Chuanping Li

Graphene Oxide-Supported Ag Nanoplates as LSPR Tunable and Reproducible Substrates for SERS Applications with Optimized Sensitivity.

Nanoparticles and nanohybrids with well-defined structures, along with tunable localized surface plasmon resonance (LSPR) properties and optimized sensitivity, are crucial and highly desired for surface-enhanced Raman spectroscopy (SERS) applications. In this article, we report on a very promising and flexible SERS platforms with a tunable LSPR response and sensitivity based on Ag nanoplates and graphene oxide (GO). The SERS detection sensitivity can be easily optimized and significantly improved by fine-tuning the LSPR band of the Ag nanoplate/GO substrates (to enhance the SERS response) during sample preparation. We applied the as-prepared SERS platform for sensitive SERS detection of 4-mercaptobenzoic acid and 4-aminothiophenol and found that the SERS signal varied markedly (by ∼10-15-fold) with the fine-tuning of the LSPR band. The SERS enhancement factor of the Ag nanoplate/GO complexes was more than 10(4) times larger than that obtained using spherical Ag nanoparticles. The as-prepared Ag nanoplate/GO platforms, because of their excellent stability and tunable LSPR properties, will find promising practical SERS applications.

Single-cell pH imaging and detection for pH profiling and label-free rapid identification of cancer-cells

Single-cell pH-sensing and accurate detection and label-free fast identification of cancer-cells are two long-standing pursuits in cell and life science, as intracellular pH plays a crucial role in many cellular events and fates, while the latter is vital for early cancer theranostics. Numerous methods based on functionalized nanoparticles and fluorescence probes have been developed for cell pH-sensing, but are often hindered for single-cell studies by their main drawbacks of complicated probe preparation and labeling, low sensitivity and poor reproducibility. Here we report a simple and reliable method for single-cell pH imaging and sensing by innovative combined use of UV-Vis microspectroscopy and common pH indicators. Accurate and sensitive pH detection on single-cell or sub-cell level with good reproducibility is achieved by the method, which enables facile single-cell pH profiling and label-free rapid identification of cancer-cells (due to distinguishable intracellular pH levels) for early cancer diagnosis, and may open a new avenue for pH-related single-cell studies.

Free-Standing Monolayered Metallic Nanoparticle Networks as Building Blocks for Plasmonic Nanoelectronic Junctions

The effective coupling of optical surface plasmons (SPs) and electron transport in a plasmonic-electronic device is one of the fundamental issues in nanoelectronics and the emerging field of plasmonics, and offer promise in providing a solution to next generation nanocircuits in which all coupling is in the near field. Attempts toward this end, however, are limited because of the integration challenge to compatible nanodevices. To date, direct electrical detection of SP-electron coupling from metallic nanostructures alone are not reported, and thus it remains a great experimental challenge. In this paper, we succeed in preparing a new suspended-film-type nanoelectronic junction, in which free-standing 2D fractal nanoparticle networks act as plasmonically active nanocomponents. Direct electrical detection of optical collective SPs was evidenced by photocurrent response of the junction upon illumination. Room-temperature I-V characteristics, differing from nonlinear to Ohmic behaviors, are found to be sensitive to the nanometer-scale morphology changes of the nanomembranes. The finding and approach may enable the development of advanced plasmonic nanocircuits and new nanoelectronics, nanophotonics, and (solar) energy applications.

Shell Thickness Engineering Significantly Boosts the Photocatalytic H2 Evolution Efficiency of CdS/CdSe Core/Shell Quantum Dots

Colloidal semiconductor quantum dots (QDs) have recently emerged as a good candidate for photocatalytic hydrogen (H2) evolution in water. A further understanding of the factors that can affect and boost the catalytic activity of the QD-based H2-generating system is of great importance for the future design of such systems for practical use. Here, we report on the fine shell thickness engineering of colloidal CdS/CdSe core/shell QDs and its effect on the photocatalytic H2 production in water. Our results show that, with the proper shell thickness, the H2 photogeneration quantum yield (ΦH2) of CdS/CdSe core/shell QDs could reach 30.9% under the illumination of 420 nm light, which is 49% larger than that of the CdS core. Furthermore, the underlying mechanism has also been tentatively proposed and discussed.

