Organic Nanodots Research Articles

P‐261: Late‐News Poster: Highly Efficient Color Conversion Layers Using Organic Nano‐dots

In this study, we report color conversion layers (CCLs) developed by new organic nano‐dots (ONDs). These ONDs, comprised of organic fluorescent materials and surfactant molecules, offer unique advantages such as tunable optical properties, high (100%) photoluminescence quantum yield (PLQY), and narrow (25‐35 nm) full‐width at half‐maximum (FWHM). Compared to the inorganic (InP) reference CCLs, OND CCLs exhibit almost double (80‐85%) color conversion efficiencies with good photo and thermal stability.

Fluorescent Organic Nano-dots as Efficient Color Conversion Layers

Fluorescent Organic Nano-dots as Efficient Color Conversion Layers

Simulating the Structure of Carbon Dots via Crystalline π‐Aggregated Organic Nanodots Prepared by Kinetically Trapped Self‐Assembly

AbstractThis work reports the successful preparation of a new type of crystalline luminescent organic nanodot (<3.5 nm) by kinetically trapped self‐assembly, which is then used as a simplified π‐packing model to simulate the structure of CDs. The precise structure and J‐aggregation‐induced photoluminescence (PL) of the nanodots are revealed by investigating the structural relationship between the nanodots and the corresponding single crystals and their properties. Compared with the single crystals, crystalline organic nanodots show longer PL lifetime, higher PL quantum yield, and narrower PL peak, indicating that they are potential organic quantum nanodots. In addition, the efficient π‐stacking environment in the corresponding single crystals can promote π‐aggregation‐induced PL anisotropy. This work indicates crystalline organic nanodots with precise structures to be potentially useful for understanding the structures of CDs and to be attractive potential luminescent materials.

Simulating the Structure of Carbon Dots via Crystalline π-Aggregated Organic Nanodots Prepared by Kinetically Trapped Self-Assembly.

This work reports the successful preparation of a new type of crystalline luminescent organic nanodot (<3.5 nm) by kinetically trapped self-assembly, which is then used as a simplified π-packing model to simulate the structure of CDs. The precise structure and J-aggregation-induced photoluminescence (PL) of the nanodots are revealed by investigating the structural relationship between the nanodots and the corresponding single crystals and their properties. Compared with the single crystals, crystalline organic nanodots show longer PL lifetime, higher PL quantum yield, and narrower PL peak, indicating that they are potential organic quantum nanodots. In addition, the efficient π-stacking environment in the corresponding single crystals can promote π-aggregation-induced PL anisotropy. This work indicates crystalline organic nanodots with precise structures to be potentially useful for understanding the structures of CDs and to be attractive potential luminescent materials.

Synthesis of fluorescent organic nano-dots and their application as efficient color conversion layers

Efficient conversion of light from short wavelengths to longer wavelengths using color conversion layers (CCLs) underpins the successful operation of numerous contemporary display and lighting technologies. Inorganic quantum dots, based on CdSe or InP, for example, have received much attention in this context, however, suffer from instability and toxic cadmium or phosphine chemistry. Organic nanoparticles (NPs), though less often studied, are capable of very competitive performance, including outstanding stability and water-processability. Surfactants, which are critical in stabilizing many types of nano-structures, have not yet been used extensively in organic NPs. Here we show the utility of surfactants in the synthesis and processing of organic NPs by thoroughly characterizing the effect of ionic and non-ionic surfactants on the properties of fluorescent organic NPs. Using this information, we identify surfactant processing conditions that result in nearly 100 % conversion of organic fluorophores into sub-micrometer particles, or nano-dots, with outstanding performance as CCLs. Such water dispersions are environmentally benign and efficiently convert light. They can be used for a range of fluorophores covering a full spectral gamut, with excellent color purity, including full-width at half-maximum (FWHM) values as low as 21 nm. Compared to inorganic (InP) reference CCLs, the organic nano-dot based CCLs show superior color conversion efficiency and substantially improved long-term stability.

