Improved room-temperature luminescence of core-shell InGaAs/GaAs nanopillars via lattice-matched passivation

Optical properties of GaAs/InGaAs/GaAs nanopillars (NPs) grown on GaAs (111)B were investigated. Employment of a mask-etching technique allowed for an accurate control over the geometry of NP arrays in terms of both their diameter and separation. This work describes both the steady-state and time-resolved photoluminescence of these structures as a function of the ensemble geometry, composition of the insert, and various shell compounds. The effects of the NP geometry on a parasitic radiative recombination channel, originating from an overgrown lateral sidewall layer, are discussed. Optical characterization reveals a profound influence of the core-shell lattice mismatch on the carrier lifetime and emission quenching at room temperature. When the latticematching conditions are satisfied, an efficient emission from the NP arrays at room temperature and below the band-gap of silicon is observed, clearly highlighting their potential application as emitters in optical interconnects integrated with silicon platforms

Visualizing the colonization dynamics of pathogenic bacteria labelled by upconverting nanoparticles inside the gut

This study intends to show the use of upconversion photoluminescence imaging to investigate the colonization and infection dynamics of a natural murine intestinal pathogen, Citrobacter rodentium (C. rodentium), which induces inflammation in mice

Automated tissue boundary detection

To address the challenge of tissue differentiation during cranial perforation surgery, presented research aims to integrate optical illumination and detection capability into rotating assemblies of surgical tools

Wavelength selection using diffuse reflectance spectra and machine learning algorithms for tissue differentiation in orthopedic surgery

DRS-based measurements of tissue types encountered in orthopedic surgery are utilized to establish a wavelength selection methodology using machine learning techniques, which enables rapid development of clinically translatable optical system

Diffuse reflectance spectroscopy for determination of optical properties and chromophore concentrations of mice internal organs in the range of 350 nm to 1860 nm

The development of photomedical modalities for diagnostics and treatment has created a need for knowledge of the optical properties of the targeted biological tissues. These properties are essential to plan certain procedures, since they determine the light absorption, propagation and penetration in tissues. One way to measure these properties is based on diffuse reflectance spectroscopy (DRS). DRS can provide light absorption and scattering coefficients for each wavelength through a non-invasive, fast and in situ interrogation, and thereby tissue biochemical information. In this study, reflectance measurements of ex vivo mice organs were investigated in a wavelength range between 350 and 1860 nm. To the best of our knowledge, this range is broader than previous studies reported in the literature and is useful to study additional chromophores with absorption in the extended wavelength range. Also, it may provide a more accurate concentration of tissue chromophores when fitting the reflectance spectrum in this extended range. In order to extract these concentrations, optical properties were calculated in a wide spectral range through a fitting routine based on an inverse Monte-Carlo look-up table model. Measurements variability was assessed by calculating the Pearson correlation coefficients between each pair of measured spectra of the same type of organ

High contrast breast cancer biomarker imaging using upconverting nanoparticles

Breast cancer is a leading cause of death in women and has scope for improvement in treatment stratification. We report the use of high contrast UCNP staining to distinguish different levels of HER2 expression in HER2 analyte control and HER2-positive breast cancer tissue biopsies. A contrast of 40 was found as compared to the negative control and 25 as compared to conventional DAB staining

Biophotonics box: educational kit for multidisciplinary outreach activities in optics and photonics

The biophotonics box enables multidisciplinary/interdisciplinary and self-paced learning with at-home experiments using low-resource components. Experiments can increase the interest of students in STEM subjects by emphasizing the real-life applications in biology and medicine

Online learning combining virtual lectures, at-home experiments and computer simulations: a multidisciplinary teaching and learning approach

We developed a fully-remote biophotonics workshop integrating webinars, computer simulations and at-home experiments to meet the needs of undergraduate students with diverse backgrounds and learning styles. Similar strategies/resources could be used in multidisciplinary programs

Perspectives on interstitial photodynamic therapy for malignant tumors

Significance: Despite remarkable advances in the core modalities used in combating cancer, malignant diseases remain the second largest cause of death globally. Interstitial photodynamic therapy (IPDT) has emerged as an alternative approach for the treatment of solid tumors. Aim: The aim of our study is to outline the advancements in IPDT in recent years and provide our vision for the inclusion of IPDT in standard-of-care (SoC) treatment guidelines of specific malignant diseases. Approach: First, the SoC treatment for solid tumors is described, and the attractive properties of IPDT are presented. Second, the application of IPDT for selected types of tumors is discussed. Finally, future opportunities are considered. Results: Strong research efforts in academic, clinical, and industrial settings have led to significant improvements in the current implementation of IPDT, and these studies have demonstrated the unique advantages of this modality for the treatment of solid tumors. It is envisioned that further randomized prospective clinical trials and treatment optimization will enable a wide acceptance of IPDT in the clinical community and inclusion in SoC guidelines for well-defined clinical indications. Conclusions: The minimally invasive nature of this treatment modality combined with the relatively mild side effects makes IPDT a compelling alternative option for treatment in a number of clinical applications. The adaptability of this technique provides many opportunities to both optimize and personalize the treatment

Multi-variable compensated quantum yield measurements of upconverting nanoparticles with high dynamic range : a systematic approach

Non-linear materials such as upconverting nanoparticles (UCNPs) are emerging technology with fast-growing applications in various fields. The power density dependence of the emission quantum yield (QY) of these non-linear materials makes them challenging to characterize using currently available commercial QY systems. We propose a multimodal system to measure QY over a wide dynamic range (1:104), which takes into account and compensates for various distorting parameters (scattering, beam profile, inner filter effect and bandwidth of emission lines). For this, a beam shaping approach enabling speckle free beam profiles of two different sizes (530 µm or 106 µm) was employed. This provides low noise high-resolution QY curves. In particular, at low power densities, a signal-to-noise ratio of >50 was found. A Tm-based core-shell UCNP with excitation at 976 nm and emission at 804 nm was investigated with the system