Structural design and catalyst screening are two most important factors for achieving exceptional electrocatalytic performance. Herein we demonstrate that constructing a three-dimensional (3D) porous Ni–Cu alloy film is greatly beneficial for improving the hydrazine oxidation reaction (HzOR) performance. A facile electrodeposition process is employed to synthesize a Ni–Cu alloy film with a 3D hierarchical porous structure. As an integrated electrode for HzOR, the Ni–Cu alloy film exhibits superior catalytic activity and stability to the Ni or Cu counterparts. The synthesis parameters are also systematically tuned for optimizing the HzOR performance. The excellent HzOR performance of the Ni–Cu alloy film is attributed to its high intrinsic activity, large electrochemical specific surface area, and 3D porous architecture which offers a “superaerophobic” surface to effectively remove the gas product in a small volume. It is believed that the Ni–Cu alloy film electrode has potential application in direct hydrazine fuel cells as well as other catalytic fields.

Carbon nanodots (CDs) formed by hydrothermal dehydration occur as mixtures of differently sized nanoparticles with different degrees of carbonization. Common ultracentrifugation has failed in sorting them, owing to their extremely high colloidal stability. Here, we introduce an ultracentrifugation method using a hydrophilicity gradient to sort such non-sedimental CDs. CDs, synthesized from citric acid and ethylenediamine, were pre-treated by acetone to form clusters. Such clusters “de-clustered” as they were forced to sediment through media comprising gradients of ethanol and water with varied volume ratios. Primary CDs with varied sizes and degrees of carbonization detached from the clusters to become well dispersed in the corresponding gradient layers. Their settling level was highly dependent on the varied hydrophilicity and solubility of the environmental media. Thus, the proposed hydrophilicity-triggered sorting strategy could be used for other nanoparticles with extremely high colloidalstability, which further widens the range of sortable nanoparticles. Furthermore, according to careful analysis of the changes in size, composition, quantum yield, and transient fluorescence of typical CDs in the post-separation fractions, it was concluded that the photoluminescence of the as-prepared hydrothermal carbonized CDs mainly arose from the particles’ surface molecular state rather than their sizes.

Au nanoring@Ag core–shell nanostructures with controllable morphologies and tunable symmetries are synthesized via the seed-mediated growth of Ag onto a sole seed: a circular Au nanoring (AuNR). The 2D isotropic AuNR is prepared firstly by chemical etching, then by galvanic replacement with HAuCl4. By delicately altering the regrowth procedure and mixing the capping agents, different Ag triangular nanoplates with embedded AuNRs in different sizes and shapes can be obtained. Furthermore, by using a single capping agent, the growth of Ag on the AuNR can be preferentially confined to a lateral or vertical mode, to form eccentric nanoplates or nanocubes in both sequence sets at room temperature. Such nanostructures with precisely controllable shape evolution not only displayed unique optical properties, but also revealed the feasibility of breaking the original dimensions, and especially symmetry, at the nanoscale using seed-mediated growth. This paves the way for future applications including catalysis, diagnosis, plasmonics, and biological and chemical sensing.

Highly stable Ag–Au triangular nanoplates and nanoframes were fabricated through well controlled galvanic reaction, which showed tunable localized surface plasmon resonance (LSPR) and efficient two-photon luminescence with the guarantee of high stability under both strong near infrared laser and tough ion-contained environments. The two-photon absorption cross section (6.34 × 104 GM) could reach double that of Au nanorods. As revealed by excitation wavelength dependent TPL spectra and the simulation of the localized electric field of the nanostructures, the TPL performance of the Ag–Au TNFs was possibly mainly determined by the matched LSPR absorbance and the Ag–Au alloys composition. The high stability and the strong TPL make the Ag–Au TNFs promising candidates for various nonlinear optical applications and further the understanding of the two-photon behavior of noble metals.

Well-dispersed Ag@rubrene core–shell nanostructures have been fabricated by an in situ chemical reaction route. The reduction in cationic precursors of rubrene˙+ by Ag atoms generated neutral rubrene molecules which had a local high concentration to realize the site-specific nucleation, and followed by the in situ growth of rubrene shell. The rubrene shell thickness can be highly tuned from 2 to 16 nm by adjusting the amount of rubrene˙+ radical cations. Such core–shell nanostructures have significant integrated multiple enhanced optical signal outputs: thickness-dependent fluorescence and SERS signals. The results show that the shell thickness and the match of local surface plasmon resonance and the excitation band of rubrene played dominant roles in fluorescence enhancement. Additionally, these nanostructures integrating the Raman-active substrate with Ag colloidal nanoparticles could obtain an enhancement factor (EF) of ∼103.

