The development of nanomaterials with high sensitivity to external stimuli such as temperature is critical to investigate the driving force of not only biological processes but also catalytic mechanisms in extreme environments. However, the instability of nano-objects at high temperatures and different environments is a serious drawback limiting often their real use. This is particularly severe in the case of bismuth-based compounds, making the development of highly stable bismuth-based nanosystems a challenge. Here, we report the synthesis of uniform crystalline lanthanide-doped Bi 2 SiO 5 nanoparticles into a silica shell of a controlled thickness (Bi 2 SiO 5 :Ln@SiO 2 ) for the design of a reliable ratiometric optical thermometer stable at high temperatures and extreme acid environments. The fine control of the SiO 2 shell thickness is modeled based on a theoretical and experimental approach. The formation of the Bi 2 SiO 5 single phase is triggered by the local reactivity between Bi 2 O 3 and SiO 2 in the Bi 2 O 3 @SiO 2 system, leading to a double-layered Bi 2 SiO 5 @SiO 2 hollow nanosystem. The potential of the Bi 2 SiO 5 :Ln@SiO 2 nanosystem as a ratiometric nanothermometer is demonstrated for the upconverting Yb−Er couple. The performances were evaluated in the wide range of linearity of the Boltzmann law (280−800 K) showing suitable values of relative sensitivity, temperature uncertainty, and repeatability (R > 99%) not only for biological applications but also to probe the temperature in extreme environments. In fact, the strategy results in an acid-inert thermal probe up to pH < 1 overcoming the weakness of bismuthbased materials to acid environments with promising properties for in situ thermometry of catalytic reactions.
Highly sensitive Boltzmann thermometry by double-layered Bi2SiO5:Yb3+,Tm3+@SiO2 hollow nanoparticles with exceptional thermometric performances and biocompatibility are demonstrated.
Bismuth-based (nano)materials have
been attracting increasing interest
due to appealing properties such as high refractive indexes, intrinsic
opacity, and structural distortions due to the stereochemistry of
6s2 lone pair electrons of Bi3+. However, the
control over specific phases and strategies able to stabilize uniform
bismuth-based (nano)materials is still a challenge. In this study,
we employed the ability of bismuth to lower the melting point of silica
to introduce a new synthetic approach able to confine the growth of
bismuth-oxide-based materials into nanostructures. Combining in situ
temperature-dependent synchrotron radiation X-ray powder diffraction
(XRPD) with high-resolution transmission electron microscopy (HR-TEM)
analyses, we demonstrate the evolution of a confined Bi2O3–SiO2 nanosystem from Bi2SiO5 to Bi4Si3O12 through
a melting process. The silica shell acts as both a nanoreactor and
a silicon source for the stabilization of bismuth silicate glass-ceramic
nanocrystals keeping the original spherical shape. The exciton peak
of Bi2SiO5 is measured for the first time allowing
the estimation of its real energy gap. Moreover, based on a detailed
spectroscopic investigation, we discuss the potential and the limitations
of Nd3+-activated bismuth silicate systems as ratiometric
thermometers. The synthetic strategy introduced here could be further
explored to stabilize other bismuth-oxide-based materials, opening
the way toward the growth of well-defined glass-ceramic nanoparticles.
Skin cancer is the most common malignant cancer with an incidence of 1 million cases/year. It is well known that exposure to UV radiation from sunlight leads the most frequent risk factors for several skin disorders including skin cancer. Sunscreen filters represent a valid protection against dangerous effects derived from UV radiation, and they can be divided in organic and inorganic UV filters. Adding, at the product formulation, molecules with booster effect, or also substances that can increase the protecting effectiveness via synergic mechanisms, can further enhance their protection activity. Moreover, this approach leads to develop formulations with high SPF (Sun Protection Factor) with a reduced content of UV filters, this is in line with the recent decisions of yet a few countries (Palau, Thailand, Philippines, and Hawaii) to ban some sunscreen filters to preserve marine environments (i.e., reef). In this work, a new class of sunscreen UV filters has been synthesized, by means the combination of physical filter and Oxisol, an antioxidant molecule with booster effect. In this study, the synthesis of new physical multifunctional ingredients is reported, by means the direct surface functionalization of inorganic filters (in particular TiO2) with Oxisol. In this study, the full characterization of these multifunctional ingredients is also reported, in addition to the cytotoxicity tests, the photocatalytic activity and the rheological properties involved on skin application.
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