The authors investigated the role of different size and morphology of cerium oxide nanoparticles (CNPs) in cellular uptake and internalization at the nano-bio interface. Atomic force microscopy (AFM) has been utilized to record changes in the membrane elasticity as a function of ceria particle morphology and concentration. Young's Modulus was estimated in presence and absence of CNPs of different sizes by gauging the membrane elasticity of CCL30 (squamous cell carcinoma) cells. Significant change in Young's Modulus was observed for CNP treatments at higher concentrations, while minimum membrane disruption was observed at lower concentrations. Studies using blocking agents specific to energy-dependent cellular internalization pathways indicated passive cellular uptake for smaller CNPs (3-5 nm). Other observations showed that larger CNPs were unable to permeate the cell membrane, which indicates an active uptake mechanism by the cell membrane. The ability of smaller CNPs (3-5 nm) to permeate the cell membrane without energy consumption by uptake pathways suggests potential for use as nanovectors for the delivery of bioactive molecules. Specifically, the passive uptake mechanism allows for the delivery of surface-bound molecules directly to the cytoplasm, avoiding the extreme chemical conditions of endosomal pathways.
Diamond is a material of choice in the pursuit of integrated quantum photonic technologies. So far, the majority of photonic devices fabricated from diamond, are made from (100)-oriented crystals. In this work, we demonstrate a methodology for the fabrication of optically-active membranes from (111)-oriented diamond. We use a liftoff technique to generate membranes, followed by chemical vapour deposition of diamond in the presence of silicon to generate homogenous silicon vacancy colour centers with emission properties that are superior to those in (100)-oriented diamond. We further use the diamond membranes to fabricate high quality microring resonators with quality factors exceeding ~ 3000. Supported by finite difference time domain calculations, we discuss the advantages of (111) oriented structures as building blocks for quantum nanophotonic devices.Diamond is an attractive platform for studies of light-matter interaction at the nanoscale[1-7]. In the past decade, defects in diamond, also known as color centers, have emerged as attractive candidates for scalable solid state quantum photonic architectures [1,6]. While earlier works were focused predominantly on nitrogen vacancy (NV) centres [8,9], recent effort is devoted to group IV defects [10][11][12][13][14][15], (e.g. the silicon vacancy (SiV)) due to their narrowband emission and a better resilience to electromagnetic fluctuations.Integration of these color centres with photonic resonators is an important challenge for several reasons. First, it enables enhancement of the photon emission flux from the single color centres (for instance by using diamond pillars [16]). Second, it provides the means to interconnect potential quantum nodes in a large network, where the emitters are coupled to individual cavities and interconnected with a waveguide [17,18]. Last, if the photonic resonator is carefully designed with coupled directional emission, one can achieve high cavity cooperativity and realise advanced quantum phenomena such as single photon switch with a solid state system [19]. However, despite the remarkable progress in nanofabrication of diamond cavities [8,20], all photonic resonators to date were fabricated from (100)-oriented diamond, primarily because this is the most common orientation provided by commercial suppliers and the difficulty in engineering and polishing (111) oriented crystals [21]. This, however, limits the potential coupling strength of many color centers to cavities since most centers studied to date have dipoles oriented along the <111> direction, and the dipole overlap with the cavity field is therefore not optimal in cavities fabricated from (100)-oriented diamond. Conversely, in (111)-oriented diamond, the overlap is optimal, and superior Purcell enhancement is expected.In the current work, we fabricated large area (111) diamond membranes that exhibit bright SiV luminescence. Consequently, these membranes were utilized to engineer high quality diamond microring resonators with quality factors of ~ 3000. Our work launches a new ...
Nitrogen-vacancy (NV) centers in nanodiamond (ND) are promising single photon source candidate for quantum technology. However, the poor NV emission rate and low outcoupling of light significantly hinder their effective use in practical implementations. To overcome this limit, we place NDs hosting NV centers on silver columnar thin films (CTFs) and measure an increase in emittance by an order of magnitude. The CTFs consist of silver nanocolumns whose length was chosen to be half the wavelength of the emitted light. The silver nanocolumns act as efficient optical antennas that couple to the NV centers via the optical near-field and outcouple the excitation energy of the NV centers effectively into the optical far-field. A large distribution of radiated powers from different NDs is observed. Computer simulations show this distribution to arise from the different orientations of the emitting dipoles with respect to the columnar axis. We also report that further structuring of the silver CTF into gratings yields higher photon emission.
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