No abstract

The development of a robust light source that emits one photon at a time will allow new technologies such as secure communication through quantum cryptography. Devices based on fluorescent dye molecules, quantum dots and carbon nanotubes have been demonstrated, but none has combined a high single-photon flux with stable, room-temperature operation. Luminescent centres in diamond have recently emerged as a stable alternative, and, in the case of nitrogen-vacancy centres, offer spin quantum bits with optical readout. However, these luminescent centres in bulk diamond crystals have the disadvantage of low photon out-coupling. Here, we demonstrate a single-photon source composed of a nitrogen-vacancy centre in a diamond nanowire, which produces ten times greater flux than bulk diamond devices, while using ten times less power. This result enables a new class of devices for photonic and quantum information processing based on nanostructured diamond, and could have a broader impact in nanoelectromechanical systems, sensing and scanning probe microscopy.

Eukaryotic cells coordinately control anabolic and catabolic processes to maintain cell and tissue homeostasis. The mechanistic target of rapamycin complex 1 (mTORC1) promotes nutrient-consuming anabolic processes, such as protein synthesis1. Here, we show that accompanying an increase in protein synthesis, mTORC1 activation also promotes an increased capacity for protein degradation. Cells with activated mTORC1 exhibited elevated levels of intact and active proteasomes through a global increase in the expression of genes encoding proteasome subunits. The increase in proteasome gene expression, cellular proteasome content, and rates of protein turnover downstream of mTORC1 were all dependent on induction of the transcription factor nuclear factor erythroid-derived 2-related factor 1 (NFE2L1 or NRF1). Genetic activation of mTORC1 through loss of the tuberous sclerosis complex tumor suppressors or physiological activation of mTORC1 in response to growth factors or feeding resulted in increased NRF1 expression in cells and tissues. We find that this NRF1-dependent elevation of proteasome levels serves to increase the intracellular pool of amino acids, which thereby influences rates of new protein synthesis. Therefore, mTORC1 signaling increases the efficiency of proteasome-mediated protein degradation for both quality control and as a mechanism to supply substrate for sustained protein synthesis.

Graphene-based metamaterials have been theoretically demonstrated as an enabler for applications as perfect absorbers, photodetectors, light emitters, modulators, and tunable spintronic devices. However, challenges associated with conventional film deposition techniques have made the multilayered metamaterial difficult to fabricate, which have severely limited experimental validations. Herein, the experimental demonstration of the phototunable graphene-based multilayered metamaterials on diverse substrates by a transfer-free, solution-phase deposition method is presented. The optical properties of the metamaterials are tuned dynamically by controllable laser-mediated conversion from graphene oxide layers into graphene counterparts, which exhibit different degrees of conversion, which would offer huge potential for devices design and fabrication. The converted graphene layers present comparable (within 10%) optical conductivity to their chemical vapor deposited analogues. Moreover, laser patterning leads to functional photonic devices such as ultrathin flat lenses embedded in the lab-on-chip device, which maintains consistency and exhibits subwavelength focusing resolution in aqueous environments without any noticeable degradation compared with the original lens. This graphene-based metamaterial provides a new experimental platform for broad applications in on-chip integrated photonic, biomedical, and microfluidic devices.