Green microalgae derived organic nanodots used as food preservative

Spirulina platensis derived organic nanodots (ND) may be used as an alternative of chemical food preservative that can increase shelf life of food and beverages. Microalgal nanodots were isolated by the supercritical carbon dioxide extraction (SCE) method. Then SCE extract was subjected to thin-layer chromatography (TLC) and fractions were screened by a well diffusion method to identify the active compound with strong antibacterial ability. A characteristic of ND is the emitting of red colour upon the absorbance of ultra-violet (UV) light. The isolated ND is active against both Gram-positive and Gram-negative bacteria that significantly avoid their auto-aggregation. The nanodots were characterized by using TEM, UV-VIS, FTIR and NMR spectroscopy. FTIR and NMR analysis revealed the presence of hydrogen-bonded hydroxyl and amide groups. In addition, ND is applied in litchi juice as a preservative to extend the shelf life. In general, our results revealed that the sensory quality i.e. colour, aroma and overall appearance were significantly affected by duration of storage. It proves that Spirulina platensis derived organic nanodots act as a strong food and beverage preservative.

Organic Nano-Dots as Efficient Color Conversion Layer

Organic Nano-Dots as Efficient Color Conversion Layer

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Soft fluorescent organic nanodots as nanocarriers for porphyrins

Novel fluorescent organic nanoparticles made from citric acid and diethylenetriamine were used as biocompatible and highly water-soluble nanocarriers for hydrophobic tetraphenylporphyrin (TPP). The tetraphenylporphyrin units were covalently attached to the nanoparticles, generating conjugated nanoparticles which retain water solubility and preserve the photophysical properties of monomeric TPP. The conjugated nanoparticles show two distinct fluorescence features: blue emission from the nanoparticle when excited in the near-UV (360 nm) and characteristic far-red emission of the TPP when excited in the visible (Soret band or Q bands). The uptake of the conjugated nanoparticles in live human neuroblastoma cancer cells was evidenced using two-photon microscopy. These experiments demonstrate that the fluorescent organic nanoparticles do act as efficient nanocarriers, allowing cell internalization of hydrophobic porphyrins. These conjugated nanoparticles appear as promising nanotools for theranostic (based on the combination of imaging and monitoring of the nanoparticle fluorescence) and therapeutic (photodynamic therapy by selectively exciting the grafted porphyrin units) modalities.

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Theranostic Nanodots with Aggregation-Induced Emission Characteristic for Targeted and Image-Guided Photodynamic Therapy of Hepatocellular Carcinoma.

Photosensitizer (PS) serves as the central element of photodynamic therapy (PDT). The use of common nanoparticles (NPs) for PDT has typically been rendered less effective by the undesirable aggregation-caused quenching (ACQ) effect, resulting in quenched fluorescence and reduced reactive oxygen species (ROS) generation that diminish the imaging quality and PDT efficacy. To overcome the ACQ effect and to enhance the overall efficacy of PDT, herein, integrin ανβ3-targeted organic nanodots for image-guided PDT were designed and synthesized based on a red emissive aggregation-induced emission (AIE) PS.Methods: The TPETS nanodots were prepared by nano-precipitation method and further conjugated with thiolated cRGD (cRGD-SH) through a click reaction to yield the targeted TPETS nanodots (T-TPETS nanodots). Nanodots were characterized for encapsulation efficiency, conjugation rate, particle size, absorption and emission spectra and ROS production. The targeted fluorescence imaging and antitumor efficacy of T-TPETS nanodot were evaluated both in vitro and in vivo. The mechanism of cell apoptosis induced by T-TPETS nanodot mediated-PDT was explored. The biocompatibility and toxicity of the nanodots was examined using cytotoxicity test, hemolysis assay, blood biochemistry test and histological staining.Results: The obtained nanodots show bright red fluorescence and highly effective 1O2 generation in aggregate state. Both in vitro and in vivo experiments demonstrate that the nanodots exhibit excellent tumor-targeted imaging performance, which facilitates image-guided PDT for tumor ablation in a hepatocellular carcinoma model. Detailed analysis reveals that the nanodot-mediated PDT is able to induce time- and concentration-dependent cell death. The use of PDT at a high PDT intensity leads to direct cell necrosis, while cell apoptosis via the mitochondria-mediated pathway is achieved under low PDT intensity.Conclusion: Our results suggest that well-designed AIE nanodots are promising for image-guided PDT applications.

