A new type of fluorescent material is presented, which is called non‐conjugated polymer dots (NCPDs). The NCPDs only possess sub‐fluorophores (which are groups such as CO, CN, NO) instead of ...typical conjugated fluorophore groups, and thus these materials should not have strong photoluminescence (PL) in the usual sense. Nevertheless, the PL of these sub‐fluorophores can be enhanced by chemical crosslinking or physical immobilization of polymer chains, which is named the crosslink‐enhanced emission (CEE) effect. The significant advances achieved by us and other groups on both experimental and theoretical aspects are discussed, and the covalent‐bond CEE, rigidity‐aggregated CEE, or supramolecular CEE in NCPDs is elaborated. Moreover, synthetic strategies, unique optical properties, and the promise of NCPDs in bio‐related fields, such as bioimaging and drug delivery, are systematically discussed.
Emission enhancement of non‐fluorophore units (called sub‐fluorophores) by crosslinking them (crosslink‐enhanced emission; CEE) is utilized in a new type of fluorescent material: non‐conjugated polymer dots (NCPDs). The CEE can be covalently bonded, rigidity aggregated, or supramolecular in nature. The synthetic strategies, optical properties, and potential applications of NCPDs in biology‐related fields are discussed.
Exploitation and utilization of sustainable energy sources has increasingly become the common theme of global social development, which has promoted tremendous development of energy conversion ...devices/technologies. Owing to excellent and unique optical/electrical properties, carbon dots (CDs) have attracted extensive research interest for numerous energy conversion applications. Strong absorption, downconversion photoluminescence, electron acceptor/donor characteristics, and excellent electron conductivity endow CDs with enormous potential for applications in optoelectronic devices. Furthermore, excellent electron transfers/transport capacities and easily manipulable structural defects of CDs offer distinct advantages for electrocatalytic applications. Recent advances in CD‐based energy conversion applications, including optoelectronic devices such as light‐emitting diodes and solar cells, and electrocatalytic reactions including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and carbon dioxide reduction reaction, are summarized. Finally, current challenges and future prospects for CD‐based energy conversion applications are proposed, highlighting the importance of controllable structural design and modifications.
Owing to excellent optical, structural, and electrical properties, carbon dots (CDs) have attracted extensive research interest for numerous energy conversion applications. Thus, optoelectronic applications of CDs involving light‐emitting diodes and solar cells, along with electrocatalytic applications for the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and carbon dioxide reduction reaction, are summarized in detail.
Beauty-full tetraquarks Bai, Yang; Lu, Sida; Osborne, James
Physics letters. B,
11/2019, Letnik:
798, Številka:
C
Journal Article
Recenzirano
Odprti dostop
In this article we present a calculation of the bbb¯b¯ tetraquark ground-state energy using a diffusion Monte Carlo method to solve the non-relativistic many-body system. The static potential for the ...four quark system is chosen to align with the flux-tube picture of QCD. Using this approach, we find that the 0++ state has a mass of 18.69±0.03GeV, which is around 100 MeV below twice the ηb mass. This bound state can behave as a four-lepton resonance via its decay to ϒ(1S)ϒ(1S)⁎→ℓ+ℓ−ℓ+ℓ−.
Carbon dots (CDs) have attracted much attention due to their excellent photoelectric properties and potential applications. Although previous studies have shown that almost all organic molecules can ...be converted into CDs via chemical carbonization, the mechanism of the conversion process remains unclear. The hydrothermal/solvothermal method commonly used to prepare CDs is complicated and leads to the generation of many by-product CDs with similar structures. Considering that the purification of the synthesized by-products is difficult, the process of CDs formation cannot be readily analyzed and understood. Herein, we use ethanol as a carbon source to synthesize white-emitting CDs (W-CDs). Column chromatography separation shows that the synthesized W-CDs are composed of blue-, cyan-, and yellow-emitting CDs that fluoresce at wavelengths corresponding to the three emission centers of W-CDs. Although the samples have similar graphitic structure, they exhibit different surface states due to variations in the degree of oxidation and carbonization. Therefore, the red-shift in their emission peaks is attributed to an increased degree of carbonization in their polymer structure. Theoretical calculations verify the experimental results, and the prepared CDs are successfully used to develop multi-color and white light-emitting diodes (LEDs).
Polymer carbon dots (PCDs) are proposed as a new class of room‐temperature phosphorescence (RTP) materials. The abundant energy levels in PCDs increase the probability of intersystem crossing (ISC) ...and their covalently crosslinked framework structures greatly suppress the nonradiative transitions. The efficient methods allow the manufacture of PCDs with unique RTP properties in air without additional metal complexation or complicated matrix composition. They thus provide a route towards the rational design of metal‐free RTP materials that may be synthesized easily. Furthermore, we find that RTP is associated with a crosslink‐enhanced emission (CEE) effect, which provides further routes to design improved PCDs with diverse RTP performance. Our results show the potential of PCDs as a universal route to achieve effective metal‐free RTP.
