NIR Absorption Research Articles

Tailor-made aromatic porphyrinoids with NIR absorption.

The highlight of this article is the recent progress in the state-of-the-art synthetic design and isolation of artificial porphyrinoids by swapping pyrrole component(s) with diverse functionalized pyrrolic(heterocyclic)/carbacycle building block(s) to compare the impact on the electronic absorption spectra and aromaticity of the incorporated isomeric/expanded porphyrinoids. Attention has been directed towards five distinct criteria of utilizing functionalized pyrrolic(heterocyclic)/aromatic hydrocarbons as synthons for NIR absorbing aromatic isomeric (N-confusion)/expanded porphyrinoids (with five/six heterocycles): (i) fused or annelated pyrrole (heterocycle), (ii) functionalized bi-pyrrole/bi-thiophene/bi-furan building blocks, (iii) azulene based carbacycle building block, (iv) vinylogous aromatic carbacycle/heterocycle(s) building block and (v) N-confused pyrrole ring(s), and N-confused fused pyrrole ring(s) leading to π-extension. These hybrid porphyrinoids are ideal candidates for basic research into macrocyclic aromaticity and for many potential applications owing to NIR absorption.

Conjugated/nonconjugated alternating copolymers for enhanced NIR-II fluorescence imaging and NIR-II photothermal-ferrotherapy.

Conjugated polymers hold great promise for NIR-II fluorescence imaging (FI)-guided NIR-II photothermal therapy (PTT) due to the advantages of easy modification of chemical structures and adjustable NIR absorption. However, to make use of these advantages, it is of paramount importance to formulate conjugated polymers with excellent solubility in organic solution, great NIR-II photothermal conversion efficiency, and high NIR-II fluorescence quantum yield. Herein, a new class of conjugated/nonconjugated alternating copolymers (CNACPs) is reported by introducing nonconjugated linkers into a conjugated backbone to modulate the extinction coefficient at 1064 nm and NIR-II fluorescence quantum yield. The NIR-II absorption, NIR-II emission, and NIR-II photothermal properties of the new CNACPs were studied. Interestingly, it is observed that longer nonconjugated linkers in CNACPs result in higher NIR-II fluorescence intensity with sufficient NIR-II absorption and NIR-II photothermal ability. With these newly developed CNACPs (BBT-C6), phototheranostic nanoparticles (BBTD6/Fe@PMA) are prepared through facile nanoprecipitation using PMA-AD-PEG as an iron ion chelator for NIR-II FI-guided NIR-II PTT/ferrotherapy synergistic therapy. In vitro and in vivo, BBTD6/Fe@PMA effectively inhibited 4T1 cells and tumor progression under 1064 nm laser irradiation. Consequently, this work provides new CNACPs by incorporating nonconjugated linkers into a conjugated backbone to design more effective NIR-II fluorescence imaging and NIR-II photothermal therapy agents.

A cysteine-induced one-pot synthesis of Au nanoparticle chains with tuneable NIR absorption and application in photothermal-chemo cancer therapy

A one-pot synthesis of AuNCs induced by l-cys and fabrication of AuNCs@mSiO2@DOX and its photothermal-chemo cancer therapy behavior.

BSA-templated ultrasmall Ag/Gd2O3 as a self-enabled nanotheranostic for MR/CT/PA tri-modality imaging and photothermal therapy.

It is becoming more and more important to effectively integrate multiple complementary diagnostic imaging and synergistic therapies into a nano-platform, but it is still challenging. Here, we used bovine serum albumin (BSA) as a template to prepare ultra-small Ag/Gd2O3 (Ag/Gd@BSA) hybrid nanoparticles with high water dispersion by a biomineralization strategy for magnetic resonance (MR)/computed tomography (CT)/photoacoustic (PA) imaging-guided photothermal therapy (PTT). Compared with commercial MR and CT contrast agents, we showed that these well-characterized BSA-templated nanotheranostics possessed higher r1 relaxivity (5.84 mM-1 s-1) and HU values. In addition, these nanotheranostics have an excellent NIR absorption feature and outstanding photothermal conversion efficiency (47.4%) in the solution phase. The in vivo imaging experiment demonstrated that the Ag/Gd@BSA hybrid nanoparticles could serve as tri-modality imaging contrast agents to enable precise diagnosis of tumors. Meanwhile, it was also revealed that Ag/Gd@BSA had ability to be an ideal nanotherapeutic agent to achieve a satisfactory tumor treatment effect through PTT. Also, we showed the good biocompatibility of Ag/Gd@BSA nanoparticles. Overall, these results indicated that Ag/Gd@BSA was an effective nanotheranostic, which could accurately identify tumor sites and realize complete tumor elimination, having great potential in clinical transformation.

