Seeded Growth of Cu_2–xSe Nanocrystals and Their Size-Dependent Phototherapeutic Effect

Abstract

Doped semiconductors supporting localized surface plasmon resonances, such as nonstoichiometric copper chalcogenides Cu 2−x Se, have been intensively researched for their potential applications in photoacoustic imaging and photothermal therapy. For these self-doped nanoparticles, their physicochemical attributes such as size and surface chemistry will not only affect their cellular uptake and biodistribution but also influence their own optical properties. Thus, optimization of the physicochemical properties is crucial for their nanobio-applications. Through a seeded growth approach, aqueous phase synthesis of monodisperse Cu 2−x Se with various sizes has been developed for the first time. Taking three different sized Cu 2−x Se NPs (35, 65, and 105 nm in diameter) as examples, their size-dependent optical cross-section, photothermal property, and cellular cytotoxicity have been investigated, and the 65 nm one displays the largest optical cross-section at 21.57 L g −1 cm −1 and best photothermal property per unit mass. In addition, Cu 2−x Se exhibits a size-dependent reactive oxygen species generation effect that is inversely proportional to their diameters. Finally, on the basis of optical property and cytotoxicity optimizations, the photothermal cancer cell ablation ability and potential use of Cu 2−x Se NPs as photoacoustic contrast enhancing agent has been demonstrated in vivo.

Quantitative Analysis of Extinction Coefficients of Tin-Doped Indium Oxide Nanocrystal Ensembles

“…μm −1 at 9399 cm −1 ), 33 the first exciton peak of 5.5 nm PbSe QDs (ϵ abs = 12.7 μm −1 at 6250 cm −1 ), 51 and commercially available infrared dyes (9.8 × 10 4 M −1 cm −1 at 12 690 cm −1 ) 52 all attenuate IR light less efficiently than ITO NCs of minimum 4.5% Sn doping and 12 nm diameter. Alternative extinction coefficient units for these samples are shown in Table S1 for comparison.…”

“…While several studies have investigated Au NP extinction coefficients, ,,,− those of most doped semiconductor NCs, particularly doped metal oxides, are not yet established. Of note, Cu 2– x Se NC dispersions yielded an extinction coefficient of 23.5 μm –1 at 9399 cm –1 for NCs 65 nm in diameter, and recently the extinction coefficient for a film of tin-doped indium oxide (ITO) NCs of 10 atomic% (at%) Sn and 12 nm diameter was reported at 24.3 μm –1 . The applications mentioned above require high extinction coefficient materials to be feasible, and given that doped metal oxide NCs show promise as strong IR absorbers, it is important to quantitatively investigate their optical extinction properties.…”

“…These values are high when compared to other IR absorbing materials. Common IR absorbing or scattering materials such as Au nanostructures ( ϵ sca = 35.5 μm –1 at 8620 cm –1 ), Cu 2– x Se NCs ( ϵ abs = 23.5 μm –1 at 9399 cm –1 ), the first exciton peak of 5.5 nm PbSe QDs ( ϵ abs = 12.7 μm –1 at 6250 cm –1 ), and commercially available infrared dyes (9.8 × 10 4 M –1 cm –1 at 12 690 cm –1 ) all attenuate IR light less efficiently than ITO NCs of minimum 4.5% Sn doping and 12 nm diameter. Alternative extinction coefficient units for these samples are shown in Table S1 for comparison.…”

The Rational Design and Biological Mechanisms of Nanoradiosensitizers

“…The intracellular ROS level induced by PEG-GNPs (6.2-61.2 nm) was also negatively correlated with NP size in HepG2 and HeLa cells [59]. In addition to GNPs, NPs of other sizes were also negatively correlated with oxidative stress levels in cancer cells, such as silica NPs [60,61], AgNPs [62], PVP-AgNPs [63] and Cu 2-x Se NPs [64].…”

Optoelectronic Impacts of Particle Size in Water-Dispersible Plasmonic Copper Selenide Nanoparticles

“…Plasmonic figures of merit such as the extinction coefficient of traditional noble metal NPs can be expressed in terms of the Mie-Gans theory, where their extinction intensities are composed of both absorption and scattering components. − Further, for noble metals, it has been widely demonstrated that the plasmonic intensity can be easily manipulated through the scattering cross-section by modulating NP size and/or shape. − For example, Jain and El-Sayed’s simulations of plasmonic Au and Ag NPs show tunable extinction coefficients as a function of increasing NP size . It was also demonstrated that the scattering intensities of the plasmonic substrates can be tuned via NP shape anisotropy and/or the formation of hot spots. − ,− To optimize and compare the performance of non-noble metal plasmonic NPs in applications such as surface-enhanced sensing, − hot carrier-driven catalysis, − and photothermal applications, , it is important to understand and compare the plasmonic extinction tunabilities of semiconductor NPs to those of their noble metal counterparts.…”