Nitrogen vacancy (NV) centers have amassed considerable interest as biologically compatible magnetometers. NV centers are point defects consisting of a substituted nitrogen adjacent to a vacancy in diamond’s lattice. These defects exhibit an optically addressable magnetic field response at room temperature, a process known as optically detected magnetic resonance (ODMR). We take advantage of the imbalanced probability of the excited magnetic spin ±1 state to transition to the ground magnetic spin 0 state through an intermediate secondary singlet pathway in NV color centers. This alternative intersystem relaxation response can provide a source of contrast for live-cell imaging with potential nano-scale resolution, as well as for measuring low concentrations of paramagnetic ions. Paramagnetic molecules generate random magnetic field fluctuations which result in a non-zero RMS field. These fluctuations can induce spin relaxation in NVs in the near field of such paramagnetic molecules. This technique is applied at room temperature without microwave control frequencies or induced magnetic fields. The relaxation time for a bulk NV sensor doped with phosphorus was measured, which compared well with referenced values. Phosphorus doping in NV diamond allows the excitation wavelength to be red shifted for a less cytotoxic effect. ODMR spectra were acquired with a helium neon (HeNe) laser.
Healthcare access in low-resource settings is compromised by the availability of affordable and accurate diagnostic equipment. The four primary poverty-related diseases – AIDS, pneumonia, malaria, and tuberculosis - account for approximately 400 million annual deaths worldwide as of 2016 estimates. Current diagnostic procedures for these diseases are prolonged and can become unreliable under various conditions. We present the development of a simple low-cost UV fluorescence multi-spectral imaging system geared towards low resource settings for a variety of biological and in-vitro applications. Fluorescence microscopy serves as a useful diagnostic indicator and imaging tool. The addition of a multi-spectral imaging modality allows for the detection of fluorophores within specific wavelength bands, as well as the distinction between fluorophores possessing overlapping spectra. The developed instrument has the potential for a very diverse range of diagnostic applications in basic biomedical science and biomedical diagnostics and imaging. Performance assessment of the microscope will be validated with a variety of samples ranging from organic compounds to biological samples.
Noninvasive glucose sensing is a Holy Grail of diabetes mellitus management. Unfortunately, despite a number of innovative concepts and a long history of continuous instrumental improvements, the problem remains largely unsolved. Here we propose and experimentally demonstrate the first successful implementation of a novel strategy based on vibrational overtone circular dichroism absorption measurements. Such an approach uses a short-wavelength infrared excitation (1000-2000 nm), which takes the advantage of lower light scattering and intrinsic chemical contrast provided by the chemical structure of D-glucose molecule. We model the propagation of circular polarized light in scattering medium using Monte Carlo simulations to show the feasibility of such approach in turbid medium and demonstrate the proof of principle using optical detection. We also investigate the possibility of using ultrasound detection through circular dichroism absorption measurements to achieve simple and sensitive glucose monitoring.
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