A plasmonic fluorescent ratiometric temperature sensor for self-limiting hyperthermic applications utilizing FRET enhancement in the plasmonic field

Nanoparticle mediated photo-induced hyperthermia holds much promise as a therapeutic solution for the management of diseases like cancer. The conventional methods of temperature measurements do not measure the actual temperature generated in the vicinity of the nanoparticles during illumination. In contrast, nano temperature sensors built on hyperthermic nanoparticles can relay local temperatures around the nanoparticles during thermal induction. In this study, we present a core shell construct consisting of a plasmonic core and a silica shell encapsulating a FRET pair of organic dyes for such application. The plasmonic core imparts photo-induced hyperthermic properties to the nanoconstruct, while the fluorescent shell enables ratiometric sensing of temperature. We see that even at a low dye encapsulation concentration, the shell displays a linear ratiometric fluorescence response to temperature and high energy transfer between the dye pair. Interestingly, Monte Carlo simulations, without considering the plasmonic core, show that the energy transfer in the system should be much smaller than that observed, confirming plasmon enhancement in the FRET energy transfer. We also show the ratiometric temperature measurement using these particles during photoinduced hyperthermia. This study suggests the use of plasmonic nanoparticles in the next generation "self-limiting" photothermal therapy.

A novel SERS sensor for the ultrasensitive detection of kanamycin based on a Zn-doped carbon quantum dot catalytic switch controlled by nucleic acid aptamer and size-controlled gold nanorods

In this study, a novel surface enhanced Raman spectroscopy (SERS) sensor was developed for the ultrasensitive determination of kanamycin in foods. The sensor used two distinct signal amplification strategies, namely the surface plasmon resonance of gold nanorods and a Zn-doped carbon quantum dots catalytic cascade oxidation-reduction reaction switch controlled by a nucleic acid aptamer. Under optimized experimental conditions, the SERS sensor demonstrated a linear range of 10^-12 to 10^-5 g mL^-1 for the detection of kanamycin, with a limit of detection of 3.03 × 10^-13 g mL^-1. Experiments with antibiotics structurally similar to kanamycin and interferrants revealed that the sensor had excellent selectivity. Milkpowder and honey samples spiked with kanamycin were assayed, with recoveries ranging from 84.1% to 107.2% and a relative standard deviation of 0.74% to 2.81% being obtained. Quantification of kanamycin in milk samples revealed no significant difference between the results obtained with the sensor and by HPLC.

Measuring temperature heterogeneities during solar-photothermal heating using quantum dot nanothermometry

Small metallic nanoparticles with appropriate surface plasmon resonance frequencies can be extremely efficient absorbers of solar radiation. This efficient absorption can lead to localized heating and highly heterogeneous temperatures. These unique optical properties have inspired research into the development of environmentally relevant solar-to-heat conversion technologies that are based on the light absorption of nanomaterials. The development of robust, reliable, and straight-forward techniques for measuring spatially resolved temperatures in photothermally heated systems can be an indispensable tool to aid future work in this area. Herein, we consider the application of a fluorescent technique that can measure spatially resolved temperatures in solar photothermal systems using CdSe quantum dots (<10 nm diameter). The local temperature of the quantum dot can be determined by monitoring the shift in its fluorescence wavelength resulting from the dilatation of the lattice with increasing temperature. To exploit this property, we fabricated Au nanorod-quantum dot architectures using linkers of varying lengths, and measured the light induced temperature change increasing more rapidly closer to the surface of an Au nanorod. We also compared the effect of Au nanorod coatings and found that silica coating leads to higher overall temperatures compared to organic stabilized Au nanorods.

