The Current Progress and Challenges of Carbonized Polymer Dot-Based Room-Temperature Phosphorescent Materials

Carbonized polymer dots(CPDs)as one type of carbon dots have attracted widespread attention in recent years.The proposal of the“shell–core”structure of CPDs leads to further thinking about the association between their special structures and luminescent properties.In recent years,great progress has been made in the field of CPD-based room-temperature phosphorescent materials.This review pays particular attention to how the special“core–shell”structure of CPDs influences the activation of roomtemperature phosphorescence(RTP).The strategies and vital factors to activate RTP for CPD-based materials in both solid state and water were reviewed in detail to elaborate on the effect of the special structure on RTP generation.Furthermore,some perspectives on the current challenges were also provided to guide the further development of CPD-based room-temperature phosphorescent materials.

Design and Synthesis of Transparent Poly(acrylonitrile-butadiene-styrene) and Relationship Between Its Phase Construction and Transparency

A series of transparent ABS（T-ABS） resins were prepared by emulsion in situ suspension polymerization. The influences of the particle size and the content of rubber particles on the transparency of T-ABS resins were studied by varying the size and content of rubber particles in a single model system（rubber particles with a uniform size）. The optical properties of T-ABS resins were investigated in a mixed system of SBR/PB particles and a hi-modal particle system（rubber particles with two different sizes, 70 and 400 nm in diameter） of SBR particles. It was found that when the size of the smaller particles （ 70 nm） in the mixed system of SBR/PB particles was in the range of 50-100 nm in diameter, the T-ABS resins showed a better transparency. These results provide a flexible and practical process for the preparation of T-ABS resins with good optical and mechanical properties.

NHS Mediated CdTe Quantum Dots/Albumin Conjugates andLabeling C. Elegans

Luminescent quantum dots（QDs） are a promising alternative to organic dyes for biomedical assays and imaging. A new conjugation method, NHS mediated conjugating, for QDs and BSA was introduced. The QDs-BSA conjugates were confirmed, and their stability has been proved. Caenorhabditis elegans（ C, elegans） were used as animal models, and the imaging of QDs in the organism was studied.

A Simple Approach to Fabricate CdS-SiO_2 Hybrid Microspheres by Producing CdS Nanoparticles on the Surface of Thiolated SiO_2 Microspheres

We have developed a simple synthetic method to prepare the hybrid microspheres of CdS nanoparticles on the surface of silica microspheres modified by（3-mercaptopropyl） trimethoxysilane（MPS）. The--SH groups of MPS can bind with the Cd^2＋ ions on the surface of SiO2. When thioacetamide releases H2S, the nanosized CdS particles（ 1-6 nm） will successfully be generated on the silica surface under the experimental conditions. The size of the CdS nanoparticles was found to be related to the concentration of Cd^2 ＋ feed and the size of silica spheres, the higher the concentration of Cd^2＋ and the larger of silica microspheres, the bigger the size of CdS nanoparticles. Techniques including UV, PL, TEM and XPS were used to characterize the CdS-SiO2 hybrid microspheres.

Red and Near-Infrared Electroluminescences from Metal-Free Phthalocyanine

Organic light emitting diodes are fabricated based on metal-free phthalocyanine （H2Pc） doped into tris-（8- hydroxyquinoline） aluminium （Alq3）. The device structure is ITO/NPB （30 nm）/Alq3： H2Pc（30 nm）/BCP（20 nm） /Alq3（20nm）/Al. In the light-emitting layers, H2Pc concentrations are varied from Owt% to 100 wt%. The emissions around 708nm and 800hm appear at low concentrations, while the emissions around 910hm and 930hm appear at high concentrations. The emissions around 708nm and 800nm are from H2Pc monomers. The emissions around 910hm and 930hm are from H2Pc aggregates. The dominant mechanism in the doped devices is direct charge trapping.

Conformations and adsorption behavior of poly(allylamine hydrochloride) studied by single molecule force spectroscopy

Poly(allylamine hydrochloride) (PAH), which is frequently used in fabricating polyelectrolyte multilayer films, was studied by single molecule force spectroscopy (SMFS). Plenty of force-extension curves with a long plateau were obtained in water, indicating that train-like structure was predominant when PAH was adsorbed on the substrate. It was found that the peak-type force-extension curves of PAH in water were not able to be fitted by the modified freely-jointed chain model. Additionally, there was a flat region in the derivative of force-extension curves. Thus, it was inferred that PAH chain in water was in a special conformation and underwent a "conformational transition" under the stretching of an external force. This phenomenon did not appear in the SMFS experiment in 1 mol/L urea solution, which indi-cated that urea was able to break the special conformation.

Ethanol-derived white emissive carbon dots:The formation process investigation and multi-color/white LEDs preparation

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).

Electron-phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots

Due to the complex core-shell structure and variety of surface functional groups,the photoluminescence(PL)mechanism of carbon dots(CDs)remain unclear.o-Phenylenediamine(oPD),as one of the most common precursors for preparing red emissive CDs,has been extensively studied.Interestingly,most of the red emission CDs based on oPD have similar PL emission characteristics.Herein,we prepared six different oPD-based CDs and found that they had almost the same PL emission and absorption spectra after purifiication.Structural and spectral characterization indicated that they had similar carbon core structures but diffferent surface polymer shells.Furthermore,single-molecule PL spectroscopy confirmed that the multi-modal emission of those CDs originated from the transitions of different vibrational energy levels of the same PL center in the carbon core.In addition,the phenomenon of"spectral splitting"of single-particle CDs was observed at low temperature,which confirmed these oPD-based CDs were unique materials with properties of both organic molecules and quantum dots.Finally,theoretical calculations revealed their potential polymerization mode and carbon core structure.Moreover,we proposed the PL mechanism of red-emitting CDs based on oPD precursors;that is,the carbon core regulates the PL emission,and the polymer shell regulates the PL intensity.Our work resolves the controversy on the PL mechanism of oPD-based red CDs.These findings provide a general guide for the mechanism exploration and structural analysis of other types of CDs.