Seeing the fate and mechanism of stem cells in treatment of ionizing radiation-induced injury using highly near-infrared emissive AIE dots

Ionizing radiation-induced skin injury is a common and severe side effect of radiotherapy suffered by cancer patients. Although the therapy using stem cells has been demonstrated to be effective, fully grasping their role in the repair of radiation-induced skin damage remains challenging owing to the lack of highly reliable cell trackers. Herein, we report the design and synthesis of a highly near-infrared emissive organic nanodots with aggregation-induced emission (AIE) characteristic, which give excellent performance in seeing the fate and regenerative mechanism of adipose-derived stem cells (ADSCs) in treatment of radiation-induced skin injury. The resultant AIE dots show a rather high quantum yield of 33% in aqueous media, prominent retention ability in ADSCs without leakage, good biocompatibility during the ADSC differentiation and proliferation as well as excellent injury relief capability on radiation-induced endothelial cells injury. In vivo studies reveal that the AIE dots are capable of serving as an effective fluorescent cell tracker to precisely trace the behavior of the transplanted ADSCs in radiation-induced skin injury-bearing mice and help to understand the ADSCs therapeutic mechanism for at least one month. This study will provide new materials and insights into the stem cell therapy of radiation-induced injury.

Thin PEGylated Carbon Nitrides: Water-Dispersible Organic Nanodots as Bioimaging Probes.

Fluorescent materials are being used for the optical/fluorescence imaging of living cells and animal models. As such, the development of heavy-metal-free, water-dispersible, and biocompatible imaging probes is still important. Carbon nitride (C3 N4 ) is used as a bioimaging probe due to its suitable optical properties, thus enhancing its biocompatibility and dispersibility in aqueous media is required. In this study, we incorporated short-chain polyethylene glycol (PEG) groups onto a carbon nitride network by the simple N-alkylation of hexaethylene glycolic mesylate with nucleophilic nitrogen atoms on oxidized carbon nitride (OCN). The PEGylated OCN (PEG-OCN) was well dispersed in water as nanodots with a lateral dimension of approximately 30 nm and a thickness of 0.5-1.2 nm and showed strong photoluminescence in the visible region. Cell-viability testing confirmed that these "heavy-metal-free" organic nanodots were highly biocompatible and noncytotoxic. In particular, the developed nanodots could provide clear confocal images of RAW 264.7 cells without weakening cell activity and displaying any aggregation in a range of concentrations (25-100 μg mL-1 ) with bright-green emission in the cytoplasm.

Aptamer-Decorated Self-Assembled Aggregation-Induced Emission Organic Dots for Cancer Cell Targeting and Imaging.

A facile and simple one-step method was developed to fabricate aptamer-decorated self-assembled organic dots with aggregation-induced emission (AIE) characteristics. With integration of the advantages of AIE aggregates with strong emission and the cell-targeting capability of aptamers, the as-prepared Apt-AIE organic nanodots can specifically target to cancer cells with good biocompatibility, high image constrast, and photostability. On the basis of this universal method, a variety of versatile organic fluorescent nanoprobes with high brightness, specific recognition, and clinical-transitional potential could be facilely constructed for biological sensing and imaging applications.

A photostable triphenylamine-based flavonoid dye: Solvatochromism, aggregation-induced emission enhancement, fabrication of organic nanodots, and cell imaging applications

Fluorescent organic nanodots are considered as the promising tools for long-term cellular imaging, due to their high luminescence, good photostability and good biocompatibility. In this study, a novel triphenylamine-based flavonoid dye with aggregation-induced emission enhancement characteristics was designed and synthesized. Based on these flavonoid dyes, the organic nanodots were facilely fabricated without further surface modification, exhibiting the low cytotoxicity, good resistance against photobleaching, and acceptable cell uptake. Remarkably, these nanodots achieved a long-term bioimaging for living cells with 70% of their initial fluorescence retained after 48 h continuously incubation. The excellent properties made the flavonoid dye the promising addition to the current library of fluorescent organic nanodots in bioimaging application.

Precise and long-term tracking of adipose-derived stem cells and their regenerative capacity via superb bright and stable organic nanodots.

Monitoring and understanding long-term fate and regenerative therapy of administrated stem cells in vivo is of great importance. Herein we report organic nanodots with aggregation-induced emission characteristics (AIE dots) for long-term tracking of adipose-derived stem cells (ADSCs) and their regenerative capacity in living mice. The AIE dots possess high fluorescence (with a high quantum yield of 25±1%), excellent biological and photophysical stabilities, low in vivo toxicity, and superb retention in living ADSCs with negligible interference on their pluripotency and secretome. These AIE dots also exhibit superior in vitro cell tracking capability compared to the most popular commercial cell trackers, PKH26 and Qtracker 655. In vivo quantitative studies with bioluminescence and GFP labeling as the controls reveal that the AIE dots can precisely and quantitatively report the fate of ADSCs and their regenerative capacity for 42 days in an ischemic hind limb bearing mouse model.

