Photon Upconverted Circularly Polarized Luminescence via Triplet–Triplet Annihilation

Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high‐energy excitation results in low‐energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion—i.e., the conversion of low‐energy light into higher‐energy emission, with a wide variety of applications—has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher‐energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon‐upconverted CPL via the triplet–triplet annihilation mechanism, focusing on the amplified dissymmetry factor g_lum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.     

Tailoring Chiroptical Activity of Iron Disulfide Quantum Dot Hydrogels with Circularly Polarized Light

Chiral inorganic nanomaterials have recently attracted significant attention because of their many important applications, such as in asymmetric catalysis and chiral sensing. Here, chiral iron disulfide quantum dots (FeS₂ QDs) are synthesized via chirality transfer using l/d ‐cysteine (Cys) as chiral ligands. The chiral FeS₂ QDs are coassembled with two gelators to produce a cogel (l ‐ or d ‐[Gel+FeS₂]) with a g‐factor value of ±0.06. Interestingly, the cogels display intense circularly polarized luminescence. More significantly, the degree of twisting (twist pitch) and the diameter of the cogels can be markedly regulated by illumination with circularly polarized light (CPL) in the ranges of 120–213 and 37–65 nm, respectively, which is caused by the CPL‐induced electron transfer. This research opens the way for the design of chiroptical devices with a wide range of functions and applications.     

One-Dimensional Chiral Copper Iodide Chain-Like Structure Cu4I4(R/S-3-quinuclidinol)3 with Near-Unity Photoluminescence Quantum Yield and Efficient Circularly Polarized Luminescence

Chiral organic−inorganic hybrid metal halide materials have shown great potential for circularly polarized luminescence (CPL) related applications for their tunable structures and efficient emissions. Here, this work combines the highly emissive Cu₄I₄ cubane cluster with chiral organic ligand R/S-3-quinuclidinol, to construct a new type of 1D Cu-I chains, namely Cu₄I₄(R/S-3-quinuclidinol)₃, crystallizing in noncentrosymmetric monoclinic P2₁ space group. These enantiomorphic hybrids exhibit long-term stability and show bright yellow emission with a photoluminescence quantum yield (PLQY) close to 100%. Due to the successful chirality transfer from the chiral ligands to the inorganic backbone, the enantiomers show intriguing chiroptical properties, such as circular dichroism (CD) and CPL. The CPL dissymmetry factor (g_lum) is measured to be ≈4 × 10⁻³. Time-resolved photoluminescence (PL) measurements show long averaged decay lifetime up to 10 µs. The structural details within the Cu₄I₄ reveal the chiral nature of these basic building units, which are significantly different than in the achiral case. This discovery provides new structural insights for the design of high performance CPL materials and their applications in light emitting devices.     

Endowing Perovskite Nanocrystals with Circularly Polarized Luminescence

Perovskite nanocrystals are attracting great interest due to their excellent photonic properties. Here, through a supramolecular self‐assembly approach, the perovskite nanocrystals (NCs) with a novel circularly polarized luminescence (CPL) are successfully endowed. It is found that the achiral perovskite NCs can coassemble with chiral gelator in nonpolar solvents, in which the gelator molecules modify the surface of the perovskite NCs. Through such cogelation, the molecular chirality can transfer to the NCs resulting in CPL signals with a dissymmetric factor (g_lum) up to 10^?3. Furthermore, depending on the molecular chirality of the gelator, the CPL sense can be selected and the mirror‐imaged CPL is obtained. Such gels can be further embedded into the polymer film to facilitate flexible CPL devices. It is envisaged that this approach will afford a new insight into the designing of the functional chiroptical materials.     

Size‐Selective Effects on Fullerene Adsorption by Nanoporous Molecular Networks

A new hierarchical self‐assembling molecular template, which can size‐selectively immobilize fullerene molecules, is reported. The molecular template is fabricated from 1,3,5‐tris(10‐carboxydecyloxy)benzene (TCDB) and triangle‐shaped macrocycles. It is observed that the two‐dimensional hydrogen‐bonded achiral TCDB network affected by the 3NN‐Macrocycle becomes a chiral network. Host and guest molecules both form chiral arrangements with hexagonal empty pores. In addition, fullerenes and other molecules such as coronene can be entrapped in the empty pores or on the 3NN‐Macrocycle molecules. The adsorption constant (K) is estimated, from which it is concluded that the different filling behaviors of the fullerenes are associated with the different sizes of the guest species. This method provides a facile approach to molecularly designed surfaces and the study of fullerene molecular arrays on the single‐molecule level.     

