We report a general strategy for designing and synthesizing inorganic nanostructures with arbitrarily prescribed three-dimensional shapes. Computationally designed DNA strands self-assemble into a stiff “nano-mold” that contains a user-specified three-dimensional cavity and encloses a nucleating gold “seed”. Under mild conditions, this seed grows into a larger cast structure that fills and thus replicates the cavity. We synthesized a variety of nanoparticles with three nanometer resolution: three distinct silver cuboids with three independently tunable dimensions, silver and gold nanoparticles with diverse cross sections, and composite structures with homo-/heterogeneous components. The designer equilateral silver triangular and spherical nanoparticles exhibited plasmonic properties consistent with electromagnetism-based simulations. Our framework is generalizable to more complex geometries and diverse inorganic materials, offering a range of applications in biosensing, photonics, and nanoelectronics.

Natural light-harvesting systems spatially organize densely packed chromophore aggregates using rigid protein scaffolds to achieve highly efficient, directed energy transfer. Here, we report a synthetic strategy using rigid DNA scaffolds to similarly program the spatial organization of densely packed, discrete clusters of cyanine dye aggregates with tunable absorption spectra and strongly coupled exciton dynamics present in natural light-harvesting systems. We first characterize the range of dye-aggregate sizes that can be templated spatially by A-tracts of B-form DNA while retaining coherent energy transfer. We then use structure-based modelling and quantum dynamics to guide the rational design of higher-order synthetic circuits consisting of multiple discrete dye aggregates within a DX-tile. These programmed circuits exhibit excitonic transport properties with prominent circular dichroism, superradiance, and fast delocalized exciton transfer, consistent with our quantum dynamics predictions. This bottom-up strategy offers a versatile approach to the rational design of strongly coupled excitonic circuits using spatially organized dye aggregates for use in coherent nanoscale energy transport, artificial light-harvesting, and nanophotonics.

The generation of nanobubbles around plasmonic nanostructures is an efficient approach for imaging and therapy, especially in the field of cancer research. We show a novel method using infrared femtosecond laser that generates ≈800 nm bubbles around off-resonance gold nanospheres using 200 mJ/cm(2) 45 fs pulses. We present experimental and theoretical work that demonstrate that the nanobubble formation results from the generation of a nanoscale plasma around the particle due to the enhanced near-field rather than from the heating of the particle. Energy absorbed in the nanoplasma is indeed more than 11 times the energy absorbed in the particle. When compared to the usual approach that uses nanosecond laser to induce the extreme heating of in-resonance nanoparticles to initiate bubble formation, our off-resonance femtosecond technique is shown to bring many advantages, including avoiding the particles fragmentation, working in the optical window of biological material and using the deposited energy more efficiently.

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We present a theoretical and experimental study that reveals the physical mechanism underlying the response of an in-resonance gold nanorod (AuNR) in water to a near-infrared ultrafast laser pulse. Results reveal the presence of two different regimes of interaction, depending on the irradiation fluence. For fluences below 3 mJ/cm 2 , AuNRs are in the so-called absorption regime and are shown to strongly absorb energy, leading to a fast temperature increase revealed by the onset of characteristic mechanical vibration of the structure. In situ measurement demonstrates a permanent deformation of the AuNRs occurring for fluences over 100 μJ/cm 2 . In the absorption regime, we show the formation of a nanoscale plasma around the structure, dominated by a photothermal emission from the AuNR, and the generation of a pressure wave. However, no cavitation occurs under the deformation threshold fluence (100 μJ/cm 2 ). For fluences over 3 mJ/cm 2 , in the near-field regime, the energy transfer is dominated by the enhanced near-field around the particle that directly ionizes and heats a nanoplasma in the surrounding water. We theoretically show that bubbles with diameters ≈ 490 nm can be generated in this near-field regime for an incident fluence of 200 mJ/cm 2 . In situ optical characterization of the produced bubbles supports this result and shows that bubbles with diameters ≈ 200−600 nm can be generated for fluences ranging 100−400 mJ/cm 2 . Important shielding of the laser−nanostructure interaction by the surrounding plasma is shown to decrease considerably the near-field enhancement, the energy absorption, and the diameter of the generated bubbles and may explain the smaller bubbles generated around in-resonance 10 × 41 nm 2 AuNRs when compared to off-resonance 25 × 60 nm 2 AuNRs and 100 nm AuNPs.

Metallic nanoparticles are routinely used as nanoscale antenna capable of absorbing and converting photon energy with subwavelength resolution. Many applications, notably in nanomedicine and nanobiotechnology, benefit from the enhanced optical properties of these materials, which can be exploited to image, damage, or destroy targeted cells and subcellular structures with unprecedented precision. Modern inorganic chemistry enables the synthesis of a large library of nanoparticles with an increasing variety of shapes, composition, and optical characteristic. However, identifying and tailoring nanoparticles morphology to specific applications remains challenging and limits the development of efficient nanoplasmonic technologies. In this work, we report a strategy for the rational design of gold plasmonic nanoshells (AuNS) for the efficient ultrafast laser-based nanoscale bubble generation and cell membrane perforation, which constitute one of the most crucial challenges toward the development of effective gene therapy treatments. We design an in silico rational design framework that we use to tune AuNS morphology to simultaneously optimize for the reduction of the cavitation threshold while preserving the particle structural integrity. Our optimization procedure yields optimal AuNS that are slightly detuned compared to their plasmonic resonance conditions with an optical breakdown threshold 30% lower than randomly selected AuNS and 13% lower compared to similarly optimized gold nanoparticles (AuNP). This design strategy is validated using time-resolved bubble spectroscopy, shadowgraphy imaging and electron microscopy that confirm the particle structural integrity and a reduction of 51% of the cavitation threshold relative to optimal AuNP. Rationally designed AuNS are finally used to perforate cancer cells with an efficiency of 61%, using 33% less energy compared to AuNP, which demonstrate that our rational design framework is readily transferable to a cell environment. The methodology developed here thus provides a general strategy for the systematic design of nanoparticles for nanomedical applications and should be broadly applicable to bioimaging and cell nanosurgery.

The laser-induced generation of vapor bubbles around gold nanoparticles (AuNPs) is a promising diagnostic and therapeutic avenue for various pathologies. The physical mechanism that leads to their formation strongly depends on the time regime of the irradiation. While the plasmonic nanobubbles induced by nanosecond and picosecond laser pulses are known to be triggered by the energy that is absorbed in the nanoparticles and diffused in the medium (thermo-mediated cavitation), we show that a different plasma-mediated mechanism occurs in the case of femtosecond pulses. In this paper, we present experimental evidence that the dimensions of laser-induced bubbles depend on the polarization of the incident laser pulse when the pulse duration is reduced below ∼1 ps. This result cannot be explained by the standard thermo-mediated cavitation process and, thus, reveals the onset of a new mechanism in the ultrafast regime. We further show that the discrepancy between the dimensions of bubbles generated from linearly and circularly polarized laser pulses can be explained using a simple model, revealing the polarization cavitation dependence as a clear signature of the plasma mechanism. This paper presents in detail the transition between both cavitation regimes and provides insight into the precise control of the cavitation dynamics at the nanoscale.