Emerging Fluorescent Nanoparticles for Non-Invasive Bioimaging.

Fluorescence-based techniques have great potential in the field of bioimaging and could bring tremendous progress in microbiology and biomedicine. The most essential element in these techniques is fluorescent nanomaterials. The use of fluorescent nanoparticles as contrast agents for bioimaging is a large topic to cover.

Real-time, label-free detection and identification of bacteria through non-invasive optical imaging.

Currently, traditional and newer molecular and mass spectrometry techniques of identifying bacteria from biological samples requires lengthy sample preparation, growth and labelling/staining assays. Thus, there is a pressing clinical need for an adjunct method that accurately identifies bacteria in real time. Here we report on the evaluation of confocal microscopy for the identification of clinically important and multi-drug resistant (MDR) bacteria in real time, using their intrinsic fluorescence features, i.

Silk Fibroin Coated Magnesium Oxide Nanospheres: A Biocompatible and Biodegradable Tool for Noninvasive Bioimaging Applications.

Fluorescent nanoparticles (NPs) have been increasingly studied as contrast agents for better understanding of biological processes at the cellular and molecular level. However, their use as bioimaging tools is strongly dependent on their optical emission as well as their biocompatibility. This work reports the fabrication and characterization of silk fibroin (SF) coated magnesium oxide (MgO) nanospheres, containing oxygen, Cr and V related optical defects, as a nontoxic and biodegradable hybrid platform for bioimaging applications.

Detection and identification of polyaromatic hydrocarbons (PAHs) contamination in soil using intrinsic fluorescence.

Polyaromatic hydrocarbons (PAHs), such as pyrene, benzo[a]pyrene, phenanthrene, and anthracene induce toxic, carcinogenic, and mutagenic effects on living organisms and are considered as primary pollutants. Traditional methods for their identification are often laborious and time-consuming and do not account for the heterogeneous nature of their distribution. Here we present confocal microscopy as a rapid and accurate technique for direct analysis of PAHs in soil samples without the complexity of sample pre-processing which might delay results for several days.

Biocompatible and Biodegradable Magnesium Oxide Nanoparticles with In Vitro Photostable Near-Infrared Emission: Short-Term Fluorescent Markers.

Imaging of biological matter by using fluorescent nanoparticles (NPs) is becoming a widespread method for in vitro imaging. However, currently there is no fluorescent NP that satisfies all necessary criteria for short-term in vivo imaging: biocompatibility, biodegradability, photostability, suitable wavelengths of absorbance and fluorescence that differ from tissue auto-fluorescence, and near infrared (NIR) emission. In this paper, we report on the photoluminescent properties of magnesium oxide (MgO) NPs that meet all these criteria.

Room-temperature single-photon emitters in titanium dioxide optical defects.

Fluorescence properties of crystallographic point defects within different morphologies of titanium dioxide were investigated. For the first time, room-temperature single-photon emission in titanium dioxide optical defects was discovered in thin films and commercial nanoparticles. Three-level defects were identified because the correlation data featured prominent shoulders around the antibunching dip.

Scalable fabrication of high-quality, ultra-thin single crystal diamond membrane windows.

High quality, ultra-thin single crystal diamond (SCD) membranes that have a thickness in the sub-micron range are of extreme importance as a materials platform for photonics, quantum sensing, nano/micro electro-mechanical systems (N/MEMS) and other diverse applications. However, the scalable fabrication of such thin SCD membranes is a challenging process. In this paper, we demonstrate a new method which enables high quality, large size (∼4 × 4 mm) and low surface roughness, low strain, ultra-thin SCD membranes which can be fabricated without deformations such as breakage, bowing or bending.

Doxorubicin loaded nanodiamond-silk spheres for fluorescence tracking and controlled drug release.

Nanoparticle (NP) based technologies have proved to be considerably beneficial for advances in biomedicine especially in the areas of disease detection, drug delivery and bioimaging. Over the last few decades, NPs have garnered interest for their exemplary impacts on the detection, treatment, and prevention of cancer. The full potential of these technologies are yet to be employed for clinical use.

Intrinsic fluorescence of selenium nanoparticles for cellular imaging applications.

Nanoparticles hold great potential in contributing to high-resolution bioimaging as well as for biomedical applications. Although, selenium (Se) nanoparticles (NPs) have been investigated owing to their potential roles in therapeutics, the imaging capability of these NPs has never been explored. This manuscript identifies the intrinsic fluorescence of Se NPs, which is highly beneficial for nanoscale imaging of biological structures.

Fluorescent Nanodiamond Silk Fibroin Spheres: Advanced Nanoscale Bioimaging Tool.

High resolution bioimaging is not only critical to the study of cellular structures and processes but it also has important applications in drug delivery and therapeutics. Fluorescent nanodiamonds (NDs) are excellent candidates for long-term bioimaging and tracking of biological structures at the nanoscale. Encapsulating NDs in natural biopolymers like silk fibroin (SF) widens their biomedical applications.

Micro-concave waveguide antenna for high photon extraction from nitrogen vacancy centers in nanodiamond.