Tumor-specific activatable biopolymer nanoparticles stabilized by hydroxyethyl starch prodrug for self-amplified cooperative cancer therapy.

Rationale: Chemodynamic therapy (CDT) is an emerging tumor-specific therapeutic strategy. However, the anticancer activity of CDT is impeded by the insufficient Fenton catalytic efficiency and the high concentration of glutathione (GSH) in the tumor cells. Also, it is challenging to eliminate tumors with CDT alone. Thus, simple strategies aimed at constructing well-designed nanomedicines that can improve therapeutic efficiency of CDT and simultaneously incorporate extra therapeutic modes as helper are meaningful and highly required.Method: Tailored to specific features of tumor microenvironment (TME), in this study, we developed a biosafe, stable and TME-activated theranostic nanoplatform (P(HSD-Cu-DA)) for photoacoustic imaging (PAI) and self-amplified cooperative therapy. This intelligent nanoplatform was fabricated following a simple one-pot coordination and polymerization strategy by using dopamine and Cu2+ as precursors and redox-responsive hydroxyethyl starch prodrugs (HES-SS-DOX) as stabilizer.Results: Interestingly, the pre-doped Cu2+ in polydopamine (PDA) framework can endow P(HSD-Cu-DA) NPs with tumor-specific CDT ability and remarkably enhance NIR absorption of PDA. PAI and biodistribution tests proved such nanoplatform can effectively accumulate in tumor tissues. Following enrichment, massive amounts of toxic hydroxyl radicals (·OH, for CDT) and free DOX (for chemotherapy) were generated by the stimulation of TME, which was further boosted by local hyperthermia. Concomitantly, in the process of activating these therapeutic functions, GSH depletion triggered by disulfide bond (-SS-) breakage and Cu2+ reduction within tumor cells occurred, further amplifying intratumoral oxidative stress. Importantly, the framework structure dominated by bioinspired polydopamine and clinical-used HES guaranteed the long-term biosafety of in vivo treatment. As a result, the mutual promotion among different components yields a potent tumor suppression outcome and minimized systemic toxicity, with one dosage of drug administration and laser irradiation, respectively.Conclusion: This work provides novel insights into designing efficient and tumor-specific activatable nanotherapeutics with significant clinical translational potential for cancer therapy.

Anisotropic plasmonic Pd-tipped Au nanorods for near-infrared light-activated photoacoustic imaging guided photothermal-photodynamic cancer therapy.

The integration of photothermal therapy (PTT) and photodynamic therapy (PDT) has become a promising cancer treatment method. Herein, anisotropic metal hetero-nanostructure Pd-tipped Au nanorods (PTA NRs) were fabricated, which exhibit plasmon-enhanced photothermal performance under near-infrared laser irradiation. Due to their anisotropic nanostructure, PTA NRs promote the generation of energetic hot electrons and prolong the separation time of electrons and holes. The hot electrons could generate heat energy through the electron-phonon relaxation process and produce reactive oxygen species through energy and electron transformation processes. Because of their high NIR absorption cross-section, as well as good photostability, PTA NRs can be used for NIR-activated photoacoustic imaging-guided PTT-PDT combination cancer therapy. Experiments in tumor-bearing mice proved that PTA NRs exhibit excellent anti-tumor effects, with little side effects on normal organs, making them promising for NIR cancer phototherapy.

Fabrication of injectable hydrogels from an anticancer peptide for local therapeutic delivery and synergistic photothermal-chemotherapy.