From Two-Dimensional Metal Organic Coordination Networks to Near-Infrared Luminescent PbS Nanoparticle/Layered Polymer Composite Materials

Two-dimensional(2-D)layered metal-organic coordination(lead methacrylate(LDMA))networks have been prepared in aqueous solution under mild conditions and their structure determined by single crystal diffraction.As the ligand used in our experiments is easily polymerized,these metal-organic coordination layers are therefore employed as precursors to fabricate cross-linked polymer layered materials throughγ-irradiated polymerization.The stabilities of the samples are signifi cantly improved afterγ-irradiation.To our knowledge,this is the fi rst time that covalent bonded polymer layered structures have been fabricated without the assistance of added surfactant or template.Such layered polymer materials cannot only act as alternatives to layered inorganic materials in some caustic environments,but also allow the generation of PbS nanoparticles(NPs)without aggregation in the polymer matrix.By exposing the polymer layer to H2S gas at room temperature,uniform PbS nanoparticles with an average size of about 6 nm are generated in situ.In addition,the resulting PbS NPs exhibit near-infrared(NIR)luminescent properties,which suggests the composite materials may be useful as active optical elements at communication wavelengths from 1300 to 1550 nm.

Advances, opportunities, and challenge for full-color emissive carbon dots

Carbon dots(CDs), novel luminescent zero-dimensional carbon nanomaterials, have been widely applied due to their low toxicity, optimal optical properties, and easy modification. However, the current controllable equipment and mechanism explanation of CDs are relatively vague and require urgent resolution.Full-color emission CDs, an essential CDs category, have attracted people’s attention given their light and color-tunable properties. In addition to a wider range of biological and optoelectronic device applications, full-color emission CDs have similar structures and significantly affected the fluorescence mechanism of CDs. At present, few studies have reported on the summary research of CDs emitted by its full color, which greatly limits the development of CDs mechanisms and applications. As such, the present review detailed the full-color CDs development status, to which a suitable method for preparing full-color CDs was presented and the existing fluorescence emission mechanism of full-color CDs was summarized.Herein, we comprehensively introduced full-color CDs applications in biology and optoelectronics. Finally,we made an outlook on the development and potential applications of full-color CDs. The present review aims to contribute novel insights and methods for understanding full-color CDs.

Cross-linking enhanced room-temperature phosphorescence of carbon dots

Currently,there is a strong drive to discover alternative materials that exhibit room-temperature phosphorescence(RTP)for displays,bioimaging,and data security.Ideally,these materials should be nontoxic,cheap,and possess controllable photoluminescent properties.Carbon dots(CDs)possess each of these characteristics,but to date,less attention has been paid to their RTP mechanism.Herein,we synthesized a series of CDs by self-crosslinking and carbonization of precursor.The resultant CDs were luminescent and exhibited a bright,micro-second afterglow lifetime.To increase the RTP,a second microwave processing step was used to coat the CDs with polyvinyl alcohol(PVA),polyacrylamide(PAM),or tetraethyl orthosilicate(TEOS),producing CDs@PVA,CDs@PAM,and CDs@TEOS composites.The core-shell structure acted to enhance crosslinking at the surface of the CDs to boost the RTP,creating abundant energy levels for intersystem crossover.In situ X-ray photoelectron spectroscopy verified electron transfer during luminescence.Finally,we present a design rule that can be used to tune the quantum yields and RTP lifetime of CDs,based on the effective stabilization of triplet excited states through the extent and strength of cross-linking.This simple strategy provides a flexible route for guiding the further development of CDs with tailored RTP properties for various applications.

A Strategy of Stabilization via Active Energy-Exchange for Bistable Electrochromic Displays

As future energy-saving optoelectronics,bistable electrochromic(EC)materials/devices have high energy efficiency for potential applications as smart windows,displays,and information/energy storage,due to their ability tomaintain optical states without consuming energy.However,further development is hindered by the lack of in-depth understanding of related key factors and universally applicable design strategies to achieve bistability.

Carbon dots are shining in the world

Carbon dots(CDs)are an emerging class of materials that has recently attracted considerable attention for biomedical and energy applications due to their strong luminescence,low toxicity,water-solubility,ease of synthesis,high surface area,and the possibility to tune their optical properties.However,such excellent properties and wide applications must be caused by their unique structure.CDs are generally considered to be a core-shell structure.

Near-infrared electroluminescent diodes based on copper hexadecafluorophthalocyanine CuPcF_(16)

We demonstrate the near-infrared （NIR） organic light-emitting devices （OLEDs） based on copper hexade-cafluorophthalocyanine （CuPcF16） doped into 2,2,2”-（1,3,5-benzenetriyl）tris-[1-phenyl-1H-benzimidazole] （TPBI）. The device structure is ITO/ NPB/ TPBI：CuPcF16/BCP/Alq3/Al. Room-temperature electro- luminescence is observed at about 1106 nm due to transitions from the first excited triplet state to the ground state （T1-S0） of CuPcF16. The result indicates that FSrster and Dexter energy transfers play a minor role in these devices, while the direct charge trapping is the dominant mechanism. The absorption spectra of CuPeF16 solution in pyridine and vacuum sublimed films on quartz have also been investigated.