Publications by authors named "Zhi-Lin Yang"

47 Publications

In Situ Raman Study of CO Electrooxidation on Pt(hkl) Single-Crystal Surfaces in Acidic Solution.

Angew Chem Int Ed Engl 2020 Dec 25;59(52):23554-23558. Epub 2020 Oct 25.

College of Energy, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, College of Environment and Ecology, State key Laboratory of Marine Environmental Science, iChEM, Xiamen University, Xiamen, 361005, China.

The adsorption and electrooxidation of CO molecules at well-defined Pt(hkl) single-crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top- and bridge-site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top-site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre-oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti-poisoning and highly effective catalysts.
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http://dx.doi.org/10.1002/anie.202010431DOI Listing
December 2020

Raman study of the photoinduced behavior of dye molecules on TiO() single crystal surfaces.

Chem Sci 2020 Apr 17;11(25):6431-6435. Epub 2020 Apr 17.

Department of Physics, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, College of Energy, College of Materials, Xiamen University Xiamen 361005 China

In dye-sensitized solar cells (DSSCs), the TiO/dye interface significantly affects photovoltaic performance. However, the adsorption and photoinduced behavior of dye molecules on the TiO substrate remains unclear. Herein, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was used to study the adsorption and photoinduced behavior of dye (N719) molecules on different TiO() surfaces. On TiO(001) and TiO(110) surfaces, the SHINERS and mass spectrometry results indicate S[double bond, length as m-dash]C bond cleavage in the anchoring groups of adsorbed N719, whereas negligible bond cleavage occurs on the TiO(111) surface. Furthermore, DFT calculations show the stability of the S[double bond, length as m-dash]C anchoring group on three TiO() surfaces in the order TiO(001) < TiO(110) < TiO(111), which correlated well with the observed photocatalytic activities. This work reveals the photoactivity of different TiO() surface structures and can help with the rational design of DSSCs. Thus, this strategy can be applied to real-time probing of photoinduced processes on semiconductor single crystal surfaces.
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http://dx.doi.org/10.1039/d0sc00588fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159273PMC
April 2020

Unveiling the size effect of Pt-on-Au nanostructures on CO and methanol electrooxidation by in situ electrochemical SERS.

Nanoscale 2020 Mar 24;12(9):5341-5346. Epub 2020 Feb 24.

Ministry of Education Key Laboratory for Analytical Science of Food Safety and Biology, Fujian Provincial Key Laboratory of Analysis and Detection Technology for Food Safety, College of Chemistry, Fuzhou University, Fuzhou, Fujian 350108, China.

In situ monitoring of electrocatalytic processes at solid-liquid interfaces is essential for the fundamental understanding of reaction mechanisms, yet quite challenging. Herein, Pt-on-Au nanocatalysts with a Au-core Pt-satellite superstructure have been fabricated. In such Pt-on-Au nanocatalysts, the Au cores can greatly amplify the Raman signals of the species adsorbed on Pt, allowing the in situ surface-enhanced Raman spectroscopy (SERS) study of the electrocatalytic reactions on Pt. Using the combination of an electrochemical method and in situ SERS, size effects of Pt on the catalytic performance of the core-satellite nanocomposites towards CO and methanol electrooxidation are revealed. It is found that such Pt-on-Au nanocomposites show improved activity and long-term stability for the electrooxidation of CO and methanol with a decrease in the Pt size. This work demonstrates an effective strategy to achieve the in situ monitoring of electrocatalytic processes and to simultaneously boost their catalytic performance towards electrooxidation.
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http://dx.doi.org/10.1039/c9nr10304jDOI Listing
March 2020

Rapid and low-cost quantitative detection of creatinine in human urine with a portable Raman spectrometer.

Biosens Bioelectron 2020 Apr 31;154:112067. Epub 2020 Jan 31.

Department of Physics, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, College of Energy, Xiamen University, Xiamen, 361005, China. Electronic address:

