Dual Emission Properties Research Articles

C-N Bond Rotation Controls Photoinduced Electron Transfer in an Aminostyrene-Stilbene Donor-Acceptor System.

We investigate energy transfer and electron transfer in a dimethylsilylene-spaced aminostyrene-stilbene donor-acceptor dimer using time-dependent density functional theory calculations. Our results confirm that the vertical S3, S2, and S1 excited states are, respectively, a local excitation on the aminostyrene, local excitation on the stilbene, and the charge-transferred (CT) excited state with electron transfer from aminostyrene to stilbene. In addition, an energy minimum with the C-N bond of the amino group twisted at about 90° is also identified on the S1 potential energy surface. This S1 state exhibits a twisted intramolecular charge transfer (TICT) character. A potential energy scan along the C-N bond torsional angle reveals a conical intersection between the S2 stilbene local excitation and the S1 CT/TICT state at a torsional angle of ∼60°. We thus propose that the conical intersection dominates the electron transfer dynamics in the donor-acceptor dimer and copolymers alike, and the energy barrier along the C-N bond rotation controls the efficiency of such a process. Moreover, we show that despite the zero oscillator strength of the S1 excited states in the CT and TICT minima, an emissive S1 state with a V-shaped conformational structure can be located. The energy of this V-shape CT structure is thermally accessible; therefore, it is expected to be responsible for the CT emission band of the dimer observed in polar solvents. Our data provide a clear explanation of the complex solvent-dependent dual emission and photoinduced electron transfer properties observed experimentally in the dimer and copolymer systems. More importantly, the identifications of the conical intersection and energy barrier along the C-N bond rotation provide a novel synthetic route for controlling emissive properties and electron transfer dynamics in similar systems, which might be useful in the design of novel organic optoelectronic materials.

Dual visible/NIR emission from organometallic iridium(III) complexes

A series of four substituted benzo[g]quinoxaline species have been synthesised and utilised as cyclometalating ligands for iridium(III). The ligands (L1-L4) were synthesised and isolated in good yield following the condensation of 2,3-diaminonaphthalene with benzil and three of its derivatives. The substituent modulated electronic properties of L1-L4 were dominated by intraligand π−π* transitions, with the fluorescence profile demonstrating vibronic features attributed to the highly conjugated nature of the chromophore. Iridium(III) complexes of the form [Ir(L)2(bipy)]PF6 were synthesised from L1-L4 in two steps. The electronic properties of the complexes reveal absorption in the UV-vis. region with spin forbidden metal-to-ligand charge transfer (MLCT) transitions possibly contributing at longer wavelengths to ca. 600 nm. Steady state luminescence (aerated, room temperature) on solutions of the complexes showed dual emissive properties in the visible and near-infra red (NIR) regions. Firstly, a vibronically structured emission in the visible region (ca. 525 nm) was attributed to ligand centred fluorescence (lifetime < 10 ns). Secondly, a broad emission peak in the NIR (ca. 950 nm) which extended to around 1200 nm was observed with corresponding lifetimes of 116–162 ns, indicative of triplet excited state emission.

Designed Synthesis of Dual Emitting Silicon Quantum Dot for Cell Imaging: Direct Labeling of Alpha 2-HS-Glycoprotein.

The innocent silicon quantum dots (SQDs) having dual emissive property (blue in VIS and red in NIR), high photostability, and freedom from auto fluorescence are designed and synthesized for the first time using ethylene glycol. A new attempt has been made for direct labeling of Alpha 2-HS-Glycoprotein (Fetuin A) through functionalization of the synthesized dots by EDC coupling. The SQDs were characterized by FTIR, TEM, AFM, XRD, EDX, DLS, and TGA. The chemistry involved in the synthesis and functionalization of dots is elucidated in detail. The synthesized SQDs are suitable for live cell imaging as well as direct labeling of the Fetuin A in the NIR region. The direct labeling technique developed for Fetuin A imaging is robust, more specific, and simple, and reduces the number of incubation and washing steps and produces better quality data compared to the conventional method using Rhodamine B.

