Small Dye Research Articles

(Invited) Kinetics and Thermodynamics of Swcnts and Bnnts Encapsulation with α-Sexithiophene in Liquid Phase

Single-Walled Carbon Nanotubes (SWNTs) and Boron Nitride Nanotubes (BNNTs) come with hollow 1D centers, which can serve to define narrow spaces for encapsulating small organic dyes. The encapsulation process is of scientific interest because it can be used to tailor the optical properties of the resulting dyes@NTs nanohybrids. Past works have shown that the dyes@SWCNT exhibits a strongly enhanced Raman scattering cross section, while the dyes@BNNTs do emit robust, generally red-shifted, luminescence at wavelengths down to the near-IR. In both cases, the nanotube protects the encapsulated dyes from photobleaching, provides high confinement, and reinforces intermolecular interactions between dyes into specific aggregation states.Here, we compare the liquid phase encapsulation process of α-sexithiophene (6T), which is a conjugated rod-like dye, inside SWCNTs and BNNTs. Raman and luminescence imaging experiments are used to monitor the 6T encapsulation process of a large ensemble of individual nanotubes in liquid-phase. This method probes statistically the encapsulation kinetics using hundreds of individual nanotubes according to various parameters (dye concentration and temperature). The results highlight a kinetic model in which single and double aggregates is formed sequentially. This kinetics and the associated thermodynamic parameters for the 6T encapsulation will be presented and discussed so as to gain a better control over the emission properties of the nanohybrids.

Ultra-bright green carbon dots with excitation-independent fluorescence for bioimaging

Current and future diagnostics urgently need imaging agents that are non-toxic and superior to clinically used small molecule dyes. Herein, we have developed luminescent green light-emitting carbon dots (GCDs) via a single-step hydrothermal reaction using a low-cost chemical precursor, p-toluenesulfonic acid. The GCDs exhibit excitation-independent fluorescence (FL) emission with the photoluminescence quantum yield of 70% and no FL quenching up to 1.25 mg/mL. The GCDs exhibit negligible cytotoxicity up to 250 µg/mL concentration in RAW 264.7 cells. Interestingly, GCDs exhibit an excitation-independent and concentration-dependent fluorescence emission behaviour. In vitro, the peak emission was obtained at 520 nm using the excitation at 430 nm. Whereas FL intensity increased with increasing concentration up to 1.25 mg/mL and a sharp decrease in FL intensity is observed upon further increasing the concentration of GCDs. Upon subcutaneously injecting the GCDs into a euthanized mouse, a similar concentration-dependent FL behaviour is evident. Background autofluorescence hinders the use of the GCDs at 420 nm excitation, however, a strong FL emission at 520 nm can be obtained by exciting subcutaneously injected GCDs at 465 nm—demonstrating excitation-independent emission characteristics. The above results indicate the potential of the non-toxic, low-cost carbon dots for diverse bioimaging applications.Graphical abstractUltra-bright green-emitting carbon dots (GCDs) with photoluminescence quantum yield of 70% were synthesized using p-toluenesulfonic acid and ethylenediamine as precursors. The GCDs were subcutaneously injected into fresh mouse cadaver for fluorescence (FL)bioimaging, showing dose-dependent FL intensity behaviour.

Triphenylamine flanked boron difluoride formazanate for NIR-II fluorescence imaging-guided photothermal therapy

Small molecular theranostic agents play the pivot roles in the biomedical field and hold high clinical translational potential. However, it is still difficult to prepare these theranostic agents through a convenient and straightforward synthetic route. Herein, based on the electron-deficient building block boron difluoride formazanate (BDF), we designed and synthesized a novel NIR-II small molecular fluorescent dye (BDF-Ph) by flanking electron-rich triphenylamine units onto BDF to hamper the intermolecular π-π interaction, thus to achieve high fluorescence quantum yield. Then donor-acceptor-donor (D-A-D) structured BDF-Ph was encapsulated into amphiphilic polystyrene-g-poly (ethylene glycol) (PS-g-PEG) to prepare NIR-II fluorescent BDF-Ph NPs. BDF-Ph NPs possessed an emission peak at 975 nm with a high fluorescence quantum efficiency of 0.32% (IR1061, Φ = 1.7%) and a high photothermal conversion efficiency of 40.1%, making it an excellent NIR-II fluorescent probe for nanotheranostics. In vivo investigation illustrated that BDF-Ph NPs exhibited strong NIR-II fluorescence signals. Meanwhile, upon exposure to 808 nm laser, BDF-Ph NPs could eradicate tumors without apparent adverse effects under the direction of NIR-II fluorescence imaging. These fascinating results confirmed that BDF-Ph NPs as an alternative theranostic nanoplatform could be used for oncotherapy.