The creatinine concentration of human urine is closely related to human kidney health and its rapid, quantitative, and low-cost detection has always been demanded. Herein, a surface-enhanced Raman spectroscopic (SERS) method for rapid and cost-effective quantification of creatinine concentrations in human urine was developed. A Au nanoparticle solution (Au sol) was used as a SERS substrate and the influence of different agglomerating salts on its sensitivity toward detecting creatinine concentrations was studied and optimized, as well as the effect of both the salt and Au sol concentrations. The variation in creatinine spectra over time on different substrates was also examined, demonstrating reproducible quantitative analysis of creatinine concentrations in solution. By adjusting the pH, a simple liquid-liquid solvent extraction procedure, which extracted creatinine from human urine, was used to increase the SERS detection selectivity toward creatinine in complex matrices. The quantitative results were compared to those obtained with a clinically validated enzymatic "creatinine kit (CK)." The limit of detection (LOD) for the SERS technique was 1.45 mg L, compared with 3.4 mg L for the CK method. Furthermore, cross-comparing the results from the two methods, the average difference was 5.84% and the whole SERS detection process could be completed within 2 min compared with 11 min for the CK, indicating the practicality of the quantitative SERS technique. This novel quantitative technique shows promises as a high-throughput platform for relevant clinical and forensic analysis.
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http://dx.doi.org/10.1016/j.bios.2020.112067DOI Listing
April 2020

Understanding the strain effect of [email protected] nanocatalysts by in situ surface-enhanced Raman spectroscopy.

Chem Commun (Camb) 2019 Jul;55(60):8824-8827

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, College of Materials, Xiamen University, Xiamen 361005, China.

A gap-mode configuration was developed for the in situ SERS study of the structure-activity relationship of [email protected] core-shell nanocatalysts, which show much better performance in the selective oxidation of benzyl alcohol compared to Pd. The in situ SERS results reveal that the tensile strain in the Pd shell could promote the activation of oxygen, thus improving the activity. Such a tensile strain effect decreases with the increase of the Pd shell thickness, leading to a volcano correlation between the activity and the shell thickness.
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http://dx.doi.org/10.1039/c9cc02639hDOI Listing
July 2019

In situ probing electrified interfacial water structures at atomically flat surfaces.

Nat Mater 2019 07 29;18(7):697-701. Epub 2019 Apr 29.

State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China.

Solid/liquid interfaces are ubiquitous in nature and knowledge of their atomic-level structure is essential in elucidating many phenomena in chemistry, physics, materials science and Earth science. In electrochemistry, in particular, the detailed structure of interfacial water, such as the orientation and hydrogen-bonding network in electric double layers under bias potentials, has a significant impact on the electrochemical performances of electrode materials. To elucidate the structures of electric double layers at electrochemical interfaces, we combine in situ Raman spectroscopy and ab initio molecular dynamics and distinguish two structural transitions of interfacial water at electrified Au single-crystal electrode surfaces. Towards negative potentials, the interfacial water molecules evolve from structurally 'parallel' to 'one-H-down' and then to 'two-H-down'. Concurrently, the number of hydrogen bonds in the interfacial water also undergoes two transitions. Our findings shed light on the fundamental understanding of electric double layers and electrochemical processes at the interfaces.
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http://dx.doi.org/10.1038/s41563-019-0356-xDOI Listing
July 2019

Probing the Location of 3D Hot Spots in Gold Nanoparticle Films Using Surface-Enhanced Raman Spectroscopy.

Anal Chem 2019 Apr 4;91(8):5316-5322. Epub 2019 Apr 4.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen , 361005 , China.

Plasmonic "hot spots" play a key role in surface-enhanced Raman scattering (SERS) enabling its ultrahigh surface sensitivity. Thus, precise prediction and control of the location of hot spots in surface nanostructures is of great importance. However, it is difficult to predict the exact location of hot spots due to complex plasmon competition and synergistic effects in three-dimensional (3D) multiparticle surface configurations. In this work, three types of [email protected]@SiO core-shell nanoparticles were prepared and a 3D hot spots matrix was assembled via a consecutive layer on layer deposition method. Combined with SERS, distinct probe molecules were integrated into different layers of the 3D multiparticle nanostructure allowing for the hot spots to be precisely located. Importantly, the hot spots could be controlled and relocated by applying different excitation wavelengths, which was verified by simulations and experimental results. This work proposes a new insight and provides a platform for precisely probing and controlling chemical reactions, which has profound implications in both surface analysis and surface plasmonics.
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http://dx.doi.org/10.1021/acs.analchem.9b00200DOI Listing
April 2019

Probing Interfacial Electronic and Catalytic Properties on Well-Defined Surfaces by Using In Situ Raman Spectroscopy.

Angew Chem Int Ed Engl 2018 Aug 31;57(35):11257-11261. Epub 2018 Jul 31.

