Near-infrared Absorption Peak Research Articles

Ultra-Narrowband Near-Infrared Responsive J-Aggregates of Fused Quinoidal Tetracyanoindacenodithiophene.

Narrowband photoresponsive molecules are highly coveted in high-resolution imaging, sensing, and monochromatic photodetection, especially those extending into the near-infrared (NIR) spectral range. Here, a new class of J-aggregating materials based on quinoidal indacenodithiophenes (IDTs) that exhibit an ultra-narrowband (full width half maxima of 22nm) NIR absorption peak centered at 770nm is reported. The spectral width is readily tuned by the length of the solubilizing alkyl group, with longer chains resulting in significant spectral narrowing. The J-aggregate behavior is confirmed by a combination of excited state lifetime measurements and single-crystal X-ray diffraction measurements. Their utility as electron-transporting materials is demonstrated in both transistor and phototransistor devices, with the latter demonstrating good response at NIR wavelengths (780nm) over a range of intensities.

Acceptor-donor-acceptor structured phototheranostics for near-infrared II fluorescent and photoacoustic imaging-guided photodynamic and photothermal synergistic therapy

Multi-modal imaging-guided synergistic photodynamic therapy (PDT) and photothermal therapy (PTT) show great benefits in cancer treatment. The phototheranostics with near-infrared (NIR) absorption, high reactive oxygen species (ROS) generation and photothermal conversion efficiency is highly desirable. Here, we designed and synthesized an “acceptor-donor-acceptor” (A-D-A) structured molecule named IDCIC, with strong absorbance in the NIR region. We further prepared IDCIC into water-soluble nanoparticles (NPs) by wrapping with 1,2-distearoylsn-glycero-3-phosphoethanolamine-N-[(polyethylene glycol)-2000]-amine (DSPE-PEG2000-NH2). The obtained IDCIC NPs show an NIR absorption peak at 760 nm and an NIR-II fluorescence spectrum peak at ∼1000 nm with a fluorescent quantum yield of 1.2%, enabling them excellent photoacoustic and NIR-II fluorescent imaging capabilities. Moreover, IDCIC NPs could simultaneously generate singlet oxygen (with a quantum yield of 9.1%), hydroxyl radicals (·OH) and heat (with a photothermal conversion efficiency of 78.9%) under 808-nm laser irradiation. Based on the above-mentioned properties, IDCIC NPs were used for dual-modal imagingguided synergistic photodynamic/photothermal therapy of cancer.

Biocompatible Chitosan Oligosaccharide Modified Gold Nanorods as Highly Effective Photothermal Agents for Ablation of Breast Cancer Cells.

Photothermal therapy (PTT) using biocompatible nanomaterials have recently attracted much attention as a novel candidate technique for cancer therapy. In this work we report the performance of newly synthesized multidentate chitosan oligosaccharide modified gold nanorods (AuNRs-LA-COS) as novel agents for PTT of cancer cells due to their excellent biocompatibility, photothermal stability, and high absorption in the near-infrared (NIR) region. The AuNRs-LA-COS exhibit a strong NIR absorption peak at 838 nm with a mean length of 26 ± 3.1 nm and diameter of 6.8 ± 1.7 nm, respectively. The temperature of AuNRs-LA-COS rapidly reached 52.6 °C for 5 min of NIR laser irradiation at 2 W/cm2. The AuNRs-LA-COS had very low cytotoxicity and exhibited high efficiency for the ablation of breast cancer cells in vitro. The tumor-bearing mice were completely ablated without tumor recurrence after photothermal treatment with AuNRs-LA-COS (25 µg/mL) under laser irradiation. In summary, this study demonstrated that AuNRs-LA-COS with laser irradiation as novel agents pave an alternative way for breast cancer therapy and hold great promise for clinical trials in the near future.

