Improvement of Photostability and NIR Activity of Cyanine Dye through Nanohybrid Formation: Key Information from Ultrafast Dynamical Studies

Abstract

Near-infrared (NIR) light harvesting has enormous importance for different potential applications in the modern era of research. Some NIR cyanine dyes such as IR820 have achieved great success in energy harvesting and cancer therapy. However, their action is limited for low photostability, considerable thermal degradation, short circulation times, and nonspecific biodistribution. Our present study is an attempt to overcome such limitations by attaching a model cyanine dye IR820 with ZnO nanoparticles. We prepared an IR820-ZnO nanohybrid and characterized it using microscopic and optical spectroscopic tools. Thermogravimetric analysis depicted greater thermal stability of the IR820-ZnO nanohybrid compared to free dye. We explored the enhancement in the photostability of IR820 upon nanohybrid formation. We detected generation of photoinduced reactive oxygen species (ROS) such as superoxide, singlet oxygen, and so forth using appropriate molecular probes. The formation of IR820-ZnO nanohybrid reduced production of photoinduced singlet oxygen. However, it revealed an alternative trend in overall ROS formation (increases total ROS) under red light illumination. To correlate the enhanced photostability of IR820 on the ZnO surface, we explored excited-state dynamical processes at the interface in nanohybrids. We illustrated the photoinduced excited-state electron-transfer process from the lowest unoccupied molecular orbital of IR820 to the conduction band of ZnO. This photoelectron-transfer process enhances the production of ROS and decreases the formation of singlet oxygen that altogether leads to improvement in photostability and overall activity. A quencher of singlet oxygen sodium azide (NaN3) was used to further confirm the direct association of singlet oxygen generation with the photostability issue of IR820. Also, ZnO is able to deliver the dye selectively in acidic environment, which suggests its diseased site-specific targeted activity. Our results provide promising improvement for potential use of IR820 through formation of a nanohybrid that could be translated for other NIR cyanine dyes.

Wide bandgap semiconductor-based novel nanohybrid for potential antibacterial activity: ultrafast spectroscopy and computational studies

“…The emission quenching in this region may be due to a nonradiative process, which is attributed to charge transfer from the NF to ZnO within the NH. 17 To understand the electron transfer from NF to ZnO NPs, TCSPC studies were performed for all samples. The timeresolved uorescence decay for 5 nm ZnO NPs (Black), free NF and 5 nm ZnO-NF was measured upon excitation with a 375 nm laser, and detected at a wavelength of 440 nm as shown in Fig.…”

“…15 Many PS have poor solubility in polar protic solvents (many dyes undergo aggregation in polar protic solvents), very short circulation time and poor photostability. 16,17 In order to avoid these limitations for both photosensitizers and inorganic nanoparticles, the formulation of an organic-inorganic (unit cell to large crystal) nanohybrid (NH) is of great importance in this eld. 18 There is a high demand for the development of stimulisensible NH just because of multifunction, multiuse and highly effective implementation.…”

Development of photo- and chemo-stable near-infrared-emitting dyes: linear-shape benzo-rosol and its derivatives as unique ratiometric bioimaging platforms

“…A key structural feature of Cy dyes is that two identical nitrogen-containing heterocycles, one with a positive charge, are resonance-stabilized through "exible" polymethine units. Cy dyes have limited photo-stability, 3 however, thwarting their use for long-term bioimaging applications. In addition, Cy dyes and their asymmetric analogues hemicyanines seem to have limited chemical stability (chemo-stability) toward some reactive biological species, such as hypochlorous acid, hydrogen sulde or bisulte, as inferred from the various cyanine-and hemicyanine-based activatable probes for these species (Table S1, ESI †).…”

A Review of Endogenous and Exogenous Contrast Agents Used in Photoacoustic Tomography with Different Sensing Configurations

“…Upon light absorption, besides fluorescence emission, some of the electrons in the first excited singlet state are shifted to the first excited triplet state via an intersystem crossing. The long-lived triplet state is then quenched by oxygen molecules, giving rise to reactive oxygen species such as singlet oxygens [ 105 ]. These highly reactive singlet oxygens will attack the polymethine chain, and subsequently, photodegrade the cyanine molecule via C–C bond cleavage [ 106 ].…”