Multilayered Dual Functional SiO2@Au@SiO2@QD Nanoparticles for Simultaneous Intracellular Heating and Temperature Measurement

This paper discusses synthesis and application of dual functional SiO₂@Au@SiO₂@QD composite nanoparticles for integrated intracellular heating with temperature motoring. The particles are of multilayered concentric structure, consisting of Au nanoshells covered with quantum dots, with the former for infrared heating through localized surface plasma resonance while the later for temperature monitoring. The key to integrate plasmonic-heating/thermal-monitoring on a single composite nanoparticle is to ensure that the quantum dots be separated at a certain distance away from the Au shell surface in order to ensure a detectable quantum yield. Direct attachment of the quantum dots onto the Au shell would render the quantum dots practically functionless for temperature monitoring. To integrate quantum dots into Au nanoshells, a quantum quenching barrier of SiO₂ was created by modifying a Stöber-like process. Materials, optical and thermal characterization was made of these composite nanoparticles. Cellular uptake of the nanoparticles was discussed. Experiments were performed on simultaneous in vitro heating and temperature monitoring in a cell internalized with the dual-functional SiO₂@Au@SiO₂@QD composite nanoparticles.

Nanoscale 3D temperature gradient measurement based on fluorescence spectral characteristics of the CdTe quantum dot probe

The existing quantum dot temperature measurement techniques can only measure the planar temperature in the cell but fails in 3D temperature investigation. We present a novel method of measuring the 3D temperature field on nano scale, combining fluorescence spectral characteristics of the CdTe quantum dot probe with optical spatial positioning. Based on dual-helix point spread function, a 3D temperature optical measurement system with a resolution of 0.625 °C is established, providing a new perspective of 3D temperature measurement inside the cell. We thus offer an original research tool for further revealing the evolution process of secretions in cell metabolism.

Quantum 3D thermal imaging at the micro-nanoscale

Real-time and accurate measurement of three-dimensional (3D) temperature field gradient maps of cells and tissues would provide an effective experimental method for analyzing the coupled correlation between metabolism and heat, as well as exploring the thermodynamic properties of nanoparticles under complex environments. In this work, a new principle of quantum 3D thermal imaging is proposed. The photoluminescence principle of quantum dots is expounded and CdTe QDs are prepared by aqueous phase synthesis. Fluorescence spectral characteristics of QDs at different temperatures are studied. The optimized algorithm of the optical spot double helix point spread function is proposed to improve the imaging, where optimized light energy increased by 27.36%. The design scheme of a quantum 3D thermal imaging system is presented. The measurement range is (-8 mm, +8 mm). The temperature is calculated according to the temperature-heat curve of quantum dots. The double helix point spread function has converted the defocus distance of QDs into the rotation angle of the double optical spot, thereby determining its position. The experimental results reveal that real-time 3D tracking and temperature measurements of quantum dots at the micro-nanoscale are achieved. Overall, the proposed nano-scale 3D quantum thermal imaging system with high-resolution may provide a new research direction and exploration of many frontier fields.

Thermal sensing with CdTe/CdS/ZnS quantum dots in human umbilical vein endothelial cells

An experimental methodology is presented to measure the temperature variation in cells with the usage of CdTe/CdS/ZnS core/shell/shell quantum dots as nanothermometers.

Imaging Local Heating and Thermal Diffusion of Nanomaterials with Plasmonic Thermal Microscopy

Measuring local heat generation and dissipation in nanomaterials is critical for understanding the basic properties and developing applications of nanomaterials, including photothermal therapy and joule heating of nanoelectronics. Several technologies have been developed to probe local temperature distributions in nanomaterials, but a sensitive thermal imaging technology with high temporal and spatial resolution is still lacking. Here, we describe plasmonic thermal microscopy (PTM) to image local heat generation and diffusion from nanostructures in biologically relevant aqueous solutions. We demonstrate that PTM can detect local temperature change as small as 6 mK with temporal resolution of 10 μs and spatial resolution of submicrons (diffraction limit). With PTM, we have successfully imaged photothermal generation from single nanoparticles and graphene pieces, studied spatiotemporal distribution of temperature surrounding a heated nanoparticle, and observed heating at defect sites in graphene. We further show that the PTM images are in quantitative agreement with theoretical simulations based on heat transport theories.