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Antimicrobial Photodynamic Therapy (aPDT) is an innovative and promising method for combating infections, reducing the risk of antimicrobial resistance compared to traditional antibiotics. Squaraine (SQ) dyes can be considered promising photosensitizers (PSs) but are generally hydrophobic molecules that can self-aggregate under physiological conditions. To overcome these drawbacks, a possible solution is to incorporate SQs inside nanoparticles (NPs). The present work deals with the design and development of innovative nanophotosensitizers based on poly lactic-co-glycolic acid (PLGA) NPs incorporating a brominated squaraine (BrSQ) with potential application in aPDT. Two designs of experiments (DoEs) based on the single emulsion and nanoprecipitation methods were set up to investigate how different variables (type of solvent, solvent ratio, concentration of PLGA, stabilizer and dye, sonication power and time) can affect the size, zeta (ζ)-potential, yield, entrapment efficiency, and drug loading capacity of the SQ-PLGA NPs. SQ-PLGA NPs were characterized by NTA, FE-SEM, and UV-Vis spectroscopy and the ability to produce reactive oxygen species (ROS) was evaluated, proving that ROS generation ability is preserved in SQ-PLGA. In vitro antimicrobial activity against Gram-positive bacteria in planktonic state using Staphylococcus aureus was conducted in different conditions and pH to evaluate the potential of these nanophotosensitizers for aPDT in the local treatment of infections. [ABSTRACT FROM AUTHOR]

Fluorescence detection has found extensive applications in various fields such as chemical analysis and biological testing. Therefore, conducting experiments related to fluorescence detection is of significant importance in undergraduate laboratory education. This experiment successfully developed a low-cost, compact open-source fluorescence spectrometer, whose performance was comprehensively evaluated and applied to the detection of real samples. The aim is to foster students' awareness and confidence in designing and creating instruments. [ABSTRACT FROM AUTHOR]

Many efforts have been made to develop near-infrared (NIR) fluorescent dyes with high efficiency for the NIR laser-induced phototherapy of cancer. However, the low tumor targetability and high nonspecific tissue uptake of NIR dyes in vivo limit their applications in preclinical cancer imaging and therapy. Among the various NIR dyes, squaraine (SQ) dyes are widely used due to their high molar extinction coefficient, intense fluorescence, and excellent photostability. Previously, benzoindole-derived SQ (BSQ) was prepared by incorporating carboxypentyl benzoindolium end groups into a classical SQ backbone, followed by conjugating with cyclic RGD peptides for tumor-targeted imaging. In this study, we demonstrate that the structure-inherent tumor-targeting BSQ not only shows a high fluorescence quantum yield in serum but also exhibits superior reactive oxygen species (ROS) generation capability under the 671 nm laser irradiation for effective photodynamic therapy (PDT) in vitro and in vivo. Without targeting ligands, the BSQ was preferentially accumulated in tumor tissue 24 h post-injection, which was the optimal timing of the laser irradiation to induce increments of ROS production. Therefore, this work provides a promising strategy for the development of photodynamic therapeutic SQ dyes for targeted cancer therapy. [ABSTRACT FROM AUTHOR]

Recent research on photothermal therapy (PTT) has sparked significant interest in the development of new organic photothermal agents (PTAs), ranging from single-molecule to aggregated levels. However, controlling aggregation pathways for PTAs with ultrahigh photothermal conversion efficiency (PCE) remains a major challenge. Herein, a two-pronged approach utilizing "H-aggregation" and "intramolecular motion" was employed to enhance the PCE of an acceptor-substituted squaraine dye (NSQs). The C2v molecular symmetry of the NSQs, which possess a ground state dipole moment (μg), promotes H-dimeric aggregates through dipole-dipole counteraction. Peripheral triphenylethylene or diphenylamine groups were added to this H-dimeric nanoplatform. This was done to enhance intramolecular motions for heat generation and also to extend conjugation, which red-shifted the optical absorption and balanced the blue-shift induced by H-aggregation. With this technique, an organic PTA with NIR-II absorption was developed, and its nanoparticle achieved a remarkable PCE of 86.3% under 1,064 nm laser excitation. Femtosecond transient absorption spectroscopy and quantum mechanical calculations demonstrated the accelerated internal conversion process in NIR-II PTAs for rapid heat generation. The NSQs nanoparticles exhibit superior photothermal therapeutic properties for in vivo photoacoustic imaging-guided PTT, demonstrating the potential of bottom-up design to enable synergistic engineering strategies towards efficient phototheranostic agents. [ABSTRACT FROM AUTHOR]

The design and development of sensitizing dyes possessing wide-wavelength photon harvesting encompassing visible to near-infrared (NIR) wavelength regions are unavoidable for increasing the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, three far-red-sensitive squaraine sensitizers were designed computationally, synthesized, and characterized, aiming towards their suitability as a potential sensitizer for DSSCs. It has been found that the incorporation of an electron acceptor moiety in the central squaraine core brought about a red shift in the absorption maximum (λmax) and the emergence of a secondary absorption band in the blue region, thus broadening the photon-harvesting window. In addition, it also lowered the dye’s HOMO energy level enabling a facile regeneration of the photo-excited dye, which improved the photovoltaic performance of SQ-223, exhibiting a photoconversion efficiency (PCE) of 4.67%. Thereafter, to address the issue of wide-wavelength photon harvesting, DSSCs were fabricated by co-adsorbing two complementary dyes SQ-223 and D-131 in various molar ratios. The DSSC fabricated with D-131 and SQ-223 in 9:1 molar ratio displayed the best photovoltaic performance with a PCE of 5.81%, a significantly higher PCE when compared to corresponding individual dye-based DSSCs containing D-131 (3.94%) and SQ-223 (4.67%).

Novel amine‐functionalized symmetrical squaraine (SQ)‐dye and fluorescein isothiocyanate (FITC)–SQ–FITC dye conjugate are designed and successfully synthesized, followed by their structural and photophysical characterizations. Symmetrical SQ dye exhibits complete fluorescence quenching in polar solvents, which is explained by considering photoinduced electron transfer (PET) as a dominant quenching pathway. In contrast, FITC–SQ–FITC dye conjugate results in a decrease in an aggregation of both SQ and FITC units and about 47 times enhancement in the far‐red fluorescence appearing at 674 nm. This profound enhancement in the far‐red fluorescence is explained by the synergistic influence of suppression of aggregation‐induced quenching (ACQ) and PET. This newly designed FITC–SQ–FITC dye conjugate shows complete quenching of the far‐red fluorescence in phosphate buffer saline (PBS) owing to very strong dye aggregation, as confirmed by spectral absorption investigation. In PBS, it strongly interacts with bovine serum albumin (BSA) (Ka = 1.1 × 104 m−1) used as a model protein breaking the dye aggregation by BSA and increasing far‐red fluorescence associated with SQ as a function of increasing BSA concentration. A profound 117 times increase in fluorescence at 674 nm with 25 times of BSA concentration suggests that the designed FITC–SQ–FITC is an excellent far‐red probe for dye‐protein interaction. [ABSTRACT FROM AUTHOR]

