Excited Dye Research Articles

Excitation of rhodamine 800 in aqueous media: a theoretical investigation.

The main goal of this work was to obtain a calculated absorption spectrum of rhodamine 800 in an aqueous solution, which most accurately reproduces the experimental one. To achieve this result, I used the hybrid functionals supported by Gaussian 16 software package. In this case, the basis set (6-31++G(d,p)) and the solvent model (IEFPCM) were not varied. The B3PW91 functional gave the best agreement with the experimental absorption spectrum of the dye in an aqueous medium. B3P86, B971, B972, B98, X3LYP, APF, HSE06, and N12SX functionals also give good absorption energy coincidence. The B3PW91/6-31++G(d,p)/IEFPCM theory level chosen in this way made it possible to calculate the various characteristics of rhodamine 800 in the ground and excited states. An important result of this work was the establishment of the vibronic nature of the short-wavelength smaller maximum of the absorption spectrum. The influence of the strong H-bond of the exocyclic nitrogen atom with the water molecule on the dye excitation was analyzed.

Reference Excitation Energies of Increasingly Large Molecules: A QMC Study of Cyanine Dyes.

We revisit here the lowest vertical excitations of cyanine dyes using quantum Monte Carlo and leverage recent developments to systematically improve on previous results. In particular, we employ a protocol for the construction of compact and accurate multideterminant Jastrow-Slater wave functions for multiple states, which we have recently validated on the excited-state properties of several small prototypical molecules. Here, we obtain quantum Monte Carlo excitation energies in excellent agreement with high-level coupled cluster for all the cyanines where the coupled cluster method is applicable. Furthermore, we push our protocol to longer chains, demonstrating that quantum Monte Carlo is a viable methodology to establish reference data at system sizes which are hard to reach with other high-end approaches of similar accuracy. Finally, we determine which ingredients are key to an accurate treatment of these challenging systems and rationalize why a description of the excitation based on only active π orbitals lacks the desired accuracy for the shorter chains.

Hybrid structure design, preparation of Ag-GO SERS optical fiber probe and its chemical, electromagnetic enhancement mechanism

Incorporating Ag-graphene oxide hybrid material (Ag-GO) on optical fiber offers a novel approach for flexible ultrasensitive detection in biomedical and environmental areas. In this work, Ag-GO surface-enhanced Raman scattering (SERS) optical fiber probe was synthesized by a SnCl2-sensitized solvothermal method and modified Hummer’s method. After optimizing SERS test parameters, SERS performance of the fiber probes synthesized by different synthetic procedures of GO, Ag-GO hybrid structures and GO concentration are compared. The obtained GO shows superior ability to quench fluorescence by reducing the photobleaching of dyes. GO with high oxidation degree is preferred. Compared to Ag and hybrid structures including GO/Ag and GO/Ag/GO, Ag/GO fiber probe exhibits strongest enhancement due to π-π stacking and charge transfer process from lone pair of electrons on GO to the molecules. Ag/GO fiber probe with 5 mg/mL GO displays strongest SERS enhancement. Apart from chemical enhancement, it is worthwhile to note that GO is also found to selectively enhance specific vibrations regarding π bond or lone pair of electrons. The fiber probe shows high sensitivity (10−9 M R6G), good reproducibility (RSD of 3.5%) and good stability. Moreover, the enhanced area of Ag-GO fiber probe occurs in core area and cladding edge. The enhancement mechanism of Ag-GO fiber probe is that, as GO provides an additional route for excited dyes to decay through its Fermi level, photobleaching of dyes is reduced by charge transfer process. The enhancement is a synergic effect of chemical enhancement of GO, electromagnetic enhancement of silver and waveguide propagation of optical fiber.

Gold nanoparticle-based supramolecular approach for dye-sensitized H2-evolving photocathodes.