The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

Heterogeneous metal interfaces play a key role in determining the mechanism and performance of catalysts. However, in situ characterization of such interfaces at the molecular level is challenging. Herein, two model interfaces, Pd and Pt overlayers on Au single crystals, were constructed. The electronic structures of these interfaces as well as effects of crystallographic orientation on them were analyzed by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) using phenyl isocyanide (PIC) as a probe molecule. A clear red shift in the frequency of the C≡N stretch (ν ) was observed, which is consistent with X-ray photoelectron spectroscopy (XPS) data and indicates that the ultrathin Pt and Pd layers donate their free electrons to the Au substrates. Furthermore, in situ electrochemical SHINERS studies showed that the electronic effects weaken Pt-C/Pd-C bonds, leading to improved surface activity towards CO electrooxidation.
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http://dx.doi.org/10.1002/anie.201805464DOI Listing
August 2018

Shell-Isolated Tip-Enhanced Raman and Fluorescence Spectroscopy.

Angew Chem Int Ed Engl 2018 06 26;57(25):7523-7527. Epub 2018 Apr 26.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces,iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

Tip-enhanced Raman spectroscopy can provide molecular fingerprint information with ultrahigh spatial resolution, but the tip will be easily contaminated, thus leading to artifacts. It also remains a great challenge to establish tip-enhanced fluorescence because of the quenching resulting from the proximity of the metal tip. Herein, we report shell-isolated tip-enhanced Raman and fluorescence spectroscopies by employing ultrathin shell-isolated tips fabricated by atomic layer deposition. Such shell-isolated tips not only show outstanding electromagnetic field enhancement in TERS but also exclude interference by contaminants, thus greatly promoting applications in solution. Tip-enhanced fluorescence has also been achieved using these shell-isolated tips, with enhancement factors of up to 1.7×10 , consistent with theoretical simulations. Furthermore, tip-enhanced Raman and fluorescence signals are acquired simultaneously, and their relative intensities can be manipulated by changing the shell thickness. This work opens a new avenue for ultrahigh resolution surface analysis using plasmon-enhanced spectroscopies.
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http://dx.doi.org/10.1002/anie.201802892DOI Listing
June 2018

Revealing the Role of Interfacial Properties on Catalytic Behaviors by in Situ Surface-Enhanced Raman Spectroscopy.

J Am Chem Soc 2017 08 25;139(30):10339-10346. Epub 2017 Jul 25.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, and ‡Department of Physics, Research Institute for Biomimetics and Soft Matter, Xiamen University , Xiamen 361005, China.

Insightful understanding of how interfacial structures and properties affect catalytic processes is one of the most challenging issues in heterogeneous catalysis. Here, the essential roles of Pt-Au and Pt-oxide-Au interfaces on the activation of H and the hydrogenation of para-nitrothiophenol (pNTP) were studied at molecular level by in situ surface-enhanced Raman spectroscopy (SERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Pt-Au and Pt-oxide-Au interfaces were fabricated through the synthesis of Pt-on-Au and Pt-on-SHINs nanocomposites. Direct spectroscopic evidence demonstrates that the atomic hydrogen species generated on the Pt nanocatalysts can spill over from Pt to Au via the Pt-Au and Pt-TiO-Au interfaces, but would be blocked at the Pt-SiO-Au interfaces, leading to the different reaction pathways and product selectivity on Pt-on-Au and Pt-on-SHINs nanocomposites. Such findings have also been verified by the density functional theory calculation. In addition, it is found that nanocatalysts assembled on pinhole-free shell-isolated nanoparticles (Pt-on-pinhole-free-SHINs) can override the influence of the Au core on the reaction and can be applied as promising platforms for the in situ study of heterogeneous catalysis. This work offers a concrete example of how SERS/SHINERS elucidate details about in situ reaction and helps to dig out the fundamental role of interfaces in catalysis.
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http://dx.doi.org/10.1021/jacs.7b04011DOI Listing
August 2017

In situ dynamic tracking of heterogeneous nanocatalytic processes by shell-isolated nanoparticle-enhanced Raman spectroscopy.

Nat Commun 2017 05 24;8:15447. Epub 2017 May 24.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Surface molecular information acquired in situ from a catalytic process can greatly promote the rational design of highly efficient catalysts by revealing structure-activity relationships and reaction mechanisms. Raman spectroscopy can provide this rich structural information, but normal Raman is not sensitive enough to detect trace active species adsorbed on the surface of catalysts. Here we develop a general method for in situ monitoring of heterogeneous catalytic processes through shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) satellite nanocomposites (Au-core silica-shell nanocatalyst-satellite structures), which are stable and have extremely high surface Raman sensitivity. By combining operando SHINERS with density functional theory calculations, we identify the working mechanisms for CO oxidation over PtFe and Pd nanocatalysts, which are typical low- and high-temperature catalysts, respectively. Active species, such as surface oxides, superoxide/peroxide species and Pd-C/Pt-C bonds are directly observed during the reactions. We demonstrate that in situ SHINERS can provide a deep understanding of the fundamental concepts of catalysis.
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http://dx.doi.org/10.1038/ncomms15447DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5458081PMC
May 2017

Probing the electronic and catalytic properties of a bimetallic surface with 3 nm resolution.

