Encoding Morphogenesis of Quasi-Triangular Gold Nanoprisms with DNA.

Properties of gold nanoparticles vary with their morphologies. Typically, the research on the properties and applications of the nonequilibrium intermediates generated by the morphological evolution of triangular gold nanoprisms is still incomplete. Herein, we employ thiol-DNA (HS-DNA) to protect the low-stability quasi-nanoprisms with different truncation degrees (R values). The presence of HS-DNA not only increases the stability of the quasi-nanoprisms in different microenvironments, but also facilitates us to investigate their intrinsic plasmonic properties related to morphology. Additionally, we serve quasi-nanoprisms loaded with HS-DNA as assembly modules and nanoplatforms for programmable self-assembly higher-order hybrid structures, as well as carriers for encoding and decoding of orthogonal barcode-like information, which opens new opportunities for developing novel building blocks for light manipulation at nanoscale.

DNA-Encoded Gold-Gold Wettability for Programmable Plasmonic Engineering.

Controlling the deposition and diffusion of adsorbed atoms (adatoms) on the surface of a solid material is vital for engineering the shape and function of nanocrystals. Here, we report the use of single-stranded DNA (oligo-adenine, oligo-A) to encode the wettability of gold seeds by homogeneous gold adatoms to synthesize highly tunable plasmonic nanostructures. We find that the oligo-A attachment transforms the nanocrystal growth mode from the classical Frank-van der Merwe to the Volmer-Weber island growth. Finely tuning the oligo-A density can continuously change the gold-gold contact angle (θ) from 35.1±3.6° to 125.3±8.0°. We further demonstrate the versatility of this strategy for engineering nanoparticles with different curvature and dimensions. With this unconventional growth mode, we synthesize a sub-nanometer plasmonic cavity with a geometrical singularity when θ>90°. Superfocusing of light in this nanocavity produces a near-infrared intraparticle plasmonic coupling, which paves the way to surface engineering of single-particle plasmonic devices.

DNA Origami-Based Nanoprinting for the Assembly of Plasmonic Nanostructures with Single-Molecule Surface-Enhanced Raman Scattering.

Metallic nanocube ensembles exhibit tunable localized surface plasmon resonance to induce the light manipulation at the subwavelength scale. Nevertheless, precisely control anisotropic metallic nanocube ensembles with relative spatial directionality remains a challenge. Here, we report a DNA origami based nanoprinting (DOBNP) strategy to transfer the essential DNA strands with predefined sequences and positions to the surface of the gold nanocubes (AuNCs). These DNA strands ensured the specific linkages between AuNCs and gold nanoparticles (AuNPs) that generating the stereo-controlled AuNC-AuNP nanostructures (AANs) with controlled geometry and composition. By anchoring the single dye molecule in hot spot regions, the dramatic enhanced electromagnetic field aroused stronger surface enhanced Raman scattering (SERS) signal amplification. Our approach opens the opportunity for the fabrication of stereo-controlled metal nanostructures for designing highly sensitive photonic devices.

DNA Origami Radiometers for Measuring Ultraviolet Exposure.

Ultraviolet (UV) light has long been known to damage nucleic acids. In this work, a DNA origami radiometer has been developed for measuring UV exposure by monitoring the morphological evolution of DNA origami nanostructures. Unlike linear DNA strands that tend to be degraded into small segments upon UV exposure, the structural complexity and interstrand connectivity of DNA origami remarkably alter the pathway of UV-induced DNA damage. A general pathway of expansion, distortion, and final disintegration is observed for DNA origami regardless of their shape and size; however the deformation kinetics is positively correlated with the number of nicks in the nanostructure. This structural continuity-dependent deformation can be translated into a DNA-based radiometer for measuring UV dose in the environment.

Gold Triangular Nanoprisms: Anisotropic Plasmonic Materials with Unique Structures and Properties.

As a novel type of anisotropic inorganic nanomaterials, gold triangular nanoprisms (AuTNPs) have been widely studied for their well-defined structures and excellent plasmonic properties. This review starts with synthetic methodology, combing through the early thermal solution method to the mature seed-mediated method and seedless method. The possible mechanisms proposed by predecessors and the problems needed to be solved are also arranged. Along with this, the important morphological evolution process of AuTNPs during synthesis and post-synthesis stages are revealed, which is of great significance for further understanding the structure of AuTNPs and developing new synthesis strategies. Finally, the applications of AuTNPs, especially associated with plasmonic properties, are listed and summarized where surface-enhanced Raman scattering (SERS), catalysis, phototherapy and biosensor are included, so that researchers can quickly comprehend the current situation, and provide a basis for further development and exploration of AuTNPs.

