The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

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Present and Future of Surface-Enhanced Raman Scattering

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

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Diverse Applications of Nanomedicine

The field of chiral inorganic nanostructures is rapidly expanding. It started from the observation of strong circular dichroism during the synthesis of individual nanoparticles (NPs) and their assemblies and expanded to sophisticated synthetic protocols involving nanostructures from metals, semiconductors, ceramics, and nanocarbons. Besides the well-established chirality transfer from bioorganic molecules, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered, including three-dimentional lithography, multiphoton chirality transfer, polarization effects in nanoscale assemblies, and others. Multiple chiral geometries were observed with characteristic scales from angstroms to microns. Uniquely high values of chiral anisotropy factors that spurred the development of the field and differentiate it from chiral structures studied before, are now well understood; they originate from strong resonances of incident electromagnetic waves with plasmonic and excitonic st...

Chiral Inorganic Nanostructures

A reconfigurable plasmonic nanosystem combines an active plasmonic structure with a regulated physical or chemical control input. There have been considerable efforts on integration of plasmonic nanostructures with active platforms using top-down techniques. The active media include phase-transition materials, graphene, liquid crystals and carrier-modulated semiconductors, which can respond to thermal, electrical and optical stimuli. However, these plasmonic nanostructures are often restricted to two-dimensional substrates, showing desired optical response only along specific excitation directions. Alternatively, bottom-up techniques offer a new pathway to impart reconfigurability and functionality to passive systems. In particular, DNA has proven to be one of the most versatile and robust building blocks for construction of complex three-dimensional architectures with high fidelity. Here we show the creation of reconfigurable three-dimensional plasmonic metamolecules, which execute DNA-regulated conformational changes at the nanoscale. DNA serves as both a construction material to organize plasmonic nanoparticles in three dimensions, as well as fuel for driving the metamolecules to distinct conformational states. Simultaneously, the three-dimensional plasmonic metamolecules can work as optical reporters, which transduce their conformational changes in situ into circular dichroism changes in the visible wavelength range.

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Reconfigurable 3D plasmonic metamolecules

Chiral self-assembled nanomaterials with biological applications have attracted great interest. In this study, DNA-driven gold-upconversion nanoparticle (Au-UCNP) pyramids were fabricated to detect intracellular microRNA (miRNA) in real time. The Au-UCNP pyramids are doubly optically active, displaying strong plasmonic circular dichroism (CD) at 521 nm and significant luminescence in 500-600 nm, and therefore can be monitored by both of them. CD will decrease while the luminescence intensity increases in the presence of miRNA. The experimental results show that the CD intensity had an outstanding linear range from 0.073 to 43.65 fmol/10 μg(RNA) and a limit of detection (LOD) of 0.03 fmol/10 μg(RNA), whereas the luminescence intensity ranged from 0.16 to 43.65 fmol/10 μg(RNA) with a LOD of 0.12 fmol/10 μg(RNA). These data indicate that the CD signal is much more sensitive to the concentration of miRNA than the luminescent signal, which is attributed to the strong CD intensity arising from the spin angular momentum of the photon interaction with chiral nanostructures and the plasmonic enhancement of the intrinsic chirality of DNA molecules in the pyramids. This approach opens up a new avenue to the ultrasensitive detection and quantification of miRNA in living cells.

Dual-Mode Ultrasensitive Quantification of MicroRNA in Living Cells by Chiroplasmonic Nanopyramids Self-Assembled from Gold and Upconversion Nanoparticles

Nanoscale plasmonic assemblies display exceptionally strong chiral optical activity. So far, their structural design was primarily driven by challenges related to metamaterials whose practical applications are remote. Here we demonstrate that gold nanorods assembled by the polymerase chain reaction into DNA-bridged chiral systems have promising analytical applications. The chiroplasmonic activity of side-by-side assembled patterns is attributed to a 7-9 degree twist between the nanorod axes. This results in a strong polarization rotation that matches theoretical expectations. The amplitude of the bisignate 'wave' in the circular dichroism spectra of side-by-side assemblies demonstrates excellent linearity with the amount of target DNA. The limit of detection for DNA using side-by-side assemblies is as low as 3.7 aM. This chiroplasmonic method may be particularly useful for biological analytes larger than 2-5 nm which are difficult to detect by methods based on plasmon coupling and 'hot spots'. Circular polarization increases for inter-nanorod gaps between 2 and 20 nm when plasmonic coupling rapidly decreases. Reaching the attomolar limit of detection for simple and reliable bioanalysis of oligonucleotides may have a crucial role in DNA biomarker detection for early diagnostics of different diseases, forensics and environmental monitoring.

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Attomolar DNA detection with chiral nanorod assemblies

The invention provides a preparation of a bisphenol A submicron magnetic molecular imprint and application of the same in the detection pre-processing of packaged food, which belong to the technical field of material chemistry and food safety. A surface molecular imprinting technology and a magnetic solid-phase extraction technology are combined, and a magnetic submicron particle wrapped by a surface molecular imprint polymer (Fe3O4@MIP) is prepared by using a bisphenol A as a template molecule. A magnetic submicron material (Fe3O4) is synthesized by a hydrothermal process, the synthesized Fe3O4 is synthesized into a silicon-wrapped magnetic microsphere (Fe3O4@SiO2) by a sol gel process, the synthesized Fe3O4@SiO2 is coupled with 2-bromo-isobutyryl bromide to form Fe3O4@SiO2@Br with Br groups on the surface, and the synthesized Fe3O4@SiO2@Br is synthesized into a submicron particle with a surface molecular imprint (Fe3O4@MIP) by an atom radical transfer process. The prepared Fe3O4@MIP is used in the detection pre-processing of packaged food which comprises liquid food, liquid food containing a certain quantity of solids and solid food.

Preparation of bisphenol A submicron magnetic molecular imprint and application of same in detection pre-processing of packaged food

Method for researching chirality of gold-silver core-shell structure dimer based on polymerase chain reaction (PCR)

Chirality research method for assembled product adopting polymerase chain reaction (PCR) based large and small gold dimer-gold core-shell structure

The invention discloses a method for researching the chirality of chain controlled assembly products of large gold and small gold based on a polymerase chain reaction (PCR), and belongs to the technical field of material chemistry. The method mainly comprises the following steps of compounding gold nanoparticles with different particle sizes of 25 nm and 10 nm; performing controlled modification on the coupling amount of surface primers of the gold nanoparticles to achieve the stability of the gold nanoparticles in a PCR system; and modifying a gold nanoparticle-primer conjugate by using polyethylene glycol 1000(PEG1000). Under suitable PCR conditions, the chain controlled assembly is performed on the large gold and the small gold, and the transmission electron microscope (TEM) representation and the circular dichroism (CD) signal research comparison are performed on the controlled assembly product. By the method, the chain controlled assembly of the large gold and the small gold are performed by the PCR method for the first time, and the chiral properties of the chain assembly products which have different lengths and are assembled by the PCR under different cycle numbers are researched and discussed for the first time.

Ding Li

Papers

Attomolar DNA detection with chiral nanorod assemblies

Preparation of bisphenol A submicron magnetic molecular imprint and application of same in detection pre-processing of packaged food

Method for researching chirality of gold-silver core-shell structure dimer based on polymerase chain reaction (PCR)

Chirality research method for assembled product adopting polymerase chain reaction (PCR) based large and small gold dimer-gold core-shell structure

Method for researching Raman properties of chain controlled assembly products of large gold and small gold based on polymerase chain reaction (PCR)