Super‐resolution microscopy, as a powerful tool of seeing abundant spatial details, typically can only distinguish a few distinct targets at a time due to the spectral crosstalk between fluorophores. Spaser (i.e., surface plasmon laser) nanoprobes, which confine lasing emission into nanoscale, offer an opportunity to eliminate such obstacle. Here, realized is narrow band stimulated emission depletion (STED) nanoscopy on spaser nanoparticles by collecting the coherent spasing signals. Demonstrated are the physics concept and feasibility of erasing spaser emission by using a depletion beam to suppress the population inversion, which lays the foundation of spaser‐based STED super‐resolution. Thanks to the small size (47 nm) and narrow spectral linewidth (3.8 nm) of the spaser nanoparticles, a 74 nm spatial resolution in STED imaging within an acquisition bandwidth of 10 nm is finally obtained. These spaser nanoparticles, if multiplexing with different wavelengths, in principle, allow for spectral‐multiplexed imaging, sensing, cytometry, and light operation of a large number of targets all at once.

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In this research, we developed a multianalyte fluorescence sensing system through a carbon dots (CDs)-based fluorescent probe that can specifically recognize Fe(III) by fluorescence quenching. The CDs prepared using black tea by a hydrothermal method show outstanding properties like low cytotoxicity, high photostability, excellent biocompatibility, and high sensitivity. It was found that the fluorescence of CDs can be quenched by micromolar concentrations of Fe(III) in both aqueous solutions as well as living cells. It is well known that glucose can be oxidized by glucose oxidase (GOx) to release H 2 O 2 , which, in turn, can oxidize Fe(II) to Fe(III). Based on this consideration, a multianalyte sensing system was established. Therefore the quantitative analysis of Fe(III), H 2 O 2 , and glucose with detection limits of 0.25 mM, 0.82 mM, and 1.71 mM, respectively, was achieved by the simple and cost-effective multianalyte CDs sensing system constructed. The sensing system showed high photostability and negligible cytotoxicity toward HeLa cells, which enables it to be applied in the visualization of Fe(III) or H 2 O 2 in living cells. The system was further applied in the detection of Fe(III) or glucose in human serum, and satisfactory results were obtained.

Delayed spasing dots with ~3-nm spectral width, ~1 mJ cm−2 threshold, and ~102-μs lifetime were developed for a bionanoprobe.

Spaser nanoparticles, with ultranarrow spectral line width, small size and good biocompatibility, offer a bright prospect as potential biological probes. Sadly, over 10 years since the first demonstration, how the structure components determine their optical performance has not been clarified. Here the effects of gain layer thickness and dye emitter density on the lasing behavior and photostability of spaser nanoparticles are theoretically and experimentally addressed. Results show that for a 16 nm gold-core cavity, gain layer of 10−15 nm is adequate to maximize the spaser emission. For this type of nanoparticle− spaser system, the minimal number of dye emitters per particle, referred to as "dye threshold", is also vital to spasing action besides the "pump threshold" of laser power. Moreover, dye emitter distribution within the gain layer could be another approach to further improve spaser performance. These contributions give us an opportunity to profoundly understand the physical essence of spaser nanoparticles and to optimize their performance for further biology application.

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In this work, a general strategy was developed for the facile synthesis of bimetallic AuM (M ¼ Pt or Pd) alloyed flowerlike-assembly nanochains (FANs) with the assistance of diprophylline as a structuredirecting and stabilizing agent. The morphologies, crystal structures, and compositions of AuPt and AuPd FANs were investigated primarily by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The formation mechanism was discussed in some detail by varying the concentration of diprophylline. The as-prepared AuM FANs displayed improved catalytic activities and better stabilities for oxygen reduction reaction (ORR) compared to commercial E-TEK Pt/C, Pt black and Pd black.

A simple, facile one-pot wet-chemical co-reduction method was developed for synthesis of porous PtAu-nanoflowers/rGO with the assistance of p-aminopyridine. The as-prepared nanocomposites displayed excellent catalytic activity for 4-nitrophenol reduction.