Main Absorption Bands Research Articles

77 % Photothermal Conversion in Blatter‐Type Diradicals: Photophysics and Photodynamic Applications

AbstractDiradicals based on the Blatter units and connected by acetylene and alkene spacers have been prepared. All the molecules show sizably large diradical character and low energy singlet‐triplet gaps. Their photo‐physical properties concerning their lowest energy excited state have been studied in detail by steady‐state and time‐resolved absorption spectroscopy. We have fully identified the main optical absorption band and full absence of emission from the lowest energy excited state. A computational study has been also carried out that has helped to identify the presence of a conical intersection between the lowest energy excited state and the ground state which produces a highly efficient light‐to‐heat conversion of the absorbed radiation. Furthermore, an outstanding photo‐thermal conversion 77.23 % has been confirmed, close to the highest in the diradicaloid field. For the first time, stable diradicals are applied to photo‐thermal therapy of tumor cells with good stability and satisfactory performance at near‐infrared region.

Understanding the Optical Properties of Doped and Undoped 9-Armchair Graphene Nanoribbons in Dispersion.

Graphene nanoribbons are one-dimensional stripes of graphene with width- and edge-structure-dependent electronic properties. They can be synthesized bottom-up in solution to obtain precise ribbon geometries. Here we investigate the optical properties of solution-synthesized 9-armchair graphene nanoribbons (9-aGNRs) that are stabilized as dispersions in organic solvents and further fractionated by liquid cascade centrifugation (LCC). Absorption and photoluminescence spectroscopy reveal two near-infrared absorption and emission peaks whose ratios depend on the LCC fraction. Low-temperature single-nanoribbon photoluminescence spectra suggest the presence of two different nanoribbon species. Based on density functional theory (DFT) and time-dependent DFT calculations, the lowest energy transition can be assigned to pristine 9-aGNRs, while 9-aGNRs with edge-defects, caused by incomplete graphitization, result in more blue-shifted transitions and higher Raman D/G-mode ratios. Hole doping of 9-aGNR dispersions with the electron acceptor F4TCNQ leads to concentration dependent bleaching and quenching of the main absorption and emission bands and the appearance of red-shifted, charge-induced absorption features but no additional emission peaks, thus indicating the formation of polarons instead of the predicted trions (charged excitons) in doped 9-aGNRs.

Some physical analysis of quaternary CuNiSbS powder for optoelectronic applications

Novel quaternary CuNiSbS chalcogenide material has been successfully prepared using a simple co-precipitation method using a mixture of solutions of the constituent elements in a chemical formula.The structure and morphological characterizations of the prepared material in powder form wereperformed via x-ray diffraction, a High-resolution transmission electron microscope (HRTEM), and a Scanning electron microscope (SEM). FTIR and diffuse reflectance spectrum of the prepared material were conducted to provide valuable information about the main absorption bands besides the energy optical band gap of the material. ACconductivity and the dielectric properties of the prepared materialusingbroadband dielectricspectroscopy (BDS) besides a magnetic analysis via a vibrating sample magnetometer (VSM) were also investigated.

Role of 5 mol% rare earth (La3+) on the structural, microstructural, and magnetic properties of cobalt chromite ceramics

Spinel oxides, which have the structure AB2O4 and are distinguished by their exceptional magnetic, electric, and multiferroic properties and exhibit a wide range of functional responses in the category of oxides. The cobalt chromate (CoCr2O4) is well-known as a multiferroic-magnetoelctric (ME) material. It belongs to the magnetic spinal oxide family and is noted for its complicated spiral ferromagnetic(FM) orderings. To enhance the magnetic properties of the CoCr2O4, in this work we have chosen Lanthanum (La3+) 0.05 mol% doped cobalt chromites (CoCr2O4) nanoparticles. The solution combustion method was utilized to synthesize the nanomaterial, where urea and glucose were used as fuels. The Structural exploration of the Co0.95La0.05 Cr2O4 nanoparticles were clarified using powder X-ray diffraction. To understand the microstructure properties we have carried out high-resolution electron microscopy and it reveals highly porous nature. In FTIR spectra the two main absorption bands at 507 cm−1 and 616 cm−1 were observed which confirm the formation of spinal chromates. The TGA results revealed a slow thermal degradation, and the sample has a thermal stability that is greater than the temperature range tested. Researchers have examined the changes in temperature and magnetic field affected the magnetic properties of materials over time (ZFC & FC). In comparison to the bulk sample, the Curie temperature at which samples transition from a paramagnetic (PM) state to a collinear short-range ferromagnetic (FM) state is significantly lower. This temperature is denoted as TC-98 K deteriorated with time in terms of quality. At low temperatures, there is no magnetic transition that can be identified between the short-range FM order and the long-range spiral spin structure. This is in contrast to the magnetic transitions that can be discovered in bulk. What gives rise to all of the intriguing qualities that have been described above is the presence of weak magnetic frustration, which is very much connected to super-exchange interactions and is found along different paths such as A-O-A, B–O–B, and A-O-B. This presence is what gives rise to all of the intriguing characteristics that have been described above.

