Red,Green, and Blue Luminescence by Carbon Dots: Full‐Color Emission Tuning and Multicolor Cellular Imaging

A facile approach for preparation of photoluminescent (PL) carbon dots (CDs) is reported. The three resulting CDs emit bright and stable red, green and blue (RGB) colors of luminescence, under a single ultraviolet‐light excitation. Alterations of PL emission of these CDs are tentatively proposed to result from the difference in their particle size and nitrogen content. Interestingly, up‐conversion (UC)PL of these CDs is also observed. Moreover, flexible full‐color emissive PVA films can be achieved through mixing two or three CDs in the appropriate ratios. These CDs also show low cytotoxicity and excellent cellular imaging capability. The facile preparation and unique optical features make these CDs potentially useful in numerous applications such as light‐emitting diodes, full‐color displays, and multiplexed (UC)PL bioimaging.     

Red,Green, and Blue Luminescence by Carbon Dots: Full‐Color Emission Tuning and Multicolor Cellular Imaging

A facile approach for preparation of photoluminescent (PL) carbon dots (CDs) is reported. The three resulting CDs emit bright and stable red, green and blue (RGB) colors of luminescence, under a single ultraviolet‐light excitation. Alterations of PL emission of these CDs are tentatively proposed to result from the difference in their particle size and nitrogen content. Interestingly, up‐conversion (UC)PL of these CDs is also observed. Moreover, flexible full‐color emissive PVA films can be achieved through mixing two or three CDs in the appropriate ratios. These CDs also show low cytotoxicity and excellent cellular imaging capability. The facile preparation and unique optical features make these CDs potentially useful in numerous applications such as light‐emitting diodes, full‐color displays, and multiplexed (UC)PL bioimaging.     

Endowing matrix-free carbon dots with color-tunable ultralong phosphorescence by self-doping

Color-tunable ultralong phosphorescence is urgently desired in optoelectronic applications. Herein, we report a new type of full-color-tunable ultralong phosphorescence carbon dots (CDs) without matrix-assistance by a self-doping method under ambient conditions. The phosphorescence color can be rationally tuned from blue to red by changing the excitation wavelength from 310 to 440 nm. The CDs exhibit an ultralong lifetime of up to 1052.23 ms at 484 nm. From the experimental data, we speculate that the excitation-dependent multi-color phosphorescence is attributed to the presence of multiple emitting centers related to carbonyl units. Given the unique color-tunability of CDs, we demonstrate their potential applications in information encryption, light detection ranging from UV to visible light and LED devices. This finding not only takes a step towards the fundamental design of full-color emissive materials, but also provides a broader scope for the applications of phosphorescent materials.

A new type of CDs with abundant carbonyl groups shows color-tunable ultralong phosphorescence from blue to red by self-doping, which was applied in information encryption and light detection.     

β-Cyclodextrin derived full-spectrum fluorescent carbon dots: The formation process investigation and biological applications

Carbon dots (CDs), a new building unit, have been revolutionizing the fields of biomedicine, bioimaging, and optoelectronics with their excellent physical, chemical, and biological properties. However, the difficulty of preparing excitation-dependent full-spectrum fluorescent CDs has seriously hindered their further research in fluorescence emission mechanisms and biomedicine. Here, we report full-spectrum fluorescent CDs that exhibit controlled emission changes from purple (380 nm) to red (613 nm) at room temperature by changing the excitation wavelength, and the excitation dependence was closely related to the regulation of sp² and sp³ hybrid carbon structures by β-cyclodextrin-related groups. In addition, by regulating the content of β-cyclodextrin, the optimal quantum yields of full-spectrum fluorescent CDs were 8.97%, 8.35%, 7.90%, 9.69% and 17.4% at the excitation wavelengths of 340, 350, 390, 410 and 540 nm, respectively. Due to their excellent biocompatibility and color tunability, full-spectrum fluorescent CDs emitted bright and steady purple, blue, green, yellow, and red fluorescence in MCF-7 cells. Moreover, we optimized the imaging conditions of CDs and mitochondrial-specific dyes; and realized the mitochondrial-targeted co-localization imaging of purple, blue and green fluorescence. After that, we also explored the effect of full-spectrum fluorescent CDs in vivo fluorescence imaging through the intratumorally, subcutaneously, and caudal vein, and found that full-spectrum fluorescent CDs had good fluorescence imaging ability in vivo.     