Two novel near‐infrared (NIR)‐sensitive unsymmetrical squaraine dyes, SQ‐258 and SQ‐259, for their suitability as a sensitizer in dye‐sensitized solar cells (DSSCs) are designed and synthesized, followed by photophysical and photovoltaic characterizations. It is demonstrated that introducing a 1,3‐indandione acceptor unit in the central squaric acid core of SQ‐259 leads to the suppression of dye aggregation owing to its nonplanar molecular geometry and the broadening of the optical absorption and photon‐harvesting window up to 800 nm. Owing to the extended wavelength photon harvesting, SQ‐259 improves the photoconversion efficiency (PCE) compared to its SQ‐258 dye counterpart. However, despite its wide wavelength photon harvesting, the improvement in the PCE of SQ‐259 is less pronounced, and this is attributed to the small driving force for injection of electrons (0.29 eV), hampered electronic coupling, and decreased electron lifetime for resistance to recombination (7.9 ms), which is confirmed by the cyclic voltammetry, quantum chemical calculation, and electrochemical impedance spectroscopic investigations, respectively. [ABSTRACT FROM AUTHOR]

The design and development of sensitizing dyes possessing wide-wavelength photon harvesting encompassing visible to near-infrared (NIR) wavelength regions are unavoidable for increasing the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, three far-red-sensitive squaraine sensitizers were designed computationally, synthesized, and characterized, aiming towards their suitability as a potential sensitizer for DSSCs. It has been found that the incorporation of an electron acceptor moiety in the central squaraine core brought about a red shift in the absorption maximum (λmax) and the emergence of a secondary absorption band in the blue region, thus broadening the photon-harvesting window. In addition, it also lowered the dye's HOMO energy level enabling a facile regeneration of the photo-excited dye, which improved the photovoltaic performance of SQ-223, exhibiting a photoconversion efficiency (PCE) of 4.67%. Thereafter, to address the issue of wide-wavelength photon harvesting, DSSCs were fabricated by co-adsorbing two complementary dyes SQ-223 and D-131 in various molar ratios. The DSSC fabricated with D-131 and SQ-223 in 9:1 molar ratio displayed the best photovoltaic performance with a PCE of 5.81%, a significantly higher PCE when compared to corresponding individual dye-based DSSCs containing D-131 (3.94%) and SQ-223 (4.67%). [ABSTRACT FROM AUTHOR]

A series of alkyl‐group‐functionalized, aniline‐ and indoline‐donor‐based, unsymmetrical visible‐light‐active squaraine dyes, AM1‐3, were designed and synthesized. Dye‐sensitized solar cell (DSSC) devices were fabricated with both I−/I3− and [Cu(tmby)2]+/2+ electrolytes. DSSC devices sensitized with the AM1 and AM2 dyes showed relatively high‐power conversion efficiency of 7.44 % and 7.22 %, respectively with I−/I3− in the absence of chenodeoxycholic acid (CDCA) than those of the AM3 dye (5.41 %). The [Cu(tmby)2]+/2+ electrolyte along with poly(3,4‐ethylenedioxythiophene) (PEDOT) as cathode material showed excellent open‐circuit potentials (VOC) of 1030, 1025, and 1001 mV with the DSSC efficiency of 8.05 %, 7.96 %, and 5.84 %, respectively, for the AM1, AM2, and AM3 dyes in the absence of CDCA. Here, the AM1 dye exhibited the maximum DSSC efficiency of 8.05 % and VOC of 1030 mV, which is the highest obtained efficiency and VOC for the visible‐light active zwitterionic unsymmetrical‐squaraine dye with copper‐based electrolyte. [ABSTRACT FROM AUTHOR]

We have elucidated the details of the photodegradation of non‐fluorinated benzoindolenine‐based SQ dyes with low photostability in solution and proposed a hypothesis to improve their photostability. Based on the results, replacing all the hydrogen atoms on the benzoindolenine ring with fluorine atoms or methylation of the oxygen anions of the non‐fluorinated benzoindolenine SQ dye resulted in improvement of photostability. Furthermore, a preliminary investigation of the synthesized SQ dyes for organic photovoltaics revealed that the O‐methylated SQ dye with bulky fluorine‐containing anions provided a much higher Voc than similar benzoindolenine‐based SQ dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] MXenes, a new family of 2D nanostructured materials, have been widely studied in the field of artificial photosynthesis due to their outstanding physicochemical properties. In this work, a series of 2,4-bis[4-(N , N -dibutylamino)phenyl] squaraine (SQ) derivatives with different number of hydroxyl groups were hybridized with Ti 3 C 2 T x MXene nanosheets, and the organic–inorganic hybrid photocatalysts were applied for water-splitting hydrogen evolution. The mass ratios of SQ @Ti 3 C 2 T x were optimized to 4 wt% for each SQ , and the best hydrogen evolution reaction (HER) rate of 28.6 μmol h−1 g−1 was achieved by SQ-3 with four OH groups. The photocatalytic ability of the hybrid comes from the outstanding light harvesting of SQ dye, sufficient active sites of Ti 3 C 2 T x , and efficient separation and transfer of the photogenerated charges via heterojunction between SQ aggregates and Ti 3 C 2 T x. This work firstly demonstrates an example of SQ sensitizer combined with MXene for hydrogen generation, which provides a new insight to further explore the MXene-based hybrid nanomaterials for water splitting hydrogen evolution. [ABSTRACT FROM AUTHOR]

Aim. One of the potential methods for treating cancer is photodynamic therapy (PDT), which involves the targeted destruction of cancer cells through the activation of photosensitizers (PS) using light irradiation. The aim of the study was to investigate the photodynamic properties of the squaraine dyes with hydrophilic and hydrophobic substituents. Methods. Fluorescence spectroscopy, UV-VIS spectroscopy, laser scanning confocal microscopy, cytotoxicity assay. Results. It was shown that all studied dyes have maximum absorption in the far-red region, which makes them suitable for PDT. It has been investigated that the squarains can form complexes with proteins, as indicated by changes in their fluorescence. The samples demonstrated minimal dark toxicity but exhibited cytotoxicity after irradiation. The cytotoxic effect of dyes with hydrophilic groups was reduced by binding to BSA. Meanwhile, a dye with hydrophobic substituents shows a photodynamic effect in the presence of albumin. All studied dyes can penetrate through the cellular membrane, stain the cell components in the cytoplasm, and do not accumulate in nuclei. Conclusions. All dyes showed low dark toxicity. However, cytotoxicity increased after irradiation with light of a wavelength of 670 nm. The binding of the dyes with hydrophilic substitutes to albumin negatively impacted their photosensitizing properties. At the same time, the dye with the highest tendency to aggregate exhibited the most significant cytotoxic effect. [ABSTRACT FROM AUTHOR]