Modular Molecular Self‐Assembly for Diversified Chiroptical Systems

Bottom‐up multicomponent molecular self‐assembly is an efficient approach to fabricate and manipulate chiral nanostructures and their chiroptical activities such as the Cotton effect and circular polarized luminescence (CPL). However, the integrated coassembly suffers from spontaneous and inherent systematic pathway complexity with low yield and poor fidelity. Consequently, a rational design of chiral self‐assembled systems with more than two components remains a significant challenge. Herein, a modularized, ternary molecular self‐assembly strategy that generates chiroptically active materials at diverse hierarchical levels is reported. N‐terminated aromatic amino acids appended with binding sites for charge transfer and multiple hydrogen bonds undergo the evolution of supramolecular chirality with unique handedness and luminescent color, generating abundant CPL emission with high luminescence dissymmetry factor values in precisely controlled modalities. Ternary coassembly facilitates high‐water‐content hydrogel formation constituted by super‐helical nanostructures, demonstrating a helix to toroid topological transition. This discovery would shed light on developing complicated multicomponent systems in mimicking biological coassembly events.     

Uncovering the Circular Polarization Potential of Chiral Photonic Cellulose Films for Photonic Applications

Circularly polarized light (CPL) is central to photonic technologies. A key challenge lies in developing a general route for generation of CPL with tailored chiroptical activity using low‐cost raw materials suitable for scale‐up. This study presents that cellulose films with photonic bandgaps (PBG) and left‐handed helical sense have an intrinsic ability for circular polarization leading to PBG‐based CPL with extraordinary | g | values, well‐defiend handedness, and tailorable wavelength by the PBG change. Using such cellulose films, incident light ranging from near‐UV to near‐IR can be transformed to passive L‐CPL and R‐CPL with viewing‐side‐dependent handedness and | g | values up to 0.87, and spontaneous emission transformed to R‐CPL emission with | g | values up to 0.68. Unprecedented evidence is presented with theoretical underpinning that the PBG effect can stimulate the R‐CPL emission. The potential of cellulose‐based CPL films for polarization‐based encryption is illustrated. The evaporation‐induced self‐assembly coupled with nanoscale mesogens of cellulose nanocrystals opens new venues for technological advances and enables a versatile strategy for rational design and scalable manufacturing of organic and inorganic CPL films for photonic applications.     

Organische Funktionsschichten in Polymerelektronik und Polymersolarzellen

Organic functional layers in polymer electronics and polymer solar cells Thin layers of organic functional polymers play the predominant role in polymer electronics like organic field effect transistors (OFET's) and in organic photovoltaic devices. The well‐known advantages of these solution‐processable materials opened the way for their welcoming now in application fields, which were fully occupied by inorganic semiconductors in the past. However, the polymer semiconductors show also some disadvantages, like a relatively low charge carrier mobility and a not yet sufficient long‐term stability. However, fore the aim of R&D for polymer electronics is not the replace of well‐tried electronic materials and technologies but the opening of new application fields for the new kind of low‐cost /low‐performance electronics. The paper presents recent results of OFET's with thin layers from conjugated polymers like poly(3‐alkylthiophenes), as active semiconducting material, and poly(4‐vinylphenol) as gate dielectricum. Experiments concerning generation of source‐drain electrodes based on polyaniline or Baytron P by laser ablation are represented. Additionally, printing techniques or laser modification are used for patterning of conducting polymers. The described polymer solar cells use for the photoactive layer a composite from polyalkylthiophenes, as light absorbing and charge generating polymer, and fullerene derivatives, responsible for fast electron transfer. Donator‐acceptor cells containing substituted fullerenes give also internationally the best efficiency with η ≈ 3%.     

Modeling the structure of fulleranes and their endohedral complexes involving small molecules with nontrivial topological properties

'In' and 'out' isomers of perhydrogenated fullerenes and endohedral fullerene complexes have only recently been incorporated into the realm of topological chemistry. The 'in' isomers are, until now, purely hypothetical while for the latter group mostly studied are the complexes with metal ions that can be obtained during the fullerenes manufacturing. Much more difficult to obtain are the complexes with small molecules buried inside fullerene cages produced by laborious synthesis involving opening the cage, inserting the guest into it, and closing the cage chemically. This complicated procedure has only recently been accomplished for a hydrogen molecule put in the C60. Two H2 molecules inside the opened C70 cage and H2O in the opened C60 have been also reported recently. Model calculations, when carefully applied, allow one to predict the possibility of obtaining endohedral fullerene complexes with small molecules and 'in' isomers of perhydrogenated fullerenes. However, such systems are too large to be reliably handled by quantum calculations. Interestingly, such a simple method as molecular mechanics seems much more trustworthy.     

