Leaky Mode Resonance of Polyimide Waveguide Couples Metal Plasmon Resonance for Surface-Enhanced Raman Scattering

Abstract

In the studies of surface-enhanced Raman scattering (SERS), it is considered to be a key point to couple the surface plasmons of metallic nanomaterials and structures to resonate, which can assist higher SERS signal enhancement. This paper is to explore a strategy for plasmon resonating based on the leaky mode resonance (LMR) of a polyimide (PI) optical waveguide (OWG), for the purpose of achieving the highly sensitive evanescent field-excited SERS. PI was chosen to build the waveguide layer due to its merits of exhibiting small extinction coefficients in the natural light frequency, low cost, high flexibility, easy fabrication, and almost no Raman spectral interference. The OWG configuration guarantees a high harvesting efficiency for the incident light. Ag nanoparticles were assembled on top of the OWG layer as plasmonic antennas to provide a large scattering cross section based on the coupling of the LMR and metal plasmon resonance (MPR), which supports highly efficient SERS radiation and being conducive to the far-field collection. The LMR-MPR coupling can facilitate stronger local electromagnetic field around the side surfaces of the Ag nanoparticles, which is favorable to the adsorption of analytes. The PI OWG-coupled MPR structure can realize the integration of SERS excitation light paths and elements, which is not only a valuable SERS enhancement configuration but also a promising technique for the surface and thin film analysis.

Optimizing crystallinity of engineered poly(lactic acid)/poly(butylene succinate) blends: The role of single and multiple nucleating agents

“…In this case, beyond choosing PLA grades with high molecular weight and high tacticity, 39,40 the formation of blends with polymers characterized by high thermal resistance, such as acetal resins 41 or polycarbonate, 42–44 with marked thermo‐mechanical characteristics, is a strategy commonly adopted. When polymeric blends are formed, the secondary phases often behave as immiscible with the PLA matrix, resulting in solid dispersions characterized by various morphologies, among which the most typical are drop‐shaped, 45–52 complex structures such as co‐continuous structures or interconnected phase structures 53–56 . As known, the characteristics of immiscibility and formation of structures in separate phases often cause deterioration of the mechanical behavior due to the formation of extensive interfaces between the different materials which do not allow an effective transfer of the applied internal stresses, and sometimes loss of the optical transparency properties.…”

Synergistic toughening effect of hybrid clay particles on poly(lactic acid)/natural rubber blend

“…On the other hand, PLA is blended with rubber or a ductile thermoplastic polymer, resulting in toughening under optimal blend composition and processing condition. [ 13–21 ] Among the candidates of the second component for PLA, natural rubber (NR) has been receiving attention since it constructs eco‐friendly blend system with PLA. But still they are immiscible and difficult to obtain the toughening effect.…”

“…Above all, interfacial interaction between phases critically affects the toughening behavior. [ 15–18,22–24 ] To induce more interaction between PLA and NR, the effect of organically modified clay particles on the PLA/NR blend has been investigated since they are localized at the blend interface inducing compatibilization of the blend as well as toughening of the blend. [ 25–27 ] In case of the PLA/NR 90/10 blend, [ 26 ] the addition of clay shows concentration‐dependent toughening effect to the blend, inducing toughening with less than 3 wt% (with 3 wt% of clay, elongation at break reaches 80% and tensile strength becomes about 30 MPa while elongation at break is near 20% and tensile strength is about 45 MPa for the neat blend).…”

“…[ 15,17 ] With the optimal content of a vulcanization initiator (dicumyl peroxide, and so on), elongation at break, tensile strength and impact strength of the blend can be increased. [ 14,15,17,18,22 ] On the other hand, to obtain well‐distribution of NR droplets in the PLA matrix, a direct modification of NR is also used. For instance, NR is epoxidized to be well distributed and be more compatible with PLA.…”

Modulation of hot regions in waveguide-based evanescent-field-coupled localized surface plasmons for plasmon-enhanced spectroscopy

“…Therefore, amplifying the incident light field by the focusing optical elements to promote the coupling process of LSPs is the main strategy in LSPR-based spectroscopy and sensing. In recent studies, waveguide-based configurations are utilized to couple LSPs for the excitation of Raman photons, which is one practical way to amplify the LSPs by the waveguide resonance [13][14][15][16][17][18][19]. These insightful studies lead us to believe that the waveguide-based evanescent field (WEF) excitation may be a unique way to couple LSPs that is superior to direct, focused laser irradiation due to higher harvesting efficiency for the incident light.…”