High-entropy alloy nanopatterns by prescribed metallization of DNA origami templates.

High-entropy multimetallic nanopatterns with controlled morphology, composition and uniformity hold great potential for developing nanoelectronics, nanophotonics and catalysis. Nevertheless, the lack of general methods for patterning multiple metals poses a limit. Here, we develop a DNA origami-based metallization reaction system to prescribe multimetallic nanopatterns with peroxidase-like activities. We find that strong coordination between metal elements and DNA bases enables the accumulation of metal ions on protruding clustered DNA (pcDNA) that are prescribed on DNA origami. As a result of the condensation of pcDNA, these sites can serve as nucleation site for metal plating. We have synthesized multimetallic nanopatterns composed of up to five metal elements (Co, Pd, Pt, Ag and Ni), and obtained insights on elemental uniformity control at the nanoscale. This method provides an alternative pathway to construct a library of multimetallic nanopatterns.

Three-dimensional electron ptychography of organic-inorganic hybrid nanostructures.

Three dimensional scaffolded DNA origami with inorganic nanoparticles has been used to create tailored multidimensional nanostructures. However, the image contrast of DNA is poorer than those of the heavy nanoparticles in conventional transmission electron microscopy at high defocus so that the biological and non-biological components in 3D scaffolds cannot be simultaneously resolved using tomography of samples in a native state. We demonstrate the use of electron ptychography to recover high contrast phase information from all components in a DNA origami scaffold without staining. We further quantitatively evaluate the enhancement of contrast in comparison with conventional transmission electron microscopy. In addition, We show that for ptychography post-reconstruction focusing simplifies the workflow and reduces electron dose and beam damage.

Probing of coupling effect induced plasmonic charge accumulation for water oxidation.

A key issue for redox reactions in plasmon-induced photocatalysis, particularly for water oxidation, is the concentration of surface-accumulating charges (electrons or holes) at a reaction site for artificial photosynthesis. However, where plasmonic charge accumulated at a catalyst's surface, and how to improve local charge density at active sites, remains unknown because it is difficult to identify the exact spatial location and local density of the plasmon-induced charge, particularly with regard to holes. Herein, we show that at the single particle level, plasmon-coupling-induced holes can be greatly accumulated at the plasmonic Au nanoparticle dimer/TiO2 interface in the nanogap region, as directly evidenced by the locally enhanced surface photovoltage. Such an accumulation of plasmonic holes can significantly accelerate the water oxidation reaction (multi-holes involved) at the interfacial reaction site, with nearly one order of magnitude enhancement in photocatalytic activities compared to those of highly dispersed Au nanoparticles on TiO2. Combining Kelvin probe force microscopy and theoretical simulation, we further clarified that the local accumulated hole density is proportional to the square of the local near-field enhancement. Our findings advance the understanding of how charges spatially distribute in plasmonic systems and the specific role that local charge density at reaction sites plays in plasmonic photocatalysis.

Nitrogen-Doped Carbon Quantum Dots from Poly(ethyleneimine) for Optical Dual-Mode Determination of Cu2+ and l-Cysteine and Their Logic Gate Operation.

In this work, nitrogen-doped carbon quantum dots from poly(ethyleneimine) (PQDs) were synthesized by a low-cost and facile one-step hydrothermal method without other reagents. A quantum yield (QY) of up to 23.2% with maximum emission at 460 nm under an excitation wavelength of 340 nm was ascribed to the high nitrogen doping (20.59%). The PQDs selectively form a blue complex with Cu2+ accompanied by strong quenching of the fluorescence emission. Meanwhile, the PQD-Cu2+ complex exhibited selective fluorescence recovery and color disappearance on exposure to l-cysteine (Cys). The electron transfer from amino or oxygen groups on the PQDs to Cu2+ leads to fluorescence quenching, and a chromogenic reaction of the cuprammonium complex results in a color change. The strong affinity between Cys and Cu2+ causes the detachment of Cu2+ from the surface of PQDs, so the color of the solution disappears and the fluorescence of PQDs recovers. Under the optimized condition, the proposed sensor was applied to detect Cu2+ in the linear range of 0-280 µM. A detection limit of 4.75 µM is achieved using fluorescence spectroscopy and 4.74 µM by monitoring the absorbance variation at 272 nm. For Cys detection, the linear range of 0-800 µM with detection limits of 28.11 µM (fluorescence determination) and 19.74 µM (peak shift determination at 272 nm) was obtained. Meanwhile, the PQD-Cu2+ system exhibits distinguishable responses to other biothiols such as l-glutathione (GSH) and dl-homocysteine (Hcy). Based on the multimode signals, an "AND" logic gate was constructed successfully. Interestingly, besides Cu2+, Fe3+ can also quench the fluorescence of PQDs and the PQD-Fe3+ system exhibits superior selectivity for Cys detection. Most importantly, the proposed assay is not only simple, cheap, and stable but also suitable for detecting Cu2+ and Cys in some real samples.