NIR-laser switched ICG/DOX loaded thermo-responsive polymeric capsule for chemo-photothermal targeted therapy

Near-infrared (NIR) light possesses great advantages for light-responsive controllable drug release, such as deep tissue penetration and low damage to healthy tissues. Herein, a targeted and NIR-triggered drug delivery system is developed based on a NIR dye, indocyanine green (ICG), and anticancer drug, doxorubicin hydrochloride (DOX)-loaded thermo-responsive block copolymer capsule, in which the drug release can be controlled via NIR irradiation and folic acid (FA) molecule endows the drug carrier with the ability of targeted receptor-mediated endocytosis. After co-encapsulation of DOX and ICG, the capsule carrier exhibited wider NIR absorption peak and the loaded DOX was released rapidly from the capsules upon irradiation by NIR laser (808nm). In addition, the results demonstrated that the FA modified capsule carrier exhibited the higher cytotoxicity to HeLa cells with NIR irradiation compared with other treatments, indicating the efficient chemo-photothermal targeted therapy.

Near-Infrared Organic Dye-Based Nanoagent for the Photothermal Therapy of Cancer.

Given their easy structural modification and good biocompatibility advantages, near-infrared (NIR) organic dyes with a large molar extinction coefficient, while a superlow fluorescence quantum yield shows considerable potential application in photothermal therapy (PTT). Herein, a new NIR-absorbing asymmetric cyanine dye, namely, RC, is designed and synthesized via the hybrid of rhodamine and hemicyanine derivatives. RC-BSA nanoparticles (NPs) are fabricated by using the bovine serum albumin (BSA) matrix. The NPs exhibit a strong NIR absorption peak at ∼868 nm and 28.7% photothermal conversion efficiency. Based on these features, RC-BSA NPs exhibit excellent performance in ablating tumor under a 915 nm laser radiation through a PTT mechanism. These NPs show no obvious toxicity to the treated mice. Thus, RC-BSA NPs can used as a new NIR laser-triggered PTT agent in cancer treatment.

Image-guided synergistic photothermal therapy using photoresponsive imaging agent-loaded graphene-based nanosheets

We report the image-guided synergistic photothermal antitumor effects of photoresponsive near-infrared (NIR) imaging agent, indocyanine green (ICG), by loading onto hyaluronic acid-anchored, reduced graphene oxide (HArGO) nanosheets. Loading of ICG onto either rGO (ICG/rGO) or HArGO (ICG/HArGO) substantially improved the photostability of photoresponsive ICG upon NIR irradiation. After 1min of irradiation, the NIR absorption peak of ICG almost disappeared whereas the peak of ICG on rGO or HArGO was retained even after 5min of irradiation. Compared with plain rGO, HArGO provided greater cellular delivery of ICG and photothermal tumor cell-killing effects upon laser irradiation in CD44-positive KB cells. The temperature of cell suspensions treated with ICG/HArGO was 2.4-fold higher than that of cells treated with free ICG. Molecular imaging revealed that intravenously administered ICG/HArGO accumulated in KB tumor tissues higher than ICG/rGO or free ICG. Local temperatures in tumor tissues of laser-irradiated KB cell-bearing nude mice were highest in those intravenously administered ICG/HArGO, and were sufficient to trigger thermal-induced complete tumor ablation. Immunohistologically stained tumors also showed the highest percentages of apoptotic cells in the group treated with ICG/HArGO. These results suggest that photoresponsive ICG-loaded HArGO nanosheets could serve as a potential theranostic nano-platform for image-guided and synergistic photothermal antitumor therapy.

Tunability and stability of gold nanoparticles obtained from chloroauric acid and sodium thiosulfate reaction

In the quest for producing an effective, clinically relevant therapeutic agent, scalability, repeatability, and stability are paramount. In this paper, gold nanoparticles (GNPs) with precisely controlled near-infrared (NIR) absorption are synthesized by a single-step reaction of HAuCl4 and Na2S2O3 without assistance of additional templates, capping reagents, or seeds. The anisotropy in the shape of gold nanoparticles offers high NIR absorption, making it therapeutically relevant. The synthesized products consist of GNPs with different shapes and sizes, including small spherical colloid gold particles and non-spherical gold crystals. The NIR absorption wavelengths and particle size increase with increasing molar ratio of HAuCl4/Na2S2O3. Non-spherical gold particles can be further purified and separated by centrifugation to improve the NIR-absorbing fraction of particles. In-depth studies reveal that GNPs with good structural and optical stability only form in a certain range of the HAuCl4/Na2S2O3 molar ratio, whereas higher molar ratios result in unstable GNPs, which lose their NIR absorption peak due to decomposition and reassembly via Ostwald ripening. Tuning the optical absorption of the gold nanoparticles in the NIR regime via a robust and repeatable method will improve many applications requiring large quantities of desired NIR-absorbing nanoparticles.