Nat Nanotechnol 2017 02 21;12(2):132-136. Epub 2016 Nov 21.

State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), MOE Key Laboratory of Spectrochemical Analysis &Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

An atomic- and molecular-level understanding of heterogeneous catalysis is required to characterize the nature of active sites and improve the rational design of catalysts. Achieving this level of characterization requires techniques that can correlate catalytic performances to specific surface structures, so as to avoid averaging effects. Tip-enhanced Raman spectroscopy combines scanning probe microscopy with plasmon-enhanced Raman scattering and provides simultaneous topographical and chemical information at the nano/atomic scale from ambient to ultrahigh-vacuum and electrochemical environments. Therefore, it has been used to monitor catalytic reactions and is proposed to correlate the local structure and function of heterogeneous catalysts. Bimetallic catalysts, such as Pd-Au, show superior performance in various catalytic reactions, but it has remained challenging to correlate structure and reactivity because of their structural complexity. Here, we show that TERS can chemically and spatially probe the site-specific chemical (electronic and catalytic) and physical (plasmonic) properties of an atomically well-defined Pd(sub-monolayer)/Au(111) bimetallic model catalyst at 3 nm resolution in real space using phenyl isocyanide as a probe molecule (Fig. 1a). We observe a weakened N≡C bond and enhanced reactivity of phenyl isocyanide adsorbed at the Pd step edge compared with that at the Pd terrace. Density functional theory corroborates these observations by revealing a higher d-band electronic profile for the low-coordinated Pd step edge atoms. The 3 nm spatial resolution we demonstrate here is the result of an enhanced electric field and distinct electronic properties at the step edges.
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http://dx.doi.org/10.1038/nnano.2016.241DOI Listing
February 2017

[Adsorption Characteristics of 2,4-D on UiO-66 from Wastewater].

Huan Jing Ke Xue 2016 Jun;37(6):2202-2210

Beijing Key Laboratory of Water Resource and Environmental Engineering, School of Water Resource and Environment, China University of Geosciences(Beijing), Beijing 100083, China.

With UiO-66 metal organic framework as the adsorbent, the influences of factors such as time, pH value, temperature on the adsorption were studied. The results showed that the adsorption effect was best at pH=4.0 for the adsorption system and the adsorption equilibrium time was 24 h. The equilibrium adsorption capacity increased with the increasing temperature and the optimal temperature should be controlled at 30℃. The adsorption of 2,4-D on UiO-66 followed Langmuir isotherm model and the adsorption kinetics could be better described by pseudo-second-order model. The intraparticle diffusion process was the rate-controlling step for adsorption processes. The results of thermodynamic calculations showed that ΔG<0, ΔH>0, ΔS>0. So the adsorption was a spontaneous, endothermic chemical process with increased randomness. The main interaction forces of adsorption were chemical bonding force and electrostatic interactions force. Results of the study suggested that UiO-66 had the potential ability for 2,4-D removal from wastewater.
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http://dx.doi.org/10.13227/j.hjkx.2016.06.025DOI Listing
June 2016

Correction: Shell-isolated nanoparticle-enhanced Raman spectroscopy study of the adsorption behaviour of DNA bases on Au(111) electrode surfaces.

Analyst 2016 Jun 15;141(12):3925. Epub 2016 Apr 15.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Correction for 'Shell-isolated nanoparticle-enhanced Raman spectroscopy study of the adsorption behaviour of DNA bases on Au(111) electrode surfaces' by Bao-Ying Wen et al., Analyst, 2016, DOI: 10.1039/c6an00180g.
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http://dx.doi.org/10.1039/c6an90033jDOI Listing
June 2016

Shell-isolated nanoparticle-enhanced Raman spectroscopy study of the adsorption behaviour of DNA bases on Au(111) electrode surfaces.

