Qiao Sun

One-pot solventless preparation of PEGylated black phosphorus nanoparticles for photoacoustic imaging and photothermal therapy of cancer

Black phosphorus (BP) nanostructures such as nanosheets and nanoparticles have attracted considerable attention in recent years due to their unique properties and great potential in various physical, chemical, and biological fields. In this article, water-soluble and biocompatible PEGylated BP nanoparticles with a high yield were prepared by one-pot solventless high energy mechanical milling technique. The resultant BP nanoparticles can efficiently convert near infrared (NIR) light into heat, and exhibit excellent photostability, which makes them suitable as a novel nanotheranostic agent for photoacoustic (PA) imaging and photothermal therapy of cancer. The in-vitro results demonstrate the excellent biocompatibility of PEGylated BP nanoparticles, which can be used for photothermal ablation of cancer cells under irradiation with NIR light. The in-vivo PA images demonstrate that these BP nanoparticles can be efficiently accumulated in tumors through the enhanced permeability retention effect. The resultant BP nanoparticles can be further utilized for photothermal ablation of tumors by irradiation with NIR light. The tumor-bearing mice were completely recovered after photothermal treatment with BP nanoparticles, in comparison with mice from control groups. Our research highlights the great potential of PEGylated BP nanoparticles in detection and treatment of cancer.

Ambient Aqueous Synthesis of Ultrasmall PEGylated Cu2−xSe Nanoparticles as a Multifunctional Theranostic Agent for Multimodal Imaging Guided Photothermal Therapy of Cancer

Ultrasmall PEGylated Cu2-x Se nanoparticles with strong near-infrared absorption have been prepared by an ambient aqueous method. The resultant water-soluble and biocompatible nanoparticles are demonstrated to be a novel nanotheranostic agent for effective deep-tissue photoacoustic imaging, computed tomography imaging, single-photon emission computed tomography imaging, and photothermal therapy of cancer.

Lead-free SnTe-based thermoelectrics: enhancement of thermoelectric performance by doping with Gd/Ag

SnTe, with the same rock-salt structure as PbTe, is a potentially attractive thermoelectric material. Pristine SnTe has poor thermoelectric performance because of its very high hole concentration resulting from intrinsic Sn vacancies, which leads to a high thermal conductivity and a low Seebeck coefficient. In this work, the thermoelectric properties of SnTe were modified by doping with different contents of gadolinium and silver. It is found that SnTe doped with optimal gadolinium (i.e. Gd0.06Sn0.94Te) exhibited extraordinarily low lattice thermal conductivity that is close to the theoretical minimum. The drastic reduction of lattice thermal conductivity is attributed to the formation of nanoprecipitates, which strongly scatter phonons by mass fluctuation between a second phase and matrix coupled with mesoscale scattering via grain boundaries. Further doping Gd0.06Sn0.94Te with Ag leads to a higher Seebeck coefficient due to the decreased carrier concentration and adjusted phase composition. Optimal Ag doping leads to a 3 times and 2 times enhancement of the figure of merit (ZT) in comparison with SnTe and Gd0.06Sn0.94Te, respectively, i.e. a ZT of ∼1.1 was obtained for 11 atom% Ag-containing Gd0.06Sn0.94Te at 873 K.

Ambient controlled synthesis of advanced core–shell plasmonic Ag@ZnO photocatalysts

Plasmonic Ag@ZnO core–shell hybrids, including hetero-nanowires and hetero-nanoparticles, have been synthesized at room temperature for application in photocatalysis. The morphology, size, crystal structure, and composition of the products were investigated by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. It was found the concentration of Zn(NO3)2·6H2O and the amount of water play crucial roles in the formation of Ag@ZnO core–shell hybrids. The resultant Ag@ZnO core–shell hybrids exhibit much higher photocatalytic activity and stability towards degradation of organic contaminants than pure ZnO nanocrystals under solar light irradiation. The one-dimensional (1D) core–shell hetero-nanowires prepared under optimal conditions (i.e. 0.6 M Zn(NO3)2·6H2O and 14.5 mL water) exhibit the best photocatalytic performance. The drastic enhancement in photocatalytic activity over the Ag@ZnO core–shell hybrids, especially the 1D core–shell hetero-nanowires, could be attributed to the synergistic effects of the surface ZnO and Ag nanowire cores with the surface plasmon resonance and the electron sink effect, as well as the unique 1D core–shell nanostructure for efficient mass transfer. The possible mechanism for degradation of rhodamine B (RhB) under solar light irradiation was discussed. This work provides a very convenient chemical route to prepare stable and highly efficient solar light driven plasmonic core–shell Ag@ZnO photocatalysts for cost-effective water purification.

Ambient synthesis of a multifunctional 1D/2D hierarchical Ag–Ag2S nanowire/nanosheet heterostructure with diverse applications

A new type of unique 1D/2D hierarchical Ag–Ag2S heterostructures is fabricated by an extremely simple solution route under ambient conditions. The morphology, size, crystal structure and composition of the products were comprehensively investigated, and it was found that the reaction time and the amount of S powder play crucial roles in the formation of well-defined 1D/2D hierarchical Ag–Ag2S heterostructures. The diffusion and Ostwald ripening processes dominate the evolution of the heterostructure. The resultant 1D/2D Ag–Ag2S hybrids exhibit great potential in Li/Na ion battery anodes, SERS detection and decoloration towards organic dyes.

