Abstracts

The quest for materials exhibiting orthogonal properties, termed multimodal/multifunctional systems, is driving the development of novel synthesis methodologies aimed at achieving precise morphological and structural control. An appealing alternative to complex core@shell systems is the controlled aggregation of diverse nanoparticles into submicrometric structures called superparticles. Given the increasing demand in nanomedicine for materials capable of locally monitoring temperature (luminescent nanothermometry) and inducing controlled localized heating under light (phototherapy), the combination of luminescent and plasmonic particles is attractive for theranostic applications. Prior to controlled aggregation steps, precise tuning of surface and spectroscopic characteristics of individual luminescent and plasmonic particles is mandatory. In this context, we have prepared several rare-earth-based nanoparticles (RE NP) with different excitation wavelengths (λ_exc), and AuNRs/AuNPs. NaYF₄:Yb, Er and NaYF₄:Nd, Yb, Er exhibited Er³⁺ emission in the green (²H_11/2 → ⁴I and ⁴S_3/2 → ⁴I_15/2) and red (⁴I_13/2 → ⁴I_15/2) regions with λ_exc of 980 and 808 nm, respectively, and both exhibited β-NaYF₄ crystal structures. Tetragonal YVO₄:Eu³⁺ particles displayed high-intensity Eu³⁺ emissions (⁵D₀ → ⁷F_n, n= 1, 2, 3 and 4) under λ_exc = 270 nm. Additionally, AuNRs were synthesized using the seed-mediated growth method, and AuNPs were prepared using the classic Turkevich method. The upconversion emission of NaYF₄ resulted in thermal sensitivities (S_R) ranging between 0.2 and 1.8% K^-1 for both samples. The individual NPs showed promising properties for further combination into superparticles for thermometry and thermal therapy. Additional studies will further comprise the control of the aggregation processes using light to initiate crosslinking between the capping agents on the particle surfaces.