Fluorescence spectroscopy is widely used in biological research. Until recently, essentially all fluorescence experiments were performed using optical energy which has radiated to the far-field. By far-field we mean at least several wavelengths from the fluorophore, but propagating far-field radiation is usually detected at larger macroscopic distances from the sample. In recent years there has been a growing interest in the interactions of fluorophores with metallic surfaces or particles. Near-field interactions are those occurring within a wavelength distance of an excited fluorophore. The spectral properties of fluorophores can be dramatically altered by near-field interactions with the electron clouds present in metals. These interactions modify the emission in ways not seen in classical fluorescence experiments. In this review we provide an intuitive description of the complex physics of plasmons and near-field interactions. Additionally, we summarize the recent work on metal-fluorophore interactions and suggest how these effects will result in new classes of experimental procedures, novel probes, bioassays and devices.

Harvesting biomechanical energy is an important route for providing electricity to sustainably drive wearable electronics, which currently still use batteries and therefore need to be charged or replaced/disposed frequently. Here we report an approach that can continuously power wearable electronics only by human motion, realized through a triboelectric nanogenerator (TENG) with optimized materials and structural design. Fabricated by elastomeric materials and a helix inner electrode sticking on a tube with the dielectric layer and outer electrode, the TENG has desirable features including flexibility, stretchability, isotropy, weavability, water-resistance and a high surface charge density of 250 μC m−2. With only the energy extracted from walking or jogging by the TENG that is built in outsoles, wearable electronics such as an electronic watch and fitness tracker can be immediately and continuously powered.

Human biomechanical energy is characterized by fluctuating amplitudes and variable low frequency, and an effective utilization of such energy cannot be achieved by classical energy-harvesting technologies. Here we report a high-efficient self-charging power system for sustainable operation of mobile electronics exploiting exclusively human biomechanical energy, which consists of a high-output triboelectric nanogenerator, a power management circuit to convert the random a.c. energy to d.c. electricity at 60% efficiency, and an energy storage device. With palm tapping as the only energy source, this power unit provides a continuous d.c. electricity of 1.044 mW (7.34 W m−3) in a regulated and managed manner. This self-charging unit can be universally applied as a standard ‘infinite-lifetime' power source for continuously driving numerous conventional electronics, such as thermometers, electrocardiograph system, pedometers, wearable watches, scientific calculators and wireless radio-frequency communication system, which indicates the immediate and broad applications in personal sensor systems and internet of things.

The first bionic membrane sensor based on triboelectrification is reported for self-powered physiological and behavioral measurements such as local internal body pressures for non-invasive human health assessment. The sensor can also be for self-powered anti-interference throat voice recording and recognition, as well as high-accuracy multimodal biometric authentication, thus potentially expanding the scope of applications in self-powered wearable medical/health monitoring, interactive input/control devices as well as accurate, reliable, and less intrusive biometric authentication systems.

We prepared silver particle dimers with single Cy5 molecules localized between coupled metal particles. The silver particles with a 20 nm diameter were chemically bound with single-stranded oligonucleotides. The dimers were formed by hybridization with double-length single-stranded oligonucleotides that contained single Cy5 molecules. The image analysis revealed that the singlemolecule fluorescence was enhanced 7-fold on the metal monomer and 13-fold on the metal dimer relative to the free Cy5-labeled oligonucleotide in the absence of metal. The lifetimes were shortened on the silver monomers and further shortened on the silver dimers, demonstrating the near-field interaction mechanism of fluorophore with the metal substrate. Finite-difference time-domain (FDTD) calculations were employed to study the distribution of electric field near the metal monomer and dimer. The coupling effect of metal particle on the fluorescence enhancement was discussed.A fluorophore behaves as an oscillating dipole to radiate energy as fluorescence. 1,2 When the fluorophore is localized near a metal surface, fluorescence can be enhanced, which we define as metal-enhanced fluorescence (MEF). [3][4][5][6][7][8][9] MEF is known to occur primarily due to the nearfield interactions of the excited-state fluorophore with the local electric fields on the metal particle that is induced by incident light. 8,9 This approach is attracting interest in developing novel nanoscale structures for biological and clinical fluorescence sensing. 10,11 Single-molecule detection (SMD) is regarded as a valuable method to study fluorophore-metal interaction at the single-molecule level because of its ability to bypass ensemble averaging and allow resolution of actual distributions of the spectral parameters. 12 Such details of the underlying distribution become crucially important when the system is heterogeneous. 13 The brightness or emission rate determines the observability of a single molecule and the photostability determines the time that it can be observed prior to photobleaching. Hence it is crucial to extend the improved ensemble spectral properties to single-molecule level. Herein, we utilized the SMD technology to investigate MEF on the metal particle at single-fluorophore level. 14 Experimentally, the silver particles were synthesized by a wet method. 15 The singlestranded oligonucleotides were first chemically bound to the metal particles, and the fluorophore-labeled complementary oligonucleotides (oligonucleotides 2 in Scheme 1) were bound to the metal particles by hybridization with the bound oligonucleotides on the metal particles. 16 According to Schatz et al., the electric field in the space between the coupled metal particles is more intense than that of a monomer. 17 Thus, we are interested in the coupling effect of the metal dimers on MEF. In this system, the metal dimers were synthesized and Experimental SectionAll reagents and spectroscopic grade solvents were used as received from Fisher or Aldrich. RC dialysis membrane ...