DNA-Guided Room-Temperature Synthesis of Single-Crystalline Gold Nanostructures on Graphdiyne Substrates.

Nobel metal nanoparticles with tunable morphologies are highly desirable due to their unique electronic, magnetic, optical, and/or catalytic features. Here we report the use of multilayered graphdyine (GD) as a substrate for the reductant-free, room-temperature synthesis of single-crystal Au nanostructures with tunable morphology. We find that the GD template rich in sp-carbon atoms possesses high affinity with Au atoms on the {111} facets, and that the intrinsic reductivity of GD facilitates the rapid growth of Au nanoplates. The introduction of single-stranded DNA strands further results in the synthesis of Au nanostructures with decreased anisotropy, i.e., polygons and flower-like nanoparticles. The DNA-guided tunable Au growth arises from the strong adsorption of DNA on the GD template that alters the uniformity of the interface, which provides a direct route to synthesize Au nanostructures with tailorable morphology and photonic properties.

Terminal deoxynucleotidyl transferase (TdT)-catalyzed homo-nucleotides-constituted ssDNA: Inducing tunable-size nanogap for core-shell plasmonic metal nanostructure and acting as Raman reporters for detection of Escherichia coli O157:H7.

Core-shell plasmonic metal nanoparticles with interior nanogaps are superior nanostructures owing to their large signal enhancement for Surface enhanced Raman spectroscopy (SERS). Herein, we incorporated Terminal deoxynucleotidyl transferase (TdT)-catalyzed DNA in the preparation of core-shell nanostructures for the detection of Escherichia coli O157:H7 (E. coli O157:H7) cells. The elongated products-homo-nucleotides-composed of long single DNA strands (hn-D) are used not only to induce tunable-size nanogaps but also as Raman reporters with consistent and uniform signal enhancement. Using this synthetic process of hn-D-embedded core-shell nanoparticles (hn-DENPs), we found that the length of hn-D strands affects the size of the nanogap. In addition, performances of the specific Raman imaging of E. coli O157:H7, high detection sensitivity of 2 CFU/mL, and the recovery of 98.1%-105.2% measured in the real food samples, make hn-DENP a biosensor that will be widely used in biological detection.

Quantizing single-molecule surface-enhanced Raman scattering with DNA origami metamolecules.

Tailored metal nanoclusters have been actively developed to manipulate light at the subwavelength scale for nanophotonic applications. Nevertheless, precise arrangement of molecules in a hot spot with fixed numbers and positions remains challenging. Here, we show that DNA origami metamolecules with Fano resonances (DMFR) can precisely localize single dye molecules and produce quantified surface-enhanced Raman scattering (SERS) responses. To enable tailored plasmonic permutations, we develop a general and programmable method for anchoring a set of large gold nanoparticles (L-AuNPs) on prescribed n-tuple docking sites of super-origami DNA frameworks. A tetrameric nanocluster with four spatially organized 80-nm L-AuNPs exhibits peak-and-dip Fano characteristics. The drastic enhancement at the wavelength of the Fano minimum allows the collection of prominent SERS spectrum for even a single dye molecule. We expect that DMFR provides physical insights into single-molecule SERS and opens new opportunities for developing plasmonic nanodevices for ultrasensitive sensing, nanocircuits, and nanophotonic lasers.

Framework nucleic acids as programmable carrier for transdermal drug delivery.

DNA nanostructures are promising drug carriers with their intrinsic biocompatibility, uniformity and versatility. However, rapid serum disintegration leads to low bioavailability at targeted sites following systemic administration, hindering their biomedical applications. Here we demonstrate transdermal delivery of framework nucleic acids (FNAs) through topical applications. By designing FNAs with distinct shapes and sizes, we interrogate their penetration on mice and human skin explant. Skin histology reveals size-dependent penetration, with FNAs ≤75 nm effectively reaching dermis layer. 17 nm-tetrahedral FNAs show greatest penetration to 350 µm from skin periphery. Importantly, structural integrity is maintained during the skin penetration. Employing a mouse melanoma model, topical application of doxorubicin-loaded FNAs accommodates ≥2-fold improvement in drug accumulation and tumor inhibition relative to topically-applied free doxorubicin, or doxorubicin loaded in liposomes and polymeric nanoparticles. Programmable penetration with minimal systemic biodistribution underlines FNA potential as localized transdermal drug delivery carriers.