Analyst 2016 Jun 22;141(12):3731-6. Epub 2016 Mar 22.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

For the first time, we used the electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (EC-SHINERS) technique to in situ characterize the adsorption behaviour of four DNA bases (adenine, guanine, thymine, and cytosine) on atomically flat Au(111) electrode surfaces. The spectroscopic results of the various molecules reveal similar features, such as the adsorption-induced reconstruction of the Au(111) surface and the drastic Raman intensity reduction of the ring breathing modes after the lifting reconstruction. As a preliminary study of the photo-induced charge transfer (PICT) mechanism, the in situ spectroscopic results obtained on single crystal surfaces are excellently illustrated with electrochemical data.
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http://dx.doi.org/10.1039/c6an00180gDOI Listing
June 2016

Self-assembly of subwavelength nanostructures with symmetry breaking in solution.

Nanoscale 2016 Feb;8(5):2951-9

State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm for Au nanospheres; 100-160 nm for Ag nanocubes) and meanwhile control the nanogaps through ultrathin silica shells of 1-5 nm thickness. The Raman tag of 4-mercaptobenzoic acid (MBA) assists the self-assembly process and endows the subwavelength asymmetric nanostructures with surface-enhanced Raman scattering (SERS) activity. Moreover, thick silica shells (above 50 nm thickness) can be coated on the self-assembled nanostructures in situ to stabilize the whole nanostructures, paving the way toward bioapplications. Single particle scattering spectroscopy with a 360° polarization resolution is performed on individual Ag nanocube and Au nanosphere dimers, correlated with high-resolution TEM characterization. The asymmetric dimers exhibit strong configuration and polarization dependence Fano resonance properties. Overall, the solution-based self-assembly method reported here is opening up new opportunities to prepare diverse multicomponent nanomaterials with optimal performance.
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http://dx.doi.org/10.1039/c5nr06738cDOI Listing
February 2016

How To Light Special Hot Spots in Multiparticle-Film Configurations.

ACS Nano 2016 Jan 25;10(1):581-7. Epub 2015 Nov 25.

State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University , Xiamen 361005, China.

The precise control over the locations of hot spots in a nanostructured ensemble is of great importance in plasmon-enhanced spectroscopy, chemical sensing, and super-resolution optical imaging. However, for multiparticle configurations over metal films that involve localized and propagating surface plasmon modes, the locations of hot spots are difficult to predict due to complex plasmon competition and synergistic effects. In this work, theoretical simulations based on multiparticle-film configurations predict that the locations of hot spots can be efficiently controlled in the particle-particle gaps, the particle-film junctions, or in both, by suppressing or promoting specific plasmonic coupling effects in specific wavelength ranges. These findings offer an avenue to obtain strong Raman signals from molecules situated on single crystal surfaces and simultaneously avoid signal interference from particle-particle gaps.
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http://dx.doi.org/10.1021/acsnano.5b05605DOI Listing
January 2016

"Smart" Ag Nanostructures for Plasmon-Enhanced Spectroscopies.

J Am Chem Soc 2015 Nov 23;137(43):13784-7. Epub 2015 Oct 23.

State Key Laboratory of Precision Spectroscopy, East China Normal University , Shanghai 200062, China.

Silver is an ideal candidate for surface plasmon resonance (SPR)-based applications because of its great optical cross-section in the visible region. However, the uses of Ag in plasmon-enhanced spectroscopies have been limited due to their interference via direct contact with analytes, the poor chemical stability, and the Ag(+) release phenomenon. Herein, we report a facile chemical method to prepare shell-isolated Ag nanoparticle/tip. The as-prepared nanostructures exhibit an excellent chemical stability and plasmonic property in plasmon-enhanced spectroscopies for more than one year. It also features an alternative plasmon-mediated photocatalysis pathway by smartly blocking "hot" electrons. Astonishingly, the shell-isolated Ag nanoparticles (Ag SHINs), as "smart plasmonic dusts", reveal a ∼1000-fold ensemble enhancement of rhodamine isothiocyanate (RITC) on a quartz substrate in surface-enhanced fluorescence. The presented "smart" Ag nanostructures offer a unique way for the promotion of ultrahigh sensitivity and reliability in plasmon-enhanced spectroscopies.
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http://dx.doi.org/10.1021/jacs.5b09682DOI Listing
November 2015

Electrochemical Tip-Enhanced Raman Spectroscopy.

J Am Chem Soc 2015 Sep 11;137(37):11928-31. Epub 2015 Sep 11.

State Key Laboratory of Physical Chemistry of Solid Surface, The MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, and ‡Department of Physics, Xiamen University , Xiamen 361005, China.