Chiroptical properties in azobenzene molecule-doped side-chain polymeric films

Thin, intrinsically achiral films of a side-chain polymeric liquid crystal system doped with photochromic azobenzene molecules exhibited dynamic chiroptical properties when irradiated with circularly polarized light (CPL). Photoinduced circular anisotropy was observed in these films with increasing CPL irradiation time. Reversible chiroptical switching was also realized by alternating irradiation with right- and left-CPL. We also monitored photoinduced chirality as a function of excitation wavelength.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

Abstract

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.     

Imprinting Chirality onto the Electronic States of Colloidal Perovskite Nanoplatelets

The direct synthesis of chiroptical organic–inorganic methylammonium lead bromide perovskite nanoplatelets that are passivated by R‐ or S‐phenylethylammonium ligands is reported. The circular dichroism spectra can be divided into two components: (1) a region associated with a charge transfer transition between the ligand and the nanoplatelet, 300–350 nm, and (2) a region corresponding to the excitonic absorption maximum of the perovskite, 400–450 nm. The temperature‐ and concentration‐dependent circular dichroism spectra indicate that the chiro‐optical response arises from chiral imprinting by the ligand on the electronic states of the quantum‐confined perovskite rather than chiral ligand‐induced stereoselective aggregation.     

Enantiomeric MOF Crystals Using Helical Channels as Palettes with Bright White Circularly Polarized Luminescence

The host–guest chemistry of metal–organic frameworks (MOFs) has enabled the derivation of numerous new functionalities. However, intrinsically chiral MOFs (CMOFs) with helical channels have not been used to realize crystalline circularly polarized luminescence (CPL) materials. Herein, enantiomeric pairs of MOF crystals are reported, where achiral fluorophores adhere to the inner surface of helical channels via biology-like H-bonds and hence inherit the helicity of the host MOFs, eventually amplifying the luminescence dissymmetry factor (g_lum) of the host l /d -CMOF (±1.50 × 10⁻³) to a maximum of ±0.0115 for the composite l /d -CMOF⊃fluorophores. l /d -CMOF⊃fluorophores in pairs generate bright color-tunable CPL and almost ideal white CPL (0.33, 0.32) with a record-high photoluminescence quantum yield of ≈30%, which are further assembled into a white circularly polarized light-emitting diode. The present strategy opens a new avenue for propagating the chirality of MOFs to realize universal chiroptical materials.     

Kinetically controlled fabrication of C60 1-dimensional crystals

Considering the current application of fullerenes in the field of organic semiconductor devices, the highly crystalline or single crystal fullerene nanostructures with controlled shape and size contains some breakthrough for improved efficiency. Recently, fullerene 1-dimensional nanostructures, including nanowhiskers and nanotubes, become attractive kind of materials since the development of liquid-liquid interface precipitation (LLIP) process. The LLIP process has critical advantage; the fabrication of highly crystalline, even single crystal, fullerene 1-dimensional nanostructures with simple apparatus. However, the fabrication fullerene 1-dimensional structures by LLIP process requires long process time from one day to several days. In order to overcome this drawback, a modified process from conventional LLIP process is suggested. In the modified LLIP process, the nucleation step and growth step were divided. For the nucleation step, saturated fullerene solution is mixed with small amount of alcohols such as 2-propanol or ethanol. For the controlled growth step, the fullerenes in the nucleated solution are precipitated by addition of alcohol, which is injected to the bottom of the solution with controlled flow rate. In this modified process, the shape of the precipitated fullerene crystals is critically dependent on the nucleation steps and the size is dependent on the precipitation rate. By combination of proper nucleation step and growth rate, a well defined fullerene 1-dimensional structures, of 200-500 nm width and of hundreds microm length can be fabricated within two hours. In addition, by controlling injection rate and degree of supersaturation, several types of 1-dimensional structures including micro-tubes can be prepared and, by changing solvent and alcohol, several shape of C60 crystals including polyhedral particles and plates can be prepared.     