Bifunctional plasmonic colloidosome/graphene oxide-based floating membranes for recyclable high-efficiency solar-driven clean water generation

Utilizing plasmonic nano-particles/structures for solar water evaporation has aroused increasing interest; however, large-scale methods are desired to boost the efficiency and improve the practicality of solar steam generation. We developed a membrane-supported floating solar steam generation system based on graphene oxide and a multiscale plasmonic nanostructure; the latter is a micrometer-sized colloidosome that was assembled from hollow and porous Ag/Au nanocubes. By taking advantage of multiscale plasmonic coupling of the particles, an extremely high solar thermal conversion efficiency up to 92% at 10 kW·m−2 (with a water evaporation rate reaching 12.96 kg·m−2·h−1) can be achieved. The TiO2 nanoparticle-modified floating system is also capable of high-efficiency dye degradation in organic-polluted water, rendering such a membrane system recyclable and scalable for practical and versatile solar-driven generation of clean water.

Pd/Ag nanosheet as a plasmonic sensing platform for sensitive assessment of hydrogen evolution reaction in colloid solutions

A nanoplasmonic hydrogen-sensing system based on palladium/silver nanosheets (Pd/Ag NSs) was developed and used for sensitive assessment of the hydrogen evolution reaction (HER) in colloid solutions. As a model HER system, the semiconductor CdS/CdSe core/shell quantum dot (QD)-based hydrogen-producing colloidal system was used, and the HER performances of QDs with two different surface coatings were assessed in this study. In the sensing system, the photocatalytically generated hydrogen reacts with Pd/Ag NSs, resulting in a gradual red-shift of localized surface plasmon resonance, which to a certain degree is almost linearly proportional to the amount of hydrogen generated. Such a nanoplasmonic hydrogen sensing platform would be useful as an alternative for optical assessment and fast selection of a highly efficient and cost-effective solar hydrogen generation system for practical applications.

Plasmonics Yields Efficient Electron Transport via Assembly of Shell-Insulated Au Nanoparticles

Summary Junctions built from metallic nanoparticles (NPs) can circumvent the diffraction limit and combine molecular/nanoelectronics with plasmonics. However, experimental advances in plasmon-assisted electron transport at the nanoscale have been limited. We construct junctions of a robust, molecule-free, suspended film, built solely from AuNPs, capped by SiO2 shells (Au@SiO2), which give insulating tunneling gaps up to 3.6 nm between the NPs. Current measured across monolayers of such AuNPs shows ultra-long-range, plasmon-enabled electron transport (P-transport), beyond the range of normal electron tunneling across insulators. This finding challenges the present understanding of electron transport in such systems and opens possibilities for future combinations of plasmonics and nanoelectronics.

Boosting Electrocatalytic Oxygen Evolution Performance of Ultrathin Co/Ni-MOF Nanosheets via Plasmon-Induced Hot Carriers

Ultrathin metal-organic framework (MOF) nanosheets with large active sites and superior catalytic properties have attracted extensive interests and are promising for oxygen evolution reaction (OER) for water splitting. Herein, we report a novel and highly efficient hetero-nanostructured OER system based on plasmonic Au nanoparticles (NPs) and ultrathin semiconductor-like Co/Ni-MOF nanosheets. The OER performance of the hybrid system can be tuned (by varying the AuNP sizes) and the oxidation current significantly enhanced to ∼10-fold with incorporated AuNPs of ∼20 nm. An onset overpotential (η) of only 0.33 V was achieved under light illumination, which was much lower than the pure Ni/Co-MOF (0.48 V). Further analysis revealed the key role of the plasmonically induced hot holes (via electric- and combined photoexcitation) in boosting the OER performance of the resulting system. The finding and the proposed concept provide a new insight for understanding the plasmon enhancements in catalysis and may open a new avenue to design MOF hetero-nanostructures with high performance for photoelectrocatalysis.

Controllable Shrinking of Glass Capillary Nanopores Down to Sub-10 nm by Wet-Chemical Silanization for Signal-Enhanced DNA Translocation

Diameter is a major concern for nanopore based sensing. However, directly pulling glass capillary nanopore with diameter down to sub-10 nm is very difficult. So, post treatment is sometimes necessary. Herein, we demonstrate a facile and effective wet-chemical method to shrink the diameter of glass capillary nanopore from several tens of nanometers to sub-10 nm by disodium silicate hydrolysis. Its benefits for DNA translocation are investigated. The shrinking of glass capillary nanopore not only slows down DNA translocation, but also enhances DNA translocation signal and signal-to-noise ratio significantly (102.9 for 6.4 nm glass nanopore, superior than 15 for a 3 nm silicon nitride nanopore). It also affects DNA translocation behaviors, making the approach and glass capillary nanopore platform promising for DNA translocation studies.