Shell-isolated Nanoparticle Research Articles

SHINERS Study of Chloride Order-Disorder Phase Transition and Solvation of Cu(100).

Shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) are used to probe Cl- adsorption and the order-disorder phase transition associated with the c(2 × 2) Cl- adlayer on Cu(100) in acid media. A two-component ν(Cu-Cl) vibrational band centered near 260 ± 1 cm-1 is used to track the potential dependence of Cl- adsorption. The potential dependence of the dominant 260 cm-1 component tracks the coverage of the fluctional c(2 × 2) Cl- phase on terraces in good agreement with the normalized intensity of the c(2 × 2) superstructure rods in prior surface X-ray diffraction (SXRD) studies. As the c(2 × 2) Cl- coverage approaches saturation, a second ν(Cu-Cl) component mode emerges between 290 and 300 cm-1 that coincides with the onset and stiffening of step faceting where Cl- occupies the threefold hollow sites to stabilize the metal kink saturated Cu <100> step edge. The formation of the c(2 × 2) Cl- adlayer is accompanied by the strengthening of ν(O-H) stretching modes in the adjacent non-hydrogen-bonded water at 3600 cm-1 and an increase in hydronium concentration evident in the flanking H2O modes at 3100 cm-1. The polarization of the water molecules and enrichment of hydronium arise from the combination of Cl- anionic character and lateral templating provided by the c(2 × 2) adlayer, consistent with SXRD studies. At negative potentials, Cl- desorption occurs followed by development of a sulfate νs(S═O) band. Below -1.1 V vs Hg/HgSO4, a new 200 cm-1 mode emerges congruent with hydride formation and surface reconstruction reported in electrochemical scanning tunneling microscopy studies.

Alternative nano-lithographic tools for shell-isolated nanoparticle enhanced Raman spectroscopy substrates.

Chemically synthesized metal nanoparticles (MNPs) have been widely used as surface-enhanced Raman spectroscopy (SERS) substrates for monitoring catalytic reactions. In some applications, however, the SERS MNPs, besides being plasmonically active, can also be catalytically active and result in Raman signals from undesired side products. The MNPs are typically insulated with a thin (∼3 nm), in principle pin-hole-free shell to prevent this. This approach, which is known as shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), offers many advantages, such as better thermal and chemical stability of the plasmonic nanoparticle. However, having both a high enhancement factor and ensuring that the shell is pin-hole-free is challenging because there is a trade-off between the two when considering the shell thickness. So far in the literature, shell insulation has been successfully applied only to chemically synthesized MNPs. In this work, we alternatively study different combinations of chemical synthesis (bottom-up) and lithographic (top-down) routes to obtain shell-isolated plasmonic nanostructures that offer chemical sensing capabilities. The three approaches we study in this work include (1) chemically synthesized MNPs + chemical shell, (2) lithographic substrate + chemical shell, and (3) lithographic substrate + atomic layer deposition (ALD) shell. We find that ALD allows us to fabricate controllable and reproducible pin-hole-free shells. We showcase the ability to fabricate lithographic SHINER substrates which report an enhancement factor of 7.5 × 103 ± 17% for our gold nanodot substrates coated with a 2.8 nm aluminium oxide shell. Lastly, by introducing a gold etchant solution to our fabricated SHINER substrate, we verified that the shells fabricated with ALD are truly pin-hole-free.

Facet-dependent adsorption of aromatic organoarsenicals on hematite: The mechanism and environmental impact

Aromatic organoarsenic feed additives have been extensively used in poultry and livestock farming; however, a risk of releasing toxic inorganic arsenic exists when they are exposed to the environment. An in-depth understanding of the adsorption -migration behavior of aromatic organoarsenicals on environmental media is limited. In this study, p-arsanilic acid (p-ASA) and roxarsone (ROX) were considered as examples to systematically study their adsorption behaviors on the surface of hematite, a representative iron oxide in soil. By comparing the adsorption abilities and adsorption kinetics of hematite exposed with different facets (hexagonal nanoplates, HNPs, mainly exposed with {001} facets and hexagonal nanocubes, HNCs, exposed with {012} facets), combined with in situ shell-isolated nanoparticle enhanced Raman spectroscopy characterization and density functional theory simulation, the facet-dependent adsorption performance was observed and the mechanism revealed. The results showed that p-ASA formed a bidentate binuclear complex on HNCs and HNPs, whereas ROX formed monodentate mononuclear and bidentate binuclear configurations on the {001} and {012} facets, respectively. These differences not only lead to facet-dependent adsorption capacities but also affect their stability, as verified by sequential extraction experiments, affecting the environmental behavior and fate of aromatic organoarsenicals. This study not only provides insights into the environmental behavior of aromatic organoarsenicals but also offers theoretical support for the development of functional adsorbents and remediation strategies.