The quantitative determination of proteins is an important parameter in biochemistry, biotechnology and immunodiagnostics, and the importance of serum albumin in clinical diagnosis should be highlighted, given that alterations in its concentration are generally associated with certain diseases. As possible probes for this purpose, squaraine dyes have been arousing the interest of many researchers due to their unique properties, such as absorption in the visible spectra, moderate relative fluorescence quantum yields and increased fluorescence intensity after non-covalent binding to specific ligands. In this work, five squaraine dyes, four of which have never been reported in the literature, were characterized and evaluated in vitro and in silico concerning their potential application as fluorescent probes for human serum albumin detection. After interaction with the protein, the fluorescence intensity increased from 12 to 41 times, depending on the dye under study. High sensitivity (1.0 × 105–5.4 × 105 nM), low detection limits (168–352 nM) and moderate quantitation limits (560–1172 nM) were obtained, proving the efficiency of the method. In addition, moderate-to-excellent selectivity was observed compared to γ-globulin proteins. Molecular docking suggests that the dyes interact more effectively with the Sudlow site I, and binding energies have been markedly higher than those of warfarin, a molecule known to bind to this site specifically. [ABSTRACT FROM AUTHOR]

Novel near-infrared sensitizers with different anchoring groups aiming toward improved stability and efficiency of dye-sensitized solar cells were synthesized. Adsorption of these dyes on the mesoporous TiO2 surface revealed the dye adsorption rate of −CH=CH-COOH (SQ-139) > −CH=C(CN)COOH (SQ-140) > −PO3H2 (SQ-143) > −CH=C(CN)PO3H2 (SQ-148) > −CH=C(CN) PO3H-C2H5 (SQ-157) > −PO3H-C2H5 (SQ-151) > −CH=CH-COOH(−PO3H2) (SQ-162). The binding strength of these dyes on mesoporous TiO2 as investigated by dye desorption studies follows SQ-162 > SQ-143 > SQ-148 > SQ-139 ≫ SQ-157∼SQ-151 ≫ SQ-140 order. The acrylic acid anchoring group was demonstrated to be an optimum functional group owing to its fast dye adsorption rate and better binding strength on TiO2 along with good photoconversion efficiency. Results of dye binding on TiO2 surface demonstrated that SQ-162 bearing double anchoring groups of phosphonic and acrylic acid exhibited > 550 times stronger binding as compared to dye SQ-140 having cyanoacrylic acid anchoring group. SQ-140 exhibited the best photovoltaic performance with photon harvesting mainly in the far-red to near-infrared wavelength region having short circuit current density, open-circuit voltage and fill factor of 14.28 mA·cm−2, 0.64 V and 0.65, respectively, giving the power conversion efficiency of 5.95%. Thus, dye SQ-162 not only solved the problem of very poor efficiency of dye bearing only phosphonic acid while maintaining the extremely high binding strength opening the path for the design and development of novel near-infrared dyes with improved efficiency and stability by further increasing the π-conjugation. [ABSTRACT FROM AUTHOR]

The theoretical description for the chlorantraniliprole electrochemical determination, assisted by the hybrid composite of squaraine dye with CuS nanoparticles has been described. The correspondent reaction mechanism has been proposed, and the correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It has been shown that the chlorantraniprole electrochemical anodical determination on high potential may be efficiently provided by cupper sulfide nanoparticles, stabilized by the squaraine dye. On the other hand, the oscillatory and monotonic instability is also possible, being caused by DEL influences of the electrochemical stage. DOI: http://dx.doi.org/10.17807/orbital.v13i3.1518

• Design and synthesis of -COOH functionalized unsymmetrical NIR squaraine dyes. • Structural variations include varying alkyl chain and -COOH spacer length. • Complete fluorescence quenching in aqueous solution due to dye aggregation. • Enhancement of fluorescence upon interaction with BSA to form dye-BSA conjugates. • Very strong binding with a ka of 107/mol and binding with BSA in 2:1 ratio. The demand for near-infrared (NIR) probes with robust and stable fluorescence signals has surged, driven by their applications in optical sensing and bioimaging. Squraine dyes as NIR fluorescent probes have gained significant traction. However, understanding their behavior in aqueous media is important for their successful application. Herein we report the synthesis and photophysical characterization of carboxy-functionalized unsymmetrical squaraine dyes capable of light absorption and emission in the near-infrared (NIR) wavelength region. Structural variations in alkyl chain length, and spacer chain length between the primary chromophore and –COOH group were systematically introduced to investigate their impact on self-assembly in aqueous media leading to dye aggregation and their differential interactions with Bovine Serum Albumin (BSA) as a model protein. In phosphate buffer (PB) the absorption intensity decreased drastically along with pronounced shoulders due to dye aggregation leading to complete fluorescence quenching. However, in the presence of BSA, the intensity of shoulder bands reduced coupled with a sharp increase in the absorption associated with monomeric dye with the increasing concentration of BSA, indicating the prevention of dye aggregation owing to dye-BSA interactions. The prevention of dye aggregation due to dye-BSA interaction also led to a tremendous increase in the fluorescence intensities as a function of the increasing BSA concentrations. Site-selective study off BSA showed that these dyes bind preferably at Site-II using hydrophilic interactions. Thus, these dyes show great potential as FRET or fluorescent on/off probes for biosensing, non-covalent labeling of proteins, and fluorescent probes for bioimaging. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding and implementing the ordered supramolecular assembly in organic photothermal materials is challenging, yet significant, for photothermal performance enhancement. Herein, an amphipathic squaraine dye (PSQ) with a poly (ethylene glycol) chain attached as a hydrophilic anchor is synthesized. In aqueous solution, PSQ spontaneously self‐assembles into uniform nanospheres (PSQ‐NSs) with well‐defined H‐dimeric substructures. Molecular dynamics simulations are conducted to illustrate the self‐assembly process. Reorganization energy calculations show that nonradiative decay is accelerated by H‐dimeric PSQ low‐frequency out‐of‐plane vibrational modes, which enables a rapid dissipation of excited‐state energy to heat. As such, the resultant H‐dimeric PSQ‐NSs exhibit ultrahigh photothermal conversion efficiency (81.2%) under laser irradiation (0.3 W cm−2, 808 nm) in water. In vitro and in vivo evaluations confirm their high stability, biocompatibility, tumor accumulation, and efficient tumor inhibition in photothermal therapy. It is expected that the self‐assembling H‐dimers will become a unique platform for the precise designing of small‐molecule PTAs for future clinical PTT applications. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) are unusual cyanine dyes with a unique resonance-stabilized zwitterionic structure. These dyes have attracted significant attention in the fields of organic electronics and organic photonics, due to their facile synthesis, intense and narrow visible and near-infrared absorption/emission, high photostability, low biotoxicity, etc. In this review, we summarize the recent progress of SQ-based fluorescent materials and their biomedical applications. After a brief introduction to SQs, general synthetic routes and design principles of SQ-based fluorescent materials, as well as their aggregation-induced luminescence behaviors, are discussed. Subsequently, their biomedical applications for cell imaging and as fluorescent sensors and therapeutic agents are introduced. Finally, a summary and perspective are given for promoting the development of SQs-based fluorescent materials. [ABSTRACT FROM AUTHOR]