Solar conversion of water into the storable energy carrier H2 can be achieved through photoelectrochemical water splitting using light adsorbing anodes and cathodes bearing O2 and H2 evolving catalysts, respectively. Herein a novel photocathode nanohybrid system is reported. This photocathode consists of a dye-sensitized p-type nickel oxide (NiO) with a perylene-based chromophore (PCA) and a tetra-adamantane modified cobaloxime reduction catalyst (Co) that photo-reduces aqueous protons to H2. An original supramolecular approach was employed, using β-cyclodextrin functionalized gold nanoparticles (β-CD-AuNPs) to link the alkane chain of the PCA dye to the adamantane moieties of the cobaloxime catalyst (Co). This new architecture was investigated by photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy. The results show that irradiation of the complete NiO|PCA|β-CD-AuNPs|Co electrode leads to ultrafast hole injection into NiO (π = 3 ps) from the excited dye, followed by rapid reduction of the catalyst, and finally H2 evolution.

Temperature dependent perylene fluorescence as a probe of local polymer glass transition dynamics.

We demonstrate how the temperature dependence of perylene's fluorescence emission spectrum doped in bulk polymer matrices is sensitive to the local glass transition dynamics of the surrounding polymer segments. Focusing on the first fluorescence peak, we show that the intensity ratio IRatio(T) = IPeak(T)/ISRR between the first peak and a self referencing region (SRR) has a temperature dependence resulting from the temperature-dependent nonradiative decay pathway of the excited perylene dye that is influenced by its intermolecular collisions with the surrounding polymers segments. For different polymer matrices, poly(methyl methacrylate) (PMMA), polystyrene (PS), poly(2-vinyl pyridine) (P2VP), and polycarbonate (PC), we demonstrate that IRatio(T) exhibits a transition from a non-Arrhenius behavior above the glass transition temperature Tg of the polymer to an Arrhenius temperature dependence with constant activation energy E below the Tg of the polymer matrix, indicating perylene's sensitivity to cooperative α-relaxation dynamics of the polymer matrix. This transition in temperature dependence allows us to identify a perylene defined local Tperyleneg of the surrounding polymer matrix that agrees well with the known Tg values of the polymers. We define a fluorescence intensity shift factor in analogy with the Williams-Landel-Ferry (WLF) equation and use literature WLF parameters for the polymer matrix to quantify the calibration factor cf needed to convert the fluorescence intensity ratio to the effective time scale ratio described by the conventional WLF shift factor. This work opens up a new characterization method that could be used to map the local dynamical response of the glass transition in nanoscale polymer materials using appropriate covalent attachment of perylene to polymer chains.

Dye Sensitization for Ultraviolet Upconversion Enhancement.

Upconversion nanocrystals that converted near-infrared radiation into emission in the ultraviolet spectral region offer many exciting opportunities for drug release, photocatalysis, photodynamic therapy, and solid-state lasing. However, a key challenge is the development of lanthanide-doped nanocrystals with efficient ultraviolet emission, due to low conversion efficiency. Here, we develop a dye-sensitized, heterogeneous core–multishelled lanthanide nanoparticle for ultraviolet upconversion enhancement. We systematically study the main influencing factors on ultraviolet upconversion emission, including dye concentration, excitation wavelength, and dye-sensitizer distance. Interestingly, our experimental results demonstrate a largely promoted multiphoton upconversion. The underlying mechanism and detailed energy transfer pathway are illustrated. These findings offer insights into future developments of highly ultraviolet-emissive nanohybrids and provide more opportunities for applications in photo-catalysis, biomedicine, and environmental science.

Organic Fluorophores for 1064nm Excited NIR-II Fluorescence Imaging.

Second near-infrared window (NIR-II) fluorescence imaging has shown great potential in the field of bioimaging. However, the excitation wavelengths of most NIR-II fluorescence dyes are in the first near-infrared (NIR-I) region, which leads to limited imaging depth and resolution. To address such issue, NIR-II fluorescence dyes with 1,064 nm excitation have been developed and applied for in vivo imaging. Compared with NIR-I wavelength excited dyes, 1,064 nm excited dyes exhibit a higher tissue penetration depth and resolution. The improved performance makes these dyes have much broader imaging applications. In this mini review, we summarize recent advances in 1,064 nm excited NIR-II fluorescence fluorophores for bioimaging. Two kinds of organic fluorophores, small molecule dye and semiconducting polymer (SP), are reviewed. The general properties of these fluorophores are first introduced. Small molecule dyes with different chemical structures for variety of bioimaging applications are then discussed, followed by the introduction of SPs for NIR-II phototheranostics. Finally, the conclusion and future perspective of this field is given.