The susceptibility of anticancer peptides to proteolytic degradation is often considered as a major weakness that limits systemic therapeutic applications. However, localized delivery of anticancer peptides via injectable hydrogels is expected to improve drug efficacy and reduce systemic toxicity. Herein, an injectable hydrogel with drug releasing properties, NIR responsiveness and pH sensitivity was developed from an anticancer peptide (KL), Fe3+ ions and protocatechualdehyde via dynamic and reversible interactions. Benefiting from the formation of Fe(III)-catechol complexes between Fe3+ ions and protocatechualdehyde within gel networks, the obtained hydrogel exhibited intrinsic NIR absorption properties for photothermal ablation of tumor cells, and remote light control of drug release. Besides, the pH-labile imine bonds between KL and protocatechualdehyde endowed the injectable gel with pH sensitivity for sustained release of KL under a mildly acidic environment, inducing membrane destabilization and facilitating the cell uptake of DOX for combinational chemotherapy. Both in vitro and in vivo experiments revealed that the injectable hydrogel exhibited a synergistic therapeutic effect on inhibiting tumor growth via combinational photothermal-chemotherapy. Therefore, this work provides a promising attempt to develop a therapeutic hydrogel from an anticancer peptide, which could work as a localized drug delivery platform for synergistic photothermal-chemotherapy.

Photocatalytic CO2 conversion of W18O49/CdSe-Diethylenetriamine with high charge transfer efficiency: Synergistic effect of LSPR effect and S-scheme heterojunction

Non-stoichiometric W18O49 (WO) prepared by solvothermal method has excellent NIR absorption due to the localized surface plasmon resonance effect caused by oxygen vacancies. This has great potential in the field of using sunlight to convert carbon dioxide into organic fuels. In addition, through the amination of CdSe, the one-dimensional/two-dimensional step-scheme (S-scheme) WO/CdSe-diethylenetriamine (WO/CdSe-D) photocatalyst with electron transmission channels driven by visible light to NIR light is constructed by microwave solvothermal method. The LSPR of WO and the synergistic effect of coupling semiconductors to construct S-scheme heterojunctions can improve light utilization and achieve efficient charge carrier transfer efficiency. The optimized photocatalyst of 35%WO/CdSe-D has the best CO2 reduction performance compared to WO and CdSe-D, and the yield is 25.37 µmol h–1 g–1. X-ray photoelectron spectroscopy was used to verify the charge transfer path of the S-scheme WO/CdSe-D heterojunction. This work provides a possibility for the application of non-stoichiometric oxides rich in oxygen vacancies in the field of photocatalytic CO2 reduction.

Short-wave and near infrared π-conjugated polymers hosted in a biocompatible microemulsion: a pioneering approach for photoacoustic contrast agents.

In the present study a biocompatible oil-in-water (O/W) microemulsion was developed carrying short-wave infrared (SWIR) π-conjugated polymers and possessing photoacoustic properties for the first time. SWIR and NIR absorbing conjugated polymers were accomplished to be dissolved in a Food & Drug Administration (FDA) approved natural oil limonene, to formulate an O/W microemulsion using biocompatible surfactants (Span80, Labrasol®). Detailed structural characterization in the absence and presence of the polymers was performed by means of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and electron paramagnetic resonance (EPR) spectroscopy. In terms of biological evaluation of the loaded microemulsions, inhibition of cell proliferation in various cancer cell lines without exhibiting significant cytotoxicity was tested through the MTT assay. The developed π-conjugated polymers hosted in O/W microemulsions represent a technological approach with a wide range of biomedical and bioelectronic applications and in this contribution, their photoacoustic properties are presented as a proof-of-concept.