Aim. Here we synthesize a series of benzoindolium squaraine dyes with N-substituents (SQ) and examine these dyes as fluorescent probes to detect serum albumins. Methods. Organic synthesis, fluorescent spectroscopy, absorption spectroscopy, fluorescent microscopy. Results. The spectral- luminescent properties of SQ dyes in the aqueous solution were investigated in the presence of bovine serum albumin (BSA), human serum albumin (HSA), equine serum albumin (ESA), ovalbumin (OVA), beta-lactoglobulin (BLG) and lysozyme (LYS), as well as in the presence of nucleic acid. The maxima of excitation spectra of the studied dyes in the buffer solution ranged within 623-673 nm, with the fluorescence emission maxima lying between 635 and 690 nm. All these dyes showed a similar increase in the fluorescence intensity with serum albumins and at the same time with the red shift up to 12 nm, which could point out the binding of the dyes to proteins. These dyes demonstrate a noticeably lower fluorescence intensity in the presence of OVA, BLG, and LYS, which structurally differ from serum albumins. The studied dyes gave no significant fluorescent response to the addition of nucleic acids. The equilibrium constants of dyes binding to BSA (K) were estimated as 3.0 ± 0.3x105 M-1 for SL-2411 and 2.4 ± 0.6x105 M-1 for SL-2412. Based on the relative values of K, we could suppose that the mechanism of dye-BSA binding is the interaction of the chromophore of the dye with the protein globule. It was shown that SL-2411 penetrates the cell membrane and distributes in the cytoplasm without co-localization with MitoTracker Green. Conclusion. These dyes could apply fluorescent spectroscopy for protein detection and potentially visualize cell components with minimum to no autofluorescence. [ABSTRACT FROM AUTHOR]

Combined photodynamic and photothermal therapy (PDT and PTT) can achieve more superior therapeutic effects than the sole mode by maximizing the photon utilization, but there remains a significant challenge in the development of related single-molecule photosensitizers (PSs), particularly those with type I photosensitization. In this study, self-assembly of squaraine dyes (SQs) is shown to be a promising strategy for designing PSs for combined type I PDT and PTT, and a supramolecular PS (TPE-SQ7) has been successfully developed through subtle molecular design of an indolenine SQ, which can self-assemble into highly ordered H-aggregates in aqueous solution as well as nanoparticles (NPs). In contrast to the typical quenching effect of H-aggregates on reactive oxygen species (ROS) generation, our results encouragingly manifest that H-aggregates can enhance type I ROS ( • OH) generation by facilitating the intersystem crossing process while maintaining a high PTT performance. Consequently, TPE-SQ7 NPs with ordered H-aggregates not only exhibit superior combined therapeutic efficacy than the well-known PS (Ce6) under both normoxic and hypoxic conditions but also have excellent biosafety, making them have important application prospects in tumor phototherapy and antibacterial fields. This study not only proves that the supramolecular self-assembly of SQs is an effective strategy toward high-performance PSs for combined type I PDT and PTT but also provides a different understanding of the effect of H-aggregates on the PDT performance.

Development of ratiometric fluorescent hypochlorite probes with strong long wavelength fluorescence in aqueous medium, high resistance to photobleaching, high sensitivity and selectivity, and low biological toxicity remains a challenge. In this work, a molecular design strategy is proposed that can transform the traditional squaraine dyes (SQs) with aggregation‐caused quenching character into aggregation‐induced emission (AIE)‐active luminogens by functionalizing the end‐groups with tetraphenylethylene units and further introducing hydrophilic sulfonate group as the side chains. The resulting TPE‐SQ5 not only emits strong deep‐red fluorescence with a high quantum yield of 11.0% and high photostability, but more encouragingly can serve as a ratiometric fluorescent hypochlorite probe with high selectivity and sensitivity (detection limit: 5.6 nm), which indeed is the first report for SQs. The detailed sensing mechanism study demonstrates that the oxindole product with sulfonate substitution is responsible for the ratiometric fluorescent response. Furthermore, TPE‐SQ5 nanoparticles with high biocompatibility and low cytotoxicity are successfully used for ratiometrically imaging exogenous and endogenous hypochlorite in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] Dye-sensitized solar cells (DSSCs) are one of the potential candidates for the fabrication of colourful and see-through solar cells for energy harvesting esthetic windows. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled amicably to realize the solar cells with good PCE and transparency. Judicious selection of dyes to bypass the light absorption in the high eye-sensitivity region (500–600 nm) is one of the plausible solutions. This was demonstrated utilizing yellow (D-131) and red (N-719) commercial dyes along with newly developed blue (SQ-138) and green coloured (SQ-140) dyes with intense and sharp light absorption mainly in the far-red to near-infrared (NIR) wavelength region. Transparent DSSCs fabricated using the most commonly used red-coloured dye N-719 although exhibited an increase in the PCE from 2.9% to 5.3% upon increasing the thickness of the transparent TiO 2 layer from 4 μm to 10 μm but resulted in a serious loss in the average visible transparency (AVT) from 58.6% to 7.3% making the DSSC non-transparent. Contrary to this, under similar thickness variations, dyes D-131, SQ-138 and SQ-140 exhibiting very high AVT of >70% maintained the AVT > 40%, which is necessary for good visual perception. [ABSTRACT FROM AUTHOR]

Introduction:olanzapine is one of the most used antipsychotic drugs in the world. Although it is efficient, it may be toxic in excess. Therefore, in this work the possibility of olanzapine electrochemical determination over an electrode, modified by the cobalt (III) oxyhydroxide in pair with its dioxide in a composite with squaraine dye. Methods: the trivariant correspondent mathematical model includes two scenarios of the drug oxidation, possible for the case, including the indirect electropolymerization of the condensed benzodiazepine molecule, like also its oxidation by sulfur atom. This model has been developed and analyzed by means of stability theory and bifurcation analysis. Results and discussion: the analysis of the model has shown that the mechanism hybridity of the electroanalytical process, alongside with the formation and decomposition of ionic compounds during its realization, augments the possibility for the oscillatory behavior realization, relatively to the simplest and commonest case. Nevertheless, the oscillatory instability is realized in parameter values far beyond the detection limit. On the other hand, the stable steady-state is easy to obtain and maintain, indicating an efficient electroanalytical process, controlled by the analyte diffusion. Conclusions: the electroanalytical process is efficient. The cobalt compound is acting as an active substance, and the dye is the mediator. [ABSTRACT FROM AUTHOR]