Rethinking the Role of Formerly Sub-Sufficient Industrial/Synthesized SEI Additive Compounds - a New Perspective

In order to improve the performance of lithium-ion batteries (LIBs), novel electrolytes are of primary importance. Recently, fluorinated cyclic phosphazene derivatives in combination with fluoroethylene carbonate (FEC) are mentioned in the literature as a promising electrolyte additive combination, which can decompose to form a dense, uniform, and thin protective layer on the surface of the anode and cathode electrode.[1,2] Additionally, suppressing further electrolyte decomposition and electrode corrosion, thus protecting the structural destruction of the electrodes, are mentioned within this electrolyte composition.[1–3] Furthermore, galvanostatic charge and discharge experiments with different cell composition materials demonstrate that fluorinated cyclic phosphazene compounds as additional additive material tend to improve cycling stability.[1,3,4] Although the electrochemical aspects of cyclic fluorinated phosphazene compounds combined with FEC are briefly introduced, it is still not fully clear how these two compound classes interact constructively during operation mode. Thus, the positive synergistic effect of FEC/Hexafluorocyclotriphosphazene (HFPN)-derivatives on the electrochemical performance during cell operation is not enlightened. The focus of this study is to investigate the complementary effect of FEC and ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN) as additive compounds in an aprotic organic electrolyte in LiNi0.5Co0.2Mn0.3O (NCM523) SiOx/C full cells. Furthermore, the formation mechanism of lithium ethyl methyl carbonate (LEMC)-EtPFPN interfacial products and the reaction mechanism of lithium alkoxide with EtPFPN are proposed and supported with DFT measurements. Additionally, a new effect of FEC regarding the SEI formation will be introduced. The EtPFPN decomposition compounds in the electrolyte after the SEI formation have been investigated via gas chromatography-mass spectrometry (GC-MS) and gas chromatography-high resolution mass spectrometry (GC-HRMS). The electrode electrolyte interface investigation of the SEI has been performed via in-situ shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and scanning electron microscopy (SEM). Constant current cycling is conducted, and in-situ Raman measurements characterize the deposition of electrolyte components and LEMC-EtPFPN traces on the SiOx/C anode material during the SEI formation. Finally, the interplay between EC, EMC, Li-alkoxide, LEMC, FEC, and EtPFPN has been visualized schematically via a reaction mechanism postulated based on analytical data of the electrolyte.[1] A. Ghaur, C. Peschel, I. Dienwiebel, L. Haneke, L. Du, L. Profanter, A. Gomez‐Martin, M. Winter, S. Nowak, T. Placke, Adv Energy Mater 2023, 2203503.[2] J. Liu, X. Song, L. Zhou, S. Wang, W. Song, W. Liu, H. Long, L. Zhou, H. Wu, C. Feng, Z. Guo, Nano Energy 2018, 46, 404–414.[3] Q. Liu, Z. Chen, Y. Liu, Y. Hong, W. Wang, J. Wang, B. Zhao, Y. Xu, J. Wang, X. Fan, L. Li, H. bin Wu, Energy Storage Mater 2021, 37, 521–529.[4] Y.-H. Liu, M. Okano, T. Mukai, K. Inoue, M. Yanagida, T. Sakai, J Power Sources 2016, 304, 9–14.

Surface-enhanced fluorescence for lipopolysaccharide analysis based on shell-isolated nanoparticle

Lipopolysaccharide (LPS) as the component of cell membrane on gram-negative bacteria played a central role on inflammatory inducer to stimulate a multi-system host response. Herein, a surface-enhanced fluorescent (SEF) sensor was developed for LPS analysis based on shell-isolated nanoparticles (SHINs). The fluorescent signal of CdTe quantum dots (QDs) was amplified by silica shell-coated Au nanoparticles (Au NPs). The 3D finite-difference time-domain (3D-FDTD) simulation revealed that this enhancement was due to local electric field amplification. This method has a linear detection range of 0.1–20 μg/mL and a detection limit of 64 ng/mL for LPS. Furthermore, the developed method was successfully applied for LPS analysis in milk and human serum sample. The results indicated that the as-prepared sensor has significant potential for selective detection of LPS in biomedical diagnosis and food safety.

