Jason

The facile assembly of shell-by-shell (SbS)-coated nanoparticles [TiO₂PAC₁₆]@shell 1–7 (PAC₁₆=hexadecylphosphonic acid), which are soluble in water and can be isolated as stable solids, is reported. In these functional architectures, an umpolung of dispersibility (organic apolar versus water) was accomplished by the noncovalent binding of ligands 1–7 to titania nanoparticles [TiO₂PAC₁₆] containing a first covalent coating with PAC₁₆. Ligands 1–7 are amphiphilic and form the outer second shell of [TiO₂PAC₁₆]@shell 1–7. The tailor-designed dendritic building blocks 3–5 contain negative and positive charges in the same molecule, and ligands 6 and 7 contain a perylenetetracarboxylic acid dimide (PDI) core (6/7) as a photoactive reporter component. In the redox and photoactive system [TiO₂PAC₁₆]@shell 7, electronic communication between the inorganic core to the PDI ligands was observed.

Nanochameleons with switchable dispersion behavior: In these new shell-by-shell architectures, ionic and redox-active amphiphiles make the difference because they form an outer ligand shell that provides polarity umpolung, water solubility, and facile nanoparticle functionalization (see figure).

The ever-growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therapy.

Responding well to silica: Mesoporous silica nanoparticles (MSN) represent one of the most promising nanocarriers for drug delivery (see figure). This concept article describes how their functionalization has allowed the design of more efficient systems by improving their specific retention and uptake with targeted and stimuli-responsive properties.

Core–shell-structured, ultrafine SnO_x/carbon nanofiber (CNF)/carbon nanotube composite films are in situ synthesized by electrospinning through a dual nozzle. The carbon shell layer functions as a buffer to prevent the separation of SnO_x particles from the CNF core, allowing full utilization of high-capacity SnO_x in both Li-ion and Na-ion batteries. The composite electrodes reveal an anomalous Li- and Na-ion storage mechanism where all the intermediate phases, like Li_xSn and Na_xSn alloys, maintain amorphous states during the entire charge/discharge process. The uniform dispersion on an atomic scale and the amorphous state of the SnO_x particles remain intact in the carbon matrix without growth or crystallization even after 300 cycles, which is responsible for sustaining excellent capacity retention of the electrodes. These discoveries not only shed new insights into fundamental understanding of the electrochemical behavior of SnO_x electrodes but also offer a potential strategy to improve the cyclic stability of other types of alloy anodes that suffer from rapid capacity decays due to large volume changes.

Li-ion and Na-ion storage behaviors of ultrafine amorphous SnO_x particles embedded in carbon nanofiber/carbon nanotube composites are investigated. They reveal an anomalous electrochemical mechanism with all intermediate phases maintaining an amorphous state during the entire charge/discharge process, which gives rise to excellent reversibility of the electrodes.

The synthesis of silica-based yolk–shell nanospheres confined with ultrasmall platinum nanoparticles (Pt NPs) stabilized with poly(amidoamine), in which the interaction strength between Pt NPs and the support could be facilely tuned, is reported. By ingenious utilization of silica cores with different surface wettability (hydrophilic vs. -phobic) as the adsorbent, Pt NPs could be confined in different locations of the yolk–shell nanoreactor (core vs. hollow shell), and thus, exhibit different interaction strengths with the nanoreactor (strong vs. weak). It is interesting to find that the adsorbed Pt NPs are released from the core to the hollow interiors of the yolk–shell nanospheres when a superhydrophobic inner core material (SiO₂Ph) is employed, which results in the preparation of an immobilized catalyst (Pt@SiO₂Ph); this possesses the weakest interaction strength with the support and shows the highest catalytic activity (88 500 and 7080 h⁻¹ for the hydrogenation of cyclohexene and nitrobenzene, respectively), due to its unaffected freedom of Pt NPs for retention of the intrinsic properties.

Forced confinement: By utilizing silica cores with different surface wettability as adsorbents, platinum nanoparticles (Pt NPs) could be confined in different locations of the yolk–shell nanoreactor with different interaction strengths between the Pt NPs and the nanoreactor (see figure). The catalyst with weakest interaction strength exhibits distinguished activity due to the freedom of Pt NPs within the nanoreactor.

The tridentate chelate nickel complexes [(CO)Ni{(PPh₂CH₂)₃CMe}] (2), [(CO)Ni{(PPh₂CH₂CH₂)₃SiMe}] (6), and [Ph₃PNi{(PPh₂CH₂CH₂)₃SiMe}] (7), as well as the bidentate complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂PPh₂}] (3) and the heterobimetallic complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂Ph₂PAuCl}] (4), have been synthesized and fully characterized in solution. All ¹H and ¹³C NMR signal assignments are based on 2D-NMR methods. Single crystal X-ray structures have been obtained for all complexes. Their ³¹P CP/MAS (cross polarization with magic angle spinning) NMR spectra have been recorded and the isotropic lines identified. The signals were assigned with the help of their chemical shift anisotropy (CSA) data. All complexes have been tested regarding their catalytic activity for the cyclotrimerization of phenylacetylene. Whereas complexes 2–4 display low catalytic activity, complex 7 leads to quantitative conversion of the substrate within four hours and is highly selective throughout the catalytic reaction.