Long-wavelength (red to near-infrared) emissive carbon dots: Key factors for synthesis,fluorescence mechanism,and applications in biosensing and cancer theranostics

Carbon dots (CDs), as a new member of carbon nanostructures, have been widely applied in extensive fields due to their exceptional physicochemical properties. While, the emissions of most reported CDs are located in the blue to green range under the excitation of ultraviolet or blue light, which severely limits their practical applications, especially in photovoltaic and biological fields. Studies that focused on synthesizing CDs with long-wavelength (red to near-infrared) emission/excitation features (simply named L-w CDs) and exploring their potential applications have been frequently reported in recent years. In this review, we analyzed the key influence factors for the synthesis of CDs with long wavelength and multicolor (containing long wavelength) emissive properties, discussed possible fluorescence mechanism, and summarized their applications in sensing and cancer theranostics. Finally, the existing challenges and potential opportunities of L-w CDs are presented.     

水相一步法合成具有双光子效应的高效橙红荧光聚合物碳点

聚合物碳纳米点是近年来新兴的一种荧光纳米探针,具有较低的生物毒性、良好的水溶性、较高的量子产率、优异的光/化学稳定性以及良好的生物相容性.目前所制备的碳点大都表现出蓝、绿色荧光发射.为实现碳点长波荧光发射,扩大其在生物标记与成像及光电显示方面的应用,本文采用水相一步法交联聚合反应制备了具有橙红荧光发射性质且具有双光子效应的聚合物碳点,发射波长为604 nm,荧光量子产率达到30.64%,并且应用在生物活体成像中.     

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 optoelectroni...     

Rapid and Large‐Scale Production of Multi‐Fluorescence Carbon Dots by a Magnetic Hyperthermia Method

The intrinsic low yield of carbon dots (CDs) is a barrier that limits practical application. Now, a magnetic hyperthermia (MHT) method is used to synthesize fluorescent CDs on a large scale (up to 85 g) in one hour (yield ca. 60 %). The reaction process is intensified by MHT since the efficient heating system enhances the energy transfer. CDs with blue, green, and yellow luminescence are synthesized by using carbamide and citrate with three different cations (Zn²⁺, Na⁺, K⁺), respectively. The CDs exhibit bright fluorescence under UV light and show excellent monodispersity and solubility in water. The alternation of photoluminescence (PL) emissions of these CDs is probably due to the difference in particle sizes and surface state. A bar coating technique is used to construct large‐area emissive polymer/CDs films. CDs can insert themselves into the polymer chains by hydrogen bonding and electrostatic interactions. Wound healing efficiency can be enhanced by the Zn‐CDs/PCL nanofibrous scaffold.     

Rapid and Large-Scale Production of Multi-Fluorescence Carbon Dots by a Magnetic Hyperthermia Method

The intrinsic low yield of carbon dots (CDs) is a barrier that limits practical application. Now, a magnetic hyperthermia (MHT) method is used to synthesize fluorescent CDs on a large scale (up to 85 g) in one hour (yield ca. 60 %). The reaction process is intensified by MHT since the efficient heating system enhances the energy transfer. CDs with blue, green, and yellow luminescence are synthesized by using carbamide and citrate with three different cations (Zn²⁺, Na⁺, K⁺), respectively. The CDs exhibit bright fluorescence under UV light and show excellent monodispersity and solubility in water. The alternation of photoluminescence (PL) emissions of these CDs is probably due to the difference in particle sizes and surface state. A bar coating technique is used to construct large-area emissive polymer/CDs films. CDs can insert themselves into the polymer chains by hydrogen bonding and electrostatic interactions. Wound healing efficiency can be enhanced by the Zn-CDs/PCL nanofibrous scaffold.     

Multicolor photochromism of two- and three-component diarylethene crystals

Novel photochromic single crystals composed of three different kinds of diarylethenes, 1,2-bis(3,5-dimethyl-2-thienyl)perfluorocyclopentene (1a), 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (2a), and 1,2-bis(2-methyl-5-p-methoxyphenyl-3-thienyl)perfluorocyclopentene (3a), have been prepared. The three-component crystals turned yellow, orange, red, purple, blue, green, or black upon irradiation with light of appropriate wavelengths. The colors of the crystals were thermally stable in the dark and completely bleached by irradiation with visible light. Such multicolored photochromic crystals have potential for the application to optoelectronic devices, such as multifrequency three-dimensional optical memory media or full-color displays.     