Room‐temperature phosphorescence: Polymer carbon dots (PCDs) showing metal‐free room‐temperature phosphorescence (RTP) have been constructed by using a facile method. The contribution of the cross‐link‐enhanced emission effect to the generation of RTP is verified and proposed as a guideline to forecast and synthesize a series of PCDs with diverse RTP performance (ISC=intersystem crossing).
Light‐emitting chiral carbonized polymer dots (Ch‐CPDs) are attracting great interest because of their extraordinary photonic properties, but modulating their band‐gap emission, especially at long ...wavelength, and maintaining their chiral structure to achieve multicolor, high‐emission Ch‐CPDs remains challenging. Reported here for the first time is the synthesis of red‐ and multicolor‐emitting Ch‐CPDs using the common precursors L‐/D‐tryptophan and o‐phenylenediamine, and a solvothermal approach at one temperature. The quantum yield of the Ch‐CPDs was between 31 % and 54 %. Supramolecular self‐assembly provided multicolor‐emitting Ch‐CPDs showing novel circularly polarized luminescence, with the highest dissymmetric factor (glum) of 1×10−2. Importantly, circularly polarized white‐emitting CPDs were fabricated for the first time by tuning the mixing ratio of the three colored Ch‐CPDs in a gel. This strategy affords exciting opportunities for designing functional chiroptical materials.
The synthesis of red‐ and multicolor‐emitting chiral carbonized polymer dots (Ch‐CPDs) is reported for the first time. The quantum yield of the Ch‐CPDs is between 31 % and 54 %. Furthermore, these Ch‐CPDs were combined with chiral gels through supramolecular self‐assembly, thereby yielding their multicolor and white circularly polarized luminescence.
When axion stars fly through an astrophysical magnetic background, the axion-to-photon conversion may generate a large electromagnetic radiation power. After including the interference effects of the ...spacially-extended axion-star source and the macroscopic medium effects, we estimate the radiation power when an axion star meets a neutron star. For a dense axion star with 10−13M⊙, the radiated power is at the order of 1011W×(100μeV/ma)4(B/1010Gauss)2 with ma as the axion particle mass and B the strength of the neutron star magnetic field. For axion stars occupy a large fraction of dark matter energy density, this encounter event with a transient O(0.1s) radio signal may happen in our galaxy with the averaged source distance of one kiloparsec. The predicted spectral flux density is at the order of μJy for a neutron star with B∼1013 Gauss. The existing Arecibo, GBT, JVLA and FAST and the ongoing SKA radio telescopes have excellent discovery potential of dense axion stars.
Electrocatalytic reactions possess wide application prospects in solving the energy crisis. Recently, the emerging 0D carbon dots (CDs) have become potential candidate materials due to their low ...cost, high conductivity, easy modification, and simple synthesis. CDs‐based composite materials showcase attractive electrocatalytic performances because of the abundant active sites and charge distribution on the material surface. Considering the complicated structure of CDs, it's important to identify the specific catalytic activity source and understand catalytic mechanisms with the aid of theoretical method. In this review, the latest advancements are presented on improving the electrocatalytic activity and stability of CDs‐based composite materials from theoretical perspective. Meanwhile, the opportunity and challenges about developing high‐performance CDs catalysts are also highlighted.
Facing the growing energy crisis, electrocatalytic reactions have made prominent contributions. The emerging carbon dots (CDs) have become attractive electrocatalyst candidates, owing to their high conductivity, easy modification, abundant active sites, and so forth. However, the complex structure renders high performance CDs debatable. It thus seems important to understand the specific property and mechanism from a theoretical view.
Development of high‐performance carbon dots (CDs) with emission wavelength longer than 660 nm (deep red emission) is critical in deep‐tissue bioimaging, yet it is still a major challenge to obtain ...CDs with both narrow full width at half maximum (FWHM) and high deep red/near‐infrared emission yield. Here, deep red emissive carbonized polymer dots (CPDs) with unprecedented FWHM of 20 nm are synthesized. The purified CPDs in dimethyl sulfoxide (DMSO) solution possess quantum yield (QY) as high as 59% under 413 nm excitation, as well as recorded QY of 31% under 660 nm excitation in the deep red fluorescent window. Detailed characterizations identify that CPDs have unique polymer characteristics, consisting of carbon cores and the shells of polymer chains, and π conjugated system formed with N heterocycles and aromatic rings governs the single photoluminescence (PL) center, which is responsible for high QY in deep red emissive CPDs with narrow FWHM. The CPDs exhibit strong absorption and emission in the deep red light region, low toxicity, and good biocompatibility, making them an efficient probe for both one‐photon and two‐photon bioimaging. CPDs are rapidly excreted via the kidney system and hepatobiliary system.
Deep red emissive carbonized polymer dots (CPDs) with unprecedented full width at half maximum around 20 nm possess recorded quantum yield of 59% and 31% under 413 and 660 nm. These CPDs have unique polymer characteristics, consist of carbon cores and the shells of polymer chains, and are successfully used as a fluorescent probe for one‐photon and two‐photon bioimaging.
PDF