The applicability of the three-step Förster resonance energy transfer (FRET) to detection of insulin amyloid fibrils was evaluated, using the chromophore system, containing Thioflavin T (ThT), 4-dimethylaminochalcone (DMC), and two squaraine dyes, referred to here as SQ1 and SQ4. The mediator chromophore DMC was found to enhance the fluorescence intensity of the terminal acceptor, SQ1, excited at 440 nm (at the absorption maximum of the principal donor, ThT), in fibrillar insulin compared to the system without DMC, providing the evidence for the cascade energy transfer in the chain ThT→DMC→SQ4→SQ1. Furthermore, the resulting Stokes shift in the four-chromophore system was 240 nm, as compared to 45 nm for the fibril-bound ThT, suggesting that higher signal-to-noise ratio is the advantage of amyloid fibril detection by multistep FRET. The maximum efficiencies of energy transfer in the insulin fibrils estimated from the quenching of the donor fluorescence in the presence of acceptor for the donor-acceptor pairs ThT-DMC, DMC-SQ4 and SQ4-SQ1 were 40%, 60% and 30% respectively, while negligible FRET occurred in the non-fibrillized protein. The most pronounced differences between fibrillar and non-fibrillized insulin were observed in the 3D fluorescence spectra. Specifically, two intensive spots centered at the emission wavelengths ~ 650 nm (SQ4) and ~ 685 nm (SQ1) were revealed at the excitation wavelength ~ 440 nm in the 3D patterns of insulin amyloid aggregates. In contrast, in the case of the non-fibrillized protein, the barely noticeable spots centered at the same wavelengths, as well as higher fluorescence intensities at the excitation above 550 nm were observed, suggesting the predominant impact of the direct excitation of SQ1 and SQ4 on their fluorescence responses. The inter-chromophore distances calculated from the experimental values of the energy transfer efficiency assuming the isotropic rotation of the dyes, were found to be 2.4, 4.5 and 4.3 nm for the ThT-DMC, DMC-SQ4 and SQ4-SQ1 pairs, respectively, revealing the different fibril binding sites for the examined dyes. The quantum-chemical calculations and simple docking studies provided evidence for the SQ1, SQ4 and ThT, DMC binding to the wet and dry interface of the insulin amyloid protofilament, respectively. The dye-protein complexes are likely to be stabilized by the hydrophobic, van der Waals, aromatic and electrostatic interactions. In summary, the above technique based on the multistep FRET can be employed for the identification and characterization of amyloid fibrils in vitro along with the classical ThT assay, allowing the increase of the amyloid detection sensitivity and lowering the probability of the pseudo-positive result. The applicability of the multistep FRET for amyloid visualization in vivo can be also tested by the involvement of the near-infrared fluorescent dyes to the cascade.

The quantitative determination of proteins is an important parameter in biochemistry, biotechnology and immunodiagnostics, and the importance of serum albumin in clinical diagnosis should be highlighted, given that alterations in its concentration are generally associated with certain diseases. As possible probes for this purpose, squaraine dyes have been arousing the interest of many researchers due to their unique properties, such as absorption in the visible spectra, moderate relative fluorescence quantum yields and increased fluorescence intensity after non-covalent binding to specific ligands. In this work, five squaraine dyes, four of which have never been reported in the literature, were characterized and evaluated in vitro and in silico concerning their potential application as fluorescent probes for human serum albumin detection. After interaction with the protein, the fluorescence intensity increased from 12 to 41 times, depending on the dye under study. High sensitivity (1.0 × 105–5.4 × 105 nM), low detection limits (168–352 nM) and moderate quantitation limits (560–1172 nM) were obtained, proving the efficiency of the method. In addition, moderate-to-excellent selectivity was observed compared to γ-globulin proteins. Molecular docking suggests that the dyes interact more effectively with the Sudlow site I, and binding energies have been markedly higher than those of warfarin, a molecule known to bind to this site specifically.

A bis(squaraine) dye equipped with alkyl and oligoethyleneglycol chains was synthesized by connecting two dicyanomethylene substituted squaraine dyes with a phenylene spacer unit. The aggregation behavior of this bis(squaraine) was investigated in non‐polar toluene/tetrachloroethane (98:2) solvent mixture, which revealed competing cooperative self‐assembly pathways into two supramolecular polymorphs with entirely different packing structures and UV/Vis/NIR absorption properties. The self‐assembly pathway can be controlled by the cooling rate from a heated solution of the monomers. For both polymorphs, quasi‐equilibrium conditions between monomers and the respective aggregates can be established to derive thermodynamic parameters and insights into the self‐assembly mechanisms. AFM measurements revealed a nanosheet structure with a height of 2 nm for the thermodynamically more stable polymorph and a tubular nanorod structure with a helical pitch of 13 nm and a diameter of 5 nm for the kinetically favored polymorph. Together with wide angle X‐ray scattering measurements, packing models were derived: the thermodynamic polymorph consists of brick‐work type nanosheets that exhibit red‐shifted absorption bands as typical for J‐aggregates, while the nanorod polymorph consists of eight supramolecular polymer strands of the bis(squaraine) intertwined to form a chimney‐type tubular structure. The absorption of this aggregate covers a large spectral range from 550 to 875 nm, which cannot be rationalized by the conventional exciton theory. By applying the Essential States Model and considering intermolecular charge transfer, the aggregate spectrum was adequately reproduced, revealing that the broad absorption spectrum is due to pronounced donor‐acceptor overlap within the bis(squaraine) nanorods. The latter is also responsible for the pronounced bathochromic shift observed for the nanosheet structure as a result of the slip‐stacked arranged squaraine chromophores. [ABSTRACT FROM AUTHOR]

The theoretical description for the chlorantraniliprole electrochemical determination, assisted by the hybrid composite of squaraine dye with CuS nanoparticles has been described. The correspondent reaction mechanism has been proposed, and the correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It has been shown that the chlorantraniprole electrochemical anodical determination on high potential may be efficiently provided by cupper sulfide nanoparticles, stabilized by the squaraine dye. On the other hand, the oscillatory and monotonic instability is also possible, being caused by DEL influences of the electrochemical stage. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) are unusual cyanine dyes with a unique resonance-stabilized zwitterionic structure. These dyes have attracted significant attention in the fields of organic electronics and organic photonics, due to their facile synthesis, intense and narrow visible and near-infrared absorption/emission, high photostability, low biotoxicity, etc. In this review, we summarize the recent progress of SQ-based fluorescent materials and their biomedical applications. After a brief introduction to SQs, general synthetic routes and design principles of SQ-based fluorescent materials, as well as their aggregation-induced luminescence behaviors, are discussed. Subsequently, their biomedical applications for cell imaging and as fluorescent sensors and therapeutic agents are introduced. Finally, a summary and perspective are given for promoting the development of SQs-based fluorescent materials.

Squaraine dyes (SQs) are an important class of polymethine dyes with a unique reasonable‐stabilized zwitterionic structure, in which electrons are highly delocalized over the conjugated bridge. These dyes can not only be easily synthesized via a condensation, but also exhibit intense absorption and emission in the visible and near‐infrared region with excellent photochemical stability, making them attractive material candidates for many photoelectric and biomedical applications. Thus, in this review, after an introduction of SQs, the recent advances of SQs in the photovoltaic field are comprehensively summarized including dye‐sensitized solar cells, organic solar cells, and perovskite solar cells. Then, the important advances in the use of SQs as the biosensors, biological imaging, and photodynamic/photothermal therapy reagents in the biomedical field are also discussed. Finally, a summary and outlook will be provided with some new perspectives for the future design of SQs. [ABSTRACT FROM AUTHOR]

Squaraine dyes are well known for their strong absorption in the visible regime. Reports on chiral squaraine dyes are, however, scarce. To address this gap, we here report two novel chiral squaraine dyes and their achiral counterparts. The presented dyes are aggregated in solution and in thin films. A detailed chiroptical study shows that thin films formed by co‐assembling the chiral dye with its achiral counterpart exhibit exceptional photophysical properties. The circular dichroism (CD) of the co‐assembled structures reaches a maximum when just 25 % of the chiral dye are present in the mixture. The solid structures with the highest relative CD effect are achieved when the chiral dye is used solely as a director, rather than the structural component. The chiroptical data are further supported by selected spin‐filtering measurements using mc‐AFM. These findings provide a promising platform for investigating the relationship between the dissymmetry of a supramolecular structure and emerging material properties rather than a comparison between a chiral molecular structure and an achiral counterpart. [ABSTRACT FROM AUTHOR]

