Shui-Chao Lin

Au@Pt Nanoparticle Encapsulated Target‐Responsive Hydrogel with Volumetric Bar‐Chart Chip Readout for Quantitative Point‐of‐Care Testing

Point-of-care testing (POCT) with the advantages of speed, simplicity, portability, and low cost is critical for the measurement of analytes in a variety of environments where access to laboratory infrastructure is lacking. While qualitative POCTs are widely available, quantitative POCTs present significant challenges. Here we describe a novel method that integrates an Au core/Pt shell nanoparticle (Au@PtNP) encapsulated target-responsive hydrogel with a volumetric bar-chart chip (V-Chip) for quantitative POCT. Upon target introduction, the hydrogel immediately dissolves and releases Au@PtNPs, which can efficiently catalyze the decomposition of H2 O2 to generate a large volume of O2 to move of an ink bar in the V-Chip. The concentration of the target introduced can be visually quantified by reading the traveling distance of the ink bar. This method has the potential to be used for portable and quantitative detection of a wide range of targets without any external instrument.

Total Structure and Electronic Structure Analysis of Doped Thiolated Silver [MAg24(SR)18]2– (M = Pd, Pt) Clusters

With the incorporation of Pd or Pt atoms, thiolated Ag-rich 25-metal-atom nanoclusters were successfully prepared and structurally characterized for the first time. With a composition of [PdAg24(SR)18](2-) or [PtAg24(SR)18](2-), the obtained 25-metal-atom nanoclusters have a metal framework structure similar to that of widely investigated Au25(SR)18. In both clusters, a M@Ag12 (M = Pd, Pt) core is capped by six distorted dimeric -RS-Ag-SR-Ag-SR- units. However, the silver-thiolate overlayer gives rise to a geometric chirality at variance to Au25(SR)18. The effect of doping on the electronic structure was studied through measured optical absorption spectra and ab initio analysis. This work demonstrates that modulating electronic structures by transition-metal doping is expected to provide effective means to manipulate electronic, optical, chemical, and catalytic properties of thiolated noble metal nanoclusters.

Ligand-Stabilized Au13Cux (x = 2, 4, 8) Bimetallic Nanoclusters: Ligand Engineering to Control the Exposure of Metal Sites

Three novel bimetallic Au-Cu nanoclusters stabilized by a mixed layer of thiolate and phosphine ligands bearing pyridyl groups are synthesized and fully characterized by X-ray single crystal analysis and density functional theory computations. The three clusters have an icosahedral Au13 core face-capped by two, four, and eight Cu atoms, respectively. All face-capping Cu atoms in the clusters are triply coordinated by thiolate or pyridyl groups. The surface ligands control the exposure of Au sites in the clusters. In the case of the Au13Cu8 cluster, the presence of 12 2-pyridylthiolate ligands still leaves open space for catalysis. All the 3 clusters are 8-electron superatoms displaying optical gaps of 1.8-1.9 eV. The thermal decomposition studies suggest that the selective release of organic ligands from the clusters is possible.

Hierarchical Assembly of a {MnII15MnIII4} Brucite Disc: Step-by-Step Formation and Ferrimagnetism

In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn7) to nonadecamer (Mn19) satisfying the relation 1 + Σn6n, where n is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn10, Mn12, and Mn14, were identified. Furthermore, the Mn19 disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn19(L)x(OH)y(N3)36-x-y](2+) (x = 18, 17, 16; y = 8, 7, 6; HL = 1-(hydroxymethyl)-3,5-dimethylpyrazole) indicating progressive exchange of N3(-) for OH(-). The high symmetry (R-3) Mn19 crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn(II)15Mn(III)4]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH3CN. The moment of nearly 50 NμB suggests Mn(II)-Mn(II) and Mn(III)-Mn(III) are ferromagnetically coupled while Mn(II)-Mn(III) is antiferromagnetic which is likely if the Mn(III) are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules.

An Intermetallic Au24Ag20 Superatom Nanocluster Stabilized by Labile Ligands

An intermetallic nanocluster containing 44 metal atoms, Au24Ag20(2-SPy)4(PhC≡C)20Cl2, was successfully synthesized and structurally characterized by single-crystal analysis and density funtional theory computations. The 44 metal atoms in the cluster are arranged as a concentric three-shell Au12@Ag20@Au12 Keplerate structure having a high symmetry. For the first time, the co-presence of three different types of anionic ligands (i.e., phenylalkynyl, 2-pyridylthiolate, and chloride) was revealed on the surface of metal nanoclusters. Similar to thiolates, alkynyls bind linearly to surface Au atoms using their σ-bonds, leading to the formation of two types of surface staple units (PhC≡C-Au-L, L = PhC≡C(-) or 2-pyridylthiolate) on the cluster. The co-presence of three different surface ligands allows the site-specific surface and functional modification of the cluster. The lability of PhC≡C(-) ligands on the cluster was demonstrated, making it possible to keep the metal core intact while removing partial surface capping. Moreover, it was found that ligand exchange on the cluster occurs easily to offer various derivatives with the same metal core but different surface functionality and thus different solubility.