In situ electrochemical Raman spectroscopy and ab initio molecular dynamics study of interfacial water on a single-crystal surface.

The dynamics and chemistry of interfacial water are essential components of electrocatalysis because the decomposition and formation of water molecules could dictate the protonation and deprotonation processes on the catalyst surface. However, it is notoriously difficult to probe interfacial water owing to its location between two condensed phases, as well as the presence of external bias potentials and electrochemically induced reaction intermediates. An atomically flat single-crystal surface could offer an attractive platform to resolve the internal structure of interfacial water if advanced characterization tools are developed. To this end, here we report a protocol based on the combination of in situ Raman spectroscopy and ab initio molecular dynamics (AIMD) simulations to unravel the directional molecular features of interfacial water. We present the procedures to prepare single-crystal electrodes, construct a Raman enhancement mode with shell-isolated nanoparticle, remove impurities, eliminate the perturbation from bulk water and dislodge the hydrogen bubbles during in situ electrochemical Raman experiments. The combination of the spectroscopic measurements with AIMD simulation results provides a roadmap to decipher the potential-dependent molecular orientation of water at the interface. We have prepared a detailed guideline for the application of combined in situ Raman and AIMD techniques; this procedure may take a few minutes to several days to generate results and is applicable to a variety of disciplines ranging from surface science to energy storage to biology.

Ampere-level current density ammonia electrochemical synthesis using CuCo nanosheets simulating nitrite reductase bifunctional nature

The development of electrocatalysts capable of efficient reduction of nitrate (NO3−) to ammonia (NH3) is drawing increasing interest for the sake of low carbon emission and environmental protection. Herein, we present a CuCo bimetallic catalyst able to imitate the bifunctional nature of copper-type nitrite reductase, which could easily remove NO2− via the collaboration of two active centers. Indeed, Co acts as an electron/proton donating center, while Cu facilitates NOx− adsorption/association. The bio-inspired CuCo nanosheet electrocatalyst delivers a 100 ± 1% Faradaic efficiency at an ampere-level current density of 1035 mA cm−2 at −0.2 V vs. Reversible Hydrogen Electrode. The NH3 production rate reaches a high activity of 4.8 mmol cm−2 h−1 (960 mmol gcat−1 h−1). A mechanistic study, using electrochemical in situ Fourier transform infrared spectroscopy and shell-isolated nanoparticle enhanced Raman spectroscopy, reveals a strong synergy between Cu and Co, with Co sites promoting the hydrogenation of NO3− to NH3 via adsorbed *H species. The well-modulated coverage of adsorbed *H and *NO3 led simultaneously to high NH3 selectivity and yield.

Insights into Electrocatalytic Surface Chemistry Via Operando Spectroscopy, Spectrometry and Stress Measurements

On the verge of harnessing CO2 as a building block for carbon-based fuels, electrocatalysis stands uniquely poised to revolutionize the chemical industry through renewable electrification. For this vision to become reality operando measurement techniques must be applied to study phenomena at the electrode-electrolyte interface. Understanding the dynamic interaction between ionic species in the electrolyte, active sites and intermediates is paramount for the systematic advancement in chemical reactivity, durability, and selectivity required to become commercially relevant. I will demonstrate a suite of operando techniques, such as shell-isolated nanoparticle enhanced Raman spectroscopy (Figure 1a), mass spectrometry (Figure 1a), and cantilever curvature measurements (Figure 1b), that enable direct measurement of adsorbates, phase state and stress dynamics, respectively, at the electrode interface. The combination of results from these measurements enables quantification of sub-monolayer coverages of surfaces species as well as coverage vs stress relationships providing the capability to effectively tune properties of the electrode surface. Complimentary use of these techniques to comprehensively study chemical reactions at heterogeneous interfaces provides new insights into atomic events critical for sustainable electrification to be realized.Figure Caption: (a) Identification of surface hydride on Cu(111) via complementary operando Raman and online mass spectrometry measurements and (b) cantilever curvature measurements combined with DFT calculations reveal the mechanism behind compressive stress due to CO adsorption. Figure 1