Construction of NaYF4:Eu@carbon dots nanocomposites for multifunctional applications

The combination of carbon dots (CDs) and rare-earth ions has attracted increasing attention due to their unique fluorescence properties. Herein, CDs are incorporated with NaYF4:Eu to form stable NaYF4:Eu@CDs nanocomposites by a simple sol-gel route. It has been demonstrated that CDs are successfully embedded in the silica layer outside NaYF4:Eu nanoparticles. These nanocomposites exhibit characteristic emissions of both CDs and NaYF4:Eu under a single excitation wavelength. By using their dual-emissive properties, the nanocomposites can act as ratiometric fluorescent sensor for selective detection of Fe3+ ions in the range of 0–350 μM. The temperature-dependent luminescent property of the nanocomposites makes them also suitable as thermometers in the range from 377 to 467 K. In addition, the luminescent color can be regularly adjusted by tuning the mass ratio of NaYF4:Eu to CDs. This combing strategy enables us to achieve dual emission of CDs and Eu3+ ions in nanocrystals, opening an avenue towards multifunctional applications in widespread fields.

Disaggregation-induced ESIPT: a novel approach towards development of sensors for hyperglycemic condition

An oxazolonapthoimidazo[1,2-a]pyridine-based fluorescence probeONIP1was designed and synthesizedviamulticomponent reaction.ONIP1was able to distinguish human serum albumin (HSA) from and glycated-HSAviamodulation of AIEE- and ESIPT-based dual channel emission properties.

Benzoperylene probe/ZnS quantum dots nanocomposite for the ratiometric detection and intracellular imaging of highly reactive oxygen species

A ratiometric nanosensor for the selective detection and intracellular imaging of highly reactive oxygen species (hROS) is developed. Benzoperylene probe and Mn-ZnS quantum dots based nanoparticles were fabricated through cost effective and simple procedures. The nanoparticles exhibit distinct excimer emission and long-lived room-temperature phosphorescence (RTP) emission at the same time under single wavelength excitation. The nanosensor shows highly sensitive and selective ratiometric response towards hROS over other ROS. The dual emission property also endows the nanoparticles the capability for sensitive live cell imaging of hROS, and the potential for real time monitoring of intracellular hROS.

Aggregation-induced emission enhancement of gold nanoclusters triggered by silicon nanoparticles for ratiometric detection of protamine and trypsin

Metal nanoclusters protected by glutathione (GSH) have attracted a wide attention due to the unique aggregation-induced emission (AIE) feature. However, the “trigger” effects of ethanol, temperature, pH values, and metal ions may restrict the application of these particles. In this work, the amino modified silicon nanoparticles (SiNPs) and GSH-capped gold nanoclusters (GSH-AuNCs) can self-assemble into well-defined spherical particles due to the electrostatic interaction. As a result, the unique aggregation-induced emission enhancement (AIEE) of GSH-AuNCs arises at 570 nm, and the SiNPs keep their own blue fluorescence at 450 nm, so a novel nanohybrid probe (SiNPs@GSH-AuNCs) with dual-emission property has been constructed. When protamine is added to SiNPs@GSH-AuNCs, the cationic protamine can compete with SiNPs and absorb onto the surface of GSH-AuNCs, which inhibits the self-assembly and leads to the fluorescence quenching of GSH-AuNCs; while trypsin can catalyze the hydrolysis of protamine, the self-assembly starts again, producing the AIEE recovery. In the whole process, the SiNPs act as an internal standard and their emission stays constant. By means of the fluorescence intensity ratios I570/I450, the linear range of protamine is from 0.15 to 3.00 μg mL−1 with the limit of detection (LOD) of 0.07 μg mL−1, and trypsin shows a linear response in the range from 10 to 100 ng mL−1 with LOD of 4.50 ng mL−1. Furthermore, this strategy exhibits good sensitivity and selectivity, and has been further validated by applying it for the determination of protamine and trypsin in serum samples.

Synthesis of the Cu-Doped Dual-Emission Fluorescent Carbon Dots and Its Analytical Application.

New Cu-doped dual-emission carbon dots (D-CDs) were synthesized rapidly and simply via a one-pot solvothermal method, and its special photoluminescence mechanism was studied. D-CDs have two fluorescence (FL) emission peaks under one-wavelength excitation and can be used as dual-signal sensor which is usually designed with two or more substances. The prepared CDs show excellent water solubility, photostability, salt tolerance, oxidation resistance, and special optical properties. The raw material ratio, solvent, pH, time, and synthesis temperature were optimized. The characterizations of CDs including transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma spectroscopic analysis, X-ray diffraction assignation of phases, thermogravimetric analysis and differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, FL spectrum, and ultraviolet-visible spectrum (UV-vis) were conducted. The investigation on mechanism indicates that the unique dual-emissive property is mainly caused by the energy-level gaps generated by the surface defects of CDs. The prepared D-CDs have good potential in dual-signal analysis and visualization sensing. To demonstrate the practical application, ferric ions, vitamin A acetate, and pH have been determined successfully.