Infrared study of the structure of silicon oxynitride films produced by plasma enhanced chemical vapor deposition

The structure of thin (∼300nm) SiOxNy (0.23≤x≤1.95, 0.01≤y≤0.32) films produced by plasma enhanced chemical vapor deposition is studied by infrared (IR) spectroscopy. The dependence of the shape of the main IR absorption band in the range of 700–1400 cm–1 upon film composition is analyzed. The IR spectra exhibit strong overlapping of the bands corresponding to absorption on Si–O and Si–N bonds. A problem of separating these components is solved. Analysis of their relative intensities provides an insight into the film structure. The films with high oxygen content are found to have a homogeneous structure similar to that of nonstoichiometric Si oxide that can be described by the random bonding model. Increase of relative Si concentration and simultaneous decrease of oxygen and nitrogen content changes the film structure to the two-phase one obeying the random mixture model. Such material may be represented as a uniform mixture of interconnecting silicon–oxygen tetrahedra (Si–OaSi4-a, a=0..4) and silicon–nitrogen pyramids (Si3N). Relative Si concentration in the Si oxynitride films and their deposition temperature are hypothesized to play a decisive role on their structure, which is supported by thermodynamic modeling.

Making leavened bread from nixtamalized whole sorghum

The aim was to determine whether nixtamalized sorghum can induce viscoelastic properties in dough-like systems and to compare its kafirin-gluten-forming properties with those reported for wet wheat gluten. By utilizing dry nixtamalization, it was observed that bread had regular loaf volume, but stiff crumb texture. Therefore, wet nixtamalization accompanied by an additional steeping period was employed. Whole sorghum dough has high G′, G’’ and complex viscosity data η* and K due to highly structured dough, suggesting cross-linked intermolecular kafirins. To the best of our knowledge, wet kafirin-gluten and whole leavened sorghum bread was obtained from sorghum using nixtamalization for the first time. The crumb was attractive and significantly softer but still needed to improve in volume for comparison with bread made of refined wheat flour. An interesting feature noted is that the non-nixtamalized sorghum sample presented relatively low springiness (0.929). In sorghum proteins, the main absorption band of the α-helix increased in nixtamalized treatments as compared to the control (non-nixtamalized) and was associated with an increase in springiness in the bread. This is an important starting point for improving the breadmaking of whole sorghum bread.

Fullerene-indene adducts (ICMA & ICBA) in an astrochemical perspective part 1: chemical thermodynamics, stability and electronic absorption spectroscopy

Both C60 fullerene and indene were detected in certain astrophysical objects. It is then possible that these two molecules may react together in space forming adducts like indene-C60 mono-adduct (ICMA) as well as the indene-C60 bis-adducts (ICBA). In view of the potential detection of such adducts in space, the chemical thermodynamics of the reaction between C60 and indene was analyzed using the thermochemical group increment approach. ICMA and ICBA were synthesized and their composition and stability was studied with thermogravimetric analysis and derivative thermogravimetry (TGA-DTG). ICBA and moreover ICMA resulted stable and strong adducts. In particular, the latter is stable up to 350 °C and this fact increases the chances to find it in space. Furthermore, the retro Diels-Alder reaction was accurately studied on ICMA with differential scanning calorimetry (DSC) and an unusually high activation energy for the decomposition was determined and explained with the chemical thermodynamic data. The electronic absorption spectra of ICMA and ICBA were studied in n-hexane and the molar extinction coefficients of the main absorption bands have been determined. A possible way to detect such adducts is through electronic absorption spectroscopy, while the infrared spectroscopy of ICMA and ICBA is analyzed and discussed in the following second part of this work.