A New Three-Component Photo-Initiating System for Visible Light Recording of Volume Holograms with Single-Pulsed Laser.

Versatile substituted electron-deficient trichloromethylarenes can easily be synthesized and combined with a Safranine O/triarylalkylborate salt to form a highly efficient three-component photo-initiation system that starts free radical polymerization to finally form holographic gratings with a single-pulsed laser. The mechanism of this photo-initiation most likely relies on an electron transfer from the borate salt into the semi-occupied HOMO of the excited dye molecule Safranine O, which after fragmentation generates an initiating alkyl radical and longer-lived dye radical species. This dye radical is most probably oxidized by the newly introduced trichloromethylarene derivative as an electron acceptor. The two generated radicals from one absorbed photon initiate the photopolymerization and form index gratings in a suitable holographic recording material. This process is purely photonic and does not require further non-photonic post treatments.

Biosensors based on peptide exposure show single molecule conformations in live cells

We describe an approach to study the conformation of individual proteins during single particle tracking (SPT) in living cells. "Binder/tag" is based on incorporation of a 7-mer peptide (the tag) into a protein where its solvent exposure is controlled by protein conformation. Only upon exposure can the peptide specifically interact with a reporter protein (the binder). Thus, simple fluorescence localization reflects protein conformation. Through direct excitation of bright dyes, the trajectory and conformation of individual proteins can be followed. Simple protein engineering provides highly specific biosensors suitable for SPT and FRET. We describe tagSrc, tagFyn, tagSyk, tagFAK, and an orthogonal binder/tag pair. SPT showed slowly diffusing islands of activated Src within Src clusters and dynamics of activation in adhesions. Quantitative analysis and stochastic modeling revealed invivo Src kinetics. The simplicity of binder/tag can provide access to diverse proteins.

Principles of modeling the fluorescence spectral dynamics of dye molecules in solutions

FSDS is Fluorescence Spectral Dynamics Simulator, designed to investigate photoinduced charge transfer and its manifestations in time-resolved fluorescence spectra of a dye in a solvent. The project is implemented in C, using the MPI library. The computer model simulates stationary absorption and fluorescence spectra, as well as the time evolution of population distributions along the solvent reaction coordinate, to calculate spectral dynamics. Excitation and relaxation of intramolecular high-frequency vibrations are described at the quantum level. FSDS can fit the physical parameters of the dyes to experimental data. The dye excitation is consistently described accounting for the finite duration of the pump pulse. The program code implements two evolutionary models: a spin-boson model within the harmonic potential and a stochastic model based on the Smoluchowski diffusion operator for an arbitrary free energy surface. Computer simulation shows the numerical coincidence of the calculations performed in the framework of these models for the harmonic free energy surface. The detail description of the code and numerical schemes are presented. Program summaryProgram Title: Fluorescence Spectral Dynamics Simulator (FSDS)CPC Library link to program files:https://doi.org/10.17632/d39rrrkvhr.1Code Ocean capsule:https://codeocean.com/capsule/6544976Licensing provisions: GPLv3Programming language: CSupplementary material: Sample configuration files, User ManualNature of problem: The time-resolved spectra contain reach information about photochemical processes. However, the chemically important information about separate elementary processes is entangled due to they proceed in parallel. Time-resolved spectra modeling allows extracting information about these processes. The presented program code makes it possible to determine the relaxation characteristics of the solvent and the times of intramolecular relaxation.Solution method: Finite-difference time-domain and Brownian dynamics simulation methods.

Dual-modality loop-mediated isothermal amplification for pretreatment-free detection of Septin9 methylated DNA in colorectal cancer.

