The resulting enhancement of the dye triplet population in the CSiNCs and CSiNCs can be probed via measurements of the yield of 1 O 2 generated by the triplet states of the dye. Table 1. The first method uses a particular trap compound such as 9,dimethylanthracene DMA , 1,3-diphenylisobenzofuran DPBF , singlet oxygen sensor green, etc.
You, For instance, the DMA trap reacts specifically with 1 O 2 to form peroxide. This chemical reaction results in changes of the absorption spectrum of DMA decaying with irradiation time. The second method is based on measurements of 1 O 2 phosphorescence and Equation 1.
A subsequent attempt to use rubrene absorbing in range — nm as the 1 O 2 trap also failed, as rubrene displayed a fast rate of the self-degradation upon irradiation with nm and Before conducting the experiments related to 1 O 2 generation, the photostability of the reference PS— phe was evaluated Figure S3.
Taking into account that acquisition of 1 O 2 luminescence using When we were satisfied that the phe was photostable, we investigated 1 O 2 generation by dye-1 and dye However, perylene derivatives have demonstrated ability to generate 1 O 2 with high quantum yield Wu et al. Figures 2B,D demonstrates phosphorescence of 1 O 2 generated via photoexcitation of dye-1 and dye-2 solutions in cyclohexane via both and The concentration of solutions with dye-1, dye-2 , and phe was adjusted to have similar absorption at the excitation wavelengths Figures 2A,C.
Figure 2. A UV-Vis absorption spectra of solutions of phe, dye-1 , and dye-2 in cyclohexane used for the generation of 1 O 2 with nm laser; B 1 O 2 phosphorescence excited via irradiation of solutions of phe and dye-1 with nm laser 75 mW ; C UV-Vis absorption spectra of solutions of phe, dye-1 , and dye-2 in cyclohexane used for the generation of 1 O 2 with Measurements with the other excitation wavelength To gain inside 1 O 2 photosensitization we measured PLQY for dye solutions prepared inside a glovebox under oxygen-free conditions.
The obtained result indicates that photosensitization of 1 O 2 occurs solely via the excite singlet state in case of dye-1 and predominantly in case of dye It appears that, around two-thirds of the excited singlet states relax via the radiative transition for dye-1 , whereas around one-third of the excited singlets transfer the energy to oxygen molecules. To obtain additional information about triplet states of dye-1 and dye-2 , we measured the emission spectra of their glassy solutions in cyclohexane at low temperature 20 K.
Assuming small, but non-zero probability of ISC, we expected to detect phosphorescence of dye-1 and dye-2 at low temperature. Figure 3 demonstrates a comparison of PL spectra collected at room temperature and 20 K. Indeed, new emission bands appear in the low temperature spectra with maxima at and nm for dye-1 and and nm for dye We attributed the appearance of these bands to the radiative T 1 —S 0 transition.
The position of these peaks is slightly blue-shifted when compared with the position of T 1 state of — nm in the unsubstituted perylene molecule Turshatov et al. Figure 3. Photoluminescence of A dye-1 and B dye-2 at temperature of and 20 K. Dashed lines represent results of deconvolution of low-temperature photoluminescence using Gaussian peaks centered at and nm for dye 1 and , , and nm for dye 2.
The chemical reaction of the dyes with H-SiNCs yields a product of conjugation that demonstrates absorption of both components. The excitation of SiNCs becomes possible via dye excitation in the range of — nm, which indicates the very short distance between dyes and SiNCs.
In contrast, the physical mixture of C6-SiNCs and the dyes does not demonstrate NIR luminescence when the sample is excited with blue light — nm. The nm laser mainly excites the dye molecule anchored to the surface of SiNCs, whereas the However, the experiment emphasizes that the CSiNCs conjugate exhibits synergistic behavior. Thus, this new conjugate can attract potential interest in photomedicine as a new chemical agent combining properties of PS and a NIR phosphor. Figure 4.
The irradiation of CSiNCs with the Indeed, the excitation of C6-SiNCs with However, the excitation of the CSiNCs conjugate with the The enhancement factor F of 1 O 2 oxygen generation with UV light We performed here the calculation of F only for one single wavelength It has been mentioned in our previous publication Beri et al.
This observation was also confirmed in the experiment with 1 O 2 generation. Under excitation with At the same time, the excitation energy can be transferred to the triplet state of the dye. The triplet state interacts with molecular oxygen. Figure 5. Schematic showing photosensitization of 1 O 2 with SiNCs using the attached dye as transmitter for the excitation energy. At The SiNCs were modified with organic dyes via the hydrosilylation reaction in the microwave reactor.
The SiNC-dye conjugates were investigated for the first time within the context of singlet oxygen generation. The singlet oxygen yield was determined via measurements of singlet oxygen phosphorescence at 1, nm in cyclohexane solutions using the comparison with the singlet oxygen phosphorescence produced by the reference PS— phe. We attributed high yield of singlet oxygen generation under In contrast to dye-1, dye-2 is a less efficient acceptor for SiNCs.
Thus, this finding indicates a large potential of the dye modified SiNCs for the production of singlet oxygen. DBe: synthesis of the dye functionalized SiNCs, characterization of SiNCs, measurement of singlet oxygen, evaluation and interpretation of the data, and writing. MJ: temperature dependent photoluminescence measurement. DBu: measurement of singlet oxygen. BR: supervision, data interpretation, and writing.
