This review focuses on metal enhanced fluorescence (MEF) and its current and future applications in biotechnology. The mechanisms of MEF are discussed in terms of the additional radiative and nonradiative decay rates caused by the close proximity of the metal. We then review the current MEF materials and structures that show promise in bioapplications. The use of electromagnetic modelling to predict fluorescent rate enhancement is then considered. We then give particular focus to the recent work carried out in the homogeneous fabrication of metal nanoparticles using colloidal lithography. It is concluded that the use of computational electromagnetic modelling alongside homogeneous fabrication techniques will lead to predictable and controllable MEF, paving the way for increased applications in biotechnology.

ZnO nanoflower arrays have significantly higher fluorescence enhancement than ZnO nanorod arrays, with broadband enhancement capability.

Zinc oxide (ZnO) nanorods (NRs) have been demonstrated as a promising platform for enhanced fluorescence-based sensing. It is, however, desirable to achieve a tuneable fluorescence enhancement with these platforms so that the fluorescence output can be adjusted based on the real need. Here we show that the fluorescence enhancement can be tuned by changing the diameter of the ZnO nanorods, simply controlled by potassium chloride (KCl) concentration during synthesis, using arrays of previously developed aligned NRs (a.k.a. aligned NR forests) and nanoflowers (NFs). Combining the experimental results obtained from ZnO nanostructures with controlled morphology and computer-aided verification, we show that the fluorescence enhancement factor increases when ZnO NRs become thicker. The fluorescence enhancement factor of NF arrays is shown to have a much stronger dependency on the rod diameter than that of aligned NR arrays. We prove that the morphology of nanostructures, which can be controlled, can be an important factor for fluorescence enhancement. Our (i) effort towards understanding the structure-property relationships of ZnO nanostructured arrays and (ii) demonstration on tuneable fluorescence enhancement by nanostructure engineering can provide some guidance towards the rational design of future fluorescence amplification platforms potentially for bio-sensing.

a b s t r a c tThere has been an increasing interest in plasmon-induced enhancement of solar cells and more recently in the direct generation of photocurrent using noble metal nanoparticles with their Localised Surface Plasmon Resonance (LSPR) in the visual part of the spectrum. In this paper we report broadband plasmon photocurrent generation using novel Au nanoparticle incorporated mesoporous TiO 2 nanotube electrodes. Plasmonic induced photocurrent due to hot electrons is observed over a broad wavelength range ( $ 500 to 1000 nm). Incident photon-to-electron conversion efficiency (IPCE) measurements undertaken showed a maximum photocurrent enhancement of 200 fold around 700-730 nm wavelength.

A strongly anisotropic etching process mediated by temperature is presented to create nano mushroom arrays from a monolayer of spheres.

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Solid‐state nanopores are implemented in new and promising platforms that are capable of sensing fundamental biomolecular constituents at the single‐molecule level. However, several limitations and drawbacks remain. For example, the current strategies based on both electrical and optical sensing suffer from low analyte capture rates and challenging nanofabrication procedures. In addition, their limited discrimination power hinders their application in the detection of complex molecular constructs. In contrast, Raman spectroscopy has recently demonstrated the ability to discriminate both nucleotides and amino acids. Herein, a plasmonic nanoassembly is proposed supporting nanopores at high density, in the order of 100 pores per µm2. These findings demonstrate that the device has a high capture rate in the range of a few fm. The pore size is ≈10 nm in diameter and provides an amplification of the electromagnetic field exceeding 103 in intensity at 785 nm. Owing to these features, single‐molecule detection is achieved by means of surface‐enhanced Raman scattering from a solution containing 50 fm DNA molecules (≈4.4 kilobase pairs). Notably, the reported spectra show an average number of 2.5 Raman counts per nucleotide. From this perspective, this number is not far from what is necessary to discriminate the DNA sequence.

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