Currently, the determination of DNA methylation is still a challenge due to the limited efficiency of enrichment, bisulfite modification, and detection. In this study, a dual-modality loop-mediated isothermal amplification integrated with magnetic bead isolation is proposed for the determination of methylated Septin9 gene in colorectal cancer. Magnetic beads modified with anti-methyl cytosine antibody were prepared for fast enrichment of methylated DNA through specific immunoaffinity (30 min). One-pot real-time fluorescence and colorimetric loop-mediated isothermal amplification were simultaneously developed for detecting methylated Septin9 gene (60 min). The real-time fluorescence generating by SYTO-9 dye (excitation: 470 nm and emission: 525 nm) and pH indicator (neutral red) was used for quantitative and visualized detection of methylated DNA. This method was demonstrated to detect methylated DNA from HCT 116 cells ranging from 2 to 0.02 ng/μL with a limit of detection of 0.02 ± 0.002 ng/μL (RSD: 9.75%). This method also could discriminate methylated Septin9 in 0.1% HCT 116 cells (RSD: 6.60%), suggesting its high specificity and sensitivity. The feasibility of this assay was further evaluated by clinical plasma samples from 20 colorectal cancer patients and 20 healthy controls, which shows the potential application in simple, low cost, quantitative, and visualized detection of methylated nucleic acids.Graphical abstract A dual-modality loop-mediated isothermal amplification (LAMP) integrated with immuno-magnetic beads (IMB) enrichment was proposed for the determination of methylated Septin9 gene in colorectal cancer (CRC).Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-021-04979-8.

Fluorescence Enhancement via Dual Coupling of Dye Molecules with Silver Nanostructures

We demonstrate the enhancement of fluorescence emitted from dye molecules coupled with two surface plasmons, i.e., silver nanoparticles (AgNPs)-induced localized surface plasmons (LSP) and thin silver (Ag) film supported surface plasmons. Excitation light is illuminated to a SiO2 layer that contains both rhodamine 110 molecules and AgNPs. AgNPs enhances excitation rates of dye molecules in their close proximity due to LSP-induced enhancement of local electromagnetic fields at dye excitation wavelengths. Moreover, the SiO2 layer on one surface of which a 50 nm-thick Ag film is coated for metal cladding (air on the other surface), acts as a waveguide core at the dye emission wavelengths. The Ag film induces the surface plasmons which couple with the waveguide modes, resulting in a waveguide-modulated version of surface plasmon coupled emission (SPCE) for different SiO2 thicknesses in a reverse Kretschmann configuration. We find that varying the SiO2 thickness modulates the fluorescent signal of SPCE, its modulation behavior being in agreement with the theoretical simulation of thickness dependent properties of the coupled plasmon waveguide resonance. This enables optimization engineering of the waveguide structure for enhancement of fluorescent signals. The combination of LSP enhanced dye excitation and the waveguide-modulated version of SPCE may offer chances of enhancing fluorescent signals for a highly sensitive fluorescent assay of biomedical and chemical substances.

Ex-Vivo Measurement of the pH in Aqueous Humor Samples by a Tapered Fiber-Optic Sensor.

A practical demonstration of pH measurement in real biological samples with an in-house developed fiber-optic pH sensor system is presented. The sensor uses 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) fluorescent dye as the opto-chemical transducer. The dye is immobilized in a hybrid sol-gel matrix at the tip of a tapered optical fiber. We used 405 nm and 450 nm laser diodes for the dye excitation and a photomultiplier tube as a detector. The sensor was used for the measurement of pH in human aqueous humor samples during cataract surgery. Two groups of patients were tested, one underwent conventional phacoemulsification removal of the lens while the other was subjected to femtosecond laser assisted cataract surgery (FLACS). The precision of the measurement was ±0.04 pH units. The average pH of the aqueous humor of patients subjected to FLACS and those subjected to phacoemulsification were 7.24 ± 0.17 and 7.31 ± 0.20 respectively.