Interfacial properties are highly important to the performance of some energy-related systems. The in-depth understanding of the interface requires highly sensitive in situ techniques that can provide fingerprint molecular information at nanometer resolution. We developed an electrochemical tip-enhanced Raman spectroscopy (EC-TERS) by introduction of the light horizontally to the EC-STM cell to minimize the optical distortion and to keep the TERS measurement under a well-controlled condition. We obtained potential-dependent EC-TERS from the adsorbed aromatic molecule on a Au(111) surface and observed a substantial change in the molecule configuration with potential as a result of the protonation and deprotonation of the molecule. Such a change was not observable in EC-SERS (surface-enhanced), indicating EC-TERS can more faithfully reflect the fine interfacial structure than EC-SERS. This work will open a new era for using EC-TERS as an important nanospectroscopy tool for the molecular level and nanoscale analysis of some important electrochemical systems including solar cells, lithium ion batteries, fuel cells, and corrosion.
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http://dx.doi.org/10.1021/jacs.5b08143DOI Listing
September 2015

Surface Plasmon-Coupled Directional Enhanced Raman Scattering by Means of the Reverse Kretschmann Configuration.

J Phys Chem Lett 2015 Jun 18;6(11):2015-9. Epub 2015 May 18.

∥State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Innovation Center of Chemistry for Energy Materials, Xiamen University, Xiamen 361005, China.

Surface-enhanced Raman scattering (SERS) is a unique analytical technique that provides fingerprint spectra, yet facing the obstacle of low collection efficiency. In this study, we demonstrated a simple approach to measure surface plasmon-coupled directional enhanced Raman scattering by means of the reverse Kretschmann configuration (RK-SPCR). Highly directional and p-polarized Raman scattering of 4-aminothiophenol (4-ATP) was observed on a nanoparticle-on-film substrate at 46° through the prism coupler with a sharp angle distribution (full width at half-maximum of ∼3.3°). Because of the improved collection efficiency, the Raman scattering signal was enhanced 30-fold over the conventional SERS mode; this was consistent with finite-difference time-domain simulations. The effect of nanoparticles on the coupling efficiency of propagated surface plasmons was investigated. Possessing straightforward implementation and directional enhancement of Raman scattering, RK-SPCR is anticipated to simplify SERS instruments and to be broadly applicable to biochemical assays.
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http://dx.doi.org/10.1021/acs.jpclett.5b00666DOI Listing
June 2015

In Situ Monitoring of Electrooxidation Processes at Gold Single Crystal Surfaces Using Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy.

J Am Chem Soc 2015 Jun 11;137(24):7648-51. Epub 2015 Jun 11.

§Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern CH-3012, Switzerland.

Identifying the intermediate species in an electrocatalytic reaction can provide a great opportunity to understand the reaction mechanism and fabricate a better catalyst. However, the direct observation of intermediate species at a single crystal surface is a daunting challenge for spectroscopic techniques. In this work, electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (EC-SHINERS) is utilized to in situ monitor the electrooxidation processes at atomically flat Au(hkl) single crystal electrode surfaces. We systematically explored the effects of crystallographic orientation, pH value, and anion on electrochemical behavior of intermediate (AuOH/AuO) species. The experimental results are well correlated with our periodic density functional theory calculations and corroborate the long-standing speculation based on theoretical calculations in previous electrochemical studies. The presented in situ electrochemical SHINERS technique offers a unique way for a real-time investigation of an electrocatalytic reaction pathway at various well-defined noble metal surfaces.
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http://dx.doi.org/10.1021/jacs.5b04670DOI Listing
June 2015

Vasculogenic mimicry is a prognostic factor for postoperative survival in patients with glioblastoma.

J Neurooncol 2013 May 16;112(3):339-45. Epub 2013 Feb 16.

Department of Neurosurgery, Zhujiang Hospital, National Key Clinic Department, Neurosurgery Institute, Key Laboratory on Brain Function Repair and Regeneration of Guangdong, Southern Medical University, Gongye Road 253, Guangzhou 510282, China.