Insights into Cu Surface Chemistry Via in-Operando nanoparticle Enhanced Vibrational Spectroscopy and Mass Spectrometry Measurements

Copper electrodeposition is a central process in the metallization of microelectronics and more recently has found use as an important electrocatalyst in the conversion of CO2 to hydrocarbons. Gaining mechanistic insight into the nature of the respective reactions requires in situ and better still in operando measurements. Herein the utility of shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and electrochemical mass spectrometry (EC-MS) to study the potential dependent anion adsorption and hydride formation on low index Cu single crystals surface will be detailed. SHINERs enables monitoring of competitive adsorption between Cl- and SO4 2- on Cu(100) and Cu(111) surfaces (Figure 1a). Saturated ordered halide adlayers are formed at potentials slightly below the open circuit potential while moving to more negative values halide is disrupted resulting with the emergence of a sulfate mode near 970 cm-1. In the case of Cu(111) the desorption of the halide adlayer is coupled to the formation of a hydride phase (Figure 1b) as evident in both SHINERS and EC-MS measurements. SHINERS was also employed to examine the adsorbate dynamics associated with superconformal electrodeposition of Cu. Specifically, competitive adsorption between Cl- and sulfonate terminated thiol/disulfide accelerators molecules was examined during Cu deposition on planar and patterned surfaces (Figure 1c). The ability of the nanoparticle reporters to float on the advancing surface is demonstrated and used to probe the additive evolution on the growth front associated with superconformal electrodeposition. This work demonstrates the capabilities of operando electrochemical measurements and their importance in achieving future technological breakthroughs.Figure 1. Capturing Cu interfacial chemistry with operando SHINERS (a) on a c(2x2)-Cl covered Cu(100) surface, (b) coupling to EC-MS to reveal the existence of hydride on Cu(111) in Cl containing electrolyte and (c) to track accelerator coverage on electrodeposited pattern surfaces. Figure 1

Mapping Surface Chemistry During Superfilling with Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy and X-ray Photoelectron Spectroscopy

Silica shell-isolated Au nanoparticles are used as reporters for shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) measurements to track and map the coverage and state of surfactant additives during electrochemical deposition. The propensity of a sub-monolayer coverage of Au@SiO2−x nanoparticles to remain segregated on advancing surfaces during Cu Damascene electrodeposition is demonstrated including enrichment (dilution) on concave (convex) surface segments. The local coverage of sulfonate-terminated disulfide (SPS) and/or thiolate (MPS) accelerator and co-adsorbed chloride is mapped during superconformal deposition on SPS-derivatized trench patterned arrays. Comparison with Cu deposition on nanoparticle-free regions indicate that for sub-monolayer coverages the Au@SiO2−x nanoparticles do not hinder the essential SPS/MPS adsorbate and metal deposition dynamics responsible for trench superfilling. X-ray photoelectron spectroscopy (XPS) studies on nanoparticle-free specimens reveal similar quantitative trends in SPS/MPS adsorbate coverage during metal deposition congruent with the effect of area change as detailed by the curvature enhanced accelerator mechanism (CEAC). SHINERS provides a powerful means for investigating the molecular details of superfilling and, more generally, surfactant mediated growth.

Electrochemical behavior of chalcocite exposed to 2-mercaptobenzothiazole aqueous solution

The flotation of copper bearing minerals is always a hot topic in the field of minerals processing. In this paper, the adsorption of a flotation collector, 2-mercaptobenzothiazole(MBT), onto a typical secondary copper sulfide mineral, chalcocite, depending on electrochemical potential was investigated with the help of shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). The MBT adsorbs through its exocyclic sulfur, in addition to its endocyclic nitrogen at negative potentials. This is because negative potentials are thermodynamically unfavorable for the adsorption to occur. Especially, chalcocite electrode that has been exposed to deep negative potential (−600 mV versus SCE) can be totally inhibited from MBT adsorption. A “cathodic passivating” process is proposed possibly accompanied by the formation of a passivation layer, kinetically preventing adsorption, even after potentials switch back to positive. Cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were also used to explain this phenomenon. The present work implicates enhanced separation efficiency of chalcocite by using electrochemical controlled flotation.