Solvothermal synthesis and electrochemical properties of S-doped Bi2Se3 hierarchical microstructure assembled by stacked nanosheets

Hierarchical S-doped Bi2Se3 microspheres assembled by stacked nanosheets were successfully synthesized as the anode of a lithium ion battery, which shows an initial discharge capacity of 771.3 mA h g−1 with great potential in energy storage.

Enhanced thermoelectric performance through synergy of resonance levels and valence band convergence via Q/In (Q = Mg, Ag, Bi) co-doping

The temperature-dependent evolution of heavy-hole valence band contribution to the Seebeck coefficients of SnTe-based thermoelectric materials is revealed in situ by neutron and synchrotron powder diffraction. The additional carriers with high effective mass are created in a heavy-hole valence band above 493 K, which contribute to the electrical transport, and lead to a significant enhancement of the Seebeck coefficient at high temperature. In addition, remarkably improved electrical transport properties are achieved through the synergetic effects of the resonance levels, the valence band convergence, and the carrier concentration optimization by co-doping with Mg & In, Ag & In and Bi & In. Significant reduction in the lattice thermal conductivity is obtained by multiscale phonon scattering over a wide spectrum via atomic point defects, nanoscale elongated screw dislocations with random directions, and the microscale grain boundaries caused by sintering. As a result, a high figure of merit, ZT, of ∼1 at 873 K is obtained for the Mg0.015In0.015Sn0.97Te sample.

Ultra-small nanocluster mediated synthesis of Nd 3+ -doped core-shell nanocrystals with emission in the second near-infrared window for multimodal imaging of tumor vasculature

In-vivo intravital short wavelength infrared (SWIR, 1000-2300u202fnm) fluorescence imaging has attracted considerable attention in the imaging of tumor vasculature due to its low background, high sensitivity, and deep penetration. It can noninvasively provide dynamic feedback on the tumorigenesis, growth, necrosis and metastasis. Herein, monodisperse Nd3+-doped core-shell downconversion luminescent nanocrystals with strong emission in the second near-infrared (NIR II) window, strong temperature-dependent paramagnetism and fast attenuation to X-rays were prepared from ultra-small nanoclusters. The use of nanoclusters resulted in very uniform bright nanocrystals with a relative quantum yield comparable to the standard dye IR-26. These bright NIR nanocrystals were modified with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] to endow with excellent water-solubility, biocompatibility and a blood circulation half-life of 5.9u202fh. They were then successfully used to demonstrate the variation of tumor vasculature with tumor progression from tumorigenesis, growth, to necrosis in the subcutaneous breast tumor through the NIR II fluorescence imaging. They were also used as contrast agent of magnetic resonance imaging (MRI) and X-ray computed tomography (CT) imaging of tumor to provide complementary anatomic structure. Their great potential in NIR II imaging of tumor was further demonstrated with an orthotopic breast tumor. Their in-vivo biosafety was also investigated by hemanalysis and histological analyses.

Vacancy engineering of Cu2−xSe nanoparticles with tunable LSPR and magnetism for dual-modal imaging guided photothermal therapy of cancer

The vacancies in the semiconductor nanocrystals not only induce unique properties, but also provide spaces for engineering them with multifunctions by the introduction of other elements. Herein, the vacancy of Cu2-xSe nanoparticles was tuned by doping with magnetic ferric ions (Fe3+) at room temperature, and the position and intensity of the near-infrared localized surface plasmon resonance (LSPR) in the resultant nanostructure can be finely controlled by altering the feeding amount of Fe3+ ions. The results of the density-functional theory (DFT) calculations show that both doping and replacement reactions are favourable. Owing to its tunable near-infrared absorption and magnetic property, the obtained hybrid nanostructure was demonstrated to be a novel nanotheranostic agent for effective deep-tissue photoacoustic imaging, magnetic resonance imaging, and photothermal therapy of cancer.

Monitoring the Opening and Recovery of the Blood–Brain Barrier with Noninvasive Molecular Imaging by Biodegradable Ultrasmall Cu2–xSe Nanoparticles

The reversible and controllable opening and recovery of the blood-brain barrier (BBB) is crucial for the treatment of brain diseases, and it is a big challenge to noninvasively monitor these processes. In this article, dual-modal photoacoustic imaging and single-photon-emission computed tomography imaging based on ultrasmall Cu2- xSe nanoparticles (3.0 nm) were used to noninvasively monitor the opening and recovery of the BBB induced by focused ultrasound in living mice. The ultrasmall Cu2- xSe nanoparticles were modified with poly(ethylene glycol) to exhibit a long blood circulation time. Both small size and long blood circulation time enable them to efficiently penetrate into the brain with the assistance of ultrasound, which resulted in a strong signal at the sonicated site and allowed for photoacoustic and single-photon emission computed tomography imaging monitoring the recovery of the opened BBB. The results of biodistribution, blood routine examination, and histological staining indicate that the accumulated Cu2- xSe nanoparticles could be excreted from the brain and other major organs after 15 days without causing side effects. By the combination of the advantages of noninvasive molecular imaging and focused ultrasound, the ultrasmall biocompatible Cu2- xSe nanoparticles holds great potential for the diagnosis and therapeutic treatment of brain diseases.