Small Molecule NIR‐II Dyes for Switchable Photoluminescence via Host –Guest Complexation and Supramolecular Assembly with Carbon Dots

Small molecular NIR‐II dyes are highly desirable for various biomedical applications. However, NIR‐II probes are still limited due to the complex synthetic processes and inadequate availability of fluorescent core. Herein, the design and synthesis of three small molecular NIR‐II dyes are reported. These dyes can be excited at 850–915 nm and emitted at 1280–1290 nm with a large stokes shift (≈375 nm). Experimental and computational results indicate a 2:1 preferable host–guest assembly between the cucurbit[8]uril (CB) and dye molecules. Interestingly, the dyes when self‐assembled in presence of CB leads to the formation of nanocubes (≈200 nm) and exhibits marked enhancement in fluorescence emission intensity (Switch‐On). However, the addition of red carbon dots (rCDots, ≈10 nm) quenches the fluorescence of these host–guest complexes (Switch‐Off) providing flexibility in the user‐defined tuning of photoluminescence. The turn‐ON complex found to have comparable quantum yield to the commercially available near‐infrared fluorophore, IR‐26. The aqueous dispersibility, cellular and blood compatibility, and NIR‐II bioimaging capability of the inclusion complexes is also explored. Thus, a switchable fluorescence behavior, driven by host–guest complexation and supramolecular self‐assembly, is demonstrated here for three new NIR‐II dyes.

A Novel Fluorescent Dye Extracted from Buddleja officinalis for Labeling Mitochondria after Fixation.

Mitochondria are versatile organelles and function by communicating with cellular ecosystems. The fluorescent colocalization analysis after fixation is a highly intuitive method to understand the role of mitochondria. However, there are few fluorescent dyes available for mitochondrial staining after fixation. In this study, a novel fluorescent dye (BO-dye), extracted from Buddleja officinalis, was applied for mitochondrial staining in fixed immortalized human oral keratinocytes. The BO-dye (excitation: 414 nm, emission: 677 nm) is a small fluorescent molecular dye, which can cross the cytomembrane without permeabilization. We assume that the BO-dye could aggregate and bind to the mitochondria stably. BO-dye exhibited a mega-Stokes shift (>250 nm), which is an important feature that could reduce self-quenching and enhance the signal-to-noise ratio. Analysis of photophysical properties revealed that the BO-dye is temperature and pH insensitive, and it exhibits superior photostability. These results indicate that BO-dye can be considered an alternative fluorescent dye for labeling mitochondria after fixation.

Dye retention and desalination behavior of MoS2 doped high-flux β-CD/TDI polyurethane nanofiltration membrane

Molybdenum disulfide nanosheets (MoS2) were dispersed in β-cyclodextrin (β-CD) aqueous solution and interfacially polymerized with toluene-2,4-diisocyanate (TDI) to prepare high flux polyurethane loose nanofiltration membrane (DSPU) with good hydrophilicity and highly negatively charged. Through infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS), the existence and distribution of MoS2 nanosheets in DSPU were characterized and confirmed. Based on the pure water flux, salt, and dye rejection rate, The optimal composition of β-CD and MoS2 in the aqueous phase was investigated. The pure water flux of DSPU-1.2–0.006 reaches 78.44 L/m2•h•bar, which is 2.4 times higher than that of the DPU membrane without MoS2 and can retention the molecular weight >416 g/mol highly negatively charged small dye molecules. The interception behavior of DSPU on 10 kinds of dye molecules with different charge abilities, molecular weight, and size was investigated. The chemical composition, cavity structure, and MoS2 nanosheet spacing of β-CD were analyzed for their correlation with DSPU interface properties, functional layer structure, and separation performance. DSPU worked stably for a long time and had an excellent antifouling performance. It has potential application performance in the field of dye desalination, separation, and purification.

