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Since about a decade, metal-induced energy transfer (MIET) has become a tool to measure the distance of fluorophores to a metal-coated surface with nanometer accuracy. The energy transfer from a fluorescent molecule to surface plasmons within a metal film results in the acceleration of its radiative decay rate. This can be observed as a reduction of the molecule’s fluorescence lifetime which can be easily measured with standard microscopy equipment. The achievable distance resolution is in the nanometer range, over a total range of about 200 nm. The method is perfectly compatible with biological and even live cell samples. In this review, we will summarize the theoretical and technical details of the method and present the most important results that have been obtained using MIET. We will also show how the latest technical developments can contribute to improving MIET, and we sketch some interesting directions for its future applications in the life sciences.

Lithium ions-doped polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) films were prepared by solution casting technique and exposed to 100 kGy gamma radiation. The structural modifications in the samples before and after irradiation were studied using X-ray diffraction XRD and UV–Vis spectroscopy. The results indicated that absorbance A(λ) and absorption index (k) increased, while semicrystalline nature of the blend decreased due to the addition of Li2SO4 and irradiation. The optical band gap Egopt of the composites showed significant decrease from 2.98 to 2.196 eV by adding Li2SO4 and from 2.83 to 2.08 eV after irradiation due to cross-linking. The Tauc’s relation indicated that allowed transitions are indirect for both irradiated and unirradiated samples. The Urbach energy (Eu) increased with increasing Li ion content and exposure to γ irradiation. The dependence of dielectric permittivity ε1, dielectric loss ε2 and optical conductivity σopt on photon energy hν was also studied.

Size and composition dependence of optical properties in alloyed semiconducting compounds is drawing the attention of researchers from past years. In the present paper; the author has studied the effect of alloying on the energy bandgap, refractive index and dielectric constant energy with variation in composition in ternary alloy of lead chalcogenides. Also, the impact of size reduction and dimension on band gap energy in lead chalcogenides is studied using a quantitative approach. The optical and electronic properties of semiconductor nanocrystals are found to vary with dimension and size. Ternary semiconducting homogeneous alloy of IV-VI group viz. PbSexS1-x is considered for studying the composition impact on electronic and optical properties. The study provides an insight of the effect of composition on the energy bandgap, refractive index and dielectric constant of PbSexS1-x and give the possibility of tuning these properties of materials based on demand. The model predications are observed in favorable agreement with the available experimental and stimulated data.

An ab initio investigation of optical and thermodynamic properties of two polymorphs of intermetallic compound Ga3Zr has been carried out by the plane-wave pseudopotential method based on density functional theory. Frequency-dependent dielectric matrix is used to determine the imaginary part of the dielectric function from which the real part has been obtained through Kramers–Kronig relations. Other optical properties, namely optical conductivity, absorption coefficient and reflectivity, are also determined. The analysis of all optical functions reveals that tetragonal Ga3Zr is slightly optically anisotropic. The absorption spectra having metallic nature show both of these to be promising materials for absorbing radiation in the UV region. The reflectivity spectra are compared with those of several compounds in the low-energy range. Due to high reflectivity in the IR and visible regions, both the studied polymorphs are promising as good coating materials in order to avoid solar heating and also as radiative cooling materials. Furthermore, the temperature and pressure dependences of all the thermodynamic parameters of the polymorphs with the cubic and tetragonal structures are calculated and analyzed for the first time using the quasi-harmonic Debye model.

Investigations into the phonon behavior provide important information on interactions between different excitations in quantum materials. We perform a detailed study of the phonon behavior in the topological insulator Sn-doped Bi 1.1 Sb 0.9 Te 2 S using infrared spectroscopy. We observe two IR-active phonon modes at about 64 and 165 cm −1 , which are labeled with α and β , respectively. While the evolution of the β mode with temperature can be well described by the expected anharmonic decay process, the α mode shifts to lower frequencies with decreasing temperature. Such an anomalous softening of the α mode may arise from the charged-phonon effect due to the coupling between this mode and the topological surface states in Sn-doped Bi 1.1 Sb 0.9 Te 2 S.