Structure Specific Adsorbate Interactions at Electrodepositing Cu Interfaces

Mechanistic understanding of interfaces during additive based electrochemical deposition of thin films is limited by lack of tools to discretely probe given features of deposits. Modern spectroelectrochemical methods that have enabled significant understanding, like surface-enhanced Raman and infrared spectroscopies (SERS and SEIRAS, respectively), are restricted by specimen geometry; SERS is closely linked to the use of rough plasmonically active surfaces while SEIRAS measurements is constrained to thin IR transparent metal films. More recently, the application of Au@SiO2 core-shell nanoparticles as “vibrational reporters” on plasmonically inactive surfaces has enabled collection of site-specific vibrational data on well-defined single crystal surfaces whereby the nanoparticle serves to channel the plasmonic energy to the nanoparticle-substrate interface. The present work utilizes this technique, Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy (SHINERS) to track relative coverages of sulfonate, chloride and methylene moieties following super-conformal Cu electrodeposition on a patterned interface (Figure 1 a,b,d). Corroborated by computational finite-element results (Figure 1 c,d) and x-ray photoelectron spectroscopy measurements, the SHINERS measurements demonstrate that during early stages of electrodeposition, on an accelerator functionalized surface, the regions with more deposition have higher coverage of sulfonate species. As deposition continues dilation of the sulfonate concentration occurs following the continual decrease in surface area of the interface. Ultimately, this work reveals the benefit from the combined use of SHINERs, photoelectron spectroscopy and computational models to further our understanding of composite electroplating and resolve complex site-specific interfacial interactions. Figure 1

Anion Influenced Hydride Formation on Cu(111) during Electrocatalysis

In aqueous systems several environmentally relevant proton-coupled electron transfer reactions such as the reduction of O2, NO3, CO or CO2 are known to proceed on Cu surfaces in combination with proton and/or water reduction. Among these, the electrochemical reduction of CO2 receives the most attention because of Cu’s unique ability to produce varying degrees of hydrogenated multicarbon products. Despite intense experimental and theoretical studies, understanding of Cu’s facet specific selectivity is still limited especially regarding the role of H in hydrogenation steps. Using operando electrochemical mass spectrometry (ECMS) and shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) this work identifies the existence of surface hydride on Cu(111) (Figure 1a) under conditions relevant for the aforementioned reduction reactions. The identified surface hydride is significantly impacted to changes in electrolyte composition, such as the cation, anion or dissolved gas species and likely has significant impact over electrocatalytic performance. ECMS plots (Figure 1b) of hydride formation and decomposition show that the stronger the binding affinity of the anion to the Cu(111) surface the larger the overpotential required for hydride formation (e.g. Cl- vs ClO4 -). Likewise, decomposition occurs at more negative potentials. Peak areas of respective vibrational modes (Figure 1 c-d) corroborate the ECMS data, also demonstrating that in the presence of Cl- (vs SO4 2-) both hydride formation and decomposition shifts negatively by nearly 100 mV. These dynamics among other more quantitative analysis of hydride coverage and kinetics will be presented within this talk. Figure 1

Electrochemical impedance spectroscopy and Raman spectroscopy studies on electrochemical interface between Au(111) electrode and ethaline deep eutectic solvent

Deep eutectic solvents (DESs) are promising candidate electrolytes in electrochemical fields due to their excellent properties. In this work, cyclic voltammetry, electrochemical impedance spectroscopy and shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) have been employed to explore the potential-dependent innermost layer structure in electrical double layer at Au(111) electrode in ethaline DES (choline chloride and ethylene glycol in a 1:2 molar ratio). It is found that chloride anions adsorption on Au(111) surface gives rise to the lifting of Au(111)-(√3 × 22) reconstruction and the abrupt increase of differential capacitance. When the potential shifts positively, a disorder-order phase transition of chloride anion adsorbate is revealed. When the potential shifts negatively, choline cations and ethylene glycol molecules adsorb on Au(111) surface with weak interaction detected by SHINERS technique. This work provides new insight into the potential-dependent adsorption and phase transition behaviors of innermost layer structure in electrical double layer in ethaline DES.