Synthesis and optical properties of novel blue‐light‐emitting poly(p‐phenylene vinylene) derivatives with pendant oxadiazole or cyano groups

Two novel poly(p‐phenylene vinylene) polymers, which carried side substituents with cyano groups or 1,3,4‐oxadiazole, were synthesized by Heck coupling. They consisted of alternating conjugated segments and nonconjugated aliphatic spacers. The polymers had moderate molecular weights, were amorphous, and dissolved readily in tetrahydrofuran and halogenated organic solvents. They were stable up to approximately 340 °C in N₂ and 290 °C in air, and the anaerobic char yield was around 60% at 800 °C. The polymer with cyano side groups emitted blue light in solutions and thin films with identical photoluminescence (PL) maximum at 450 nm; this supported the idea that chain interactions were hindered even in the solid state. The PL maximum of this polymer in thin films was blueshifted upon annealing at 120 °C, indicating a thermochromic effect as a result of conformational changes in the polymer backbone. The polymer containing side substituents with oxadiazole rings emitted blue light in solutions with a PL maximum at 474 nm and blue‐greenish light in thin films with a PL maximum at 511 nm. The PL quantum yields of the polymers in tetrahydrofuran were 0.13–0.24. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1768–1778, 2004     

酪氨酸微波水热法制备碳点及其在Fe3+检测和荧光标记方面的应用

以酪氨酸为原料,乙二胺为钝化剂,采用绿色、简便的微波辅助水热法制备了尺寸均一、分散性好的碳点.通过调节乙二胺的加入量可以在一定程度上对碳点尺寸进行调节.所得碳点可以通过改变激发波长实现蓝光到绿光的转变,且荧光强度随激发光波长的红移也保持了一定的强度.所得碳点对Fe³⁺具有很好的选择性猝灭,被用于检测Fe³⁺时检测限为0.82 nmol/L,检出限为2.98 nmol/L.所制备碳点具有良好的生物相容性和低细胞毒性,被用于标记AD293细胞时标记位置为细胞质.     

Novel conjugated polymer poly(benzobisoxazole-2,6-diylvinylene): synthesis and evidence of aggregate formation in methanesulfonic acid

A new conjugated polymer poly(benzobisoxazole-2,6-diylvinylene) (PBOV) has been synthesized as an analogue of poly(p-phenylene benzobisoxazole) (PBO). The comparison between PBOV and PBO has been carried out by Fourier transform infrared spectroscopy, thermogravimetric analysis, UV, and photoluminescence (PL) spectroscopy. The UV absorption peaks, PL excitation and emission wavelengths of PBOV have a significant red-shift due to the better electronic delocalization. Similar to PBO, it can be observed in the PL spectra of PBOV at various concentrations in methanesulfonic acid (MSA) that the intensity of emission was depressed and the highly structured emission spectra gradually changed to featureless, red-shifted, and broad spectra with increasing concentration. The change in emission spectra can be attributed to the existence of the interchain aggregates, although PBOV does not show highly ordered structure as PBO does.     

A Polydiacetylene Supramolecular System That Emits Red,Green, and Blue Fluorescence

A polymer system based on polydiacetylene (PDA) supramolecules that emits red, green, and blue fluorescence has been constructed. The three‐color emitting system is comprised of red‐fluorescent PDA vesicles in which green‐fluorescent fluorescein molecules are encapsulated. Finally, the blue‐fluorescence component is introduced by reacting terminal amine groups on the PDA vesicle surfaces with fluorescamine. Thin PDA‐polymer‐containing poly(vinyl alcohol) films formed by using this strategy display red, green, and blue fluorescence upon excitation with light at specific wavelengths.

     

Tunable light emission from carbon dots by controlling surface defects

Carbon dots (CDs) are metal-free fluorescent materials that can be used in optical and electronic devices, but few studies have focused on one-step synthesis routes for CDs with tunable color and high photoluminescence quantum yield (PLQY). Herein, CDs with tunable light emission were synthesized using a novel amide-assisted solvothermal approach. The as-prepared CDs were well dispersed and homogeneous, with average diameters of approximately 2.0–4.0 nm, depending on the dopants. Owing to the surface states with different ratios of nitrogen- and oxygen-related species, different CDs can exhibit blue, green, red, or white emission with relatively high PLQYs of 61.6%, 41.3%, 29.1% and 19.7%, respectively. XPS measurements, in conjunction with DFT calculations, indicate that nitrogen substitution (pyridinic/pyrrolic nitrogen) dominates the blue emission, while introducing oxygen functional groups lowered the LUMO energy level, which resulted in redder emission. In addition, the CDs are demonstrated as a bioimaging probe in both in vitro and in vivo assays, and the white light CDs have been demonstrated to be potential fluorescent materials for white-light-emitting diode (WLED).     