Supramolecular Nanostructures of Chiral Perylene Diimides with Amplified Chirality for High‐Performance Chiroptical Sensing

Chiral supramolecular nanostructures with optoelectronic functions are expected to play a central role in many scientific and technological fields but their practical use remains in its infancy. Here, this paper reports photoconductive chiral organic semiconductors (OSCs) based on perylene diimides with the highest electron mobility among the chiral OSCs and investigates the structure and optoelectronic properties of their homochiral and heterochiral supramolecular assemblies from bottom‐up self‐assembly. Owing to the well‐ordered supramolecular packing, the homochiral nanomaterials exhibit superior charge transport with significantly higher photoresponsivity and dissymmetry factor compared with those of their thin film and monomeric equivalents, which enables highly selective detection of circularly polarized light, for the first time, in visible spectral range. Interestingly, the heterochiral nanostructures assembled from co‐self‐assembly of racemic mixtures show extraordinary chiral self‐discrimination phenomenon, where opposite enantiomeric molecules are packed alternately into heterochiral architectures, leading to completely different optoelectrical performances. In addition, the crystal structures of homochiral and heterochiral nanostructures have first been studied by ab initio X‐ray powder diffraction analysis. These findings give insights into the structure–chiroptical property relationships of chiral supramolecular self‐assemblies and demonstrate the feasibility of supramolecular chirality for high‐performance chiroptical sensing.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.     

Computational Study of Structure and Thermochemistry of Some Endo‐ and Exohedral Fullerene Derivatives

Abstract

DFT calculations were applied to the problem of fullerene isomerism. Two classes of thermally stable fullerene derivatives are considered: endohedral metallofullerenes, which in some cases reveal carbon cage topology different from that observed in the empty fullerenes of the same size, and fullerene fluorides, which have uniquely rich number of theoretically possible isomers.     

Reconfigurable Plasmonic Chirality: Fundamentals and Applications

Molecular chirality is a geometric property that is of great importance in chemistry, biology, and medicine. Recently, plasmonic nanostructures that exhibit distinct chiroptical responses have attracted tremendous interest, given their ability to emulate the properties of chiral molecules with tailored and pronounced optical characteristics. However, the optical chirality of such human-made structures is in general static and cannot be manipulated postfabrication. Herein, different concepts to reconfigure the chiroptical responses of plasmonic nano- and micro-objects are outlined. Depending on the utilized strategies and stimuli, the chiroptical signature, the 3D structural conformation, or both can be reconfigured. Optical devices based on plasmonic nanostructures with reconfigurable chirality possess great potential in practical applications, ranging from polarization conversion elements to enantioselective analysis, chiral sensing, and catalysis.     

Chiroptical effects in planar achiral plasmonic oriented nanohole arrays

Chiroptical effects are routinely observed in three dimensional objects lacking mirror symmetry or quasi-two-dimensional thin films lacking in-plane mirror symmetry. Here we show that symmetric plasmonic planar arrays of circular nanoholes produced strong chiroptical responses at visible wavelengths on tilting them with respect to the incident light beam due to the collective asymmetric nature of their surface plasmon excitations. This extrinsic chiroptical effect can be stronger than the local chiroptical response in arrays of intrinsically chiral nanoholes and may be useful for chiral sensing and negative refraction.     

Face colorings and chiral face colorings of icosahedral giant fullerenes: C80 to C240

Abstract

Combinatorial techniques based on Sheehan’s modification of P?lya’s theorem and M?bius inversion technique together with character cycle indices are applied to face colorings of giant fullerenes. These techniques are applied to icosahedral fullerenes, C₈₀ with a chamfered dodecahedron structure, a chiral fullerene C₁₄₀, icosahedral C₁₈₀ and C₂₄₀ with a chamfered truncated icosahedron geometry. The techniques are shown to provide both achiral and chiral face colorings of giant fullerenes for (a) coloring only pentagons with all hexagons painted white, (b) coloring hexagonal faces with all pentagons kept white, (c) both pentagons and hexagons painted with variable colors from a single set, and (d) both pentagons and hexagons painted with variable colors but chosen from two different sets. We have shown that in order to produce chiral colorings for the I_h fullerenes at least 2 black colors and remaining being white are needed when both pentagons and hexagons are varied. Results provide new insights into facial labeling and facial dynamics of fullerenes, while therefore being fully prepared to be inscribed in the new so called neutrosophical science (of carbon) nano-structural physical-chemistry.