Gas-phase electronic action absorption spectra of protonated oxygen-functionalized polycyclic aromatic hydrocarbons (OPAHs)

Context. Extended red emission (ERE) denotes a broad unassigned feature extending from 540 to 800 nm observed in many regions of the interstellar medium (ISM), and is thought to originate from photoluminescence of cosmic dust. However, definitive assignment of specific carriers remains to be achieved. Aims. Our aim is to investigate the photoabsorption spectra of astrophysically relevant protonated oxygen-functionalized polycyclic aromatic hydrocarbons (OPAHs) to probe their ability to absorb photons in the near-ultraviolet (UV) and visible (vis) spectral region and to search for any low-lying electronic states that may account for the ERE. Methods. Gas-phase electronic action absorption spectra of the protonated OPAHs were recorded in the spectral range of 200–700 nm using the ELISA ion-storage ring. Additional time-dependent density functional theory (TD-DFT) calculations were performed to compute excited state transitions that complement the experimental spectra. Results. A set of five protonated (O)PAHs was considered, namely pentacene and the four oxygen-functionalized PAHs, pentacenequinone, pentacenetetrone, anthraquinone, and phenathrenequinone. All pentacene-related species show a main absorption band between 400 and 500 nm, while the smaller OPAHs, anthraquinone and phenanthrenequinone, generally absorb further to the blue compared to the pentacenes. Interestingly, pentacenequinone and phenanthrenequinone exhibit wide absorption plateaus towards the red side of their main absorption band(s), which places them among the potential candidates to contribute to ERE. Additional photodissociation mass spectra reveal the formation of smaller functionalized PAHs and small oxygen-bearing species. Conclusions. Our results demonstrate the ability of OPAHs to absorb in the UV/vis spectral region. Among the four studied OPAHs, two revealed very broad absorption characteristics at wavelengths up to 700 nm, which makes them suitable candidates to contribute to a part of the ERE spectrum. Moreover, these two OPAHs, pentacenequinone and phenanthrenequinone, could dissociate efficiently into oxygen-bearing molecules and smaller functionalized PAHs in photon-dominated regions (PDRs) of the ISM.

RAINBOW Organic Solar Cells: Implementing Spectral Splitting in Lateral Multi-Junction Architectures.

While multi-junction geometries have the potential to boost the efficiency of organic solar cells, the experimental gains yet obtained are still very modest. This work proposes an alternative spectral splitting device concept in which various individual semiconducting junctions with cascading bandgaps are laid side by side, thus the name RAINBOW. Each lateral sub-cell receives a fraction of the spectrum that closely matches the main absorption band of the given semiconductor. Here, simulations are used to identify the important material and device properties of each RAINBOW sub-cell. Using the resulting design rules, three systems are selected, with narrow, medium, and wide effective bandgaps, and their potential as sub-cells in this geometry is experimentally investigated. With the aid of a custom-built setup that generates spectrally spread sunlight on demand, the simulations are experimentally validated, showing that this geometry can lead to a reduction in thermalization losses and an improvement in light harvesting, which results in a relative improvement in efficiency of 46.6% with respect to the best sub-cell. Finally, a working proof-of-concept monolithic device consisting of two sub-cells deposited from solution on the same substrate is fabricated, thus demonstrating the feasibility and the potential of the RAINBOW solar cell concept.

Theoretical study of lithium oxide clusters adsorbed on anatase TiO2 surface

The search for materials that have broad applicability as photocatalysts is growing interest. Titanium dioxide (TiO2) is a semiconductor with demonstrated photocatalytic properties, and its improvement with lithium oxide (LO) adsorption (LO-TiO2) is investigated using density functional theory (DFT). The modeling of the electronic structure of three types of LO as lithium oxide (Li2O)n, lithium peroxide (Li2O2)n, and lithium superoxide radical (LiO2)n (n = 1,2,3) adsorbed on anatase TiO2 shows an increase in their reactivities. The bandgap energy decreases in the range of 3.07–0.33 eV compared to TiO2 (3.2 eV) and conducting states from LO and 2p orbital of O(TiO2) towards 3d orbital of titanium (TiO2) are generated. The Independent Gradient Model and the intrinsic bond strength index are applied to gain insight into the intermolecular interactions between LO and TiO2. These results are coherent with that predicted by the interaction energy of LO-TiO2, which suggests that the more stable systems are (Li2O)2 and (Li2O2)3. Optical properties calculated with TD-DFT show a visible shift of the main absorption band compared to TiO2. The theoretical results show that the adsorption of lithium oxide onto a TiO2 surface would be an excellent strategy to produce a material as a visible light-activated photocatalyst.