A previous report has confirmed the existence and clinical significance of vasculogenic mimicry (VM) in glioma. However, its conclusions about the negative clinical significance of VM in glioblastoma are based on a small group of patients and, thus, might be unconvincing. The aim of the present study was to reevaluate the clinical significance of VM in glioblastoma. Patients were classified as VM-positive or VM-negative according to CD34 and periodic acid-Schiff staining. The association between VM and the clinical characteristics of the patients was analyzed. Univariate and multivariate analyses were carried out to identify the independent prognostic factors for overall survival using the Cox regression hazard model. Survival times were estimated using the Kaplan-Meier method and compared using the log-rank test. Of all 86 glioblastomas, 23 were found to have VM. The presence of VM in glioblastoma was not associated with gender, age, Karnofsky performance status, hydrocephalus, tumor burden, microvessel density, tumor relapse, or the extent of tumor resection. The univariate and multivariate analyses revealed that VM is an independent prognostic factor for overall survival. The median survival time for patients with VM was 11.17 months compared with 16.10 months for those without VM (P = 0.017). In addition to VM, an age of 65 years or older, a KPS of 60 or less, a large tumor burden are significant prognostic factors for patient survival. Our data suggest that VM might be an independent adverse prognostic factor in newly diagnosed GBM, further prospective studies are needed to answer this question.
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http://dx.doi.org/10.1007/s11060-013-1077-7DOI Listing
May 2013

Surface analysis using shell-isolated nanoparticle-enhanced Raman spectroscopy.

Nat Protoc 2013 Jan 13;8(1):52-65. Epub 2012 Dec 13.

State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China.

Surface-enhanced Raman scattering (SERS) is a powerful fingerprint vibrational spectroscopy with a single-molecule detection limit, but its applications are generally restricted to 'free-electron-like' metal substrates such as Au, Ag and Cu nanostructures. We have invented a shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique, using Au-core silica-shell nanoparticles ([email protected](2) NPs), which makes SERS universally applicable to surfaces with any composition and any morphology. This protocol describes how to prepare shell-isolated nanoparticles (SHINs) with different well-controlled core sizes (55 and 120 nm), shapes (nanospheres, nanorods and nanocubes) and shell thicknesses (1-20 nm). It then describes how to apply SHINs to Pt and Au single-crystal surfaces with different facets in an electrochemical environment, on Si wafer surfaces adsorbed with hydrogen, on ZnO nanorods, and on living bacteria and fruit. With this method, SHINs can be prepared for use in ~3 h, and each subsequent procedure for SHINERS measurement requires 1-2 h.
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http://dx.doi.org/10.1038/nprot.2012.141DOI Listing
January 2013

Epigastric heteropagus conjoined twins: two case studies and associated DNA analysis.

Clinics (Sao Paulo) 2012 ;67(5):527-9

Sun Yat-sen University, The First Affiliated Hospital of Guangzhou, Department of Pediatric Surgery, People's Republic of China.

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http://dx.doi.org/10.6061/clinics/2012(05)22DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351264PMC
February 2013

Synthesis, characterization, and 3D-FDTD simulation of [email protected] nanoparticles for shell-isolated nanoparticle-enhanced Raman spectroscopy.

Langmuir 2012 Jun 11;28(24):9140-6. Epub 2012 May 11.

State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

Au-seed Ag-growth nanoparticles of controllable diameter (50-100 nm), and having an ultrathin SiO(2) shell of controllable thickness (2-3 nm), were prepared for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Their morphological, optical, and material properties were characterized; and their potential for use as a versatile Raman signal amplifier was investigated experimentally using pyridine as a probe molecule and theoretically by the three-dimensional finite-difference time-domain (3D-FDTD) method. We show that a SiO(2) shell as thin as 2 nm can be synthesized pinhole-free on the Ag surface of a nanoparticle, which then becomes the core. The dielectric SiO(2) shell serves to isolate the Raman-signal enhancing core and prevent it from interfering with the system under study. The SiO(2) shell also hinders oxidation of the Ag surface and nanoparticle aggregation. It significantly improves the stability and reproducibility of surface-enhanced Raman scattering (SERS) signal intensity, which is essential for SERS applications. Our 3D-FDTD simulations show that Ag-core SHINERS nanoparticles yield at least 2 orders of magnitude greater enhancement than Au-core ones when excited with green light on a smooth Ag surface, and thus add to the versatility of our SHINERS method.
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http://dx.doi.org/10.1021/la3005536DOI Listing
June 2012

Extraordinary enhancement of Raman scattering from pyridine on single crystal Au and Pt electrodes by shell-isolated Au nanoparticles.

J Am Chem Soc 2011 Oct 16;133(40):15922-5. Epub 2011 Sep 16.

