A synergetic strategy of NIR-Ⅱ squaraine dyes with ultrahigh photothermal conversion efficiency for photothermal therapy

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 “Haggregation” and “intramolecular motion” was employed to enhance the PCE of an acceptor-substituted squaraine dye(NSQs).The C2vmolecular 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 redshifted 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.

Anisotropy in Third-Order Nonlinear Optical Susceptibility of a Squarylium Dye in a Nematic Liquid Crystal

A squarylium dye is dissolved in 4-cyano-4＇-pentylbiphenyl （SCB） and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB layers exhibit high anisotropy. The third-order nonlinear optical responses and susceptibilities X^（3）e of squarylium dye in 5CB are measured with light polarizations parallel and perpendicular to the orientational direction by the resonant femtosecond degenerate four-wave mixing （DFWM） technique. Temporal profiles of the DFWM signal of the oriented squarylium dye-5CB layers with light polarizations parallel and perpendicular to the orientational direction are measured with a time resolution of 0.3ps （FWHM）, and are found to consist of two components, i.e., the coherent instantaneous nonlinear response and slow response due to the formation of excited molecules. A high anisotropic ratio of x^（3）e, 10.8 ：k 1.2, is observed for the oriented layers.

A squaraine based fluorescent probe for mercury ion via coordination induced deaggregation signaling

Due to the high affinity between dithiocarbamate （DTC） and Hg2＋, a fluorescent probe based on squaraine chromophore with DTC side arm for Hg2＋ via coordination induced deaggregation signaling has been designed and synthesized. Squaraine has a high tendency to aggregate in aqueous solution, and such self-aggregation usually results in a dramatic absorption spectral broadening with fluorescence emission quenching. The combination of the DTC side arm of the probe with Hg2＋ induces steric hindrance, leading to the deaggregation of the dye complex, companying with a fluorescence emission restoration. In EtOH-H2O （20：80, v/v） solution, this ＂turn on＂ fluorescent probe has high selectivity and sensitivity toward Hg2＋ over other metal ions, and the limit of detection for Hg2＋ was estimated as 2.19 × 10^-8 mol/L by 3σ/k.

Influence of thermal annealing-induced molecular aggregation on film properties and photovoltaic performance of bulk heterojunction solar cells based on a squaraine dye

Squaraine （SQ） dyes have been considered as efficient photoactive materials for organic solar cells. In this work, we purposely controlled the molecular aggregation of an SQ dye, 2,4-bis[4-（N,N-dibutylamino）-2-dihydroxyphenyl] SQ （DBSQ- （OH）2） in the DBSQ（OH）2：[6,6]-phenyl-Cel-butyric acid methyl ester （PCBM） blend film by using the thermal annealing method, to study the influence of the molecular aggregation on film properties as well as the photovoltaic performance of DBSQ（OH）2：PCBM-based bulk heterojunction （BHJ） solar cells. Our results demonstrate that thermal annealing may change the aggregation behavior of DBSQ（OH）2 in the DBSQ（OH）2：PCBM film, and thus significantly influence the surface morphology, optical and electrical properties of the blend film, as well as the photovoltaic performance of DBSQ（OH）2：PCBM BHJ cells.

Synthesis and properties of a novel squaraine dye modified by ferrocene

A novel squaraine dye（SQ） modified by ferrocene has been synthesized through（E）-dodecyl-2-ferrocenyl vinyl-1H-pyrrole and squaric acid.The molecular structure of SQ was characterized by ~1H NMR,^（13）C NMR,MS and elemental analysis.SQ is high soluble in common solvents.The maximum absorptions of SQ in different solvents are in the range of 708-734 nm,exhibiting positive solvatochromism with increasing solvent polarity.The optical and electrical properties of SQ indicate that it is a promising electron donor material for bulk-heterojunction organic solar cell.

A novel squaraine dye with squaramide as a scaffold and the colorimetric detection of amine

A novel unsymmetrical squaramide-linked squaraine dye（SQ） has been synthesized through squaramide 3 and semisquaraine 6. The molecular structure of SQ has been characterized by ~1H NMR,IR and MS.Due to the influence of the hydrogen bond and the solvent effect,SQ exhibits unique spectral properties compared with typical squaraine dyes.For its excellent ability of binding primary amine,SQ is a promising receptor of recognizing primary amine.

Unravelling the bottleneck of phosphonic acid anchoring groups aiming toward enhancing the stability and efficiency of mesoscopic solar cells

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 TiO_(2) surface revealed the dye adsorption rate of –CH=CH–COOH (SQ-139)>–CH=C(CN)COOH (SQ-140)>–PO_(3)H_(2) (SQ-143)>–CH=C(CN)PO_(3)H_(2) (SQ-148)>–CH=C(CN)PO_(3)H–C_(2)H_(5) (SQ-157)>–PO_(3)H–C_(2)H_(5) (SQ-151)> –CH=CH–COOH(–PO_(3)H_(2)) (SQ-162). The binding strength of these dyes on mesoporous TiO_(2) 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 TiO_(2) along with good photoconversion efficiency. Results of dye binding on TiO_(2) 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.