Gold Nanotetrapods with Unique Topological Structure and Ultranarrow Plasmonic Band as Multifunctional Therapeutic Agents.

Owing to their excellent surface plasmonic properties, Au nanobranches have drawn increasing attention in various bioapplications, such as contrast agents for photoacoustic imaging, nanomedicines for photothermal therapy, and carriers for drug delivery. The monodispersity and plasmonic bandwidth of Au nanobranches are of great importance for the efficacy of those bioapplications. However, it is still a challenge to accurately synthesize size- and shape-controlled Au nanobranches. Here we report a facile seed-mediated growth method to synthesize monodisperse Au nanotetrapods (NTPs) with tunable and ultranarrow plasmonic bands. The NTPs have a novel D2d symmetry with four arms elongated in four ⟨110⟩ directions. The growth mechanism of NTPs relies on the delicate kinetic control of deposition and diffusion rates of adatoms. Upon laser irradiation, the PEGylated NTPs possess remarkable photothermal conversion efficiencies and photoacoustic imaging properties. The NTPs can be applied as a multifunctional theranostic agent for both photoacoustic imaging and image-guided photothermal therapy.

Synergistic Reducing Effect for Synthesis of Well-Defined Au Nanooctopods With Ultra-Narrow Plasmon Band Width and High Photothermal Conversion Efficiency.

Branched Au nanoparticles have attracted intense interest owing to their remarkable properties and a wide variety of potential applications in surface-enhanced Raman spectroscopy (SERS), photothermal therapy, photoacoustic imaging, and biomedicines. The morphology and spatial arrangement of branches play the most crucial role in the determination of their properties and applications. However, it is still a synthetic challenge to control the exact arm numbers of branches with specific spatial arrangements. Here we report a facile method for the kinetically controlled growth of Au nanooctopods (NOPs) with a high yield (81%), monodispersity, and reproducibility by using the synergistic reducing effect of ascorbic acid and 1-methylpyrrolidine. The NOPs have eight arms elongated along <111> directions with uniform arm lengths. Due to their well-defined size and shape, NOPs show ultra-narrow surface plasmon band width with a full width at half maximum of only 76 nm (0.20 eV). Upon irradiation with laser, the NOPs possessed excellent photothermal conversion efficiencies up to 83.0% and photoacoustic imaging properties. This work highlights the future prospects of using NOPs with desired physicochemical properties for biomedical applications.

Chiral Plasmonic Nanochains via the Self-Assembly of Gold Nanorods and Helical Glutathione Oligomers Facilitated by Cetyltrimethylammonium Bromide Micelles.

Gold nanorods are excellent anisotropic building blocks for plasmonic chiral nanostructures. The near-infrared plasmonic band of nanorods makes them highly desirable for biomedical applications such as chiral bioimaging and sensing, in which a strong circular dichroism (CD) signal is required. Chiral assemblies of gold nanorods induced by self-associating peptides are especially attractive for this purpose as they exhibit plasmonic-enhanced chiroptical activity. Here, we showed that the presence of cetyltrimethylammonium bromide (CTAB) micelles in a gold nanorod solution promoted the self-association of l-/d-glutathione (GSH) and significantly enhanced the chirality of the resulting plasmonic nanochains. Chiroptical signals for the ensemble in the presence of CTAB micelles were 20 times greater than those obtained below the critical micelle concentration of CTAB. The strong optical activity was attributed to the formation of helical GSH oligomers in the hydrophobic core of the CTAB micelles. The helical GSH oligomers led the nanorods to assemble in a chiral, end-to-end crossed fashion. The CD signal intensities were also proportional to the fraction of nanorods in the nanochains. In addition, finite-difference time-domain simulations agreed well with the experimental extinction and CD spectra. Our work demonstrated a substantial effect from the CTAB micelles on gold nanoparticle assemblies induced by biomolecules and showed the importance of size matching between the inorganic nanobuilding blocks and the chiral molecular templates (i.e., the GSH oligomers in the present case) in order to attain strong chiroptical activities.

A Dy4 single-molecule magnet and its Gd(iii), Tb(iii), Ho(iii), and Er(iii) analogues encapsulated by an 8-hydroxyquinoline Schiff base derivative and ß-diketonate coligand.

Five new tetranuclear complexes based on an 8-hydroxyquinoline Schiff base derivative and the ß-diketone coligand, [Ln4(acac)4L6(µ3-OH)2]·CH3CN·0.5CH2Cl2 (Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5); HL = 5-(benzylidene)amino-8-hydroxyquinoline; acac = acetylacetonate) have been synthesized, and structurally and magnetically characterized. Complexes 1-5 have similar tetranuclear structures. Each LnIII ion is eight coordinated and its coordination polyhedra can be described as being in a distorted square-antiprismatic geometry. The magnetic studies reveal that 1 features the magnetocaloric effect (MCE) with the magnetic entropy change of -ΔSm(T) = 25.08 J kg-1 K-1 at 2 K for ΔH = 7 T, and 3 displays the slow magnetic relaxation behavior of Single Molecule Magnets (SMMs) with the anisotropic barrier of 86.20 K and the pre-exponential factor τ0 = 2.99 × 10-8 s.

Modulation of the relaxation dynamics of linear-shaped tetranuclear rare-earth clusters through utilizing different solvents.

Nine new tetranuclear centrosymmetric linear complexes, [RE4(dbm)8L2(DMF)2]·nCH2Cl2·mC2H3N (RE = Y (1), Tb (2), Dy (3), Ho (4), Er (5), Lu (6)) and [RE4(dbm)8L2(C2H5OH)2]·nCH3CN (RE = Tb (7), Dy (8), Ho (9)) (HL = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-8-hydroxyquinoline and dbm = 1,3-diphenyl-1,3-propanedione) have been synthesized. Complexes 1-9 are tetranuclear complexes. Magnetic studies reveal that both DyIII-based complexes (3 and 8) exhibit single-molecule magnet (SMM) behavior under a zero dc field. Furthermore, complex 3 presents one relaxation process under a zero dc field, while application of an external dc field (1500 Oe) induces multi-relaxation signals of the ac magnetic susceptibility.