Magnetoplasmon-surface phonon polaritons coupling effects in radiative heat transfer

In this letter, based on the quantum Hall regime of magneto-optical graphene, we have theoretically investigated the coupling of magnetoplasmon polaritons (MPP) to surface phonon polaritons (SPhPs) by investigating the radiative heat transfer between two graphene-coated SiO2 slabs. By applying an external magnetic field, the separated branches of intraband and interband MPP can both couple with SPhPs to form tunable modes, which remould the energy transport of the system. The heat transfer mechanism is completely changed from enhancement to attenuation due to the strong coupling, and the thermal stealthy is realized for the graphene. The letter has great significance for the graphene-based magneto-optical devices.Comment: 4 pages, 4 figure

Photothermal conversion and transfer in photothermal therapy: From macroscale to nanoscale

Photothermal therapy (PTT) is a promising alternative therapy for benign or even malignant tumors. To improve the selective heating of tumor cells, target-specific photothermal conversion agents are often included, especially nanoparticles. Meanwhile, some indirect methods by manipulating the radiation and heat delivery are also adopted. Therefore, to gain a clear understanding of the mechanism, and to improve the controllability of PTT, a few issues need to be clarified, including bioheat and radiation transfer, localized and collective heating of nanoparticles, etc. In this review, we provide an introduction to the typical bioheat transfer and radiation transfer models along with the dynamic thermophysical properties of biological tissue. On this basis, we reviewed the most recent advances in the temperature control methods in PTT from macroscale to nanoscale. Most importantly, a comprehensive introduction of the localized and collective heating effects of nanoparticle clusters is provided to give a clear insight into the mechanism for PPT from the microscale and nanoscale point of view

Anisotropic scattering characteristics of nanoparticles in different morphologies: improving the temperature uniformity of tumors during thermal therapy using forward scattering

Precise control of the thermal damage area is the key issue during thermal therapy, which can be achieved by manipulating the light propagation in biological tissue. In the present work, a method is proposed to increase the uniformity of the specific absorption rate (SAR) distribution in tumors during laser-induced thermal therapy, which is proved to be effective in reducing the thermal damage of healthy tissue. In addition, a better way of manipulating light propagation in biological tissue is explored. It is found that the anisotropic scattering characteristics of nanoparticles are strongly dependent on their shapes, sizes, orientations, and incident wavelengths, which will strongly affect the light propagation in nanoparticle embedded biological tissue. Therefore, to obtain a better outcome from photothermal therapy, the scattering properties of nanoparticles are very important factors that need to be taken into consideration, along with the absorption efficiency. Further investigation finds that nanoparticles that predominantly scatter to the forward direction are favorable in obtaining a larger penetration depth of light, which will improve the uniformity of SAR and temperature distributions. This paper is meaningful for the application of nanoparticle-assisted laser-induced thermal therapy

Nanoparticle hybrids as efficient theranostic nanoagents with enhanced near-infrared optical absorption and scattering

The design of high-efficiency theranostic nanoagents that can be utilized in tumor diagnosis and treatment has been investigated extensively in recent years. However, most of the existing nanoagents consist of uncommon materials and complex shell structures. Despite the efforts that have been made, the development of a simple and easily synthesized theranostic nanoplatform that can be applied in optical-based imaging-guided photothermal therapy still remains a challenge. In this paper, we investigated the optical characteristics of nanoparticle aggregates as potential theranostic nanoplatforms. The mechanism of spectrum shifting and the optical properties of contacting and non-contacting short nanochains were investigated. It was found that the near-field interaction of the gold nanosphere will not shift the localized surface plasmon resonance peak to the near-infrared region. However, when the nanospheres are connected to each other, a low energy resonance peak will be excited. On this basis, a simple hybrid theranostic nanoagent consisting of different nanosphere clusters was proposed. The nanohybrid exhibits high absorption and low scattering in the first near-infrared window (NIR-I) and high scattering and near-zero absorption in the second NIR (NIR-II). This characteristic can be beneficial to tumor diagnosis and treatment, i.e., NIR-I for photothermal therapy and NIR-II for optical imaging. Numerical results show that the performance of the proposed hybrid theranostic nanoagent remains excellent even with the existence of potential impuritie

Passive control of temperature distribution in cancerous tissue during photothermal therapy using optical phase change nanomaterials

Thermal therapy is a very promising alternative treatment for benign tumor, in which the temperature control is a key issue to avoid unwanted thermal damage of healthy tissue. However, the active temperature control methods usually require the assistance of real-time and accurate temperature monitoring devices. Even though, the lag of temperature control is inevitable. Therefore, in the present work, a passive control method is proposed to improve the uniformity of temperature distribution inside tumorous tissue during laser induced thermal therapy (LITT). Optical phase change nanoparticles (O-PCNPs) are utilized to replace the commonly used noble metal nanoparticles to enhance and adjust the localized light absorption in tumor. In the early stage of LITT, the O-PCNPs is used to improve the specific absorption rate in the targeted region. However, after the local temperature reaches a certain level (phase transition temperature), the O-PCNPs convert from amorphous state to crystalline state. By carefully selecting the size, shape, and laser wavelength, the absorption cross section of O-PCNPs could drop dramatically after phase transition. Therefore, in the high temperature zone the local temperature increasing rate reduces due to the reduction of local heat generation rate. On the contrary, the temperature increasing rate rises in the low temperature zone since more energy is transferred to the deeper tissue. In the present work, results show that SiO2@VO2 nanoshells can be applied as thermal contrast agents to improve the temperature uniformity in tumor during LITT

Nanoparticle manipulation using plasmonic optical tweezers based on particle sizes and refractive indices

As an effective tool for micro/nano-scale particle manipulation, plasmonic optical tweezers can be used to manipulate cells, DNA, and macromolecules. Related research is of great significance to the development of nanoscience. In this work, we investigated a sub-wavelength particle manipulation technique based on plasmonic optical tweezers. When the local plasmonic resonance is excited on the gold nanostructure arrays, the local electromagnetic field will be enhanced to generate a strong gradient force acting on nanoparticles, which could achieve particle sorting in sub-wavelength scale. On this basis, we explored the plasmonic enhancement effect of the sorting device and the corresponding optical force and optical potential well distributions. Additionally, the sorting effect of the sorting device was investigated in statistical methods, which showed that the sorting device could effectively sort particles of different diameters and refractive indices

Plasmonic Optical Tweezers for Particle Manipulation: Principles, Methods, and Applications

Inspired by the idea of combining conventional optical tweezers with plasmonic nanostructures, a technique named plasmonic optical tweezers (POT) has been widely explored from fundamental principles to applications. With the ability to break the diffraction barrier and enhance the localized electromagnetic field, POT techniques are especially effective for high spatial-resolution manipulation of nanoscale or even subnanoscale objects, from small bioparticles to atoms. In addition, POT can be easily integrated with other techniques such as lab-on-chip devices, which results in a very promising alternative technique for high-throughput single-bioparticle sensing or imaging. Despite its label-free, high-precision, and high-spatial-resolution nature, it also suffers from some limitations. One of the main obstacles is that the plasmonic nanostructures are located over the surfaces of a substrate, which makes the manipulation of bioparticles turn from a three-dimensional problem to a nearly two-dimensional problem. Meanwhile, the operation zone is limited to a predefined area. Therefore, the target objects must be delivered to the operation zone near the plasmonic structures. This review summarizes the state-of-the-art target delivery methods for the POT-based particle manipulating technique, along with its applications in single-bioparticle analysis/imaging, high-throughput bioparticle purifying, and single-atom manipulation. Future developmental perspectives of POT techniques are also discussed