Rare earth-doped mixed Ni–Cu–Zn ferrites as an effective photocatalytic agent for active degradation of Rhodamine B dye

In this study, a series of Gd3+-doped mixed Ni–Cu–Zn ferrites with composition of Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 (x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol–gel method. The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix. A rise in the Gd3+ concentration leads to an increase in crystallite size and lattice parameter. In Fourier transform infrared spectra, two main absorption bands belonging to the spinel structure are observed. The high-frequency bands (υ1) represent the tetrahedral complex, while the low-frequency bands (υ2) signify the octahedral complex. The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV, depending on their size. The magnetic characteristics of the material, such as saturation magnetization and coercivity are significantly altered with the concentration of Gd3+ in the solution. Using Rhodamine B (RhB) as a model organic pollutant, an in-depth investigation of the photocatalytic activity of the compounds was carried out. The present outcomes show that adding an adequate amount of Gd3+ significantly enhances the number of hydroxyl radicals produced by the ferrite, in turn, increasing the photocatalytic activity of the material. Mechanism elucidated by scavenger studies reveals that •OH and holes are the primary reactive radicals responsible for the degradation process. Prepared photocatalysts show an insignificant performance loss in five consecutive cycles. Thus, it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.

Effects of Chromium(III) Ion Doping on Structural, Optical, and Magnetic Properties of Nickel–Cobalt Ferrite Nanoparticle

Chromium(III)-doped nickel–ferrite nanoparticles, with the general formula Ni0.5Co0.5CrxFe2−xO4 (x = 0.0, 0.10, and 0.20), were prepared by the sol–gel method. The prepared samples were sintered at 700°C for 5 hr. The XRD result showed that the prepared samples are in single-phase partially inverse cubic spinel ferrite structures with space group Fd3m. From the XRD characterization, the average crystallite size for all samples decreased from 39.54 to 30.42 nm and the lattice parameters are found to be 0.8324, 0.8320, and 0.8314 nm for x = 0.0, 0.10, and 0.20, respectively. The energy dispersive X-ray (EDX) spectroscopy analysis confirmed the presence of all ions as per the stoichiometric ratios. The vibrating sample magnetometer measurements revealed that the saturation magnetization (Ms), remnant magnetization (Mr), and coercive fields are found to be decreased with increasing concentration of Cr3+ ions. The UV–vis spectroscopy analysis showed that the energy bandgap (Eg) increased with increasing the concentration of Cr3+ ion from 1.61 to 1.96 eV. The Fourier transform infrared spectra show the two main absorption bands at 407–424 cm−1 and 547–588 cm−1 corresponding to stretching vibrations of metal–oxygen in the octahedral and tetrahedral sites, respectively.

Transient “cis-Peak” Is Present in Excited-State Absorption of Central-cis Isomers of Carotenoids

Application of femtosecond time-resolved transient absorption spectroscopy on all-trans and central-cis isomers of two exemplary carotenoids, lutein and spirilloxanthin, performed at room and cryogenic temperatures in the spectral range expanded toward UV revealed new spectroscopic transient features for the cis isomers. Notably, particularly for the central-cis spirilloxanthin, a very distinct additional transient absorption band is observed on the short wavelength side of the main excited-state absorption band of the S1 state, having the same temporal characteristics as the latter one. This band is absent in transient absorption spectra of all-trans isomers, suggesting it could be assigned to "transient cis-peak." Overall, the results show that the "transient" counterpart of the spectral marker of cis-isomers of carotenoids, or the so-called cis-peak, is detectable in the excited-state absorption spectrum and could be attributed to electronic transition from the S1 state. This new transient spectral band could be very useful for spectroscopic experiments targeting the dynamics of carotenoid isomers and their severely distorted forms.

