ξ. On the other hand, T → T internal conversion is inhibited owing to spatial separation, i.e., T on CbDBT and T on Cz, respectively. Also, combination of very fast radiative decay from T to S owing to large ξ, the efficient solution-phase ORTP emission from the T state was finally achieved.
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http://dx.doi.org/10.1021/acs.jpclett.0c02180DOI Listing
October 2020

Tuneable red, green, and blue single-mode lasing in heterogeneously coupled organic spherical microcavities.

Light Sci Appl 2020 28;9:151. Epub 2020 Aug 28.

CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 China.

Tuneable microlasers that span the full visible spectrum, particularly red, green, and blue (RGB) colors, are of crucial importance for various optical devices. However, RGB microlasers usually operate in multimode because the mode selection strategy cannot be applied to the entire visible spectrum simultaneously, which has severely restricted their applications in on-chip optical processing and communication. Here, an approach for the generation of tuneable multicolor single-mode lasers in heterogeneously coupled microresonators composed of distinct spherical microcavities is proposed. With each microcavity serving as both a whispering-gallery-mode (WGM) resonator and a modulator for the other microcavities, a single-mode laser has been achieved. The colors of the single-mode lasers can be freely designed by changing the optical gain in coupled cavities owing to the flexibility of the organic materials. Benefiting from the excellent compatibility, distinct color-emissive microspheres can be integrated to form a heterogeneously coupled system, where tuneable RGB single-mode lasing is realized owing to the capability for optical coupling between multiple resonators. Our findings provide a comprehensive understanding of the lasing modulation that might lead to innovation in structure designs for photonic integration.
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http://dx.doi.org/10.1038/s41377-020-00392-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7455725PMC
August 2020

sp/sp Hybridized Carbon as an Anode with Extra Li-Ion Storage Capacity: Construction and Origin.

ACS Cent Sci 2020 Aug 21;6(8):1451-1459. Epub 2020 Jul 21.

Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.

Doping in carbon anodes can introduce active sites, usually leading to extra capacity in Li-ion batteries (LIBs), but the underlying reasons have not been uncovered deeply. Herein, the dodecahedral carbon framework (N-DF) with a low nitrogen content (3.06 wt %) is fabricated as the anode material for LIBs, which shows an extra value of 298 mA h g during 250 cycles at 0.1 A g. Various characterizations and theoretical calculations demonstrate that the essence of the extra capacity mainly stems from non-coplanar sp/sp hybridized orbital controlling non-Euclidean geometrical structure, which acts as new Li-ion active sites toward the excess Li adsorption. The electrochemical kinetics and transmission electron microscope further reveal that the positive and negative curvature architectures not only provide supernumerary Li storage sites on the surface but also hold an enhanced (002) spacing for fast Li transport. The sp/sp hybridized orbital design concept will help to develop advanced electrode materials.
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http://dx.doi.org/10.1021/acscentsci.0c00593DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7453565PMC
August 2020

Effect of the Fluoro-Substituent Position on the Crystal Structure and Photoluminescence of Microcrystals of Platinum β-Diketonate Complexes.

Inorg Chem 2020 Aug 28;59(16):11316-11328. Epub 2020 Jul 28.

Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.

Molecular packing has an important effect on the photophysical properties of crystalline materials. We demonstrate in this work the modulation of molecular packing and emission properties of microcrystals by minor molecular structural variations. Four platinum β-diketonate complexes, with two fluoro substituents () or one fluoro atom substituted on different positions of the auxiliary phenylpyridine ligand (-) have been synthesized. These complexes were used to prepare one-dimensional microcrystals with well-defined shapes and uniform sizes. Although - display similar emission spectra in the solution state, the corresponding microcrystals display different emission colors from green to yellow and orange. In addition, different temperature-responsive (80-298 K) emission spectral changes have been observed from these microcrystals, including the intensity variation of the locally excited (LE) emission without obvious wavelength shifts, competition between the LE and metal-metal-to-ligand charge-transfer emissions, and the sole wavelength shift of the π-π excimer emissions. These differences in emission properties are rationalized by different molecular packings of these materials, as revealed by single-crystal X-ray analyses.
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http://dx.doi.org/10.1021/acs.inorgchem.0c00887DOI Listing
August 2020

Engineering Platinum-Oxygen Dual Catalytic Sites via Charge Transfer towards Highly Efficient Hydrogen Evolution.

Angew Chem Int Ed Engl 2020 Sep 13;59(40):17712-17718. Epub 2020 Aug 13.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.

