Alex Buts

Virtual porous carbons: what they are and what they can be used for

We use the term “virtual porous carbon” (VPC) to describe computer-based molecular models of nanoporous carbons that go beyond the ubiquitous slit pore model and seek to engage with the geometric, topological and chemical heterogeneity that characterises almost every form of nanoporous carbon. A small number of these models have been developed and used since the early 1990s. These models and their use are reviewed. Included are three more detailed examples of the use of our VPC model. The first is concerned with the study of solid-like adsorbate in nanoporous carbons, the second with the absolute assessment of multi-isotherm based methods for determining the fractal dimension, and the final one is concerned with the fundamental study of diffusion in nanoporous carbons.

Hardware implementation and calibration of background noise for an integration-based fluorescence lifetime sensing algorithm

A new integration based fluorescence lifetime imaging microscopy (FLIM) called IEM has been proposed to implement lifetime extraction [J. Opt. Soc. Am. A25, 1190 (2008)]. A real-time hardware implementation of the IEM FLIM algorithm suitable for single photon avalanche diode arrays in nanometer-scale CMOS technology is now proposed. The problems of reduced pixel readout bandwidth and background noise are studied and a calibration method suitable for FPGA implementation is introduced. In particular, the relationship between signal-to-noise ratio and background noise is considered based on statistics theory and compared with a rapid lifetime determination method and maximum-likelihood estimator with-without background correction. The results are also compared with Monte Carlo simulations giving good agreement. The performance of the proposed methods has been tested on monoexponential decay experimental data. The high flexibility, wide range, and hardware friendliness make IEM the best candidate for system-on-chip integration to our knowledge.

Absolute assessment of adsorption-based microporous solid characterisation methods

This chapter outlines an absolute assessment process based on molecular simulation. This process is a useful tool in determining the correctness or methods, and the consistency and meaningfulness of quantities. These capabilities are demonstrated by application of the absolute assessment process to methods for determining the pore size distribution, mean coordination number of the pore network, and the fractal dimension. The assessment shows that the pore size distribution is another way of presenting the energy distribution, and that the concept of “pore size” is only weakly linked to actual pore size. It also reveals that while the only method currently available for determining the mean coordination number of microporous solids yield a quantity with meaning, it does not relate to the coordination number relevant to transport in the pore network, which is substantially higher.

FPGA implementation of a video-rate fluorescence lifetime imaging system with a 32×32 CMOS single-photon avalanche diode array

A new integration based fluorescence lifetime imaging microscopy (FLIM) called IEM has been proposed to implement lifetime calculations [1]. A real-time hardware implementation of this IEM FLIM algorithm suitable for a single photon avalanche diode (SPAD) array in 0.13µm CMOS technology is now implemented on FPGA. A widefield microscope was adapted to accommodate the array and test it on biological applications. Video-rate fluorescence lifetime imaging has been achieved, by performing parallel 32×32 lifetime calculations, realizing the first, compact, and low-cost FLIM camera.