A Simple Strategy to Construct Amorphous Metal-Free Room Temperature Phosphorescent and Multi-Color Materials.

It is urgent to develop a universal strategy for producing small organic molecules exhibiting efficient room temperature phosphorescence (RTP). An important contribution made by Ma and Tian et al. provides a general and applicable strategy to obtain amorphous organic molecules with efficient RTP emission by simply modifying phosphors onto β-cyclodextrin (β-CD). The nonradiative decay processes and oxygen quenching have been significantly suppressed by the strong intermolecular hydrogen bonding between β-CD derivatives. Furthermore, the cavity of β-CDs endows them with the ability to incorporate the adamantane moiety of the fluorescent guest molecules to construct a supramolecular system which exhibits excellent RTP-fluorescence dual emission properties and multicolor emission by altering the host to guest ratio and the excitation wavelength.

Design of "Click" Fluorescent Labeled 2'-deoxyuridines via C5-[4-(2-Propynyl(methyl)amino)]phenyl Acetylene as a Universal Linker: Synthesis, Photophysical Properties, and Interaction with BSA.

Microenvironment-sensitive fluorescent nucleosides present attractive advantages over single-emitting dyes for sensing inter-biomolecular interactions involving DNA. Herein, we report the rational design and synthesis of triazolyl push-pull fluorophore-labeled uridines via the intermediacy of C5-[4-(2-propynyl(methyl)amino)]phenyl acetylene as a universal linker. The synthesized nucleosides showed interesting solvatochromic characteristic and/or intramolecular charge transfer (ICT) features. A few of them also exhibited dual-emitting characteristics evidencing our designing concept. The HOMO-LUMO distribution showed that the emissive states of these nucleosides were characterized with more significant electron redistribution between the C5-[4-(2-propynyl(methyl)amino)]phenyl triazolyl donor moiety and the aromatic chromophores linked to it, leading to modulated emission property. The solvent polarity sensitivity of these nucleosides was also tested. The synthesized triazolyl benzonitrile (10C), naphthyl (10E), and pyrenyl (10G) nucleosides were found to exhibit interesting ICT and dual (LE/ICT) emission properties. The dual-emitting pyrenyl nucleoside maintained a good ratiometric response in the BSA protein microenvironment, enabling the switch-on ratiometric sensing of BSA as the only protein biomolecule. Thus, it is expected that the new fluorescent nucleoside analogues would be useful in designing DNA probes for nucleic acid analysis or studying DNA-protein interactions via a drastic change in fluorescence response due to a change in micropolarity.

Diketopyrrolopyrrole-doped hybrid FONs as two-photon absorbing and dual-emission fluorescent nanosensors for Hg2+

Fluorescent organic nanoparticles (FONs) with dual-emission and two-photon fluorescence emission are promising sensing tools. In this work, novel hybrid FONs with two-photon absorption and dual-emission properties were used to detect Hg2+. The FONs were prepared by the co-self-assembly of amphiphilic furyl diketopyrrolopyrrole (DPP1) and tetraphenylethylene (TPE1) in water. Inside the water-soluble FONs, DPP1 worked as a two-photon absorption material and an effective Hg2+ receptor with emission peak at 540 nm. Meanwhile, TPE1, a typical aggregation-induced emission (AIE) molecule, maintained the nanostructure’s stability and offered another distinguishable fluorescent signal at 470 nm as the internal reference. These hybrid FONs were successfully used in the ratiometric and two-photon fluorescence detection of Hg2+ in water. The FONs showed selective and sensitive Hg2+ detection with a limit of detection of ca. 13 nM. Tests on tap-water samples indicated good reliability of the FONs in practical application. Furthermore, the FONs were used in cell imaging, and results demonstrated their potential application in biological sensing.

Simple coating synthesis and enhanced luminescence behaviour of LiLa(MoO4)2:Eu3+@NaF

A series of LiLa(MoO4)2:Eu3+@ (NaF)y wt were prepared with a simple coating method. XRD results confirm that NaF coating will cause the slight expand of the lattice volume for the sample. Strongly enhanced emission effect inducing by NaF coating is observed. The emission spectra (PL) intensity of the optimal sample, LiLa(MoO4)2:Eu3+0.06 @ (NaF)0.025wt is as high as 4.8 times of that of LiLa(MoO4)2:Eu3+0.06. Furthermore, dual emission properties inducing by NaF coating are observed. Enhancement emission of Eu3+ is a major effect, and increasing R is a minor effect. The optimal coating content of NaF is 2.5 wt%, which the corresponding chromaticity coordinates excited at 465 nm is x = 0.6650, y = 0.3347, which is nearly as same as the NTSC (National Television Standard Committee) standard values for red (x = 0.67, y = 0.33). So, it is a potential red-emitting phosphor with high R values (R = 5.89) for blue light-based white LED.