Mapping Adsorbates with Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy to Understand Rapid Superconformal Filling of Cu Trenches

Additive adsorbates are widely used as surfactants to guide morphological and microstructural evolution during electrochemical deposition of thin films. Even though this strategy has been employed for several decades understanding of the mechanisms at play on the interface remain limited. Modern spectroelectrochemical methods, from surface-enhanced Raman spectroscopy (SERS) to surface-enhanced infrared spectroscopy (SEIRAS) and non-linear optical methods like sum frequency generation (SFG) can provide significant insight into the composition, structure, and dynamics of the surfactant adsorbates through their vibrational signatures. on nominally static surfaces. Each strategy is limited to specimen geometry; SERS is closely linked to the use of rough, plasmonically-active surfaces while SEIRAS measurements are constrained to thin, IR-transparent, metallic films. In the last decade, a significant advance was the introduction of nanoparticle reporters, based largely on silica coated Au nanoparticles, that enable Raman spectroscopy studies on well-defined, single-crystal surfaces whereby the nanoparticle serves to channel the plasmonic energy to the nanoparticle-substrate interface. The silica or alternative coating materials are designed to be inert with respect to the chemistry of the adsorbate species under study while remaining thin enough to allow effective focusing of the optical energy. This approach has been adopted by several researchers interested in understanding molecular adsorption on well-defined, single-crystal surfaces, the electrical double layer, and numerous aspects of reactivity related to catalysis, batteries, electrodeposition, etc. The present work demonstrates the use of Au@SiO2 (core-shell) nanoparticles, also known as SHINERS (Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy), to enable in situ vibrational spectroscopic measurements during electroplating of comparatively smooth, rapidly advancing, surfaces. In particular, the ability of the reporters to float on an advancing surface while responding to area change is used to reveal important, area-driven changes in adsorbate coverage. This study also opens a new avenue for exploring the intersection of analytical surface chemistry and composite electroplating. Figure 1

Applications of Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

The surface-enhanced Raman scattering (SERS) is mainly used as an analysis or detection tool of biological and chemical molecules. Since the last decade, an alternative branch of the SERS effect has been explored, and named shell-isolated nanoparticle Raman spectroscopy (SHINERS) which was discovered in 2010. In SHINERS, plasmonic cores are used for enhancing the Raman signal of molecules, and a very thin shell of silica is generally employed for improving the thermal and chemical stability of plasmonic cores that is of great interest in the specific case of catalytic reactions under difficult conditions. Moreover, thanks to its great surface sensitivity, SHINERS can enable the investigation at liquid–solid interfaces. In last two years (2019–2020), recent insights in this alternative SERS field were reported. Thus, this mini-review is centered on the applications of shell-isolated nanoparticle Raman spectroscopy to the reactions with CO molecules, other surface catalytic reactions, and the detection of molecules and ions.

A universal polymer shell-isolated nanoparticle (SHIN) design for single particle spectro-electrochemical SERS sensing using different core shapes.

Shell-isolated nanoparticles (SHINs) have attracted increasing interest for non-interfering plasmonic enhanced sensing in fields such as materials science, biosensing, and in various electrochemical systems. The metallic core of these nanoparticles is isolated from the surrounding environment preventing direct contact or chemical interaction with the metal surface, while still being close enough to enable localized surface plasmon enhancement of the Raman scattering signal from the analyte. This concept forms the basis of the shell isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique. To date, the vast majority of SHIN designs have focused on SiO2 shells around spherical nanoparticle cores and there has been very limited published research considering alternatives. In this article, we introduce a new polymer-based approach which provides excellent control over the layer thickness and can be applied to plasmonic metal nanoparticles of various shapes and sizes without compromising the overall nanoparticle morphology. The SHIN layers are shown to exhibit excellent passivation properties and robustness in the case of gold nanosphere (AuNP) and anisotropic gold nanostar (AuNS) core shapes. In addition, in situ SHINERS spectro-electrochemistry measurements performed on both SHIN and bare Au nanoparticles demonstrate the utility of the SHIN coatings. Correlated confocal Raman and SEM mapping was achieved to clearly establish single nanoparticle SERS sensitivity. Finally, confocal in situ SERS mapping enabled visualisation of the redox related molecular structure changes occurring on an electrode surface in the vicinity of individual SHIN-coated nanoparticles.