The negatively charged nitrogen-vacancy colour center (NV(-) center) in nanodiamond is an excellent single photon source due to its stable photon generation in ambient conditions, optically addressable nuclear spin state, high quantum yield and its availability in nanometer sized crystals. In order to make practical devices using nanodiamond, highly efficient and directional emission of single photons in well-defined modes, either collimated into free space or waveguides are essential. This is a Herculean task as the photoluminescence of the NV centers is associated with two orthogonal dipoles arranged in a plane perpendicular to the NV defect symmetry axis.

Lifetime Reduction and Enhanced Emission of Single Photon Color Centers in Nanodiamond via Surrounding Refractive Index Modification.

The negatively-charged nitrogen vacancy (NV(-)) center in diamond is of great interest for quantum information processing and quantum key distribution applications due to its highly desirable long coherence times at room temperature. One of the challenges for their use in these applications involves the requirement to further optimize the lifetime and emission properties of the centers. Our results demonstrate the reduction of the lifetime of NV(-) centers, and hence an increase in the emission rate, achieved by modifying the refractive index of the environment surrounding the nanodiamond (ND).

Emission Properties of Fluorescent Nanoparticles Determined by Their Optical Environment.

The emission rate of a radiating dipole within a nanoparticle is crucially dependent on its surrounding refractive index environment. In this manuscript, we present numerical results on how the emission rates are affected for nanoparticles in a homogenous and substrate environment. These results are general, applicable to any refractive index distribution and emitter.

Filling schemes at submicron scale: development of submicron sized plasmonic colour filters.

The pixel size imposes a fundamental limit on the amount of information that can be displayed or recorded on a sensor. Thus, there is strong motivation to reduce the pixel size down to the nanometre scale. Nanometre colour pixels cannot be fabricated by simply downscaling current pixels due to colour cross talk and diffraction caused by dyes or pigments used as colour filters.

Development of a templated approach to fabricate diamond patterns on various substrates.

We demonstrate a robust templated approach to pattern thin films of chemical vapor deposited nanocrystalline diamond grown from monodispersed nanodiamond (mdND) seeds. The method works on a range of substrates, and we herein demonstrate the method using silicon, aluminum nitride (AlN), and sapphire substrates. Patterns are defined using photo- and e-beam lithography, which are seeded with mdND colloids and subsequently introduced into microwave assisted chemical vapor deposition reactor to grow patterned nanocrystalline diamond films.

Synthesis and characterization of biocompatible nanodiamond-silk hybrid material.

A new hybrid material consisting of nanodiamonds (NDs) and silk has been synthesized and investigated. NDs can contain bright fluorescence centers, important for bioprobes to image biological structures at the nanoscale and silk provides a transparent, robust matrix for these nanoparticles in-vivo or in-vitro. The ND-silk hybrid films were determined to be highly transparent in the visible to near infrared wavelength range.

Reconfigurable, defect-free, ultrahigh-Q photonic crystal microcavities for sensing.

We propose a new approach for creating reconfigurable high-Q cavities in defect-free photonic crystal slabs (PCSs). The approach relies on selective air-hole infiltration in otherwise defect-free PCSs. We show that using this method we can design ultrahigh-Q microcavities, with Q~10(6).

Broadband and robust optical waveguide devices using coherent tunnelling adiabatic passage.

We numerically demonstrate an optical waveguide structure for the coherent tunnelling adiabatic passage of photons. An alternative coupling scheme is used compared to earlier work. We show that a three rib optical waveguide structure is robust to material loss in the intermediate waveguide and variations to the waveguide parameters.

Dynamic stabilization of the optical resonances of single nitrogen-vacancy centers in diamond.

We report electrical tuning by the Stark effect of the excited-state structure of single nitrogen-vacancy (NV) centers located ≲100  nm from the diamond surface. The zero-phonon line (ZPL) emission frequency is controllably varied over a range of 300 GHz. Using high-resolution emission spectroscopy, we observe electrical tuning of the strengths of both cycling and spin-altering transitions.

Near-surface spectrally stable nitrogen vacancy centres engineered in single crystal diamond.

A method for engineering thin (<100 nm) layers of homoepitaxial diamond containing high quality, spectrally stable, isolated nitrogen-vacancy (NV) centres is reported. The photoluminescence excitation linewidth of the engineered NVs are as low as 140 MHz, at temperatures below 12 K, while the spin properties are at a level suitable for quantum memory and spin register applications. This methodology of NV fabrication is an important step toward scalable and practical diamond based photonic devices suitable for quantum information processing.

Single-photon emission and quantum characterization of zinc oxide defects.

Room temperature single-photon emission and quantum characterization is reported for isolated defects in zinc oxide. The defects are observed in thin films of both in-house synthesized and commercial zinc oxide nanoparticles. Emission spectra in the red and infrared, second-order photon correlation functions, lifetime measurements, and photon count rates are presented.

Nanodiamond induced high-Q resonances in defect-free photonic crystal slabs.

We demonstrate that a high-Q photonic crystal cavity can be induced by the presence of a nanodiamond (ND) on the air-hole side wall in an otherwise defect-free photonic crystal. The ND itself acts as the perturbation, increasing the average refractive index, necessary to define the cavity; therefore self-aligned with the cavity. Such cavities are potentially useful for exploiting cavity quantum electro-dynamic interactions between fluorescent NDs and the cavity.