Enhanced photocatalytic performance of PANI-rGO-MnO2 ternary composite for degradation of organic contaminants under visible light

This work examines the potential of conducting polymers with transition metal oxides as a photocatalyst in environmental remediation. A visible light-responsive ternary composite of PANI-rGO-MnO2 was synthesized and evaluated its photocatalytic activity of a cationic dye (i.e., methylene blue, MB) in an aqueous solution. The surface morphologies and structural properties of the synthesized PANI, PANI-rGO, and PANI-rGO-MnO2 were examined. In the case of ternary composite, the successful growth/incorporation of MnO2 nanoparticles into the PANI-rGO composite was demonstrated. Furthermore, the lowered optical band gap of the ternary composite illustrates the extended light absorption range for the PANI-rGO-MnO2 photocatalyst. The photocatalytic experiments show that the PANI-rGO-MnO2 ternary composite exhibited significantly enhanced catalytic and photocatalytic activity for 90% degradation of methylene blue (MB) under visible light irradiation within 2 h. It could be attributed to synergistic effects by (i) facilitating the electron transfer from excited by reduced graphene oxide from the excited dye to PANI-MnO2 and (ii) reducing the recombination of photogenerated electron/hole pairs originating from the heterostructure of the ternary composite. The present work provides new insights into the synthesis of conducting polymer PANI, PANI-rGO, and the ternary composite of PANI-rGO-MnO2 as an efficient photocatalyst, and the developed composites would have potential applications in environmental remediation related fields.

Hydrostatic Pressure-Controllable Chiroptical Properties of Chiral Perylene Bisimide Dyes: A Chiral Aggregation Case

Hydrostatically pressurized spectroscopic and lifetime decay analyses of optically active perylene bisimides were demonstrated in the pressure range of 0.1-320 MPa to show a π-stacked aggregation. The hydrostatic pressure-induced excitation and circular dichroism spectral changes of the fluorescence perylene dye enabled us to differentiate the slight pressure-sensitive aggregates. This work will lead to a new strategy for creating a pressure-responsive supramolecular polymerization material.

Molecular engineering of thienothiophene or dithienopyrrole-based π-spacers for dye-sensitized solar cells (DSSCs) with D-π-A architecture: A DFT/TD-DFT study

The impact of divergent π-spacers including thienothiophene-2,5-dione (Ω1), thieno[3,4-b]thiophene (Ω2), thieno[2,3-b]thiophene (Ω3), or dithieno[3,2-b:2′,3′-d]pyrrole (Ω4) scaffolds linked with 2-phenylthiophene (Ψ1-2; differ from their binding order), 2,2′-bithiophene (Ψ3) or thiophene (Ψ4) subunits on the structural and photophysical properties of carbazole-based donor-π-acceptor type dyes were investigated by performing density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, respectively. According to the ground-state optimization and frequency calculations; ƐHOMO, ƐLUMO, bandgap (Ɛgap) energies, ionization potential (I), electron affinity (A), hardness (η), hyper-hardness (Γ), chemical potential (μ), dipole moment (μ), and electrophilicity index (ω) was determined. TD-CAM-B3LYP calculations were then used to enlighten light-harvesting efficiency (LHE), maximum absorbance wavelength (λmax), oscillator strength (f), excited-state lifetime (τ), the oxidation potential of the excited dye (εdye∗), the driving force (ΔGinject) of the electron injection, reorganization energy (ΔGregen), and open-circuit photovoltage (VOC) parameters.

Excited state proton transfer dye with an emission quantum yield up to 60% upon Zn2+ coordination

Intramolecular excited state proton transfer (ESIPT) dyes are appealing for metal ion sensing because of their large apparent Stokes-shift, environmental sensitivity, and turn-on fluorescence capabilities. Here we introduce 1,3-bis(2-pyridylimino)-4,7-dihydroxyisoindole (2) as a new ESIPT sensing motif. The 2,5-bis(2-pyridylimino)pyrrole portion of 2 readily coordinates Hg2+, Zn2+, Co2+, Cu2+, and Ni2+ ions and results in a visible red-shift in absorption. While coordination of Hg2+, Co2+, Ni2+, and Cu2+ completely quenches emission, coordination to Zn2+ increases the ESIPT emission quantum yield from 25% to 60%. Unlike traditional ESIPT sensors, the metal ion binding site of 2 is intrinsic to the chromophore but is not the ESIPT site, thus enabling the selective modification of each functionality. As proof of concept, we use bromobutyrate as an alcohol protecting group whose cleavage by hydrazine results in turn-on fluorescence response. Collectively these results demonstrate the 1,3-bis(2-pyridylimino)-4,7-dihydroxyisoindole motif is sensitive to several stimuli (i.e. metal ion, base, solvent, and N2H4) and is a promising scaffolding for sensing applications.