Characterization of Electrodeposited Cu Interfaces Via Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy

The advent of SERS created a new avenue for investigating interfacial phenomena by coupling the localized surface plasmon resonance (LSPR) of metal nanostructures to the inelastic scattering properties of molecules. Seeing a 104-fold enhancement in Raman signals, SERS scattering events were used to identify adsorbed molecules and substrate-surface structural conformations. But, even with the advent of SERs, Raman spectroscopy was still confined to LSPR active materials with roughened surfaces. However, recent technical modifications to SERS, such as shell-isolation and localized probe modes, have shown potential for the operando investigation of flat non-plasmon active single-crystal surfaces. Shell-isolated Nanoparticle Enhanced Raman Spectroscopy(SHINERS) provides two parallel paths for electric field enhancement of non-plasmon active surfaces while minimizing chemical perturbations by encasing reporters in a chemically inert shell (Figure 1). This technique can be used to perform measurements before, during, and after electrodeposition to gain an understanding for changes at metal-solution interfaces under an applied bias. SHINERS serves as a great utility to not only understand surface adsorbates, but to also characterize how dynamic surfaces respond to surface adsorbates. The precarious nature of metastable surfaces (e.g. metallic Cu) make capturing surface information challenging, preventing accurate structure-activity assignments necessary to fully understand the system. The lack of techniques (operando, especially) capable of evaluating functional interfaces, vs model systems, has further inhibited understanding of surface phenomena. Breaking these limits, will enable novel findings that afford new understanding and strategies to develop refined interfaces and processes. Herein, we report the synthesis of Au@SiO2 core-shell nanoparticles and their application to track the state of interfacial phenomena on electrodeposited Cu surfaces (Figure 1).Figure 1. Electron microscopy images of Au-SiO2 nanoparticles (a) dispersed on Cu Trenches (b) for shell-isolated nanoparticle enhanced Raman spectroscopy (c) measurements to probe for surface adsorbates, which shows enhancement relative to the bare Cu surface (d). Figure 1

Electrochemical SHINERS investigation of the adsorption of butyl xanthate and 2-mercaptobenzothiazole on pyrite

In this paper, shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) has been applied to investigate the adsorption of typical collectors, butyl xanthate and 2-mercaptobenzothiazole (MBT), on pyrite surface. With the help of inert shell isolated gold nanoparticles as electric field enhancers, high quality electrochemical spectra were obtained in relation to real-world flotation conditions, enabling the quantitative identification of the chemical reactions occurring only on the mineral surface. It has been found that polysulphide anions are predominant oxidation product of pyrite after abrading and above 0 mV vs Ag/AgCl. Both the adsorption of xanthate and MBT are suppressed on pre-oxidized pyrite surface. The pre-formed polysulphide is diminished at negative potentials, which are favourable for collector’s adsorption. Compared to xanthate, MBT shows greater resistance to pyrite oxidation and a broader potential window for adsorption due to the presence of two “minerophilic” groups (endocyclic nitrogen atom bonding in addition to the interaction through the exocyclic S atom). Single exocyclic S atom bonding is predominant in more favarouble adsorption environments. Dithiolate, the oxidation products of xanthate and MBT, has been precluded due to the high stability of adsorbed collector. This is inconsistent with the ex-situ XPS measurement where air exposure may induce oxidation.

In-Operando characterization of Electrochemical Interfaces Via Shiners: Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy

The advent of SERS created a new avenue for investigating interfacial phenomena by coupling the localized surface plasmon resonance (LSPR) of metal nanostructures to the inelastic scattering properties of molecules. Seeing a 104-fold enhancement in Raman signals, SERS scattering events were used to identify adsorbed molecules and substrate-surface structural conformations. But, even with the advent of SERs, Raman spectroscopy was still confined to LSPR active materials with roughened surfaces. However, recent technical modifications to SERS, such as shell-isolation and localized probe modes, have shown potential for the in-operando investigation of flat non-plasmon active single-crystal surfaces. Shell-isolated Nanoparticle Enhanced Raman Spectroscopy(SHINERS) provides two parallel paths for electric field enhancement of non-plasmon active surfaces while minimizing chemical perturbations by encasing reporters in a chemically inert shell (Figure 1). This technique can be used to perform in-operando measurements during electrochemical processes to bridge the gap between observing and understanding the state of metallic interfaces under an applied bias. This serve as a great utility to not only understand surface adsorbates, but to also characterize dynamic surfaces (e.g. Cu) that undergo reconstruction in response to the applied biases. Such metastable surfaces can impede capturing surface structure information, preventing accurate structure-activity assignments necessary to further understanding of the system. Furthermore, a lack of in-operando technology has inhibited the characterization of active sites and surface phenomena via in-situ measurements. These limitations have resulted in uncertainty of how novel findings are interconnected and ways to design refined interfaces. Herein, I report the synthesis of SiO2 encapsulated Au NPs and their application in-operando to track the state of Cu interfaces under varying electrochemical and chemical conditions. Figure 1