Translating Molecular Recognition into a Pressure Signal to enable Rapid, Sensitive, and Portable Biomedical Analysis

Herein, we demonstrate that a very familiar, yet underutilized, physical parameter—gas pressure—can serve as signal readout for highly sensitive bioanalysis. Integration of a catalyzed gas-generation reaction with a molecular recognition component leads to significant pressure changes, which can be measured with high sensitivity using a low-cost and portable pressure meter. This new signaling strategy opens up a new way for simple, portable, yet highly sensitive biomedical analysis in a variety of settings.

Versatile fabrication of aligned SnO2nanotube arrays by using various ZnO arrays as sacrificial templates

In this paper, we describe an effective two-step method for fabricating aligned SnO2nanotube arrays by using various pre-synthesized ZnO nanorod arrays as sacrificial templates. The composition and structure of as-synthesized SnO2nanotube arrays were analyzed in detail by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Because there is a special epitaxial relation between the SnO2 walls and ZnO templates, the walls building the SnO2nanotubes are highly orientated and nearly single-crystalline. Our present study provides an opportunity to investigate related physical and chemical properties and potential applications of such aligned SnO2nanotubes with nearly single-crystalline nature.

Pentagon-fused hollow fullerene in C78 family retrieved by chlorination.

C(78) is one of the most widely investigated higher fullerenes. Among its huge isomer family, only one non-IPR (IPR = isolated pentagon ring) cage, the C(2)-symmetric (#22010)C(78), was previously stabilized by endohedral derivatization. Here we report a new C(1)-symmetric non-IPR hollow isomer, (#23863)C(78), which was captured as (#23863)C(78)Cl(8) and then subjected to a regioselective substitution reaction with benzyl hydroperoxide to form (#23863)C(78)(OOCH(2)C(6)H(5))Cl(7). The structural connectivity of (#23863)C(78), which contains a pair of fused pentagons, was confirmed by single-crystal X-ray diffraction analysis of the (#23863)C(78)(OOCH(2)C(6)H(5))Cl(7) molecule, which shares the same fullerene core with (#23863)C(78)Cl(8); support for the structure is provided by comparable IR measurements and computation. Theoretical studies suggest that the differences in C-Cl bond length, intermediate stability, and steric effects of the involved molecules account for the chemical regioselectivity of the substitution reaction.

Assembly of silver Trigons into a buckyball-like Ag180 nanocage

Significance Here we present a striking outcome from the alliance between chemistry and mathematics in the design, synthesis, and characterization of a silver cage, Ag180. In principle, the design replaces each carbon atom of C60 with a triplet of argentophilicity-bonded silver atoms to produce a 3.4.6.4 (1,1) polyhedron with sixty 3-gons, ninety 4-gons, twelve 5-gons, and twenty 6-gons. Results from mass spectroscopy suggest an assembly mechanism in solution based on such triplets––the Silver-Trigon Assembly Road (STAR). Indeed, the STAR mechanism may be a general synthetic pathway toward even larger silver polyhedral cages. Besides its fundamental appeal, this synthetic cage may be considered for use as a molecular luminescent thermometer. Buckminsterfullerene (C60) represents a perfect combination of geometry and molecular structural chemistry. It has inspired many creative ideas for building fullerene-like nanopolyhedra. These include other fullerenes, virus capsids, polyhedra based on DNA, and synthetic polynuclear metal clusters and cages. Indeed, the regular organization of large numbers of metal atoms into one highly complex structure remains one of the foremost challenges in supramolecular chemistry. Here we describe the design, synthesis, and characterization of a Ag180 nanocage with 180 Ag atoms as 4-valent vertices (V), 360 edges (E), and 182 faces (F)––sixty 3-gons, ninety 4-gons, twelve 5-gons, and twenty 6-gons––in agreement with Euler’s rule V − E + F = 2. If each 3-gon (or silver Trigon) were replaced with a carbon atom linked by edges along the 4-gons, the result would be like C60, topologically a truncated icosahedron, an Archimedean solid with icosahedral (Ih) point-group symmetry. If C60 can be described mathematically as a curling up of a 6.6.6 Platonic tiling, the Ag180 cage can be described as a curling up of a 3.4.6.4 Archimedean tiling. High-resolution electrospray ionization mass spectrometry reveals that {Ag3}n subunits coexist with the Ag180 species in the assembly system before the final crystallization of Ag180, suggesting that the silver Trigon is the smallest building block in assembly of the final cage. Thus, we assign the underlying growth mechanism of Ag180 to the Silver-Trigon Assembly Road (STAR), an assembly path that might be further employed to fabricate larger, elegant silver cages.

Single‐Crystalline Rhodium Nanosheets with Atomic Thickness

CO confinement strategy for ultrathin Rh nanosheets: CO is introduced as a confining agent to regulate the anisotropic growth of unique 2D structure. The single‐crystalline Rh nanosheets have a thickness of three to five atomic layers and tunable edge length ranging from 500 to 1300 nm. By understanding the formation mechanism, surface‐clean Rh nanosheets are also prepared and display better catalytic performance that their surfactant‐capped nanosheets.