Ultrathin metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties. Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques, but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst.

The increase of antibiotic resistance in bacteria has become a major concern for successful diagnosis and treatment of infectious diseases. Over the past few decades, significant progress has been achieved on the development of nanotechnology-based medicines for combating multidrug resistance in microorganisms. Among this, silver nanoparticles (AgNPs) hold great promise in addressing this challenge due to their broad-spectrum and robust antimicrobial properties. This review illustrates the antibacterial mechanisms of silver nanoparticles and further elucidates how different structural factors including surface chemistry, size, and shape, impact their antibacterial activities, which are expected to promote the future development of more potent silver nanoparticle-based antibacterial agents.

Uniform plasmonic Pd@Au core-shell bimetallic nanoplates are synthesized by seeded growth strategy. Surface modified with SH-PEG makes it good biocompatibility, prolonged blood circulation, and relatively high tumor accumulation. Enhanced tumor contrast effects can be obtained for in vivo photoacoustic/CT imaging after intravenous injection of Pd@Au-PEG. Moreover, efficient photothermal tumor ablation is achieved, guided by the imaging techniques. This work promises further exploration of the superiority of 2D nanostructures for in vivo biomedical applications.

Efficient renal clearance is of fundamentally important property of nanoparticles for their in vivo biomedical applications. In this work, we report the successful synthesis of ultra-small Pd nanosheets (SPNS) with an average diameter of 4.4 nm and their application in photothermal cancer therapy using a near infrared laser. The ultra-small Pd nanosheets have strong optical absorption in the NIR region and high photothermal conversion efficiency (52.0%) at 808 nm. After being surface-functionalized with reduced glutathione (GSH), the SPNS-GSH was administered to mice to investigate the biodistribution, photothermal efficacy and tumor ablation in vivo. The in vivo photothermal therapy studies clearly demonstrate that surface modification with GSH allows the nanosheets to exhibit prolonged blood circulation and thus high accumulation in tumors. Upon 808 nm NIR irradiation, the tumors can be completely ablated. More importantly, with the size below the renal filtration limit (<10 nm), the GSHylated Pd nanosheets can be nicely cleared from body through the renal excretion route and into urine. Together with the high efficacy of NIR photothermal therapy, the unique renal clearance properties make the ultra-small Pd nanosheets promising for practical use in photothermal cancer therapy.

Plasmonic core shell bimetal nanoplates: A facile seeded-growth strategy is developed to prepare uniform plasmonic Pd@Ag core-shell bimetallic nanoplates. The as-prepared Pd@Ag nanoplates are not only uniform in both size and shape, but also display tunable SPR properties and significantly enhanced photothermal stability as compared with 2D pure-Ag nanostructures. They can thus be readily used as stable substrates for MR surface-enhanced Raman scattering and as NIR absorbers for photothermal cancer therapy.NSFC[21021061, 20925103, 20923004, 20871100]; Fok Ying Tung Education Foundation[121011]; MOST of China[2011CB932403, 2009CB930703]; NSF of Fujian Province[2009J06005]; Key Scientific Project of Fujian Province[2009HZ0002-1

Polypyrrole nanoparticles (PPy NPs) exhibit strong absorption in the near infrared (NIR) region. With an excellent photothermal efficiency of ~45% at 808 nm, sub-100 nm PPy NPs are demonstrated to be a promising photothermal agent for in vivo cancer therapy using NIR irradiation.

Novel concave Pd nanocrystals with uniform diameter were successfully prepared in the presence of formaldehyde. While the outer surfaces of the as-prepared concave Pd nanocrystals are {111}, the faces concave toward the polyhedral center are high-surface-energy {110} faces. The degree of concavity and therefore the percentage of {110} of the nanocrystals are tunable by varying the amount of formaldehyde and the reaction temperature. Owing to the existence of active {110} facets, the electrocatalytic activity of the concave Pd nanocrystals displays dependency on their degree of concavity.

Hollow mesoporous zirconia nanocapsules (hm‐ZrO2) with a hollow core/porous shell structure are demonstrated as effective vehicles for anti‐cancer drug delivery. While the highly porous feature of the shell allows the drug, doxorubicin(DOX), to easily pass through between the inner void space and surrounding environment of the particles, the void space in the core endows the nanocapsules with high drug loading capacity. The larger the inner hollow diameter, the higher their DOX loading capacity. A loading of 102% related to the weight of hm‐ZrO2 is achieved by the nanocapsules with an inner diameter of 385 nm. Due to their pH‐dependent charge nature, hm‐ZrO2 loaded DOX exhibit pH‐dependent drug releasing kinetics. A lower pH offers a faster DOX release rate from hm‐ZrO2. Such a property makes the loaded DOX easily release from the nanocapsules when up‐taken by living cells. Although the flow cytometry reveals more uptake of hm‐ZrO2 particles by normal cells, hm‐ZrO2 loaded DOX release more drugs in cancer cells than in normal cells, leading to more cytotoxicity toward tumor cells and less cytotoxicity to healthy cells than free DOX.