Solid-state Fluorescence from Carbon Dots Widely Tunable from Blue to Deep Red through Surface Ligand Modulation

Carbon dots (CDs) find widespread attention due to their remarkable fluorescent and electronic properties. However, aggregation-caused quenching currently limits the application of CDs in colored displays. The construction of CDs with color-tunable solid-state fluorescence (SSF) is rarely reported, since the preparation of SSF CDs is technically challenging. Herein, through surface ligand modulation, SSF CDs with an emission-color span of almost 300 nm (from blue to deep red) were obtained. In-depth structure-property studies reveal that intra- and inter-molecular hydrogen-bonding inside SSF CDs provokes the emission properties in the aggregated state. Photodynamic characterizations demonstrate emission wavelengths can be switched smoothly by deliberately altering conjugation ability between substituent ligands and CDs core. Three-dimensional printing patterning is used to create a range of emissive objects, demonstrating the commercial potential for use in optical lamps.     

Heteroblastic Development and Shade-avoidance in Response to Blue and Red Light Signals in Acacia implexa

Information from blue (400–500 nm) and red (660–730 nm) wavelengths is used by plants to determine proximity of neighbors or actual shading. Plants undergo trait changes in order to out-compete neighbors or accommodate shading. Heteroblasty, the dramatic shift from one leaf type to another during juvenility, can be influenced by the light environment although it is unknown whether cues from blue or red (or both) are driving the developmental process. Seedlings of three populations of Acacia implexa (Mimosaceae) collected from low, medium and high rainfall habitats were grown in a factorial design of high/low blue and red light to determine how light signals affect heteroblasty and patterns of biomass allocation. Low blue light significantly delayed heteroblasty in the low rainfall population and low red light significantly delayed in the low and high rainfall populations. Low blue light increased stem elongation and decreased root biomass whereas low red light induced a strong shade-avoidance response. These results were consistent across populations although the low rainfall population showed greater trait variability in response to red light signals. We conclude that red light conveys a greater information signal than blue light that affects heteroblasty and seedling development in A. implexa .     

Effects of Selenium and Light Wavelengths on Liquid Culture of <Emphasis Type="Italic">Cordyceps militaris</Emphasis> Link

To investigate the effects of selenium and light wavelengths on the growth of liquid-cultured Cordyceps militaris and the main active components’ accumulation, culture conditions as selenium selenite concentrations and light of different wavelengths were studied. The results are: adenosine accumulation proved to be significantly selenium dependent (R ² = 0.9403) and cordycepin contents were determined to be not significantly selenium dependent (R ² = 0.3845) but significantly enhanced by selenium except for 20 ppm; there were significant differences in cordycepin contents, adenosine contents, and mycelium growth caused by light wavelengths: cordycepin, blue light > pink light > daylight, darkness, red light; adenosine, red light > pink light, darkness, daylight, blue light; and mycelium growth, red light > pink light, darkness, daylight > blue light. In conclusion, light wavelength had a significant influence on production of mycelia, adenosine, and cordycepin, so lightening wavelength should be changed according to target products in the liquid culture of C. militaris.     

Photoactivated Fluorescence Enhancement in F,N‐Doped Carbon Dots with Piezochromic Behavior

Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co‐doped carbon dots (F,N‐doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N‐doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue‐shift of the fluorescence emission from 586 nm to 550 nm. F,N‐doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N‐doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure‐triggered aggregation‐induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high‐pressure conditions and enhances their anti‐photobleaching.     

Red,green and blue aggregation‐induced emissive carbon dots

As one of the most promising fluorescent nanomaterials, carbon dots (CDs) have been extensively studied for their fluorescent properties in solution. However, research on the synthesis of multicolor solid-state fluorescence (SSF) CDs (from blue to red) is rarely reported. Herein, we used o-phenylenediamine, m-phenylenediamine and p-phenylenediamine with dithiosalicylic acid (DTSA) in the solvothermal reaction using acetic acid as a solvent to obtain aggregation-induced emissive (AIE) CDs of red (620 nm), green (520 nm), and blue (478 nm), respectively. XPS spectra and TEM image show that with the red-shift of luminescence, the particle size and content of C=O of the CDs gradually increases. Finally, based on the non-matrix solid-state multicolor luminescence characteristics of CDs, the application of white light LED devices is realized. Besides, based on the fat-soluble properties of CDs, fingerprint detection applications are realized.