State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

We used shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to systematically study the adsorption of pyridine on low-index Au(hkl) and Pt(hkl) single crystal electrodes. Our gold-core silica-shell nanoparticles ([email protected](2) NPs) boost the intensity of Raman scattering from molecules adsorbed on atomically flat surfaces. The average enhancement factor reaches 10(6) for Au(110) and 10(5) for Pt(110), which is comparable to or even greater than that obtained for bare gold NPs (a widely adopted SERS substrate). 3D-FDTD simulations reveal that this large enhancement is due to the transfer of the "hotspots" from NP-NP gaps to NP-surface gaps. We also found that the SHINERS intensity strongly depends on the surface crystallographic orientation, with differences up to a factor of 30. Periodic DFT calculations and theoretical analysis of dielectric functions indicate that this facet-dependence is predominantly governed by the dielectric property of the surface. The results presented in this work may open up new approaches for the characterization of adsorbates and reaction pathways on a wide range of smooth surfaces.
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http://dx.doi.org/10.1021/ja2074533DOI Listing
October 2011

Synthesis and characterization of gold nanoparticles coated with ultrathin and chemically inert dielectric shells for SHINERS applications.

Appl Spectrosc 2011 Jun;65(6):620-6

State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, China.

We very recently reported a new spectroscopic application for expanding the versatility of surface Raman called "shell-isolated nanoparticle-enhanced Raman spectroscopy" or "SHINERS". The most important and most difficult part of the SHINERS experiment is the effective transfer of the strong electromagnetic field from a gold core through the isolating silica or alumina shell to the probed surface. For this it is essential that the chemically inert dielectric shell be ultrathin (2-5 nm) yet pinhole-free. Herein we describe experimental and theoretical aspects of our SHINERS method in more detail. We provide a protocol for the synthesis and characterization of optimized shell-isolated nanoparticles (SHINs), and we examine the advantages of SHINERS nanoparticles over bare gold nanoparticles. We also present high-quality Raman spectra obtained from gold and platinum single-crystal surfaces in an electrochemical environment by our SHINERS technique. SHINERS is a simple and cost-effective approach that expands the flexibility of surface-enhanced Raman scattering (SERS) for an unprecedented diversity of applications in materials and surface sciences.
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http://dx.doi.org/10.1366/10-06140DOI Listing
June 2011

Shell-isolated nanoparticle-enhanced Raman spectroscopy: expanding the versatility of surface-enhanced Raman scattering.

Annu Rev Anal Chem (Palo Alto Calif) 2011 ;4:129-50

State Key Laboratory of Physical Chemistry of Solid Surfaces, Key Laboratory of Analytical Sciences and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Surface-enhanced Raman scattering (SERS) is a powerful technique for detection and characterization because of its extremely high sensitivity and the rich structural information that it can offer. However, most SERS substrates are composed of Au, Ag, or Cu, and a lack of substrate generality has greatly limited the breadth of the use of SERS. Recently, we have devised a method by which SERS can be obtained from virtually any surface. Au nanoparticles are coated with ultrathin silica shells. The Au core provides Raman signal enhancement; the silica shell prevents the core from coming into direct contact with probe/analyte molecules or the surface over which these particles are spread (i.e., prevents the contamination of the chemical system under study). In the present review, we expand upon previous discussion of the enhancement mechanism; procedures for the synthesis and characterization of our nanoparticles; and applications in surface chemistry, electrochemistry, and inspection.
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http://dx.doi.org/10.1146/annurev.anchem.111808.073632DOI Listing
October 2011

Tunable SERS from aluminium nanohole arrays in the ultraviolet region.

Chem Commun (Camb) 2011 Apr 21;47(13):3909-11. Epub 2011 Feb 21.

Department of Physics, Xiamen University, Xiamen, 361005, China.

Ordered Al nanohole arrays for tunable UV-SERS are theoretically proposed and simulated by using FDTD method. The properly designed Al nanohole arrays produce stable and predictable Raman enhancement under the deep UV laser illumination. The SERS enhancement factor as high as 5 to 6 orders of magnitude is attained in the optimal geometry. The correlation between the SERS and EOT is studied in detail.
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http://dx.doi.org/10.1039/c0cc05311bDOI Listing
April 2011

Core-shell nanoparticle based SERS from hydrogen adsorbed on a rhodium(111) electrode.

Chem Commun (Camb) 2011 Feb 7;47(7):2023-5. Epub 2011 Jan 7.

State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

We present the first in situ surface Raman spectra of hydrogen on rhodium under electrochemical conditions using gold-core rhodium-shell ([email protected]) nanoparticles for SERS or gold-core silica-shell ([email protected](2)) nanoparticles for SHINERS. The advantage of SHINERS lies in the versatility to study single crystal surfaces such as the H-Rh(111) system.
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http://dx.doi.org/10.1039/c0cc04049eDOI Listing
February 2011
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