Structural Evolution of Evaporated Lead Phthalocyanine Thin Films for Near-Infrared Sensitive Solar Cells

In this work, we focus on the deposition conditions as a means to control the structural evolution of lead phthalocyanine (PbPc) films in order to promote the triclinic structure, thereby inducing a shift in the absorption spectrum toward the near-infrared (NIR). Absorption spectra of PbPc films exhibit an enhanced NIR absorption peak at a wavelength of λ = 900 nm upon (i) increasing film thickness, (ii) increasing substrate temperature, or (iii) decreasing evaporation rate. X-ray diffraction measurements correlate the enhancement of the NIR absorption peak with an improved crystallinity and increased average volume of triclinic domains in the mixed monoclinic−triclinic films. As the surface structure of 10 and 60 nm thick films differ, this implies an asymmetric layer structure with a semicrystalline monoclinic film close to the substrate, evolving to a predominantly triclinic structure in the upper part of the film. We have demonstrated the use of structural control of the PbPc layer in a planar heterojunction solar cell with NIR-sensitivity. Decreasing the evaporation rate results in solar cells with significantly enhanced short-circuit current density (JSC), because of the change in absorption in combination with the longer exciton diffusion length that was estimated for donor layers exhibiting a predominantly triclinic structure. Overall, an optimized solar cell yields a power conversion efficiency of 2.6% (2.1% when correcting for the solar spectrum mismatch), and has external quantum efficiencies above 11% from λ = 320−990 nm with a peak value of 34% at λ = 900 nm.

Specific intramolecular electronic interactions of a photogenerated styrylpyridinyl radical and a parent cation in meso-2,4-bis(4-(4-nitrostyryl)pyridiniumyl)pentane

Steady state photolysis of tetraphenylborate salts of meso-2,4-bis(4-(4-nitrostyryl)pyridiniumyl)pentane and 1,3-bis(4-(4-nitrostyryl)pyridiniumyl)propane has been studied by absorption and electron paramagnetic resonance (EPR) spectroscopy in solution at room temperature. The absorption spectra of these compounds upon irradiation at 405 nm in an inert atmosphere showed a strong peak in the visible region and two broad peaks in the near infrared (NIR) region. The meso-2,4-pentane derivative caused stronger electronic interaction between a photogenerated styrylpyridinyl radical and a parent styrylpyridinium cation, and hence showed two slightly blue shifted NIR bands around 920 and 1734 nm compared with those in the 1,3-propane derivative. During storage in the dark, the NIR absorption peak at longer wavelength gradually changed its shape and showed a new band at 1559 nm, which increased until 20 h and was maintained over 100 h. The nature of electronic interactions responsible for such specific NIR bands was studied in detail spectroscopically. EPR spectra clearly indicated that the unpaired electron was not shared completely between two chromophores as in a normal dimer radical cation but was exchanged rather rapidly between them, probably due to the conformational confinement at one end of these molecules.

Spectral Dispersion of Third-Harmonic Generation in Thin Films Containing Transition Metal Complexes

The optical third-harmonic generation technique has been used in a study of several transition metal complexes having different near-infrared (NIR) absorption features. The complexes were dispersed in polymer matrices, and the molecular second hyperpolarizabilities γ(3ω;ω,ω,ω) were derived from thin film Maker fringe measurements at 1064 and 1907 nm. Dispersion measurements of the complexes TBA[Ni(dmit)2] and TBA[Pd(dmit)2], both having strong NIR transitions, were performed in the region from 1065 to 1480 nm, revealing resonances in the NIR. For the TBA[Ni(dmit)2] complex a maximum γ-value of 20 × 10-33 esu was observed at approximately 1325 nm, red-shifted by 172 nm (0.14 eV) compared with the position of the NIR absorption peak at 1153 nm. For the TBA[Pd(dmit)2] complex the exact location of the resonance could not be determined definitively but was shifted to or even beyond 1480 nm. The maximum γ-value of the Pd-complex was more than 2.5 times that of the Ni-complex. The γ-values were strongly influenced by a number of resonances (one-, two-, and three-photon resonances); however, no clear correlation with the near-infrared transition was observed.