Williamson-Hall and Size-strain plot based micro-structural analysis and evaluation of elastic properties of Dy3+ substituted Co-Zn nano-spinels

Polycrystalline Co-Zn nanoferrites doped with rare earth Dy3+ ions having general chemical formula Co0.9Zn0.2DyxFe1.9-xO4 (x = 0.0, 0.015, 0.03, 0.045 and 0.06) were synthesized via sol-gel auto-combustion route. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform Infrared Spectra (FTIR) were performed to investigate the structural, microstructral, surface morphology and elastic properties. Well indexed XRD patterns confirm the phase purity and cubic spinel structure of the samples. Fractional doping of Dy3+ ions shifts the Bragg’s lines slightly towards the lower angles which in turn increases the lattice lengths from 8.3795 Å to 8.3834 Å. The strain induced in the crystal lattice was estimated by using Williamson-Hall and Size – Strain Plot methods. Both methods confirm that the tensile type strain was induced in the crystal lattice and increases with the substitution of Dy3+ ions. Surface morphology of the samples was studied by using SEM images which reveals that the grains are almost spherical in nature and the size obtained is analogues with XRD results. FTIR spectra shows the existence of two main absorption bands within the wave number range 388 – 586 cm−1 which confirm the characteristics of spinel ferrites. Elastic properties were estimated by using FTIR data. Elastic moduli and Debye temperature increases with the substitution of Dy3+ ions which are interpreted on the basis of interatomic bondings.

Structural,Spectral and Electrical Properties of BaNi2-xZnxFe16O27 Nanoparticles Ferrites

In the current study, w-type BNF-NPs synthesis via ceramic method.the effects of zinc ions doping on the physical properties of BNF-NPs were analyzed. The formation of BNF-NPs emphasized by XRD, FTIR, UV-Visible spectroscopy and electrical conductivity measurement. The phases structure , crysttallite size and lattice parameters wrere evaluated using XRD results. Hexagonal structure with a single phase apeares, the average grain size was found to be in Nano scale from 32 to 34 nm, while the lattice parameters increased slolly as the doping concentration of zinc ions increases. The spectra of FTIR showed main absorption bands which confirmed formation of hexagonal ferrite phase. UV-VIS analysis was also performed and found that the band gaps were in the semiconducting region and increased with increasing zinc concentration. The AC conductivity of the samples decreased with increasing zinc content and showed a dependence on the frequency and temperature. Additionally, as frequency increase the σac conductivity showed dispersion that decreased as temperature increased.dispersion decreases as the temperature increases.

Probing Colossal Carbon Rings.

Carbon aggregates containing between 10 and 30 atoms preferentially arrange themselves as planar rings. To learn more about this exotic allotrope of carbon, electronic spectra are measured for even cyclo[n]carbon radical cations (-) using two-color photodissociation action spectroscopy. To eliminate spectral contributions from other isomers, the target cyclo[n]carbon radical cations are isomer-selected using a drift tube ion mobility spectrometer prior to spectroscopic interrogation. The electronic spectra exhibit sharp transitions spanning the visible and near-infrared spectral regions with the main absorption band shifting progressively to longer wavelength by ≈100 nm for every additional two carbon atoms. This behavior is rationalized with a Hückel theory model describing the energies of the in-plane and out-of-plane π orbitals. Photoexcitation of smaller carbon rings leads preferentially to neutral C3 and C5 loss, whereas rings larger than tend to also decompose into two smaller rings, which, when possible, have aromatic stability. Generally, the observed charged photofragments correspond to low energy fragment pairs, as predicted by density functional theory calculations (CAM-B3LYP-D3(BJ)/cc-pVDZ). Using action spectroscopy it is confirmed that and photofragments from rings have cyclic structures.

Structural, thermoluminescence and optical properties of Nd3+ doped Y2O3 nanophosphor for dosimeter and optoelectronics applications

For potential gamma ray dosimetry and near-infrared laser material applications, solution combustion synthesis was used to create undoped and trivalent neodymium doped Y2O3. X-ray powder diffraction was used to analyze the annealed materials. It was discovered that they had a cubic Y2O3 single phase structure up to a dopant level of 2 mol%. The higher dopant concentrations showed the existence of a Nd2O3 solid solution. The crystallite sizes were determined using Scherrer and Williamson-Hall equations and were found to decrease with dopant content. Characterization of the nanocrystals by X-ray photoelectron spectroscopy confirmed excellent stoichiometric control. The γ-ray irradiated phosphors showed a thermoluminescence (TL) peak at about 394 K that sub linearly increased in intensity up to 7 kGy and thereafter decreased. A computerized glow curve deconvolution algorithm was used to analyze the measured complex TL glow curves produced for the phosphors exposed to γ-rays. The 60Co γ-ray irradiated Nd3+ doped Y2O3 sample exhibited peaks at 395, 445, 496 and 596 K with the corresponding activation energies in the range of 1.20-1.32 eV. These were attributed to the F, F+ and V-centers. The main absorption bands, i.e., at 590 and 812 nm for the Nd:Y2O3 nanocrystals. As the host's Nd3+ content increased, the optical band gap decreased. Three major emission bands at wavelengths of 871–957, 1045–1137, and 1306–1379 nm were associated with Nd3+ transitions of 4F3/2→4I9/3, 4F3/2→4I11/3 and 4F3/2→4I13/3, According to calculations, the 4F3/2 energy level's PL lifespan for Nd3+ doped Y2O3was between 68 and 247 µs.

