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Herein, we have synthesized a series of three-photon fluorescent Pt(II) complexes targeting a tumor-associated biothiol, cysteine (Cys), which allows it to be detected without any interference from other intracellular proteins. We focused on how to significantly improve the fluorescence response of Cys

Optical polarization has attracted considerable research attention by extra detection dimension in angular space, flourishing modern optoelectronic applications. Nonetheless, purposive polarization controlling at nanoscales and even at the single-particle level constitutes a challenge. Plasmonic nanoantenna opens up new perspectives in polarization state modification. Herein, we report angular-dependent upconversion luminescence (UCL) of rare-earth ions doped upconversion nanoparticles (UCNPs) in both emission and excitation polarization via constructing angularly anisotropic plasmonic local-field distributions in gold nanorods (Au NRs) antennae with different configurations at a single-particle level. The UCL of UCNP tailored by plasmonic Au NRs nanoantennae is enhanced and exhibits linear polarization. The highest enhancement factor of 138 is obtained in the collinear Au NR-UCNP-Au NR configuration under parallel excitation. Simultaneously, the maximum degree of linear polarization (DOLP) of UCL with factors of 85% and 81% are achieved in the same structure in emission and excitation polarization measurements, respectively. The observed linear polarizations and UCL enhancements are due to varied resonant responses at 660 nm and the anisotropic near-field enhancement in different nanoantennae-load UCNP. The theoretical simulations reveal the periodic changing of near-field enhancement factors of nanoantennae in angular space with the incident light polarization angles and are well-matched with the experimental results.

Conventional photosensitizers (PSs) often have shorter excitation wavelengths and poor cancer cell targeting, resulting in a limited tissue penetration depth and increased biotoxicity, which are significant barriers to ensuring effective photodynamic therapy (PDT)

We numerically demonstrate a Z -shaped metal-based metamaterial to realize an active polarization-controlled plasmon-induced transparency (PIT). The metamaterial unit cell contains two horizontal Au bars and a vertical Au bar. Simply by varying the incident light polarization, a tunable PIT can be achieved due to the reversible conversion of bright and dark modes between the horizontal and vertical Au bars. Moreover, a switchable PIT window modulation can be accomplished via changing the geometrical parameters, and the theoretical fittings according to the coupled Lorentz oscillator model display consistency with the simulated results. Our proposed metamaterials provide a promising strategy for fabricating compact PIT devices such as optical switching, sensing, and selective filters.

Vertically aligned gold nanorod arrays have attracted much attention for their fascinating optical properties. Different from longitudinal surface plasmon wavelength (LSPW) and edge-to-edge spacing of gold nanorods, the role of gold nanorod diameter in plasmonic enhancement ability of vertical gold nanorod arrays has rarely been explored. In this work, we selected gold nanorods with similar LSPW but two different diameters (22 and 41 nm), the optical properties of which are dominated by absorption and scattering cross sections, respectively. The vertically aligned arrays of these gold nanorods formed by evaporation self-assembly are coupled with nonlinear ZnO nanocrystal films spin-coated on their surfaces. It was found that the gold nanorod array with a larger diameter can enhance the second harmonic generation (SHG) of ZnO nanofilm by a factor of 27.0, while it is about 7.3 for the smaller gold nanorod array. Theoretical simulations indicate that such stronger enhancement of the larger vertical gold nanorod array compared with the smaller one is due to its stronger scattering ability and greater extent of near-field enhancement at SHG fundamental wavelength. Our work shows that the diameter of gold nanorods is also an important factor to be considered in realizing strong plasmon enhancement of vertically aligned gold nanorod arrays.

Active control of electromagnetically induced transparency (EIT) in metamaterials promises tremendous potential applications. However, previously reported strategies most require sensitive materials as well as additional experimental apparatus, which are inconvenient for on-chip operation and restrain their implementations in fully integrated design. We propose a low-loss all-dielectric metamaterial with orthogonal double bright modes, which shows a narrowband transparency window at 950.05 nm with a high Q-factor of 2111. Just by varying the incident light polarization angle, an on-to-off in-situ EIT modulation without changing Q-factor is perfectly achieved, and the modulation depth can be up to 99.7%. Additionally, optical control of group delay with up to 36.22 ps is also demonstrated. This work provides a simple route to design chip-scale devices with optically dynamic controllability and finds fascinating applications in low-loss active slow light devices, optical switch and sensitive bio-sensing.

A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.

An experimental prototype of a single stage ammonia-water absorption chiller was designed, built and tested. The thermodynamic models of the components, based on the First and Second Laws, have been assembled so as to quantify the simultaneous heat and mass transfer processes occurring within the exchangers. Calculated results were compared with experimental data. The results show that the cooling effect of experimental prototype was found between 1900 and 2200 W with the COP between 0.37 and 0.40. It is concluded that internal losses are dominated by heat and mass transfer dissipation, the cooling capacity is also limited by the condenser or absorber mass transfer performance. The contribution of the components to internal entropy production is analyzed. It shows that heat losses from the generator have a strong effect on the system performance.