Fluorescence coupling to internal modes of 1D photonic crystals characterized by back focal plane imaging

The coupling of fluorescence with surface electromagnetic modes, such as surface plasmons on thin metal films or Bloch surface waves (BSWs) on truncated one-dimensional photonic crystals (1DPCs), are presently utilized for many fluorescence-based applications. In addition to the surface wave, 1DPCs also support other electromagnetic modes that are confined within the 1DPC structure. These internal modes (IMs) have not received much attention for fluorescence coupling due to lack of spatial overlap of their electric fields with the surface bound fluorophores. However, our recent studies have indicated that the fluorescence coupling with IMs occurs quite efficiently. This observed internal mode-coupled emission (IMCE) is (similar to BSW-coupled emission) indeed wavelength dependent, directional and S-polarized. In this paper, we have carried out back-focal plane imaging to reveal that the IMs of 1DPCs can couple with surface bound excited dye molecules, with or without a BSW mode presence. Depending on the emission wavelength, the coupling is observed with BSW and IMs or only IMs of the 1DPC structure. The experimental results are well matching with numerical simulations. The occurrence of IMCE regardless of the availability of BSWs removes the dependence on just the surface mode for obtaining coupled emission from 1DPCs. The observation of IMCE is expected to widen the scope of 1DPCs for surface-based fluorescence sensing and assays.

New excited state intramolecular proton transfer dyes based on naphthalenediimides (NDI) and its population of triplet excited state

The dyes of Naphthalenediimides (NDI) conjugated and non-conjugated with 2-(2-Hydroxyphenyl)Benzothiazole (N-1~N-5) were prepared. The compounds showed dramatically red-shifted UV–vis absorption (483–611 nm) and emission (538–635 nm) compared with traditional ESIPT compound (HBT). Among them, N-1 shows obvious dual emission at 538 nm (enol form), 682 nm (keto form) in PhCH3 and large Stokes shift (up to 144 nm), which is one of the evidence for the characteristics of ESIPT. Time-resolved transient absorption demonstrated triplet excited states were populated upon photoexcitation for all the compounds. Especially for N-3 and N-4, the life time of triplet excited states (τT) are 48.0 μs and 148.5 μs, respectively. The lifetime of triplet excited state were also observed in N-1 (τT = 72.0 μs) and N-2 (τT = 121.1 μs). The population of triplet excited states of all the compounds were testified by photooxidation for 1, 3-diphenylisobenzofuran. N-3 and N-4 exhibit much efficient photooxidative ability than N-1, N-2 and N-5.

Engineering couplings for exciton transport using synthetic DNA scaffolds

Summary Control over excitons enables electronic energy to be harnessed and transported for light harvesting and molecular electronics. Such control requires nanoscale precision over the molecular components. Natural light-harvesting systems achieve this precision through sophisticated protein machinery, which is challenging to replicate synthetically. Here, we introduce a DNA-based platform that spatially organizes cyanine chromophores to construct tunable excitonic systems. We synthesized DNA-chromophore nanostructures and characterized them with ensemble ultrafast and single-molecule spectroscopy and structure-based modeling. This synthetic approach facilitated independent control over the coupling among the chromophores and between the chromophores and the environment. We demonstrated that the coupling between the chromophores and the environment could enhance exciton transport efficiency, highlighting the key role of the environment in driving exciton dynamics. Control over excitons, as reported here, offers a path toward the development of designer nanophotonic devices.