Constructing chemical stable 4-carboxyl-quinoline linked covalent organic frameworks via Doebner reaction for nanofiltration

Covalent linkages are the key component of covalent organic frameworks (COFs). The development of stable and functional linkages is essential to expand the COFs family and broaden their application prospects. In this work, we report the synthesis of crystalline and chemical stable 4-carboxyl-quinoline linked COFs (QL-COFs) via Doebner reactions in both one-pot (OP) and post-synthetic modification (PSM) methods. Both methods can be universally applied to most of the reported imine COFs family via bottom-up construction or linkage conversion. Owing to the contractive pore size, more hydrophilic structure and better chemical stability than the conventional imine COFs endowed by 4-carboxyl-quinoline linkage, QL-COFs are supposed to possess a wider application range. We further demonstrate the nanofiltration membrane (NFM) based on QL-COF exhibited a desirable separation capacity with high rejection for small dye molecules (> 90%), high water permeance (850 L m−2 h−1 MPa−1) and tolerance of extreme conditions (1 M HCl/NaOH), which were benefitted from the enhanced properties of QL-COFs. Additionally, efficient ion sieving properties were also achieved by QL-COF membrane. We anticipate that this work opens up a way for the construction of robust and functional COFs materials for practical applications.

In Situ Electroporation on PERFECT Filter for High-Efficiency and High-Viability Tumor Cell Labeling.

Labeling-assisted visualization is a powerful strategy to track circulating tumor cells (CTCs) for mechanism study (e.g., tumor metastasis). Due to the rarity of CTCs in the whole blood, efficient simultaneous enrichment and labeling of CTCs are needed. Hereby, novel in situ electroporation on a previously-developed micropore-arrayed filter (PERFECT filter) is proposed. Benefiting from the ultra-small-thickness and high-porosity of the filter plus high precision pore diameter, target rare tumor cells were enriched with less damage and uniform size distribution, contributing to enhanced molecular delivery efficiency and cell viability in the downstream electroporation. Various biomolecules (e.g., small molecule dyes, plasmids, and functional proteins) were used to verify this in situ electroporation system. High labeling efficiency (74.08 ± 2.94%) and high viability (81.15 ± 3.04%, verified via live/dead staining) were achieved by optimizing the parameters of electric field strength and pulse number, ensuring the labeled tumor cells can be used for further culture and down-stream analysis. In addition, high specificity (99.03 ± 1.67%) probing of tumor cells was further achieved by introducing fluorescent dye-conjugated antibodies into target cells. The whole procedure, including cell separation and electroporation, can be finished quickly (<10 min). The proposed in situ electroporation on the PERFECT filter system has great potential to track CTCs for tumor metastasis studies.

Photocatalytic self-cleaning EVAL membrane by incorporating bio-inspired functionalized MIL-101(Fe) for dye/salt separation

This work was expected to develop a new loose NF membrane with facile materials to conduct dye/salt separation and endow it with versatile capacities to offer an applicable solution to treat textile wastewater. Ethylene vinyl alcohol (EVAL) was first chosen to fabricate loose nanofiltration (NF) membrane through non-solvent induced phase separation (NIPS) method. Besides, MIL-101(Fe) showed outstanding photocatalytic capacity in degrading organic molecules while a low-cost bio-inspired coating, catechol, was utilized to modify MIL-101(Fe). A combination of modified MIL-101(Fe) and EVAL could have a high water permeability (43.2 L·m−2·h−1·bar−1) with superior rejection to small molecule negative charged dyes (Chlorazol black T: 99.8%, Congo Red: 99.7%, Eriochrome black T: 98.4%) and low rejection to various salts (Na2SO4: 4.8 %, NaCl: 2.1 %, MgCl2: 2.9%, MgSO4: 4.9% and CaCl2: 3.3%). Meanwhile, the EVAL loose NF membrane with the best performance had excellent antifouling capacity and long-term stability in EBT/Na2SO4 separation. Moreover, the membrane could degrade dyes to self-clean the membrane surface through photocatalytic process, which originated from the Fe-O clusters in MIL-101(Fe).