Enhancing Intersystem Crossing by Intermolecular Dimer-Stacking of Cyanine as Photosensitizer for Cancer Therapy

Enhancing Intersystem Crossing by Intermolecular Dimer-Stacking of Cyanine as Photosensitizer for Cancer Therapy

Electro-optical characteristics of cholesteric liquid crystal films based on CuS nanoparticles

The CuS nanoparticles (NPs) coated by poly(vinylpyrrolidone) (PVP) layer were doped into bistable liquid crystal (LC) film to provide an electric, thermal or optical phase-shift controllable films. The CuS/PVP NPs could form a compatible NIR absorbing film, which could generate heat to switch LC film from planar texture to focal conic texture. The appropriate content of CuS/PVP NPs was provided to achieve fast thermal response, satisfactory dispersion and clear display brightness. The novel LC film containing 0.8 wt.% CuS/PVP NPs could save almost 51% time at thermal elimination, comparing to LC mixture without NIR absorbent. The hybrid organic-inorganic functional bistable LC material reported here extend and open up new application of LC writing tablets.

Structure and optical properties of GeTe film controlled by amorphous to crystalline phase transition

GeTe films have been showed great applications in the field of optical devices, especially in infrared absorption due to their narrow band gap. In this paper, amorphous GeTe (a-GeTe) film was prepared by pulsed laser deposition. Then, crystalline GeTe (c-GeTe) film was obtained by annealed in a tubular furnace at 200 °C. The X-ray diffraction indicates that GeTe film is transferred from amorphous to crystalline phase after annealing. The X-ray photoelectron spectroscopy shows that the presence of Ge and Te elements corresponding to the structure of GeTe. The high resolution transmission electron microscope also indicates that the disordered structure of GeTe film is transferred into ordered. Compared with a-GeTe film, the optical property of c-GeTe film has higher absorbance at 0.94 on 1100 nm measured by UV–Vis–NIR absorption spectroscopy. According to the calculation results, the optical band gaps of c-GeTe film and a-GeTe film are 0.82 eV and 0.87 eV respectively, indicating that the c-GeTe films is more favorable for photon transition. Fourier transform infrared spectroscopy also confirms that the infrared absorption properties of c-GeTe films is superior to those of the a-GeTe film. These results provide a fundamental research for the application of c-GeTe film in the field of infrared absorption.

Spectral characteristics of Tb3+ doped ZnF2–K2O–Al2O3–B2O3 glasses for epoxy free tricolor w-LEDs and visible green laser applications

In the current work, a series of Zinc Potassium Alumino fluoroborate (ZKAlFB) glasses doped with different concentrations of Terbium ions (Tb3+) were synthesized by employing the melt-quench technique. The spectroscopic properties of the as-prepared glass samples were examined using characterization techniques like XRD, FT-IR, DSC, UV–vis–NIR absorption and emission to unlock their utility in photonic devices. Absorption spectral information was used to determine the nature of bonding between Tb3+ ions and its surrounding ligands. FT-IR spectral information recorded for an undoped glass has been used to understand various functional groups present in the as-prepared ZKAlFB glass. The DSC thermogram was used to estimate glass thermal stability (ΔT) and transition temperature (Tg) of the as-prepared ZKAlFB glass. The Judd-Ofelt (J-O) intensity parameters estimated from absorption spectral data are correlated with the emission spectral profiles to estimate radiative properties. The photoluminescence (PL) intensity of the as-prepared ZKAlFBTb glasses is found to be maximum for 1 mol% of Tb3+ ions and beyond decreases showing concentration quenching. Using PL spectral data, the CIE color coordinates, and Correlated Color Temperature (CCT) values were evaluated to understand the suitability of the as-prepared glasses for green color emitting photonic devices. The experimental lifetime values estimated from the decay profiles are decreasing with elevation in Tb3+ ion concentration due to energy transfer through the cross-relaxation process. Quantum efficiency (η), emission cross-section (σse), CIE and CCT values obtained for 1 mol% Tb3+ ions doped ZKAlFB glass demonstrates its superiority in fabricating epoxy free tricolor w-LEDs and visible green lasers.

