Enzymatic luminescent systems are a promising tool for rapid detection of heavy metals ions for water quality assessment. Nevertheless, their widespread use is limited by the lack of test procedure automation and available sensitive handheld luminometers. Herein we describe integration of disposable microfluidic chips for bioluminescent enzyme-inhibition based assay with a handheld luminometer, which detection system is based on a thermally stabilized silicon photomultiplier (SiPM). Microfluidic chips were made of poly(methyl methacrylate) by micro-milling method and sealed using a solvent bonding technique. The composition of the bioluminescent system in microfluidic chip was optimized to achieve higher luminescence intensity and storage time. Results indicate that developed device provided comparable sensitivity with bench-scale PMT-based commercial luminometers. Limit of detection for copper (II) sulfate reached 2.5 mg/L for developed biosensor. Hereby we proved the concept of handheld enzymatic optical biosensors with disposable chips for bioassay. The proposed biosensor can be used as an early warning field-deployable system for rapid detection of heavy metals salts and other toxic chemicals, which affect bioluminescent signal of enzymatic reaction.

Properties of the field electron emission for diamond/pyrocarbon nanocomposites produced from diamond particles surrounded by an ${\mathrm{sp}}^2-\mathrm{bonded}$ pyrocarbon matrix are considered as functions of a size of diamond particles selected in the range of 5 nm–5 μm, and of an average thickness of the pyrocarbon shell controlled by the pyrocarbon/diamond mass ratio varied from 0 to 0.5. The low-threshold emission at fields of ⩾1 V/μm with “no activation/no hysteresis” $\mathrm{I–V}$ behavior was observed for these materials using tungsten tip microprobes as well as a fluorescent screen. A specially designed scanning tunneling-field emission microscope was used for simultaneous mapping of field emission intensity, topography, work function, and electrical resistivity to study the mechanisms of the emission from the composites and well-emitting chemical vapor deposition diamond films. It was found that for both of the materials emission centers are associated with interfaces between diamond and ${\mathrm{sp}}^2-\mathrm{bonded}$ carbon phases. Possible mechanisms of the low-field electron emission for the diamond/graphite composites including local field enhancement are analyzed. A model of the low-field emission based on quantum well effect at the diamond/graphite interface is proposed and discussed.

In this paper, we experimentally investigate optical and spin properties of NV centers in aggregates of detonation nanodiamonds. We show that despite the small size of nanodiamonds forming the aggregate, the NV centers in these aggregates exhibit spin properties comparable to similar size nanodiamonds grown by other methods, but with brightness enhanced by a factor of 2.