Low Light Amplification Threshold and Reduced Efficiency Roll-Off in Thick Emissive Layer OLEDs from a Diketopyrrolopyrrole Derivative.

External quantum efficiency (EQE) roll-off under high current injection has been one of the major limiting factors toward the development of organic semiconductor laser diodes (OSLDs). While significant progress in this regard has been made on organic semiconductors (OSCs) emitting in the blue-green region of the visible spectrum, OSCs with longer wavelength emission (>600nm) have fallen behind in both material development and the advancement in device architectures suitable for the realization of OSLDs. Therefore, to make simultaneous incremental advancements, a host-guest system comprising of a high performing poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) polymer and an efficient small molecule laser dye, dithiophenyl diketopyrrolopyrrole (DT-DPP), is used. This combination provides an extremely low amplified spontaneous emission threshold of 4.2µJcm-2 at an emission wavelength of 620nm. The solution-processed organic light-emitting diodes (OLEDs) fabricated using this system exhibit a high external quantum efficiency (EQE) of 2.6% with low efficiency roll-off and high current injection up to 90Acm-2 to yield ultrahigh luminance of over 1.5millioncdm-2 .

Twins of Minimalistic Carbon Dots: Uniform Emitting‐Units and Molecular Level Repeatable Photoluminescence

AbstractUnderstanding the photoluminescence mechanism of carbon dots (C‐dots) is both of fundamental and technical significance. However, it has remained an extreme challenge due to C‐dots’ indeterminate constitution and complicated composition/structure. Herein, a combined processing system, namely extraction and subsequent preparative thin layer chromatography for C‐dots separation is presented. Benefiting from its powerful separation performances, two minimalistic C‐dots with almost identical structure and optical properties (named as “twin” C‐dots) are well separated. Then, by contrastive analysis, a photophysical picture for the C‐dots’ photoluminescence is presented: The C‐dots’ photoluminescence comes from uniform surface polycyclic aromatic hydrocarbon units instead of the whole particles, which is both size‐ and oxygen‐independent. The products not only are highly bright and stable against photobleaching, but possess repeatable photoluminescence with molecular level accuracy. So, the C‐dots favorably integrate the advantages from small molecule dyes to photoluminescent nanomaterials, which is unprecedented and desirable for property exploration and application expansion.

Triphenylamine-based conjugated microporous polymers as dye adsorbents and supercapacitors

Background: Conjugated microporous polymers CMPs have unique position among porous materials thus they are studied widely. Realistically, triphenylamine (TPA) derivatives generally possess high aromaticity, redox capabilities, high charge motilities, and outstanding electronic features, therefore designing CMPs based on TPA derivatives could result in fantastic properties.Methods: We performed one-pot coupling and polycondensation of a boronated triphenylamine derivative (TPA-3Bor) with bromobenzene (Bz-4Br) and bromopyrene (Py-4Br) derivatives to obtain two new TPA-based conjugated microporous polymers (TPA-Bz and TPA-Py CMPs, respectively). The successful synthesis of two TPA CMPs and their features were examined via Fourier transform infrared (FTIR) and 13C solid state NMR spectroscopies.Significant Findings: These two CMPs displayed attractive adsorptive properties toward the small dye molecule rhodamine B (RhB) from an aqueous solution. Outstanding adsorption performance, rapid kinetics, and good reusability suggest that our CMPs could function as effective adsorbents for RhB and, perhaps, other pollutants from wastewater. Moreover, our TPA-based CMPs displayed effective and stable performance when introduced as electrodes for supercapacitors, with capacitances as high as 78 F g–1 at a current density of 1 A g–1 as well as high stability. This study emphasizes the importance of conjugation and planarity in the future design of such materials.

