Encapsulation of Dual Emitting Giant Quantum Dots in Silica Nanoparticles for Optical Ratiometric Temperature Nanosensors

Abstract

Accurate temperature measurements with a high spatial resolution for application in the biomedical fields demand novel nanosized thermometers with new advanced properties. Here, a water dispersible ratiometric temperature sensor is fabricated by encapsulating in silica nanoparticles, organic capped PbS@CdS@CdS “giant” quantum dots (GQDs), characterized by dual emission in the visible and near infrared spectral range, already assessed as efficient fluorescent nanothermometers. The chemical stability, easy surface functionalization, limited toxicity and transparency of the silica coating represent advantageous features for the realization of a nanoscale heterostructure suitable for temperature sensing. However, the strong dependence of the optical properties on the morphology of the final core–shell nanoparticle requires an accurate control of the encapsulation process. We carried out a systematic investigation of the synthetic conditions to achieve, by the microemulsion method, uniform and single core silica coated GQD (GQD@SiO2) nanoparticles and subsequently recorded temperature-dependent fluorescent spectra in the 281-313 K temperature range, suited for biological systems. The ratiometric response—the ratio between the two integrated PbS and CdS emission bands—is found to monotonically decrease with the temperature, showing a sensitivity comparable to bare GQDs, and thus confirming the effectiveness of the functionalization strategy and the potential of GQD@SiO2 in future biomedical applications.

A Comprehensive Review of Synthesis, Applications and Future Prospects for Silica Nanoparticles (SNPs)

“…In this respect, various researchers covalently linked the compounds; such as fluorophores and tetramethyl rhodamine isothiocyanate dye, onto the silica nanoparticles. The fabricated materials showed water soluble and less/non-toxic conduct with promising results, hence a worthy substitute for QDs [90][91][92][93][94]. Moreover, the adhesive properties of SNPs have been utilized by researchers to synthesize glue like material, which is shown to be less invasive compared to commonly used tissue adhesives like cyanoacrylate [22].…”

Highly sensitive and selective detection of glutathione using ultrasonic aided synthesis of graphene quantum dots embedded over amine-functionalized silica nanoparticles

“…TEM images of the amino-functionalized silica nanoparticles depict spherical structures with uniform particle sizes in the range of 30–40 nm ( Fig S2 A-B). Preliminary experiments indicated the need for the pre-modification of silica with APTS to contribute to the immobilization of GQDs over the SiNPs surface [38] , [39] . EDX analysis ( Fig.…”

Luminescence Thermometry Beyond the Biological Realm

“…Alternatives such as carbon-based QDs − and group I-III-VI 2 compounds have been developed due to concerns over both the cellular and environmental toxicity of heavy metal QD materials . Many groups have also developed multilayer QDs consisting of varying compositions of cores and multiple layers of shells ,,− and have incorporated QDs in composites with other types of nanoparticles. , Typical QDs are smaller than 20 nm in size and include only a few hundred or thousands of atoms within the lattice, leading to quantum confinement effects since the characteristic size of the QD is comparable to the exciton Bohr radius . QDs have a discrete valence and conduction band, which gives rise to a forbidden energy bandgap in between.…”