Two-photon absorption in penicillamine capped CdS tetrapods

Abstract

Synthesized penicillamine stabilized CdS tetrapods showed two-photon absorption in a wavelength range between 600 and 850 nm, and strong two-photon excited emission upon near infrared excitation. These water soluble colloidal, semiconducting nanoparticles show potential for applications in nonlinear bioimaging.

Functional CdS-Au Nanocomposite for Efficient Photocatalytic, Photosensitizing, and Two-Photon Applications

“…Juxtaposition of the time-resolved photoluminescence decay curves ( Figure 3) shows that the presence of Au nanostructures at the CdS NPs surface reduces the lifetimes of CdS NPs, especially for CdS-5Au and CdS-7.5Au samples. The calculated τ values (short and long components) for assynthesized CdS NPs were close to those reported by us for similar systems [23] (full exponential fitting parameters can be found in Table S1), and decreased with increasing Au concentrations; the strongest lifetime reduction (approximately 50%) was observed for CdS-7.5Au NPs. Those results are consistent with the photoluminescence quenching studies, suggesting that the electron transfer occurs faster in heteroparticles with larger metal domains.…”

“…Figure 6 shows photoluminescence spectra of CdS-5Au upon femtosecond laser excitation at 750 nm, with the maximum at approximately 520 nm. Two-photon absorption cross-section calculation results obtained in this work are presented in Table 1 and compared to the values already reported for identically synthesized CdS NPs [23]. The CdS-5Au NPs absorption cross section reaches 15.8 × 10 3 GM upon excitation at 725 nm, exceeding the corresponding value for CdS NPs.…”

“…Interestingly, embedment of gold nanostructures on CdS NPs not only significantly enhances their reduction and oxidation capabilities, making them promising candidates for photocatalytic and photosensitizing applications, but also preserves their two-photon brightness so that the resulting material may perform multiple functions at the same time. Two-photon absorption cross-section calculation results obtained in this work are presented in Table 1 and compared to the values already reported for identically synthesized CdS NPs [23]. The CdS-5Au NPs absorption cross section reaches 15.8 × 10 3 GM upon excitation at 725 nm, exceeding the corresponding value for CdS NPs.…”

“…Two-photon absorption cross sections σ 2 and two-photon brightness σ 2 × QY of as-prepared CdS-Au NPs in comparison with CdS NPs characterized in a previous work[23]. Exc.…”

“…They are widely considered as optical agents for applications requiring longer excitation wavelengths such as in medical diagnosis, for instance, photodynamic two-photon cancer therapy or two-photon bioimaging, where excitation in the range of biological transmission window (650-900 nm) is preferred [21,22]. In fact, semiconductor nanoparticles are being widely characterized with respect to their NLO characteristics, as they possess significant advantages for the above-mentioned applications such as stability upon high-energy light exposure (no bleaching) and high luminescence quantum yields [23,24]. They have been reported to display large two-photon absorption (TPA) cross sections with maxima of up to 10 3 GM for PbS [25] and InP@ZnS [24] QDs; up to 10 4 GM order of magnitude for CdS [23,26,27], CdSe [28,29], and PbSe [25] QDs; or even larger for 1D and 2D nanoparticles, depending on the size, shape, medium, and characterization method.…”