Low concentration doping effects of holmium on structural and spectroscopic properties of cobalt ferrite

The spinel ferrite structure with the formula of MFe2O4(M = Co, Ni, Zn, or other metals) can be described as a cubic, closely packed arrangement of oxygen atoms, and M2+and Fe3+ions can occupy either tetrahedral (A) or octahedral (B) sites. Cobalt ferrites doped with Ho with the compositional formula CoFe2-xHoxO4, where x = 0, 0.005, 0.01, 0.015 and 0.02 are prepared by solid state reaction method. The results from XRD data reveal the single phase nature of materials and lattice parameters are found to increase with increasing rare earth dopant concentration. The spectroscopic techniques such as FTIR and Raman spectra are employed to characterize the low concentrated Ho doped cobalt ferrites. Two main absorption bands are observed in the range of 380–600 cm−1 in the FTIR spectra. The results are discussed in the paper.

Thermally activated delayed fluorescence of a Ir(III) complex: absorption and emission properties, nonradiative rates, and mechanism.

One recent experimental study reported a Ir(III) complex with thermally activated delayed fluorescence (TADF) phenomenon in solution, but its luminescent mechanism is elusive. In this work, we combined density functional theory (DFT), time-dependent DFT (TDDFT) and multi-state complete active space second-order perturbation theory (MS-CASPT2) methods to investigate excited-state properties, photophysics, and emission mechanism of this Ir(III) complex. Two main absorption bands observed in experiments can be attributed to the electronic transition from the S0 state to the S1 and S2 states; while, the fluorescence and phosphorescence are generated from the S1 and T1 states, respectively. Both the S1 and T1 states have clear metal-to-ligand charge transfer (MLCT) character. The present computational results reveal a three-state model including the S0, S1 and T1 states to rationalize the TADF behavior. The small energy gap between the S1 and T1 states benefits the forward and reverse intersystem crossing (ISC and rISC) processes. At 300 K, the rISC rate is five orders of magnitude larger than the phosphorescence rate therefore enabling TADF. At 77 K, the rISC rate is sharply decreased but remains close to the phosphorescence rate; therefore, in addition to the phosphorescence, the delayed fluorescence could also contribute to the experimental emission. The estimated TADF lifetime agrees well with experiments, 9.80 vs. 6.67 μs, which further verifies this three-state model.

NIR emitting BODIPY dyes for pH sensing

The ease of functionalization of BODIPY dyes provides scope for preparing pH indicators by introducing suitable functional groups. In this work, two dimethylamino substituted BODIPY dyes 3 and 4 with styryl and phenylbuta-1,3-dienyl groups introduced at the 3,5-positions were synthesized, characterized, and studied for use as pH indicators. Incorporation of the electron-rich vinylene substituents yielded dyes that absorb in the NIR region with emission wavelengths of 796 and 797 nm for 3 and 4, respectively, in dimethylsulfoxide (DMSO). Time-dependent density functional theory (TD-DFT) calculations were performed to study the effect of adding an extra alkene bond in 4 on the photophysical properties. The extra alkene bond in 4 resulted in a 3 nm shift in the main NIR region absorption band, lower molar extinction coefficient values, higher emission wavelength, and a decrease in fluorescence quantum yield in all solvents studied. Upon protonation of the amino groups, a large blue shift is observed in both the absorption and emission wavelengths, along with an increase in the fluorescence quantum yields and longer fluorescence lifetimes. The [Formula: see text] values for 3 and 4 were estimated to be 2.9 (± 0.05) and 1.2 (± 0.05), respectively.