Construction of solvent resistance O‐PASS@UiO‐66‐NH2/O‐PASS composite membrane for methylene blue removal

AbstractThe purification of dye wastewater plays a critical role in water pollution treatment. Adsorption is a cheap and effective separation technology but is limited by the reuse of adsorption materials. Ultrafiltration membranes have a relatively high flux but their pores are too large to reject small dye molecules. In this study, negatively charged oxidized poly (arylene sulfide sulfone) (O‐PASS) membrane, NMP pretreatment oxidized O‐PASS (N‐O‐PASS) membrane, and O‐PASS@UiO‐66‐NH2/O‐PASS composite membranes were fabricated to retain cationic methylene blue (MB) from wastewater by combining ultrafiltration and adsorption techniques. The increased porosity of the N‐O‐PASS membrane provides more available adsorption sites for an equilibrium MB adsorption amount of 22.5 (mg g−1) and 100% rejection in the first 10 min during ultrafiltration with a pure water flux of 162.32 (L m−2 h−1 bar−1). Due to the enhanced hydrophilicity and separating property by deposited UiO‐66‐NH2 particles and PASS resin, O‐PASS@UiO‐66‐NH2/O‐PASS composite membrane shows a flux of 170.32 (L m−2 h−1 bar−1) and a 100% MB rejection in 60 min with great reusability. The O‐PASS@UiO‐66‐NH2/O‐PASS composite membrane is a new promising membrane for the removal of dyes from wastewater. Meanwhile, the superior solvent resistance endows it great adaptability in wide applications, especially in harsh conditions.

Small molecule diffusion in poly-(olygo ethylene glycol methacrylate) based hydrogels studied by fluorescence correlation spectroscopy

Understanding just how solutes such as small molecules, polymers or proteins diffuse in “smart” hydrogels is a key factor in developing potential applications. In this work, we used fluorescence correlation spectroscopy (FCS) to study how structural parameters (length of side groups, network density) influence the diffusion of small dye molecules in poly (oligo (ethylene glycol) methyl ether methacrylates) (POEGMAs) hydrogels. Two diffusion components were found and attributed to (i) Fickian-like diffusion slowed only by steric effects, and (ii) diffusion slowed by interactions with the polymer. The relationship between the diffusion component (i) and the polymer concentration showed two regimes with different slopes in both hydrogels and solutions of non-crosslinked polymers, additionally studied for reference. The threshold between these regimes depended on the polymer hydrophilicity/hydrophobicity and the presence of cross-links. The release time of the model drug (ibuprofen) proved to be shorter in the case of denser hydrogel networks than for looser ones. This means that the drug affinity to the polymer network is the crucial parameter determining release processes, while the diffusion factor is of secondary and minor importance.

Surface Functionalization of Rod-Shaped Viral Particles for Biomedical Applications.

While synthetic nanoparticles play a very important role in modern medicine, concerns regarding toxicity, sustainability, stability, and dispersity are drawing increasing attention to naturally derived alternatives. Rod-shaped plant viruses and virus-like particles (VLPs) are biological nanoparticles with powerful advantages such as biocompatibility, tunable size and aspect ratio, monodispersity, and multivalency. These properties facilitate controlled biodistribution and tissue targeting for powerful applications in medicine. Ongoing research efforts focus on functionalizing or otherwise engineering these structures for a myriad of applications, including vaccines, imaging, and drug delivery. These include chemical and biological strategies for conjugation to small molecule chemical dyes, drugs, metals, polymers, peptides, proteins, carbohydrates, and nucleic acids. Many strategies are available and vary greatly in efficiency, modularity, selectivity, and simplicity. This review provides a comprehensive summary of VLP functionalization approaches while highlighting biomedically relevant examples. Limitations of current strategies and opportunities for further advancement will also be discussed.

Novel PE and APC tandems: Additional near-infrared fluorochromes for use in spectral flow cytometry.

