Site-Selective Deposition of Metal–Organic Frameworks on Gold Nanobipyramids for Surface-Enhanced Raman Scattering

Abstract

Site-selective deposition of metal−organic frameworks (MOFs) on metal nanocrystals has remained challenging because of the difficult control of the nucleation and growth of MOFs. Herein we report on a facile wet-chemistry approach for the selective deposition of zeolitic imidazolate framework-8 (ZIF-8) on anisotropic Au nanobipyramids (NBPs) and nanorods. ZIF-8 is selectively deposited at the ends and waist and around the entire surface of the elongated Au nanocrystals. The NBPbased nanostructures with end-deposited ZIF-8 exhibit the best surfaceenhanced Raman scattering (SERS) performance, implying that molecules can be concentrated by ZIF-8 at the hot spots. In addition, the SERS signal exhibits good selectivity for small molecules because of the molecular sieving effect of ZIF-8. This study opens up a promising route for constructing plasmonic nanostructures with site selectively deposited ZIF-8, which hold enormous potential for molecular sensing, optical switching, and plasmonic catalysis.

Anisotropic silica coating on gold nanorods boosts their potential as SERS sensors

“…2,11,12 Because the tips produce a much stronger field enhancement, much attention has been paid to localize analyte mole-cules at the tips of the AuNRs to exploit the enhanced electric field at the AuNR surface, mainly for SERS and fluorescence enhancement. 1,2,[10][11][12][13][14][15][16][17][18][19][20][21][22] Various methods to direct analyte or probe molecules to the tips of AuNRs such as the utilization of the lower areal density of the surfactant layer on the tips of the AuNRs, 14,15 orienting the nanorods in such a way to block the sides from accepting molecules, 16,17 and binding supposed "tip" and "side" specific molecules to target the different crystal faces of the nanorod. 18,19 While "tip-specific" adsorption is apparently possible, these systems suffer from drawbacks which hinder their applicability: (1) the solution-based measurements and protocols suffer from poor reproducibility because of induced aggregation which non-uniformly creates plasmonic hotspots, (2) fixing dry nanoparticles on the surface of a substrate similarly suffers from non-uniform plasmonic hot spot formation and (3) extensive surface modification could block incoming analytes and make the surface of the AuNRs inaccessible.…”

Polydopamine stabilizes silver nanoparticles as a SERS substrate for efficient detection of myocardial infarction

“…Yang et al selectively deposited zeolitic imidazolate framework-8 (ZIF-8) on anisotropic Au nanobipyramids (NBPs) and nanorods, where ZIF-8 worked as concentration molecules at hotspots, thus exhibiting excellent SERS performance. 25 Meng et al designed a graphene (G)–silver nanoparticle (AgNP)–silicon (Si) sandwich chip SERS substrate to quantitatively detect bacteria, where graphene played a key role in inducing charge-transfer resonance. 26 However, their synthesis process is complicated and time-consuming, and their applications and biocompatibility in SERS bioassays still need to be broadened and improved.…”

Assembly of gold nanorods functionalized by zirconium-based metal–organic frameworks for surface enhanced Raman scattering

“…20,21 Core@shell nanostructures formed by encapsulating plasmonic nanocrystals within MOFs have been demonstrated as multi-functional platforms for SERS detection, catalysis and drug delivery. [22][23][24][25] The MOF shell can stabilize the plasmonic nanocrystals and enrich target molecules close to the metal surface, which are beneficial for improving the performance of the plasmonic nanocrystalbased SERS platform. 23 Necklace-like core@shell Ag@zeolitic imidazolate frameworks-8 (ZIF-8) heterostructured nanowires were reported for SERS detection of crystal violet molecules with an excellent reproducibility.…”