Ag@zinc–tetraphenylporphyrin (Ag@ZnTPP) core–shell nanostructures have been fabricated by in situ chemical deposition. Unusual thickness-dependent fluorescence allowed their colour to be tuned from blue to red by simply increasing the shell thickness from ∼2 nm to ∼9 nm. The competition between metal enhancement and the self-absorption effect of ZnTPP has been shown to be the main reason for this variation.

Density gradient ultracentrifuge separation was employed to study the phase transition of Yb3+/Er3+ co-doped NaYF4 from α-phase to β-phase. It was found that the cubic α-phased NaYF4 was rich in Y, exhibited predominantly red luminescence, whilst the newly formed hexagonal β-phased NaYF4 had relatively higher Yb and Er atomic ratios, exhibited green luminescence most strongly.

A series of mesoporous SnO2 nanospheres were prepared in ethanol/water mixed solvents with pore-forming surfactant (CTAB) involved. Surprisingly, the nanospheres assembled from SnO2 nanocones exhibited higher sensitivity to ethanol than hollow and amorphous-core counterparts, and more importantly, such submicrometer-sized spheres all showed linear responses to external ethanol concentration, similar to those extremely small spheres. Careful structure characterizations revealed their inner structure and crystallization behavior differences. It was finally concluded that the growth model difference significantly affected the inner structures (or assembly fashions) of these nanospheres, and consequently determined their sensing performances.

Ag@zinc–tetraphenylporphyrin (Ag@ZnTPP) core–shell nanostructures have been fabricated by in situ chemical deposition. Unusual thickness-dependent fluorescence allowed their colour to be tuned from blue to red by simply increasing the shell thickness from ∼2 nm to ∼9 nm. The competition between metal enhancement and the self-absorption effect of ZnTPP has been shown to be the main reason for this variation.

Density gradient ultracentrifuge separation was employed to study the phase transition of Yb3+/Er3+ co-doped NaYF4 from α-phase to β-phase. It was found that the cubic α-phased NaYF4 was rich in Y, exhibited predominantly red luminescence, whilst the newly formed hexagonal β-phased NaYF4 had relatively higher Yb and Er atomic ratios, exhibited green luminescence most strongly.

Well-dispersed Ag@rubrene core–shell nanostructures have been fabricated by an in situ chemical reaction route. The reduction in cationic precursors of rubrene˙+ by Ag atoms generated neutral rubrene molecules which had a local high concentration to realize the site-specific nucleation, and followed by the in situ growth of rubrene shell. The rubrene shell thickness can be highly tuned from 2 to 16 nm by adjusting the amount of rubrene˙+ radical cations. Such core–shell nanostructures have significant integrated multiple enhanced optical signal outputs: thickness-dependent fluorescence and SERS signals. The results show that the shell thickness and the match of local surface plasmon resonance and the excitation band of rubrene played dominant roles in fluorescence enhancement. Additionally, these nanostructures integrating the Raman-active substrate with Ag colloidal nanoparticles could obtain an enhancement factor (EF) of ∼103.

Au nanoring@Ag core–shell nanostructures with controllable morphologies and tunable symmetries are synthesized via the seed-mediated growth of Ag onto a sole seed: a circular Au nanoring (AuNR). The 2D isotropic AuNR is prepared firstly by chemical etching, then by galvanic replacement with HAuCl4. By delicately altering the regrowth procedure and mixing the capping agents, different Ag triangular nanoplates with embedded AuNRs in different sizes and shapes can be obtained. Furthermore, by using a single capping agent, the growth of Ag on the AuNR can be preferentially confined to a lateral or vertical mode, to form eccentric nanoplates or nanocubes in both sequence sets at room temperature. Such nanostructures with precisely controllable shape evolution not only displayed unique optical properties, but also revealed the feasibility of breaking the original dimensions, and especially symmetry, at the nanoscale using seed-mediated growth. This paves the way for future applications including catalysis, diagnosis, plasmonics, and biological and chemical sensing.