Amorphous Metal-Free Room-Temperature Phosphorescent Small Molecules with Multicolor Photoluminescence via a Host-Guest and Dual-Emission Strategy.

Metal-free room-temperature phosphorescence (RTP) materials offer unprecedented potentials for photoelectric and biochemical materials due to their unique advantages of long lifetime and low toxicity. However, the achievements of phosphorescence at ambient condition so far have been mainly focused on ordered crystal lattice or on embedding into rigid matrices, where the preparation process might bring out poor repeatability and limited application. In this research, a series of amorphous organic small molecular compounds were developed with efficient RTP emission through conveniently modifying phosphor moieties to β-cyclodextrin (β-CD). The hydrogen bonding between the cyclodextrin derivatives immobilizes the phosphors to suppress the nonradiative relaxation and shields phosphors from quenchers, which enables such molecules to emit efficient RTP emission with decent quantum yields. Furthermore, one such cyclodextrin derivative was utilized to construct a host-guest system incorporating a fluorescent guest molecule, exhibiting excellent RTP-fluorescence dual-emission properties and multicolor emission with a wide range from yellow to purple including white-light emission. This innovative and universal strategy opens up new research paths to construct amorphous metal-free small molecular RTP materials and to design organic white-light-emitting materials using a single supramolecular platform.

A pillared-layered copper(i) halide-based metal-organic framework exhibiting dual emission, and piezochromic and thermochromic properties with a large temperature-dependent emission red-shift.

We report a new copper halide-based compound [Cu6I6Br2C16H32N4] (1) with a 3D 2-fold interpenetrated framework structure. Upon excitation at 290 nm and 350 nm, compound 1 shows dual emission at ca. 500 nm and ca. 530 nm. As the temperature decreased from 300 K down to 6 K, the luminescent properties of compound 1 show large red shifts of 120 nm and 72 nm, respectively.

Dual emission via remote control of molecular rotation of o-carborane in the excited state by the distant substituents in tolane-modified dyads

Dual-emissive properties are reported based on the tolane-o-carborane dyads with various substituents.

Blackening of aza-BODIPY analogues by simple dimerization: panchromatic absorption of a pyrrolopyrrole aza-BODIPY dimer

Dimerization of the so-called pyrrolopyrrole aza-BODIPY via a bithienyl linkage led to the creation of a novel black dye with dual emission and panchromatic absorption properties in the Vis/NIR region.

Abstract 4016: Homogeneous BTK occupancy assay for pharmacodynamic assessment of GS-4059 target engagement

Abstract Burton’s Tyrosine Kinase (BTK) plays an important role in B cell signaling, cell proliferation and survival. Hence, it is an attractive target for therapeutic intervention in B cell malignancies and autoimmune disorders. GS-4059 (ONO-4059) is a covalent, potent and selective inhibitor of BTK in clinical development for CLL, NHL, and rheumatoid arthritis. Accurate measurement of target coverage in early stage clinical studies is critical to informing dose selection for GS-4059 in more advanced clinical studies. We developed a novel duplex homogeneous BTK occupancy assay to enable quantitative measurement of GS-4059 binding to human BTK for assessing target coverage in the clinic. The assay is based on Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) and simultaneously measures the levels of free BTK (BTK that is not bound to GS-4059 in treated human PBMCs ex vivo or PBMCs from patients treated with GS-4059 in clinical studies) as well as the levels of total BTK protein. We took advantage of the dual wavelength emission property of Terbium (Tb) to serve as energy donor for 2 fluorescent energy acceptors with distinct excitation and emission spectra. We designed and synthesized a GS-4059 analog with biotin conjugate which showed equal potency to GS-4059, suggesting that it binds in the same BTK pocket. To detect free BTK, a Tb-coupled anti-BTK antibody was used as the FRET energy donor and G2-strepavidin-bound biotinylated GS-4059 as the energy acceptor. Total BTK was detected in the same well with a second D2-coupled anti-BTK antibody that binds to a different BTK epitope as the FRET energy acceptor. The use of a common detection reagent in this multiplexed format allows measurement of free and total BTK levels in the same well data. The assay was characterized and qualified using full length purified recombinant human BTK protein and PBMCs derived from healthy volunteers and CLL patients. Preliminary data indicate the assay is also suitable for assessing BTK occupancy in bone marrow derived cells. Using this assay, we evaluated the BTK synthesis rate following a 1 hour high dose (5 μM) treatment of GS-4059 in BTK inhibitor resistant ABC-DLBCL and GCB-DLBCL tumor cells. While negligible new BTK synthesis was observed in BTK inhibitor sensitive DLBCL cells, the free BTK level in the inhibitor resistant tumor cells recovered rapidly post-treatment. In summary, we have established a homogeneous TR-FRET based BTK occupancy assay that simultaneously measures free and total BTK levels in the same well, yielding quantitative BTK occupancy data to support GS-4059 clinical development. Citation Format: Helen Yu, Hoa Truong, Scott A. Mitchell, John J. Gosink, Julie Lin, Joy Y. Feng, Juliane M. Jürgensmeier, Andrew N. Billin, Ren Xu, Siddhartha Mitra. Homogeneous BTK occupancy assay for pharmacodynamic assessment of GS-4059 target engagement [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4016. doi:10.1158/1538-7445.AM2017-4016