Fusion of visible-to-near-infrared and mid-infrared spectroscopy to estimate soil organic carbon

Spectral techniques such as visible-to-near-infrared (VIS–NIR) and mid-infrared (MIR) spectroscopies have been regarded as effective alternatives to laboratory-based methods for determining soil organic carbon (SOC). Research to explore the potential of the fusion of VIS–NIR and MIR absorbance for improving SOC prediction is needed, since each individual spectral range may not contain sufficient information to yield reasonable estimation accuracy. Here, we investigated two data fusion strategies that differed in input data, including direct concatenation of full-spectral absorbance and concatenation of selected predictors by optimal band combination (OBC) algorithm. Specifically, continuous wavelet transform (CWT) was adopted to optimize the spectral data before and after data fusion. Prediction models for SOC were developed using partial least squares regression. Results demonstrated that estimations for SOC using MIR absorbance (i.e., validation R2 = 0.45–0.64) generally outperformed those using VIS–NIR (i.e., validation R2 = 0.20–0.44). Compared to the raw absorbance counterparts, CWT decomposing could improve the prediction accuracy for SOC, for both the individual absorbance and the fusion of VIS–NIR and MIR absorbance. Among all the models investigated, the combinational use of VIS–NIR and MIR using OBC fusion at CWT scale of 1 yielded the optimal prediction, providing the highest validation R2 of 0.66. This model with 10 selected spectral parameters as input is of small total data volume, large processing speed and efficiency, confirming the potential of OBC in fusing both types of spectral data. In summary, CWT decomposing and OBC strategy are powerful algorithms in analyzing the spectral data, and allow the VIS–NIR and MIR spectral fusion models to improve the SOC estimation.

Structural, optical, morphological properties of silver doped cobalt oxide nanoparticles by microwave irradiation method

The synthesis of silver doped cobalt oxide nanoparticles by microwave-assisted method and their structural, optical, antibacterial activities are presented in this study. The doping concentrations were chosen as 5, 10, 15, and 20 wt percentages. The sample was undergone powder X-ray diffraction studies and the result shows the good crystalline nature of the sample. Also, the average crystallite size increases from 13.95 nm, 21.26 nm, 26.13 nm, and 28.35 nm with different doping concentrations. The transmission electron microscopy image shows cubic and spherical morphology. The optical properties were tested by UV–vis–NIR absorption spectrum. It indicates the decrease of band gap value. From the antibacterial activity studies, the 20 wt % Ag doped nanoparticles exhibit better activity.

Bioactivity of PEGylated Graphene Oxide Nanoparticles Combined with Near-Infrared Laser Irradiation Studied in Colorectal Carcinoma Cells.

Central focus in modern anticancer nanosystems is given to certain types of nanomaterials such as graphene oxide (GO). Its functionalization with polyethylene glycol (PEG) demonstrates high delivery efficiency and controllable release of proteins, bioimaging agents, chemotherapeutics and anticancer drugs. GO–PEG has a good biological safety profile, exhibits high NIR absorbance and capacity in photothermal treatment. To investigate the bioactivity of PEGylated GO NPs in combination with NIR irradiation on colorectal cancer cells we conducted experiments that aim to reveal the molecular mechanisms of action of this nanocarrier, combined with near-infrared light (NIR) on the high invasive Colon26 and the low invasive HT29 colon cancer cell lines. During reaching cancer cells the phototoxicity of GO–PEG is modulated by NIR laser irradiation. We observed that PEGylation of GO nanoparticles has well-pronounced biocompatibility toward colorectal carcinoma cells, besides their different malignant potential and treatment times. This biocompatibility is potentiated when GO–PEG treatment is combined with NIR irradiation, especially for cells cultured and treated for 24 h. The tested bioactivity of GO–PEG in combination with NIR irradiation induced little to no damages in DNA and did not influence the mitochondrial activity. Our findings demonstrate the potential of GO–PEG-based photoactivity as a nanosystem for colorectal cancer treatment.

Optical and Thermal Properties of Acid Red Doped Triglycine Acetate Crystal for Optoelectronic Applications

AbstractA positive change in crystal can be induced by dye. Pure and Acid Red 1 dye (AR) doped triglycine acetate (TGAc) single crystals are synthesized by solution approach to enrich the characteristics of pure TGAc crystals. The crystalline nature of the grown crystals is investigated using powder X‐ray diffraction. The Scherrer method has been used to calculate the crystallite size of both developed crystals and is compared to the Williamson and Hall method. Fourier transform infrared spectroscopy confirms the existence of several functional groups as well as dye inclusion in the produced crystals. Four distinct absorption bands are found in UV–vis–NIR absorption spectra at the location where AR dye is inserted into the TGAc matrix. Different optical constants, such as optical bandgap (Eg), extinction coefficient (k), refractive index (n) and optical conductivity (σ) are measured for both samples based on transmittance measurements. The thermal stability and decomposition temperature of 0.05 mol% AR dye doped TGAc are found to be higher. The doped crystals' improved optical characteristics and thermal stability prove their applicability for optoelectronic applications.