Organic nanoparticles composed of Fréchet-type dendrons: synthesis, characterization, self-assembly and reversible guest encapsulation.

Novel organic nanoparticles composed of Fréchet-type dendrons have been synthesized by a simple one-pot reaction, which involved etching off the gold core in a first generation gold nanoparticle-cored dendrimer (AuG1). Dissolution of the Au core leads to the generation of numerous dendron radicals in a small volume, which underwent very fast coupling and addition reactions to form the Fréchet-type dendron nanoparticles (FDNs). The FDNs were found to be nearly monodispersed with an average size of 3 nm. NMR, TEM and MALDI-TOF analysis suggested that the FDNs are extremely dense organic structures made up of Fréchet-type dendrons. Although the FDNs do not contain any self-assembling motifs, such as hydrogen bonding moieties, they exhibited time and concentration dependent morphological transformations, leading to the formation of larger spherical aggregates and fibrous networks. Morphological transformations were probed using TEM, AFM and DLS studies. The self-assembly was found to be reversible. The morphological transformation of FDNs was exploited for the encapsulation and on-demand release of guest molecules.

Non-blinking, highly luminescent, pH- and heavy-metal-ion-stable organic nanodots for bio-imaging.

Heavy-metal-free, organic-small-molecule-based fluorescent nanodots (Sdots, 31-60 nm in diameter) based on 2,7-di(4-(diphenylamino)phenyl-2,1,3-benzothiadiazol-7-yl)-9,9'-spirobifluorene (Spiro-BTA) were prepared through a simple solution process. The Sdots show not only non-blinking and high-brightness fluorescence but also stability in various pH conditions and heavy metal ion solutions. More importantly, Spiro-BTA Sdots demonstrate obviously much higher brightness with very high signal-to-background ratio in Hela cell, compared with common CdSe/ZnS QDs. In addition, they exhibit large Stokes shifts, broad absorption spectra, and low toxicity to living cells which enable their applications as good fluorescence probes for bio-imaging. Further application of Sdots for folate receptor-mediated live-cell endocytosis was demonstrated by non-convalent modification with folic acid linked multidentate ligands.

From Graftable Biphotonic Chromophores to Water‐Soluble Organic Nanodots for Biophotonics: The Importance of Environmental Effects

The photophysical and two-photon absorption (TPA) properties of biphotonic chromophores with one or two phenol pendant units were studied and compared with that of a model biphotonic quadrupolar chromophore. A water-soluble dendritic structure was then synthesized by using the pendant moieties as starting points for the construction of dendritic branches. We show that the polarity of the environment significantly modulates both the fluorescence and the TPA responses of the different chromophoric derivatives. This extends to more subtle effects that involve phenol pendant moieties that were found to act as discrete solvating units and to modify both the photophysics and the TPA response of the chromophore. This demonstrates the high sensitivity of the TPA response of quadrupolar derivatives to minute alterations in the environment. Moreover, the dendritic branches were found to behave as a peculiar cybotactic environment that was able to tune the fluorescence and TPA response of the inner chromophore by creating a polar environment. This reveals a new direction for exploiting such effects by playing on the dendritic architecture (e.g., the nature and shape of the building blocks, the geometry and position of the chromophore) to modulate the TPA responses.

Light-Induced Ostwald Ripening of Organic Nanodots to Rods

Ostwald ripening allows the synthesis of 1D nanorods of metal and semiconductor nanoparticles. However, this phenomenon is unsuccessful with organic π-systems due to their spontaneous self-assembly to elongated fibers or tapes. Here we demonstrate the uses of light as a versatile tool to control the ripening of amorphous organic nanodots (ca. 15 nm) of an azobenzene-derived molecular assembly to micrometer-sized supramolecular rods. A surface-confined dipole variation associated with a low-yield (13-14%) trans-cis isomerization of the azobenzene moiety and the consequent dipole-dipole interaction in a nonpolar solvent is believed to be the driving force for the ripening of the nanodots to rods.