A dual-site catalyst allows for a synergetic reaction in the close proximity to enhance catalysis. It is highly desirable to create dual-site interfaces in single-atom system to maximize the effect. Herein, we report a cation-deficient electrostatic anchorage route to fabricate an atomically dispersed platinum-titania catalyst (Pt /Ti O ), which shows greatly enhanced hydrogen evolution activity, surpassing that of the commercial Pt/C catalyst in mass by a factor of 53.2. Operando techniques and density functional calculations reveal that Pt /Ti O experiences a Pt-O dual-site catalytic pathway, where the inherent charge transfer within the dual sites encourages the jointly coupling protons and plays the key role during the Volmer-Tafel process. There is almost no decay in the activity of Pt /Ti O over 300 000 cycles, meaning 30 times of enhancement in stability compared to the commercial Pt/C catalysts (10 000 cycles).
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http://dx.doi.org/10.1002/anie.202008117DOI Listing
September 2020

A Photoisomerization-Activated Intramolecular Charge-Transfer Process for Broadband-Tunable Single-Mode Microlasers.

Angew Chem Int Ed Engl 2020 Sep 15;59(37):15992-15996. Epub 2020 Jul 15.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.

Miniaturized lasers with high spectral purity and wide wavelength tunability are crucial for various photonic applications. Here we propose a strategy to realize broadband-tunable single-mode lasing based on a photoisomerization-activated intramolecular charge-transfer (ICT) process in coupled polymer microdisk cavities. The photoisomerizable molecules doped in the polymer microdisks can be quantitatively transformed into a kind of laser dye with strong ICT character by photoexcitation. The gain region was tailored over a wide range through the self-modulation of the optically activated ICT isomers. Meanwhile, the resonant modes shifted with the photoisomerization because of a change in the effective refractive index of the polymer microdisk cavity. Based on the synergetic modulation of the optical gain and microcavity, we realized the broadband tuning of the single-mode laser. These results offer a promising route to fabricate broadband-tunable microlasers towards practical photonic integrations.
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http://dx.doi.org/10.1002/anie.202007361DOI Listing
September 2020

Singlet Fission in a Pyrrole-Fused Cross-Conjugated Skeleton with Adaptive Aromaticity.

J Am Chem Soc 2020 Jun 27;142(23):10235-10239. Epub 2020 May 27.

Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, China.

Singlet fission (SF) materials hold the potential to increase the power conversion efficiency of solar cells by reducing the thermalization of high-energy excited states. The major hurdle in realizing this potential is the limited scope of SF-active materials with high fission efficiency, suitable energy levels, and sufficient chemical stability. Herein, using theoretical calculation and time-resolved spectroscopy, we developed a highly stable SF material based on dipyrrolonaphthyridinedione (DPND), a pyrrole-fused cross-conjugated skeleton with a distinctive adaptive aromaticity (dual aromaticity) character. The embedded pyrrole ring with 4+2 π-electron features aromaticity in the ground state, while the dipole resonance of the amide bonds promotes a 4 π-electron Baird's aromaticity in the triplet state. Such an adaptive aromaticity renders the molecule efficient for the SF process [(S) ≥ 2(T)] without compromising its stability. Up to 173% triplet yield, strong blue-green light absorption, and suitable triplet energy of 1.2 eV, as well as excellent stability, make DPND a promising SF sensitizer toward practical applications.
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http://dx.doi.org/10.1021/jacs.0c00089DOI Listing
June 2020

Regulating Charge Transfer of Lattice Oxygen in Single-Atom-Doped Titania for Hydrogen Evolution.

Angew Chem Int Ed Engl 2020 Sep 14;59(37):15855-15859. Epub 2020 May 14.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.

Single-atom catalysts have attracted much attention. Reported herein is that regulating charge transfer of lattice oxygen atoms in serial single-atom-doped titania enables tunable hydrogen evolution reaction (HER) activity. First-principles calculations disclose that the activity of lattice oxygen for the HER can be regularly promoted by substituting its nearest metal atom, and doping-induced charge transfer plays an essential role. Besides, the realm of the charge transfer of the active site can be enlarged to the second nearest atom by creating oxygen vacancies, resulting in further optimization for the HER. Various single-atom-doped titania nanosheets were fabricated to validate the proposed model. Taking advantage of the localized charge transfer to the lattice atom is demonstrated to be feasible for realizing precise regulation of the electronic structures and thus catalytic activity of the nanosheets.
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http://dx.doi.org/10.1002/anie.202004510DOI Listing
September 2020

A small bimetallic AgCu nanocluster with dual emissions within and against Kasha's rule.

