Both the nonclose-packed structure and the large refractive index contrast of guanine nanocrystals and cytosols in iridophores play a vital role in the dynamic camouflage of chameleons, including the bright skin color and color tuning sensitivity to external stimulus. Here, the nonclose-packed photonic crystals consisting of ZnS nanospheres and polymers, which have similar refractive indices with guanine nanocrystals and cytosols, respectively, are constructed by a twostep filling strategy. ZnS@SiO 2 nanospheres are self-assembled to build intermediate close-packed photonic crystals followed by filling polymers in their interstices. The nonclose-packed photonic crystal is successfully achieved when the silica portion is etched by HF solution and refilled by polymers. Excitingly, the stimulus response of the designed photonic crystal is as sensitive as the skin of chameleons due to the similar contrast of refractive indices and nonclose-packed structure. The reflection peak of the structure can blue-shift more than 200 nm as the temperature increases from 30 to 55 °C or under 20% compressional strain. This work not only builds the nonclose-packed photonic crystals by introducing a two-step filling strategy but also proves that high refractive contrast in photonic crystals is an effective strategy to achieve ultrasensitivity, which is highly desirable for various applications.

In this article we have investigated the electrical control of the exchange coupling (J) between donor-bound electrons in silicon with a detuning gate bias, crucial for the implementation of the two-qubit gate in a silicon quantum computer. We found that the asymmetric 2P-1P system provides a highly tunable exchange curve with mitigated J-oscillation, in which 5 orders of magnitude change in the exchange coupling can be achieved using a modest range of electric field (3 MV/m) for~15-nm qubit separation. Compared with the barrier gate control of exchange in the Kane qubit, the detuning gate design reduces the gate density by a factor of~2. By combining large-scale atomistic tight-binding method with a full configuration interaction technique, we captured the full two-electron spectrum of gated donors, providing state-of-the-art calculations of exchange energy in 1P-1P and 2P-1P qubits.npj Quantum Information (2016) 2, 16008; doi:10.1038/npjqi.2016.8; published online 12 April 2016 INTRODUCTION Donor qubits in silicon are promising candidates for spin-based quantum computation as they have exceptionally long T 1 (refs 1-3) and T 2 times 4-6 and offer both electron and nuclear spins for encoding quantum information 5-8 utilising commonly used silicon device technology. With recent demonstration of single qubits in silicon with both electronic and nuclear spins of donors, 5,7 the next biggest challenge is to demonstrate two-qubit gates based on the exchange interaction. Ideally, the exchange coupling J in a two-qubit gate needs to be tuned electrically by several orders of magnitude between an 'Off' and an 'On' state within a small and realisable bias range. To achieve this, the popular Kane architecture uses a J-gate between two phosphorus donors to tune the J-coupling. Recently A-gates that tune the hyperfine interaction for individual qubits have been demonstrated. 9 However, in the long run such a J-and A-gate architecture leads to a high gate density, requiring ultra-small gate widths to minimise electrical cross-talk between gates, and precise donor positioning relative to gates. Moreover, the tunability of the exchange coupling is limited both by the electric field range the J-gate can produce and by the field ionisation of the electrons to the surface. Previous calculations have also shown that the J-coupling oscillates as a function of donor separation due to crystal momentum states, 10 and is therefore sensitive to atomic-scale placement errors. All these issues lead to severe constraints in the implementation of a two-qubit gate in donors.In this work, we introduce an alternative design for an exchange gate in a two-qubit donor system, which allows flexibility in device fabrication and in tuning the exchange coupling. In principle, this new design can (1) eliminate the need for additional J-gates between the donors, (2) function with a range of donor separations, (3) provide an~5 orders of magnitude J-tunability within a modest E-field range of~3 MV/m and lowered 'Off' state exchange and (4) mitigate th...

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Multiplexed microRNA (miRNA) quantification has a demonstrated value in clinical diagnosis. In this paper, novel mussel-inspired photonic crystal (PhC) barcodes with graphene oxide (GO) encapsulation for multiplexed miRNA detection are presented. Using the excellent adhesion capability of polydopamine, the dispersed GO particles can be immobilized on the surfaces of the PhC barcodes to form an additional functional layer. The GO-decorated PhC barcodes have constant characteristic reflection peaks because the GO immobilization process not only maintains their periodic microstructure but also enhances their stability and anti-incoherent lightscattering capability. The immobilized GO particles are shown to enable high-sensitivity miRNA screening on the surface of the PhC barcodes by integration with a hybridization chain reaction amplification strategy. Because the PhC barcodes have stable encoding reflection peaks, multiplexed low-abundance miRNA quantification can also be achieved rapidly, accurately, and reproducibly by employing different GO-decorated PhC barcodes. These features should make GO-encapsulated PhC barcodes ideal for many practical applications.