A novel coumarin-benzopyrylium based near-infrared fluorescent probe for Hg2+ and its practical applications

A novel colorimetric and ratiometric NIR fluorescent probe for Hg2+ was designed and synthesized based on a coumarin-benzopyrylium platform. The ring-open form of the probe exhibits NIR absorption (670 nm) and emission (720 nm). The probe shows high sensitivity, high selectivity and rapid response (30 s) to Hg2+. The detection limit was as low as 6.94 nM. The probe shows high stability in a wide pH range from 2 to 10. Moreover, the probe can be employed for detecting Hg2+ in food and biological samples.

Porphyrinoid-Carbon Nanostructure Systems and Fused Porphyrin-Graphene Nanoribbons

Phthalocyanines (Pcs) have emerged as excellent light harvesting antennas for incorporation into D-A systems, mainly in connection with carbon nanostructures, like endohedral metallofullerenes, SWCNT and graphene, as acceptor or donor moieties, in which the Pc has been attached, covalently or through supramolecular interactions [1]. They are among the few molecules that reveal an intense red and NIR absorption and therefore, constitute also promising dyes in molecular photovoltaics. Pcs have a great chemical versatility, which allows to modify their electronic character and their physical-chemical properties by organic synthesis, by introducing substituents in the periphery or modifying the structure of the macrocycle. Most recently they have reached good efficiency values participating as hole transporting materials in Carbon-based Perovskite sensitized solar cells (PSSCs). Pcs are be appropriately designed to adapt well to the electronic levels of the different types of perovskite. Through a rational design, structure-property relationships will be established that will gradually improve the performance of the devices.On the other hand on-surface synthesis offers a versatile approach to fabricate novel carbon-based nanostructures that cannot be obtained via conventional solution chemistry. Within the family of such nanomaterials, graphene nanoribbons (GNRs) hold a privileged position due to their high potential for different applications. One of the key issues for their application in molecular electronics lies in the fine-tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non-benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) represents a highly appealing strategy [2]. Reference s[1] G. Bottari, M. Á. Herranz, L. Wibmer, M. Volland, L. Rodríguez-Pérez, D. M. Guldi, A. Hirsch, N. Martín, F. D’Souza, T. Torres, Chem . Soc . Rev . 2017, 46 , 4464-4500; G. de la Torre, G. Bottari, T. Torres, Energy Mater. 2017, 1601700[2] L. M. Mateo, Q. Sun, S. Decurtins, S.-X. Liu, J. J. Bergkamp, K. Eimre, C. A. Pignedoli, P. Ruffieux, G. Bottari, R. Fasel, T. Torres, Angew. Chem. Int. Ed. 2020, 59, 1355-1355.

Design of Persistent and Stable Porous Radical Polymers by Electronic Isolation Strategy

AbstractConjugated organic radical polymers with stable radical features are difficult to design because the π conjugation in the polymer backbones makes the radicals readily delocalize and tend to undergo covalent bonding processes. In this work, we report an electronic isolation strategy to design stable porous radical polymers by homocoupling reaction from a meta‐position active monomer. The meta linkage ensures less conjugation in the polymer skeletons, localizes the resonant radicals, and prevents them from recombination. The resulting porous radical polymer exhibits exceptional radical characters with ultralow band gap of 0.68 eV, strong yet extended UV/Vis‐NIR absorption up to 1800 nm, and high spin density. The above features make the polymer very promising in the photothermal conversion with record‐high photothermal temperature increment of ≈∼240 °C and striking solar‐driven water evaporation efficiency of 96.8 %. Our results demonstrate the feasibility of electronic isolation of radicals for producing outstanding photothermal materials.