Nanoscale 2020 Apr 30;12(14):7864-7869. Epub 2020 Mar 30.

State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100090, China.

Single crystals of a small bimetallic AgCu nanocluster protected by six ligands of 2,4-dimethylbenzene thiol are synthesized by a one-pot procedure of wet chemistry. This AgCu nanocluster bears a trigonal bipyramid metallic core with two copper atoms located on both sides of a triangular Ag. Interestingly, the six Cu-Ag side edges of the trigonal bipyramid are fully protected by the six ligands giving rise to reinforced stability and high chemical purity. More interestingly, this AgCu cluster shows strong dual fluorescence emissions in both ultraviolet visible (UV-vis) and near infrared (NIR) regions. Theoretical calculations reproduce the absorption and fluorescence spectra where the NIR emission at 824 nm is assigned to the S→ S transition, while the simultaneous emission in the visible band is due to the radiation of highly excited states and is against Kasha's rule.
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http://dx.doi.org/10.1039/d0nr00471eDOI Listing
April 2020

Lasing from an Organic Micro-Helix.

Angew Chem Int Ed Engl 2020 Jun 28;59(27):11080-11086. Epub 2020 Apr 28.

State Key Laboratory of Applied Organic Chemistry (SKLAOC), Key Laboratory of Special Function Materials and Structure Design (MOE), College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China.

Organic solid-state semiconductor lasers are attracting ever-increasing interest for their potential application in future photonic circuits. Despite the great progress made in recent years, an organic laser from 3D chiral structures has not been achieved. Now, the first example of an organic nano-laser from the micro-helix structure of an achiral molecule is presented. Highly regular micro-helixes with left/right-handed helicity from a distyrylbenzene derivative (HM-DSB) were fabricated and characterized under microscope spectrometers. These chiral micro-helixes exhibit unique photonic properties, including helicity-dependent circularly polarized luminescence (CPL), periodic optical waveguiding, and length-dependent amplified spontaneous emission (ASE) behavior. The successful observation of laser behavior from the organic micro-helix extends our understanding to morphology chirality of organic photonic materials and provides a new design strategy towards chiral photonic circuits.
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http://dx.doi.org/10.1002/anie.202002797DOI Listing
June 2020

Enhancing multiphoton upconversion through interfacial energy transfer in multilayered nanoparticles.

Nat Commun 2020 03 4;11(1):1174. Epub 2020 Mar 4.

Beijing National Laboratory for Molecular Science, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, 100190, Beijing, China.

Photon upconversion in lanthanide-doped upconversion nanoparticles offers a wide variety of applications including deep-tissue biophotonics. However, the upconversion luminescence and efficiency, especially involving multiple photons, is still limited by the concentration quenching effect. Here, we demonstrate a multilayered core-shell-shell structure for lanthanide doped NaYF, where Er activators and Yb sensitizers are spatially separated, which can enhance the multiphoton emission from Er by 100-fold compared with the multiphoton emission from canonical core-shell nanocrystals. This difference is due to the excitation energy transfer at the interface between activator core and sensitizer shell being unexpectedly efficient, as revealed by the structural and temperature dependence of the multiphoton upconversion luminescence. Therefore, the concentration quenching is suppressed via alleviation of cross-relaxation between the activator and the sensitizer, resulting in a high quantum yield of up to 6.34% for this layered structure. These findings will enable versatile design of multiphoton upconverting nanoparticles overcoming the conventional limitation.
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http://dx.doi.org/10.1038/s41467-020-14879-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7055352PMC
March 2020

Materials chemistry and engineering in metal halide perovskite lasers.

Chem Soc Rev 2020 Feb;49(3):951-982

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

The invention and development of the laser have revolutionized science, technology, and industry. Metal halide perovskites are an emerging class of semiconductors holding promising potential in further advancing the laser technology. In this Review, we provide a comprehensive overview of metal halide perovskite lasers from the viewpoint of materials chemistry and engineering. After an introduction to the materials chemistry and physics of metal halide perovskites, we present diverse optical cavities for perovskite lasers. We then comprehensively discuss various perovskite lasers with particular functionalities, including tunable lasers, multicolor lasers, continuous-wave lasers, single-mode lasers, subwavelength lasers, random lasers, polariton lasers, and laser arrays. Following this a description of the strategies for improving the stability and reducing the toxicity of metal halide perovskite lasers is provided. Finally, future research directions and challenges toward practical technology applications of perovskite lasers are provided to give an outlook on this emerging field.
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http://dx.doi.org/10.1039/c9cs00598fDOI Listing
February 2020

Revealing the Nature of Singlet Fission under the Veil of Internal Conversion.