Visibly opaque and near‐infrared transmitting (VONIRT) materials play a crucial role in forensic detection, security imaging, night‐vision photography, and biomedical applications. In this work, the development of such material using alpha‐formamidinium lead iodide based perovskite nanocrystals (PNCs) and squaraine (SQ) dyes is described. It is achieved by gradually increasing the size of PNCs followed by attaching them with a novel low‐bandgap SQ dye as capping ligand. The acid group present in the SQ dye efficiently interacts with the surface of the nanocrystals via non‐covalent interactions. Incorporation of SQ dyes onto PNCs yields composite films with uniform transmittance of below 2% in the visible region (380–740 nm) and above 60% in the NIR region, the prime requisites for VONIRT materials. Further, the addition of SQ dyes imparts better moisture stability and high film quality to the nanocrystals. Opaqueness in the visible region and excellent NIR transparency of the nanocomposite make them useful as a security material and for NIR photography application. [ABSTRACT FROM AUTHOR]

The increasing demand for reliable near-infrared (NIR) probes exhibiting enduring fluorescence in living systems and facile compatibility with biomolecules such as peptides, antibodies or proteins is driven by the increasing use of NIR imaging in clinical diagnostics. To address this demand, a series of carboxy-functionalized unsymmetrical squaraine dyes ( SQ-27 , SQ-212 , and SQ-215 ) along with non-carboxy-functionalized SQ-218 absorbing and emitting in the NIR wavelength range were designed and synthesized followed by photophysical characterization. This study focused on the impact of structural variations in the alkyl chain length, carboxy functionality positioning, and spacer chain length on dye aggregation and interaction with bovine serum albumin (BSA) as a model protein. In phosphate buffer (PB), the absorption intensity of the dyes markedly decreased accompanied by pronounced shoulders indicative of dye aggregation, and complete fluorescence quenching was seen in contrast to organic solvents. However, in the presence of BSA in PB, there was a enhancement in absorption intensity while regaining the fluorescence coupled with a remarkable increase in the intensity with increasing BSA concentrations, signifying the impact of dye-BSA interactions on preventing aggregation. Further analysis of Job's plot unveiled a 2:1 interaction ratio between BSA and all dyes, while the binding studies revealed a robust binding affinity ( K a ) in the order of 10 7 /mol. SQ-212 and SQ-215 were further tested for their in vitro and in vivo imaging capabilities. Notably, SQ-212 demonstrated nonpermeability to cells, while SQ-215 exhibited easy penetration and prominent cytoplasmic localization in in vitro studies. Injection of the dyes into laboratory mice showcased their efficacy in visualization, displaying stable and intense fluorescence in tissues without toxicity, organ damage, or behavioral changes. Thus, SQ-212 and SQ-215 are promising candidates for imaging applications, holding potential for noninvasive cellular and diagnostic imaging as well as biomarker detection when coupled with specific vectors in living systems.

In this work several symmetrical indolenine squaraine dyes with different groups positioned on the four-membered central ring, such as sulfur, barbituric acid, amino and methylamino, were synthesized, and their structures were fully characterized. All dyes displayed intense and narrow absorption bands in the visible region. To evaluate their singlet oxygen formation ability, the 1,3-diphenylisobenzofuran assay was used. The degradation of these squaraine dyes upon light exposure was evaluated in order to infer about their photostability. The in vitro potential of these compounds as photosensitizers for photodynamic therapy was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay in several tumor (Caco-2, MCF-7 and PC-3) and non-tumor (NHDF and N27) cell lines, using a custom-built LED based light exposure system emitting radiation with the central wavelength close to the maximum absorption wavelength of the squaraine dyes. The indolenine squaraine dyes showed a high ability to produce singlet oxygen and good photostability. The zwitterionic dyes, namely the unsubstituted dye, the barbituric acid derivative and the monothiosquaraine dye, showed relevant photodynamic activity. It was noteworthy that the unsubstituted squaraine dye exhibited a cytotoxic selectivity for the Caco-2 tumor cell line when compared to the NHDF normal cell line. Image 1 • New symmetrical squaraine dyes derived from indolenine were synthesized. • Ability to generate singlet oxygen was evaluated by the DPBF assay. • Photostability of the dyes was studied. • Photodynamic activity was evaluated in normal and tumoral cell lines. • Studies to determine the cellular location of the dyes were performed. [ABSTRACT FROM AUTHOR]

• Water-soluble squaraine dyes (SQOH and SQPY) were developed and SQOH didn't aggregate in aqueous solutions. • Fast detection of aldehydes in aqueous media based on the squaraine-hydrazine adducts was reported. • Detection limit for formaldehyde was around 60 μM and response time was less than 1 s. Capitalizing on the nucleophilic addition of hydrazine toward the central cyclobutenyl core and affinity of aldehydes to hydrazine group, two water-soluble squaraine dyes (SQOH and SQPY) were synthesized as sensitive colorimetric and fluorescent chemosensors for aldehydes. The color change from blue to colorless and back to blue these sensors underwent was readily observed, even by the naked eyes. The response was fast (less than 1 s) and the detection limit for formaldehyde as an example was about 60 μM. In contrast to the previous nucleophilic attack to squaraines and the other amine references studied, this work underwent a whole ON-OFF-ON sensing circle based on the characteristics of hydrazine. Meanwhile, the different photophysical properties of the two squaraines related to their different structures were also demonstrated. Importantly, a possible sensing mechanism is proposed suggesting these types of dyes hold great potential in the area of rapid, sensitive, and convenient detection of aldehydes. [ABSTRACT FROM AUTHOR]

Abstract A combination of near infra-red (NIR) photon harvesting and cobalt electrolytes having deeper redox energy level are needed for the fabrication of high efficiency dye-sensitized solar cells (DSSCs). A logical molecular design of unsymmetrical squaraine dye (SQ-110) as a representative of NIR dyes has been demonstrated to function well in DSSC using cobalt complex redox electrolyte. Problem of mass transport limitations due to the bulky cobalt complex ions leading to relatively enhanced charge recombination was amicably solved by single as well as multiple compact metal oxide surface passivation on both of the transparent conducting oxide substrate as well as mesoporous TiO 2. Complete absence of light absorption beyond 550 nm wavelength region by D-35 and utilization of a complementary light harvesting dye SQ-110 led to efficient wide wavelength photon harvesting. DSSC fabricated using a dye cocktail of D-35 and SQ-110 in 4:1 ratio resulted in to photoconversion efficiency (PCE) of 7.2%, which is much higher as compared to the constituent individual sensitizers D-35 (3.6%) and SQ-110 (1.9%). This synergistic enhancement in PCE by dye cocktail was associated with the mutual co-operation of respective dyes in terms controlling the dye aggregation and complementary photon harvesting. In this dye cocktail system, D-35 is involved in the prevention of dye aggregation, lower wavelength photon harvesting and energy transfer induced photocurrent enhancement. Highlights • Efficient far-red sensitization with cobalt-redox shuttle and newly designed sensitizer (SQ-110). • Dramatically enhanced PCE by dye-cocktail as compared to individual dyes D-35 and SQ-110. • Synergistic and mutual cooperation on aggregation control by individual dyes in dye cocktail. • Dual role of D-35 as complementary photon harvester and dye de-aggregating agent for SQ-110. [ABSTRACT FROM AUTHOR]

