Subscriber access provided by UNIV OF DURHAM
Surfaces, Interfaces, and Applications
Tunable Plasmonic Cavity for Label-free Detection of Small Molecules Jung A Kwon, Chang Min Jin, Yonghee Shin, Hye Young Kim, Yura Kim, Taewook Kang, and Inhee Choi ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b01550 • Publication Date (Web): 23 Mar 2018 Downloaded from http://pubs.acs.org on March 23, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Materials & Interfaces
Tunable Plasmonic Cavity for Label-free Detection of Small Molecules Jung A Kwon1, Chang Min Jin1, Yonghee Shin2, Hye Young Kim1, Yura Kim1, Taewook Kang2,* and Inhee Choi1,* 1
Department of Life Science, University of Seoul, Seoul 130-743, Republic of Korea
2
Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 121-742,
Republic of Korea
KEYWORDS: Plasmonic Cavity; small molecule detection; plasmonic detection platform; plasmonic resonance energy transfer (PRET); surface enhanced Raman scattering (SERS)
ACS Paragon Plus Environment
1
ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 30
ABSTRACT Owing to its high sensitivity and high selectivity along with rapid response time, plasmonic detection has gained considerable interest in a wide variety of sensing applications. In order to improve the fieldwork applicability and reliability of plasmonic detection, the integration of plasmonic nanoparticles into optical devices is desirable. Herein, we propose an integrated labelfree detection platform comprising a plasmonic cavity that allows sensitive molecular detection via either surface-enhanced Raman scattering (SERS) or plasmon resonance energy transfer (PRET). A small droplet of metal ion solution spontaneously produces a plasmonic cavity on the surface of uncured polydimethylsiloxane (PDMS), and as PDMS is cured, the metal ions are reduced to form a plasmonic antennae array on the cavity surface. Unique spherical feature and the integrated metallic nanoparticles of the cavity provide excellent optical functions to focus the incident light in the cavity and to re-scatter the light absorbed by the nanoparticles. The optical properties of the plasmonic cavity for SERS or PRET are optimized by controlling the composition, size, and density of the metal nanoparticles. By using the cavity, we accomplish both 1000-fold sensitive detection and real-time monitoring of reactive oxygen species secreted by live cells via PRET. In addition, we achieve sensitive detection of trace amounts of toxic environmental molecules such as chloromethylisothiazolinone/ methylisothiazolone (CMIT/MIT) and bisphenol A, as well as several small biomolecules like glucose, adenine, and tryptophan, via SERS.
ACS Paragon Plus Environment
2
Page 3 of 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Materials & Interfaces
INTRODUCTION The label-free optical detection of small molecules is essential to various sensing applications ranging from diagnostics to imaging. Recently, plasmonic optical detection methods such as surface-enhanced Raman scattering (SERS) and plasmon resonance energy transfer (PRET) have drawn considerable attention due to their high sensitivity, high selectivity, and short response time.1-5 These methods typically utilize metallic nanostructures with the desired optical properties, wherein the nanostructures are fabricated by either top-down or bottom-up approaches. For SERS application, colloidal nanoparticles1,
6-7
and two or three-dimensional
arrays of nanoparticles8-12 with tailored far-field and near-field properties have been used. On the other hand, single plasmonic nanoparticles with plasmon bands that adequately match the absorption bands of neighboring target molecules have been used for label-free PRET detection.13-16 In order to improve the utility and reliability of such plasmonic detection methods, metallic nanostructures need to be integrated into optical devices. However, there have been few reports on the spontaneous integration of metallic nanoparticles into optical devices and their subsequent application to SERS or PRET. Herein, we demonstrate a novel integrated detection platform using a plasmonic cavity for the sensitive detection of various small molecules via label-free optical detection modes such as SERS and PRET. The plasmonic cavity is formed by exploiting rapid and spontaneous reactions at the three-dimensional interface between liquid PDMS and an aqueous droplet containing metal ions. The optical properties of the plasmonic cavity can be tuned and optimized for applications to SERS and PRET by adjusting the composition, density, and size of the metallic nanoparticles that are integrated on the surface of the cavity. Figure 1 illustrates the tunable optical functions and properties (e.g., colors and scattering) of the plasmonic cavities by
ACS Paragon Plus Environment
3
ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 4 of 30
integrating various metallic nanoparticles on their spherical surfaces. A plasmonic cavity can have two optical functions, as angular reflector to accumulate an incident light in the cavity, and as nanoscale photon sources to scatter absorbed light into the cavity. Moreover, strong near-field enhancement between metal nanostructures on the cavity is expected. Thus, the plasmonic cavity would be very useful for label-free molecular detections such as SERS and PRET. When using a redox active molecule-based PRET, upon exposure of toxicants to live cells in the cavity, reactive oxygen species (ROS) generated from the cells are monitored in real time. It is also possible to detect various biologically and environmentally relevant small molecules inside these cavities with high sensitivity and selectivity via SERS. RESULTS AND DISCUSSION Morphological and optical characterization of plasmonic cavities Plasmonic cavities were spontaneously prepared using the method illustrated in Figure 2a. When a small droplet of a metal ion solution is placed into liquid PDMS, a spherical liquid-liquid interface is immediately (