Recent advances in flow cytometry instrumentation and fluorochrome chemistries have greatly increased fluorescent conjugated antibody combinations that can be used reliably and easily in routine experiments. The Cytek Aurora flow cytometer was first released with three excitation lasers (405, 488, and 640 nm) and incorporated the latest Avalanche Photodiode (APD) technology, demonstrating significant improvement in sensitivity for fluorescent emission signals longer than 800 nm. However, there are limited commercially available fluorochromes capable of excitation with peak emission signals beyond 800 nm. To address this gap, we engineered six new fluorochromes: PE-750, PE-800, PE-830 for the 488 nm laser and APC-750, APC-800, APC-830 for the 640 nm laser. Utilizing the principal of fluorescence resonance energy transfer (FRET), these novel structures were created by covalently linking a protein donor dye with an organic small molecule acceptor dye. Additionally, each of these fluorochrome conjugates were shown to be compatible with fixation/permeabilization buffer reagents, and demonstrated acceptable brightness and stability when conjugated to antigen-specific monoclonal antibodies. These six novel fluorochrome reagents can increase the numbers of fluorochromes that can be used on a spectral flow cytometer.

Bacterial resting membrane potential: a case study with Bacillus subtilis

Bacterial membrane potential changes (Δψ) play an important role in bacterial metabolism and cellular processes as well as cell to cell communications in a biofilm. However, existing tools for reading Δψ quantitatively in individual bacterial cells as well as in bacterial communities are limited. A fluorescence lifetime imaging microscopy (FLIM) technique in combination with photo-induced electron transfer (PeT) based small molecule voltage sensitive dyes have been employed to quantify absolute resting membrane potential for individual Bacillus subtilis cells.

Exploring the structural dynamics of DNA using fluorescence polarization microscopy and optical tweezers

DNA structural transitions facilitate genomic processes, mediate drug-DNA interactions, and inform the development of emerging DNA-based biotechnology. Here, we use concurrent fluorescence polarization imaging and DNA manipulation experiments to probe the structure of DNA conformations that form under high tension and topological constraints. First, we employ polarization imaging of DNA intercalators (small dye molecules that slide between the DNA base-pairs) to probe the structure of S-DNA, an elongated conformation that can be accessed by mechanical overstretching of (relaxed) B-DNA.

The Mechanochemical Synthesis and Activation of Carbon-Rich π-Conjugated Materials.

Mechanochemistry uses mechanical force to break, form, and manipulate chemical bonds to achieve functional transformations and syntheses. Over the last years, many innovative applications of mechanochemistry have been developed. Specifically for the synthesis and activation of carbon‐rich π‐conjugated materials, mechanochemistry offers reaction pathways that either are inaccessible with other stimuli, such as light and heat, or improve reaction yields, energy consumption, and substrate scope. Therefore, this review summarizes the recent advances in this research field combining the viewpoints of polymer and trituration mechanochemistry. The highlighted mechanochemical transformations include π‐conjugated materials as optical force probes, the force‐induced release of small dye molecules, and the mechanochemical synthesis of polyacetylene, carbon allotropes, and other π‐conjugated materials.

A Transient Initiator for Polypeptoids Postpolymerization α‐Functionalization via Activation of a Thioester Group

AbstractHere, a postpolymerization modification method for an α‐terminal functionalized poly‐(N‐methyl‐glycine), also known as polysarcosine, is introduced. 4‐(Methylthio)phenyl piperidine‐4‐carboxylate as an initiator for the ring‐opening polymerization of N‐methyl‐glycine‐N‐carboxyanhydride followed by oxidation of the thioester group to yield an α‐terminal reactive 4‐(methylsulfonyl)phenyl piperidine‐4‐carboxylate polymer is utilized. This represents an activated carboxylic acid terminus, allowing straightforward modification with nucleophiles under mild reaction conditions and provides the possibility to introduce a wide variety of nucleophiles as exemplified using small molecules, fluorescent dyes, and model proteins. The new initiator yielded polymers with well‐defined molar mass, low dispersity, and high end‐group fidelity, as observed by gel permeation chromatography, nuclear magnetic resonance spectroscopy, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy. The introduced method can be of great interest for bioconjugation, but requires optimization, especially for protein conjugation.