Abstract Squaraine dyes have attracted increasing attention as photovoltaic materials for organic solar cells (OSCs) because of their facile and low-cost synthesis, intense and broad absorption in the visible and near-infrared (Vis-NIR) regions as well as colorful films. Herein, we report the synthesis of a novel π-D 1 -A-D 2 type squaraine dye (DTT-USQ-11) with a low optical bandgap of 1.50 eV. In comparison with the classic D 1 -A-D 2 type squaraine dye (USQ-11), DTT-USQ-11 demonstrates a lower optical bandgap, deeper highest occupied molecular orbital (HOMO) energy level, and higher hole mobility. Consequently, solution-processed bulk heterojunction small molecular OSC fabricated with the DTT-USQ-11 /PC 71 BM blend film exhibits a much higher power conversion efficiency (PCE: 5.69%) compared with the classical USQ-11 /PC 71 BM system (PCE: 4.15%). This enhanced PCE can be attributed to the simultaneous increase in the open-circuit voltage, short-circuit current density and fill factor of the DTT-USQ-11 -based devices. Graphical abstract Image 1 Highlights • A new π-D 1 -A-D 2 type low bandgap squaraine is developed for organic solar cells. • A PCE of 5.69% is obtained for squaraine-based organic solar cells. • This squaraine exhibits a low bandgap of 1.50 eV and relatively deep HOMO of −5.14 eV. • The π-D 1 -A-D 2 structure maybe an important way for squaraine to achieve high PCE. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis, characterization and single crystal X ray analysis of bis(3,5-dimethyl-1H-pyrrol-2-yl)-based squaraine dyes. • High solubility and high absorptivity (ε = 5.2 × 105 M−1 cm−1) and absorption in the red/NIR region for two new squaraines. • Application in organic solar cells with device architecture: ITO/ MoO 3 /Squaraine/C 60 /BCP/Al. Abstract We report the material characterization and single crystal Xray analysis of bis(3,5-dimethyl-1H-pyrrol-2-yl)-3-oxocyclobut-1-en-1-olate (PSQ) and a derivative of this symmetric squaraine dye with a thiophene substituent (NSP) that has high solubility and high absorptivity (ε = 5.2 × 105 M−1 cm−1) in the 500–800 nm region of the solar spectrum, making it a potential candidate for application in organic photovoltaics (OPVs). The squaraine derivatives show markedly broader absorption in the solid state than in solution. Photoluminescent quantum yields for PSQ and NSP are low (Φ PL = 0.014 and 0.047 respectively). OPVs were fabricated using the following architecture: ITO/ MoO 3 (120 Å)/ Squaraine (80–85 Å)/ C 60 (400 Å)/ BCP (100 Å)/ Al (1000 Å), BCP = bathocuproine. Devices fabricated with thin films of PSQ give higher fill factors (FF), photocurrent and better performance under 1 sun, AM1.5 G simulated illumination: open-circuit voltage V oc = 0.43 V, short-circuit current J sc = 5.17 mA/cm2, FF = 0.52, and power conversion efficiency η = 1.15%, compared with NSP based OPVs: V oc = 0.56 V, short-circuit current J sc = 4.34 mA/cm2, FF = 0.42, and power conversion efficiency η = 1.02%. [ABSTRACT FROM AUTHOR]

Abstract A new family of asymmetrical 1,2-squaraine dyes (1,2-SQs) were designed and synthesized in high yields. The photophysical analysis presented that these 1,2-SQs showed strong red fluorescence in crystal state but weak fluorescence in solution, suggesting their aggregation-induced emission enhancement (AIEE) properties. Single crystals X-ray diffraction revealed that the intense fluorescence in the crystal state can be attributed to the effects of long alkyl chains or large group substituents in the molecules, which efficiently prevented the tight intermolecular contact and reduced π–π interactions. The biocompatibility and cell imaging applications of SQ4 were further investigated. The results demonstrated that SMMC-7721 cell can be clearly imaged by SQ4, which inferred SQ4 had excellent biocompatibility and potential value for bioimaging. Graphical abstract Image 1 Highlights • Crystal red fluorescent 1,2-SQs were designed and easily prepared with high fluorescence quantum yield (up to 42.45%). • 1,2-SQs exhibited typical aggregation-induced emission enhancement (AIEE) properties. • SQ4 showed excellent biocompatibility and can be used for cell imaging. [ABSTRACT FROM AUTHOR]

Isomeric biscyanomethylene-substituted 1,3- and 1,2-pyrilo-4-squaraines have been synthesized. The formation of a dye, derivative of 1,2-squarate, from the derivative of 1,3-squarate has been demonstrated for the first time. Electronic absorption spectra of the synthesized dyes have been studied. The molecular and crystal structure has been investigated by X-ray diffraction analysis. Both isomeric dyes exist in the cis-conformation. [ABSTRACT FROM AUTHOR]

• Two novel Squaraine dyes (SQI-5 and SQI-6) were synthesized and employed as NIR sensitizers in DSSCs. • Both theoretical calculations and experimental data indicated the suitability of the HOMO and LUMO levels of the dyes as DSSCs. • Compared with SQI-5, SQI-6 sensitizer exhibited better photovoltaic performance. The utilization of near-infrared (NIR) photons holds paramount importance in the realm of electricity conversion, as it offers a promising avenue to enhance the capabilities of dye-sensitized solar cells (DSSCs). In light of this, a pioneering effort was made to synthesize two novel Squaraine (SQI-5 and SQI-6) dyes that comprise two functional groups (-SO 3 H and -COOH) with the aim of producing efficient far-red sensitizers that could be applied in DSSCs. The efficacy of the recently developed dyes was extensively evaluated using diverse analytical techniques, which confirmed their exceptional solubility in multiple organic solvents. Investigation into the adsorption behavior of the SQI-5 and SQI-6 sensitizers on mesoporous TiO 2 showed that the -COOH anchoring group demonstrated a higher rate of adsorption compared to the -SO 3 H group, whereas the stability of the adsorbed dyes was superior for -COOH as opposed to -SO 3 H following dye desorption tests. Both theoretical and experimental methods were employed to evaluate the impact of the anchoring groups on the energy levels of the HOMO- LUMO. Despite having a high binding strength, favorable energy cascade, and decreased dye loading, the SQI-5 sensitizers featuring a sulfonic acid anchoring group demonstrated poor photovoltaic performance in comparison to SQI-6, which featured -COOH anchoring group and recorded the best photovoltaic performance compared to SQI-5 sensitizer investigated. SQI-6 achieved a power conversion efficiency (PCE) of 4.21% after simulating solar irradiation, as evidenced by its short-circuit current density (Jsc), open circuit voltage (Voc), and fill factor(FF) of 14.2 mA/cm2, 0.69 V, and 0.45, respectively. This advancement represents a significant step forward for DSSCs and paves the way for a more efficient future of DSSCs in the near-infrared (NIR) region. [Display omitted] [ABSTRACT FROM AUTHOR]