Tripod classic: Three Ni⁰ complexes of tripodal chelating phosphine ligands, as well as a bidentate complex and a heterobimetallic Ni⁰/Au^I complex, were synthesized and fully characterized. The catalytic activities and selectivities of the complexes were assessed for the cyclotrimerization of phenylacetylene.

A novel synergistic TiO₂-MoO₃ (TO-MO) core–shell nanowire array anode has been fabricated via a facile hydrothermal method followed by a subsequent controllable electrodeposition process. The nano-MoO₃ shell provides large specific capacity as well as good electrical conductivity for fast charge transfer, while the highly electrochemically stable TiO₂ nanowire core (negligible volume change during Li insertion/desertion) remedies the cycling instability of MoO₃ shell and its array further provides a 3D scaffold for large amount electrodeposition of MoO₃. In combination of the unique electrochemical attributes of nanostructure arrays, the optimized TO-MO hybrid anode (mass ratio: ca. 1:1) simultaneously exhibits high gravimetric capacity (ca. 670 mAh g⁻¹; approaching the hybrid's theoretical value), excellent cyclability (>200 cycles) and good rate capability (up to 2000 mA g⁻¹). The areal capacity is also as high as 3.986 mAh cm⁻², comparable to that of typical commercial LIBs. Furthermore, the hybrid anode was assembled for the first time with commercial LiCoO₂ cathode into a Li ion full cell, which shows outstanding performance with maximum power density of 1086 W kg_total ⁻¹ (based on the total mass of the TO-MO and LiCoO₂) and excellent energy density (285 Wh kg_total ⁻¹) that is higher than many previously reported metal oxide anode-based Li full cells.

Synergistic TiO₂-MoO₃ core–shell nano­wire array anode is developed, showing high capacity (ca. 670 mAh g⁻¹; 3.986 mAh cm⁻²), excellent cycleability (>200 times), and good rate performance. Ultrahigh energy density (285 Wh kg_total ⁻¹) and power density (1086 W kg_total ⁻¹) are further achieved for a full cell LIB device assembled using the TiO₂-MoO₃ hybrid array as anode and commercial LiCoO₂ film as cathode.

Hollow bioactive glass spheres with mesoporous shells were prepared by using dual soft templates, a diblock co-polymer poly(styrene-b-acrylic acid) (PS-b-PAA) and a cationic surfactant cetyltrimethylammonium bromide (CTAB). Hollow mesoporous bioactive glass (HMBG) spheres comprise the large hollow interior with vertical mesochannels in shell, which realize large uptake of drugs and their sustained release. The formation of hydroxyapatite layer on the surface of HMBG particles shows the clear evidence for promising application in bone regeneration.

Bone crunch! Hollow bioactive glass spheres with mesoporous shells were prepared by using a dual soft template. Hollow mesoporous bioactive glass (HMBG) spheres comprise the large hollow interior with vertical mesochannels in the shell. The formation of a hydroxyapatite layer on the surface of HMBG particles shows clear evidence for promising applications in bone regeneration (see scheme).

Controlling the assembly and functionalization of molecular metal oxides [M_xO_y]ⁿ⁻ (M=Mo, W, V) allows the targeted design of functional molecular materials. While general methods exist that enable the predetermined functionalization of tungstates and molybdates, no such routes are available for molecular vanadium oxides. Controlled design of polyoxovanadates, however, would provide highly active materials for energy conversion, (photo-) catalysis, molecular magnetism, and materials science. To this end, a new approach has been developed that allows the reactivity tuning of vanadium oxide clusters by selective metal functionalization. Organic, hydrogen-bonding cations, for example, dimethylammonium are used as molecular placeholders to block metal binding sites within vanadate cluster shells. Stepwise replacement of the placeholder cations with reactive metal cations gives mono- and difunctionalized clusters. Initial reactivity studies illustrate the tunability of the magnetic, redox, and catalytic activity.

Stepwise functionalization of a vanadium oxide cluster by one or two functional metal centers is achieved by using a molecular placeholder approach. The novel strategy provides access to redox-, catalytically, and magnetically active molecular materials.

Development of novel nanocatalysts for the highly efficient in situ synthesis of H₂O₂ from H₂ and O₂ in the electro-Fenton (EF) process has potential for the remediation of water pollution. In this work, AuPd/carbon nanotube (CNT) nanocatalysts were successfully synthesized by the facile aggregation of AuPd bimetals on CNTs. Characterization by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy indicated that pure AuPd bimetallic heterogeneous nanospheres (≈20 nm) were well dispersed outside the CNTs, which resulted in better catalytic performance than Pd/CNTs alone: 0.36 M H₂O₂ was synthesized; 0.05 M Fe²⁺ optimally initiated the EF process due to the superior in situ Fe²⁺ regeneration; and the organic pollutant removal reached 100 % at 37 min, with a pseudo-first-order kinetic constant k₁=0.051 min⁻¹. Moreover, structural insights before/after catalysis revealed that Au strengthened the construction of the nanocrystals, avoided negative deactivation caused by AuPd agglomeration, and immobilized the active Pd(111). The catalytic stability of AuPd/CNTs over ten cycles implied long durability and promising applications of this material.

Bimetallic catalysts: AuPd/carbon nanotube (CNT) nanocomposites were synthesized and used as three-dimensional electrodes in the electro-Fenton process. They exhibited superior catalytic activity in the in situ production of H₂O₂ from H₂ and O₂, in situ regeneration of Fe²⁺, and removal efficiency of organic pollutants such as dimethylacetamide (see figure).