Angew Chem Int Ed Engl 2020 Jan 16;59(5):2003-2007. Epub 2019 Dec 16.

Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing, 100048, P. R. China.

Singlet fission (SF) holds the potential to boost the maximum power conversion efficiency of photovoltaic devices. Internal conversion (IC) has been considered as one of the major competitive deactivation pathways to transform excitation energy into heat. Now, using time-resolved spectroscopy and theoretical calculation, it is demonstrated that, instead of a conventional IC pathway, an unexpected intramolecular singlet fission (iSF) process is responsible for excited state deactivation in isoindigo derivatives. The TT state could form at ultrafast rate and nearly quantitatively in solution. In solid films, the slipped stacked intermolecular packing of a thiophene-functionalized derivative leads to efficient triplet pair separation, giving rise to an overall triplet yield of 181 %. This work not only enriches the pool of iSF-capable materials, but also contributes to a better understanding of the iSF mechanism, which could be relevant for designing new SF sensitizers.
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http://dx.doi.org/10.1002/anie.201912202DOI Listing
January 2020

Single-molecule level control of host-guest interactions in metallocycle-C complexes.

Nat Commun 2019 10 10;10(1):4599. Epub 2019 Oct 10.

Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, UT, 84112, USA.

Host-guest interactions are of central importance in many biological and chemical processes. However, the investigation of the formation and decomplexation of host-guest systems at the single-molecule level has been a challenging task. Here we show that the single-molecule conductance of organoplatinum(II) metallocycle hosts can be enhanced by an order of magnitude by the incorporation of a C guest molecule. Mechanically stretching the metallocycle-C junction with a scanning tunneling microscopy break junction technique causes the release of the C guest from the metallocycle, and consequently the conductance switches back to the free-host level. Metallocycle hosts with different shapes and cavity sizes show different degrees of flexibility to accommodate the C guest in response to mechanical stretching. DFT calculations provide further insights into the electronic structures and charge transport properties of the molecular junctions based on metallocycles and the metallocycle-C complexes.
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http://dx.doi.org/10.1038/s41467-019-12534-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6787074PMC
October 2019

Morphology independent triplet formation in pentalene films: Singlet fission as the triplet formation mechanism.

J Chem Phys 2019 Sep;151(12):124701

Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, China.

Singlet fission (SF), a spin-allowed multiexciton generation process, experienced renewed interest in the last decade due to its potential to increase the efficiency of photovoltaic devices. The hurdles now lie in the limited range of SF-capable materials and demanding morphology requirement for an efficient fission process. Although primary fission to yield triplet pair (TT) can occur independently of film morphology in intramolecular singlet fission (iSF) materials, the separation of the TT state has been shown to be highly dependent on the packing motif and morphologies. In this work, we have demonstrated that both iSF and triplet pair separation processes took place irrelevant of molecular order and/or film morphology in a series of pentalene compounds. With the >180% fission efficiency, the suitable triplet energy levels, and the long lifetime of the triplet excitons, these iSF systems can be integrated into practical photovoltaic application.
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http://dx.doi.org/10.1063/1.5097192DOI Listing
September 2019

Hybrid Three-Dimensional Spiral WSe Plasmonic Structures for Highly Efficient Second-Order Nonlinear Parametric Processes.

Research (Wash D C) 2018 9;2018:4164029. Epub 2018 Dec 9.

Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

Two-dimensional (2D) layered materials, with large second-order nonlinear susceptibility, are currently growing as an ideal candidate for fulfilling tunable nanoscale coherent light through the second-order nonlinear optical parametric processes. However, the atomic thickness of 2D layered materials leads to poor field confinement and weak light-matter interaction at nanoscale, resulting in low nonlinear conversion efficiency. Here, hybrid three-dimensional (3D) spiral WSe plasmonic structures are fabricated for highly efficient second harmonic generation (SHG) and sum-frequency generation (SFG) based on the enhanced light-matter interaction in hybrid plasmonic structures. The 3D spiral WSe, with AA lattice stacking, exhibits efficient SH radiation due to the constructive interference of nonlinear polarization between the neighboring atomic layers. Thus, extremely high external SHG conversion efficiency (about 2.437×10) is achieved. Moreover, the ease of phase-matching condition combined with the enhanced light-matter interaction in hybrid plasmonic structure brings about efficient SHG and SFG simultaneously. These results would provide enlightenment for the construction of typical structures for efficient nonlinear processes.
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http://dx.doi.org/10.1155/2018/4164029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750081PMC
December 2018

8.78% Efficient All-Polymer Solar Cells Enabled by Polymer Acceptors Based on a B←N Embedded Electron-Deficient Unit.