AT: development of a paper concept, supervision data interpretation, and writing. All authors contributed to the manuscript revision, read, and approved the submitted version. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ahmed, G. Quantum confinement-tunable intersystem crossing and the triplet state lifetime of cationic porphyrin—CdTe quantum dot nano-assemblies.
Ahuja, S. Bakalova, R. Quantum dots as photosensitizers? Beri, D. Highly photoluminescent and stable silicon nanocrystals functionalized via microwave-assisted hydrosilylation. RSC Adv. Improved photon absorption in dye-functionalized silicon nanocrystals synthesized via microwave-assisted hydrosilylation. Dalton Trans. Blacha-Grzechnik, A. Efficient generation of singlet oxygen by perylene diimide photosensitizers covalently bound to conjugate polymers.
A Callaghan, S. The good, the bad, and the ugly — controlling singlet oxygen through design of photosensitizers and delivery systems for photodynamic therapy. Campillo, N. Differential oxygenation in tumor microenvironment modulates macrophage and cancer cell crosstalk: novel experimental setting and proof of concept. Camussi, I. Acs Sustain. Cao, Z. In vitro cellular behaviors and toxicity assays of small-sized fluorescent silicon nanoparticles. Nanoscale 9, — The discussion will be accompanied by in vitro and in vivo examples, in an attempt to highlight advancements in the field and future prospects for the more widespread application of photodynamic therapy.
Callaghan and M. Senge, Photochem. To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given.
Read more about how to correctly acknowledge RSC content. Fetching data from CrossRef. This may take some time to load. Loading related content. Jump to main content. Jump to site search. The solvents dioxane and water are miscible in all proportions. Steady state irradiations were performed in a home-made setup using a high-pressure W mercury arc lamp. The nm Hg line was isolated with optical and chemical filters. Temperature was kept constant by the use of a cell-holder thermostat.
The maximum fluorescence intensity of indole derivative was monitored at nm for an excitation wavelength at nm. The UVA irradiation at nm, with a fluence rate of The PSO absorption extinction coefficient at nm vary from to M -1 cm -1 in dioxane to water solutions, respectively. The substrate photodegradation was monitored by the decrease in the 3MI fluorescence intensity at the maximum of its emission band, where PSO emission is absent see Figure 1.
No changes on 3MI emission band shape were observed in samples with irradiation time. In this study no attempts were made to analyze the photoproducts. The Ge-detector with a preamplifier, surface area of 0. Aqueous ludox scatter solutions were used to monitoring the fast decay signal due to the apparatus function.
Both unwanted signals, i. The time profiles of the PSO triplet-triplet absorption were determined by the third harmonic excitation light nm of a Nd:YAG laser from a Spectra Physics time-resolved flash photolysis equipment. Solutions were prepared by bubbling N 2 followed by vacuum degassing.
Samples were monitored at the maximum of T-T absorbance at nm. The chemical rate constants of PSO triplet reaction with 3MI k chem 3MI were measured by steady-state irradiation procedure, in the absence of molecular oxygen. The molecular oxygen concentration in the different solvent mixtures was determined assuming a linear additivity of the molecular oxygen solubilities, in dioxane 7.
Since the half width of the fluorescence band of the indole derivative is unchanged with irradiation time, we assumed that photoproducts were not fluorescent at the monitored 3MI emission wavelength. Moreover, the fluorescence intensity monitored at nm belongs only to 3MI emission since at this wavelength the PSO fluorescence signal is negligible, being 10 3 lower than that of the indole derivative Figure 1. Triplet quenching of PSO molecules by 3MI substrate was studied by flash photolysis in degassed solutions.
The lifetime of PSO triplet excited state is concentration dependent. The reciprocal of the observed PSO triplet lifetime plotted as a function of the 3MI substrate concentrations were determined by laser flash photolysis. The observed rate constant is given by Equation These results compare with those obtained for PSO triplet self quenching in water 20 and in ethano.
These values are of the same order of magnitude of those already reported in water, for PSO triplet quenching by tryptophan. The transient species formed after PSO excitation and the deactivation pathways are shown in the Scheme 1. The differential equation that describes the 3MI concentration decrease with irradiation time, assuming that the concentration of products is equal to the concentration of 3MI disappearing, is given by:.
The solution of Equations 4 and 5 together does not yield an analytical function of [3MI] vs time. The classical approach to overcome this problem is to assume steady state conditions for the transient species, i.
Doing so, the reaction rate, v N2 is given by the differential Equation 6, where N 2 stands for nitrogen-saturated solution. Since the observed decrease of 3MI concentration with the irradiation time is always exponential, it means that [3MI] should appear just in the numerator of Eq. From the fitting, values of 2.
Moreover, in deuterated water, the use of different PSO concentrations leads to the same k chem 3MI values. Therefore, in D 2 O, an invariant value for the chemical rate constant, k chem 3MI was assumed. In the absence of molecular oxygen the indole derivative, 3MI, can easily react by electron transfer to triplet PSO to yield ion radicals Type I pathway.
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