Single crystals of pure potassium dihydrogen phosphate (KDP) and Reactive Orange 16 or Remazol Brilliant Orange dye-doped (0.1, 0.2 and 0.3 mol%) KDP single crystals were grown by slow evaporation method with the vision to improve the properties of pure KDP crystal. Enhanced dielectric, optical, thermal and NLO properties have been achieved by dye doping. The crystallinity and phase purity of the grown crystals were analysed by PXRD. The identification of various functional groups and dye incorporation in the grown crystals was confirmed qualitatively by FTIR analysis. The linear optical study on pure and dye-doped crystals was carried out using UV–Vis–NIR spectroscopy. The optical band gap, extinction coefficient, refractive index and optical conductivity were calculated using the transmittance spectra for all the samples. The thermal stability and the decomposition temperature were found to increase with the concentration of the dopant. This indicates the high quality of the crystal as well as its perfection. The SHG efficiency measurements were taken for the grown crystals and found that the SHG efficiency increases with doping concentration. The enhanced optical constants, thermal stability and second harmonic generation ability confirm the suitability of the grown crystals for solid-state laser materials.

Indium sulfide thin films were prepared by chemical bath deposition method on glass substrates for about 40 min as deposition time and 60 °C as deposition temperature. The films were post-annealed at different temperatures such as 100 °C, 200 °C, 300 °C and 400 °C, for about 1 h. Structural and optical properties of In2S3 thin films after post-annealing process have been investigated. The crystallinity and nanostructures of the films were studied by using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy analysis. Optical reflectance and transmittance of layers were measured in the wavelength of 300–1100 nm by spectrophotometer instrument. Kramers–Kronig relations were used to calculate the optical constants. The X-ray diffraction measurements showed transformation of an amorphous nature to a crystalline structure by increasing the annealing temperature. The atomic force microscopy images showed by increasing the annealing temperature, the roughness of the thin films increased. The scanning electron microscopy images revealed that growth rate increased consistently with the increase in annealing temperature and well-dispersed quasi-spherical nanoparticles with high agglomeration rate are formed at 400 °C. The energy-dispersive X-ray spectroscopy results show reduction in the S/In ratio from 1.61 to 1.49 when annealing temperature increased. Optical results showed the highest optical band gap of 3.65 eV was achieved at the highest annealing temperature (400 °C).

The generation of second harmonic (SH) in the structure (SiO 2 /MnF 2 /graphene) N /ZrO 2 has been investigated with the matrix transfer method. The theoretical simulation results show that the effect of the graphene (Gr) on SH outputs above or below the surface is obvious. The SH outputs compared with the same structure only without the Gr layer are greatly enhanced, even about two or three orders at some special cases. Also, the position and intensity of the SH outputs can be effectively tuned by an external magnetic field. An optimal structure is determined through investigating the effect of the Gr positions and dielectrics on the SH outputs. Finally, a critical cycle unit N = 8 is checked out, while the SH outputs begin to decrease once N > 8 . These interesting results may be helpful to the development and utilization of nonlinear devices in the THz frequency field.

Laser induced damage threshold (LIDT) of nano-porous antireflective silica thin films is measured using 10 ns laser pulses at λ = 532 nm. The thin films are prepared by dip-coating of BK7 substrates and then drying them by three different heating methods, to see how their LIDT and transmission are affected. Furthermore, using SEM imaging, the morphology of the laser induced damages is inspected and compared to those of similar samples, previously irradiated by femtosecond laser pulses at λ = 800 nm. The images evidently show that in the regions damaged by nanosecond pulses, the silica nanoparticles are melted and fused to each other, while in the samples irradiated by femtosecond pulses, the silica nanoparticles are sputtered and dispersed around, in the damaged area. The SEM images clearly demonstrate the different damage mechanisms involved in the nanosecond and femtosecond regimes of interaction.

Effect of Cu2+ content on different properties was investigated. Mg1−xCuxO (0.05 ≤ x ≤ 0.2) powder was prepared via solid-state reaction. The samples were examined by X-ray diffraction, and the results were analyzed by using Full Prof program by employing Rietveld refinement technique. The results showed that samples with Cu content up to x = 0.15 had a single phase of MgO rock salt structure type and for x = 0.2 two phases were detected, namely MgO rock salt structure and Cu2O cuprite cubic phase. Also, it was found a small increase in the lattice constants with increasing the Cu content. Moreover, the crystallite size was found to decrease with increasing the Cu concentration. The morphology was studied by transmission electron microscopy. The optical energy gap was calculated, and it was found that it has two values. The energy gaps decreased with increasing the Cu content. The dielectric constant ε′, the loss factor tan δ and conductivity increased with increasing Cu concentration. This increase can be directly related to the increase in the concentration of charge carriers and interfacial polarization effects. The saturation magnetization and the retentivity were found to decrease with the increase in Cu concentrations, but the coercivity increased with increasing Cu content.