Adv Mater 2019 Nov 18;31(44):e1904585. Epub 2019 Sep 18.

Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry Institute of Chemistry Chinese Academy of Sciences, Beijing, 100190, China.

In the field of all-polymer solar cells (all-PSCs), all efficient polymer acceptors that exhibit efficiencies beyond 8% are based on either imide or dicyanoethylene. To boost the development of this promising solar cell type, creating novel electron-deficient units to build high-performance polymer acceptors is critical. A novel electron-deficient unit containing B←N bonds, namely, BNIDT, is synthesized. Systematic investigation of BNIDT reveals desirable properties including good coplanarity, favorable single-crystal structure, narrowed bandgap and downshifted energy levels, and extended absorption profiles. By copolymerizing BNIDT with thiophene and 3,4-difluorothiophene, two novel conjugated polymers named BN-T and BN-2fT are developed, respectively. It is shown that these polymers possess wide absorption spectra covering 350-800 nm, low-lying energy levels, and ambipolar film-transistor characteristics. Using PBDB-T as the donor and BN-2fT as the acceptor, all-PSCs afford an encouraging efficiency of 8.78%, which is the highest for all-PSCs excluding the devices based on imide and dicyanoethylene-type acceptors. Considering that the structure of BNIDT is totally different from these classical units, this work opens up a new class of electron-deficient unit for constructing efficient polymer acceptors that can realize efficiencies beyond 8% for the first time.
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http://dx.doi.org/10.1002/adma.201904585DOI Listing
November 2019

Real-Space Imaging of Orbital Selectivity on SrTiO(001) Surface.

ACS Appl Mater Interfaces 2019 Oct 27;11(40):37279-37284. Epub 2019 Sep 27.

Department of Physics , Beijing Normal University , Beijing 100875 , China.

Real-space access of the orbital degree of freedom in complex oxides is still challenging due to intricate electronic hybridization. Here, we report a direct observation of reproducible orbital-selective tunneling on a novel SrTiO(001) surface by scanning tunneling microscopy. The electronic structures reversibly switch between two different sets of symmetries depending on the sample bias, which is accompanied by a remarkable change in energy-dependent spectroscopy data. Tunneling spectrum combined with density functional theory calculations elucidates that symmetry-breaking at the surface determines the crystal-splitting field of e/t orbitals with a strong in-plane anisotropy so that electrons alternatingly fill e and t orbitals during the imaging process with different biases. This surface superstructure provides a new strategy toward understanding orbital textures and orbital selectivity in complex oxides.
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http://dx.doi.org/10.1021/acsami.9b11724DOI Listing
October 2019

Multiscale Buffering Engineering in Silicon-Carbon Anode for Ultrastable Li-Ion Storage.

ACS Nano 2019 Sep 22;13(9):10179-10190. Epub 2019 Aug 22.

State Key Laboratory of Multi-Phase Complex Systems, Institute of Process Engineering , Chinese Academy of Sciences (CAS) , Zhongguancun Beiertiao 1 Hao , Beijing 100190 , People's Republic of China.

Silicon-carbon (Si-C) hybrids have been proven to be the most promising anodes for the next-generation lithium-ion batteries (LIBs) due to their superior theoretical capacity (∼4200 mAh g). However, it is still a critical challenge to apply this material for commercial LIB anodes because of the large volume expansion of Si, unstable solid-state interphase (SEI) layers, and huge internal stresses upon lithiation/delithiation. Here, we propose an engineering concept of multiscale buffering, taking advantage of a nanosized Si-C nanowire architecture through fabricating specific microsized wool-ball frameworks to solve all the above-mentioned problems. These wool-ball-like frameworks, prepared at high yields, nearly matching industrial scales (they can be routinely produced at a rate of ∼300 g/h), are composed of Si/C nanowire building blocks. As anodes, the Si-C wool-ball frameworks show ultrastable Li storage (2000 mAh g for 1000 cycles), high initial Coulombic efficiency of ∼90%, and volumetric capacity of 1338 mAh cm. TEM proves that the multiscale buffering design enables a small volume variation, only ∼19.5%, reduces the inner stresses, and creates a very thin SEI. The perfect multiscale elastic buffering makes this material more stable compared to common Si nanoparticle-assembled counterpart electrodes.
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http://dx.doi.org/10.1021/acsnano.9b03355DOI Listing
September 2019
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