Transmission laser welding of plastic is typically achieved by incorporating a laser absorbing dye into one of the two pieces of plastic one wishes to weld together and mediating the welding process using a laser emitting light at a suitable wavelength. Desirable properties of laser absorbing dyes include: (1) the dye is colorless in the visible region but absorbs strongly in the region at the wavelength where the laser emits, (2) the dye has a good conversion of the energy from the laser to heat, (3) the dye is stable enough to be incorporated into the molten plastic, (4) the dye is soluble in the plastic of choice to give an even distribution in the plastic, and (5) the dye is nontoxic. Here, we explore an alternative approach to achieve laser welding of colorless plastics using a laser dye that is colored, but that can be bleached after the welding process. Nonsymmetrical squaraine dyes were prepared by condensation of squaric acid and two equivalents of various 3,5‐dimethoxy‐N,N‐dialkylanilines. After the incorporation into polyethylene and laser welding, the plastic was bleached either by heat treatment or by irradiation with a high pressure Xe‐lamp giving colorless polyethylene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2245–2254 Laser welding of plastic is explored by incorporating colored (blue) unsymmetrical squaraine dyes into polyethylene plastic. After laser welding, the color from the dye was bleached either by heat treatment or by irradiation with a high pressure Xe‐lamp giving colorless welded polyethylene. [ABSTRACT FROM AUTHOR]

Squaraine dyes AM‐1′ and AM‐1 bearing adamantyl termini were synthesized and spectroscopically characterized. AM‐1′ exhibited intense absorption and sharp emission in the far‐red to near‐infrared (NIR) spectral region. The degenerate two‐photon absorption (2PA) spectrum of AM‐1′ was obtained over a broad spectral range with a maximum cross section of ca. 360 GM. In aqueous solutions, AM‐1′ displayed a strong tendency for J‐aggregation and the reference AM‐1 exhibited entirely different aggregation behavior. We conclude that both the terminal pendant groups and substituents adjacent to the squaraine core play important roles in determining the aggregation behaviors and optical properties of the resultant squaraine dyes. Further an AM‐1′/β‐cyclodextrin complex dramatically suppressed squaraine π–π stacking and dissociated the J‐aggregate. Fluorescence microscopy imaging of HCT 116 cells incubated with the complex was accomplished, suggesting the potential application of this complex in fluorescence bioimaging. [ABSTRACT FROM AUTHOR]

In this report, we investigated the impact of adding a large π-extended squaraine dye to the classic bulk heterojunction P3HT:PC61BM system. The compound, SQIQ-A, is a bis-indole squaraine dye appended with acetylene-indoloquinoxaline end-capping units that exhibits strong optical absorption in thin film from 650 to 750 nm, beyond the absorption wavelength cut-off for P3HT:PC61BM films (ca. ∼650 nm). The dye SQIQ-A can form H- or J-aggregates (blue or red shifting the optical absorption profiles) via solvent vapour annealing with CHCl3 or THF, respectively, thus providing a simple method to control the morphology and optical properties of the molecule. Ternary blended films composed of P3HT:PC61BM:SQIQ-A (1:1:0.3 mass ratio) were investigated as-cast, after solvent vapour annealing, and after thermal annealing. Films were characterized using optical absorption spectroscopy, X-ray diffraction, atomic force microscopy, and polarized light microscopy. Solar cells were fabricated using an inverted architecture in air and analysed using current-voltage and external quantum efficiency measurements. It was found that solar cells thermally annealed at 130 °C for 10 min gave good power conversion efficiencies of 3%, similar to the control P3HT:PC61BM but with improved fill factors and noticeable photocurrent generation from 650 to 760 nm where the SQIQ-A molecule absorbs. Exposure to solvent vapour (CHCl3 or THF) results in aggregation of all components but specifically leads to the formation of micron-sized domains, lowering the overall photovoltaic performance. [ABSTRACT FROM AUTHOR]

The dual-pendant sulfonate bis(indolenine)squaraines with 1,8-diazabicyclo[5.4.0]undec-7-enium cations has been prepared and examined with reference to the previously studied bis-piperidinium analogue. The X-ray crystal structure of the bis-(1,8-diazabicyclo[5.4.0]undec-7-enium) dye (crystals from the reaction solution) revealed that this compound crystallizes with two molar equivalence of toluene. The fluorescence intensities of the dye in the presence of an equimolar amount of BSA in both water and 10 mM Tris/HCl buffer were comparable to those of the bis-piperidinium compound. The dye also proved comparable to the bis-piperidinium compound as a colorimetric stain for gel electrophoresis, but unlike the bis-piperidinium compound, the dye did not fluoresce in the stained gel upon irradiation with 300 nm light. An additional experiment examined the use of the bis-piperidinium compound as both colorimetric and fluorimetric stain for bacterial cells. [ABSTRACT FROM AUTHOR]

Abstract: The achievement of an ultrastrong coupling regime between surface plasmon modes generated by gold conical pits arrays and excitons associated to squaraine dye is demonstrated. Numerical and experimental steady‐state reflection measurements demonstrate a remarkable Rabi splitting of 860 meV, to date the largest reported value involving surface plasmon modes. Furthermore, the dynamics of the hybrid states under the ultrastrong coupling regime is investigated by transient absorption spectroscopy. The results show that the upper bands are too short‐lived to be detected, while the lower bands have a relatively shorter lifetime with respect to the bleaching recovery of pure squaraine dye. This result contradicts the behaviour of systems in strong coupling regimes, suggesting a different photophysics between strong and ultrastrong coupled systems. [ABSTRACT FROM AUTHOR]

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The synthesis of several aminosquaraine cationic dyes displaying strong absorption within the so-called phototherapeutic window (650–850 nm) is described. Their cytotoxicity, under dark and illuminated conditions, was tested against several human tumor cell lines (breast, lung, cervical and hepatocellular carcinomas) and non-tumor porcine liver primary cells. All compounds showed to inhibit the growth of the tumor cells upon irradiation more than in the absence of light, in more or less extension, clearly exhibiting photodynamic activity. The photosensitizing ability against some cell lines, together with the low toxicity for the non-tumor primary PLP2 cells displayed by some of the compounds synthetized, turns them into potential candidates as photosensitizers for PDT. [ABSTRACT FROM AUTHOR]

Solar cells sensitized by polypyridyl Ru(II) complexes exhibit relatively high efficiency, however those photo-sensitizers did not absorb the photons in the far-red and near-infrared region. At present, squaraine dyes have received considerable attention as their attractively intrinsic red light absorption and unusual high molar extinction coefficient. Here we applied density functional theory and time dependent density functional theory to investigate the properties of electronically excited states of four squaraine dyes and their complexes with fullerene C 70 . The influences of different functionals, basis sets and solvent effects are evaluated. To understand the photophysical properties, the investigations are basing on a classification method which splits the squaraine dyes and their complexes with fullerene C 70 into two units to characterize the intramolecular density distribution. We present the signatures of their electronically excited states which are characterized as local excitation or charge-transfer excitation. The relationship between open-circuit voltage and the number of intramolecular hydrogen bonds in squaraine dyes are discussed. [ABSTRACT FROM AUTHOR]