Photostable Ratiometric Pdot Probe for in Vitro and in Vivo Imaging of Hypochlorous Acid.

Developing probes for the detection of reactive oxygen species (ROS), a hallmark of many pathophysiological process, is imperative to both understanding the precise roles of ROS in many life-threatening diseases and optimizing therapeutic interventions. We herein report an all-in-one fluorescent semiconducting polymer based far-red to near-infrared (NIR) Pdot nanoprobe for the ratiometric detection of hypochlorous acid (HOCl). The fabrication takes the advantage of flexible polymer design by incorporating target-sensitive and target-inert fluorophores into a single conjugated polymer to avoid leakage or differential photobleaching problems existed in other nanoprobes. The obtained nanoprobe has improved performance in HOCl sensing, such as high brightness, ideal far-red to NIR optical window, excellent photostability, self-referenced ratiometric response, fast response, and high selectivity. The dual-emission property allows the sensitive imaging of HOCl fluctuations produced in living macrophage cells and peritonitis of living mice with high contrast. This study not only provides a powerful and promising nanoprobe to be potentially used in the investigations of in situ HOCl status of diseases in living systems but also puts forward the design strategy of a new category of ratiometric fluorescent probes facilitating precise and reliable measurement in biological systems.

Coating synthesis and enhanced photoluminescence of NaCl@LiLa(MoO4)2:Eu3+

A series of NaCl@LiLa(MoO4)2:0.05Eu3+ (denoted as NaCl@LLMO:0.05Eu3+) were prepared by a simple coating method. Dual emission properties induced by coating NaCl are discussed. The influence of coating NaCl on the luminescence properties of Eu3+ ions were studied. The coating of NaCl results in much more influence on the emission intensities than on the R values (R=I2/I1, where I2 and I1 are the peak area of 5D0→7F2 and 5D0→7F1 emissions of Eu3+ ions, respectively) of Eu3+ ions in these samples. The optimal coating content of NaCl is 48wt% with the corresponding sample (NaCl)0.48 wt@LLMO:0.05Eu3+,whose PL intensity is as high as 1.79 times of that without coating NaCl. (NaCl)0.48wt@LLMO:0.05Eu3+ is a potential red-emitting phosphor with high R values (R=8.29) for blue light-based white LED.

A gelable pure organic luminogen with fluorescence-phosphorescence dual emission

Pure organic luminogens with room temperature phosphorescence (RTP) have drawn much attention due to their fundamental importance and promising applications in optoelectronic devices, bioimaging, sensing, etc. Fluorescence-phosphorescence dual emission at room temperature, however, is rarely observed in pure organic materials. Herein, we reported a metal- and heavy-atom free pure organic luminogen with tert -butyl groups, D t BuCZBP, which is ready to form organogels in dimethylsulfoxide (DMSO). It emits prompt and delayed fluorescence, as well as RTP, namely dual emission in as-prepared solid, gels and polymeric films. To the best of our knowledge, it is the first example of metal- and heavy-atom free pure organic gelator with RTP emission. Such unique RTP and moreover dual emission properties in different states make D t BuCZBP a potential material for diverse applications.