Optical Interference-Free Surface-Enhanced Raman Scattering CO-Nanotags for Logical Multiplex Detection of Vascular Disease-Related Biomarkers

Matrix metalloproteinases (MMPs), specifically MMP-2, MMP-7, and MMP-9, have been discovered to be linked to many forms of vascular diseases such as stroke, and their detection is crucial to facilitate clinical diagnosis. In this work, we prepared a class of optical interference-free SERS nanotags (CO-nanotags) that can be used for the purpose of multiplex sensing of different MMPs. Multiplex detection with the absence of cross-talk was achieved by using CO-nanotags with individual tunable intrinsic Raman shifts of CO in the 1800–2200 cm^–1 region determined by the metal core and ligands of the metal carbonyl complex. Boolean logic was used as well to simultaneously probe for two proteolytic inputs. Such nanotags offer the advantages of convenient detection of target nanotags and high sensitivity as validated in the ischemia rat model

Facile Synthesis of [101]-Oriented Rutile TiO₂ Nanorod Array on FTO Substrate with a Tunable Anatase–Rutile Heterojunction for Efficient Solar Water Splitting

Generating a sustainable energy source through photoelectrochemical (PEC) water splitting requires a suitable photocatalyst. A [101]-oriented rutile TiO₂ nanorod (NR) array in heterojunction with anatase on a fluorine-doped tin oxide (FTO) substrate is successfully prepared using a facile single-step hydrothermal process. The presence of anatase phase over the predominant rutile NRs’ surface is confirmed by transmission electron microscopy and tip-enhanced Raman spectroscopy. Solar water-splitting performances of anatase–rutile heterojunction with low energy (101) and high energy (001) rutile facets are compared. The low energy (101) facet rutile–anatase heterojunction shows higher photoconversion efficiency of 1.39% at 0.49 V_RHE than the high energy (001) facet rutile–anatase heterojunction (0.37% at 0.73 V_RHE). The mechanism for enhanced photocatalytic activity of the low energy (101) facet rutile–anatase heterojunction has been proposed. The role of NaCl in tuning the anatase portion, morphology, and PEC water-splitting performance has also been studied

Self-Assembled Chiral Gold Supramolecules with Efficient Laser Absorption for Enantiospecific Recognition of Carnitine

Stereospecific recognition of chiral molecules is ubiquitous in chemical and biological systems, thus leading to strong demand for the development of enantiomeric drugs, enantioselective sensors, and asymmetric catalysts. In this study, we demonstrate the ratio of d-Cys and l-Cys playing an important role in determining the optical properties and the structures of self-assembled Cys–Au­(I) supramolecules prepared through a simple reaction of tetrachloroaurate­(III) with chiral cysteine (Cys). The irregularly shaped −[d-Cys–Au­(I)]_<i>n</i>– or – [l-Cys–Au­(I)]_<i>n</i>– supramolecules with a size larger than 500 nm possessing strong absorption in the near-UV region and chiroptical characteristics were only obtained from the reaction of Au­(III) with d-Cys or l-Cys. On the other hand, spindle-shaped −[d/l-Cys–Au­(I)]_<i>n</i>– supramolecules were formed when using Au­(III) with mixtures of d/l-Cys. Our results have suggested that Au­(I)···Au­(I) aurophilic interactions, and stacked hydrogen bonding and zwitterionic interactions between d/l-Cys ligands are important in determining their structures. The NaBH₄-mediated reduction induces the formation of photoluminescent gold nanoclusters (Au NCs) embedded in the chiral −[d-Cys–Au­(I)]_<i>n</i>– or −[l-Cys–Au­(I)]_<i>n</i>– supramolecules with a quantum yield of ca. 10%. The as-formed Au NCs/–[d-Cys–Au­(I)]_<i>n</i>– and Au NCs/–[l-Cys–Au­(I)]_<i>n</i>– are an enantiospecific substrate that can trap l-carnitine and d-carnitine, respectively, and function as a nanomatrix for surface-assisted laser desorption/ionization mass spectrometry (LDI-MS). The high absorption efficiency of laser energy, analyte-binding capacity, and homogeneity of the Au NCs/–[Cys–Au­(I)]_<i>n</i>– allow for quantitation of enantiomeric carnitine down to the micromolar regime with high reproducibility. The superior efficiency of the Au NCs/–[d-Cys–Au­(I)]_<i>n</i>– substrate has been further validated by quantification of l-carnitine in dietary supplements with accuracy and precision. Our study has opened a new avenue for chiral quantitation of various analytes through LDI-MS using metal nanocomposites consisting of NCs and metal–ligand complexes

Simple Replacement Reaction for the Preparation of Ternary Fe_1–<i>x</i>PtRu_<i>x</i> Nanocrystals with Superior Catalytic Activity in Methanol Oxidation Reaction

The finding of new metal alloyed nanocrystals (NCs) with high catalytic activity and low cost to replace PtRu NCs is a critical step toward the commercialization of fuel cells. In this work, a simple cation replacement reaction was utilized to synthesize a new type of ternary Fe_1–<i>x</i>PtRu_<i>x</i> NCs from binary FePt NCs. The detailed structural transformation from binary FePt NCs to ternary Fe_1–<i>x</i>PtRu_<i>x</i> NCs was analyzed by X-ray absorption spectroscopy (XAS). Ternary Fe₃₅Pt₄₀Ru₂₅, Fe₃₁Pt₄₀Ru₂₉, and Fe₁₇Pt₄₀Ru₄₃ NCs exhibit superior catalytic ability to withstand CO poisoning in methanol oxidation reaction (MOR) than do binary NCs (FePt and J-M PtRu). Also, the Fe₃₁Pt₄₀Ru₂₉ NCs had the highest alloying extent and the lowest onset potential among the ternary NCs. Furthermore, the origin for the superior CO resistance of ternary Fe_1–<i>x</i>PtRu_<i>x</i> NCs was investigated by determining the adsorption energy of CO on the NCs’ surfaces and the charge transfer from Fe/Ru to Pt using a simulation based on density functional theory. The simulation results suggested that by introducing a new metal into binary PtRu/PtFe NCs, the anti-CO poisoning ability of ternary Fe_1–<i>x</i>PtRu_<i>x</i> NCs was greatly enhanced because the bonding of CO–Pt on the NCs’ surface was weakened. Overall, our experimental and simulation results have indicated a simple route for the discovery of new metal alloyed catalysts with superior anti-CO poisoning ability and low usage of Pt and Ru for fuel cell applications

Unraveling the Structure of Magic-Size (CdSe)₁₃ Cluster Pairs

Cadmium selenide is a II–VI semiconductor model system known for its nanoparticle preparation, growth mechanism, luminescence properties, and quantum confinement studies. For the past 2 decades, various thermodynamically stable “magic-size nanoclusters (MSCs)” of CdSe have been observed, isolated, and theoretically calculated. Nevertheless, none of the proposed structures were experimentally confirmed due to the small crystal domains beyond the diffraction limit. With a combination of nondestructive SAXS, WAXS, XRD, XPS, EXAFS, and MAS NMR techniques, we were able to verify the phase transformation, shape, size dimension, local bonding, and chemical environments of (CdSe)₁₃ nanoclusters, which are indicative of a paired cluster model. These experimental results are consistent with the size, shape, bond lengths, dipole moment, and charge densities of the proposed “paired-tubular geometry” predicted by computational approaches. In this article, we revisit the formation pathway of the mysterious (CdSe)₁₃ nanoclusters and propose a paired cluster structure model for better understanding of II–VI semiconductor nanoclusters