Jesum A. Fernandes

Advanced reactor engineering with 3D printing for the continuous-flow synthesis of silver nanoparticles

The implementation of advanced reactor engineering concepts employing additive manufacturing is demonstrated. The design and manufacturing of miniaturised continuous flow oscillatory baffled reactors (mCOBR) employing low cost stereolithography based 3D printing is reported for the first time. Residence time distribution experiments have been employed to demonstrate that these small scale reactors offer improved mixing conditions at a millimetre scale, when compared to tubular reactors. Nearly monodisperse silver nanoparticles have been synthesised employing mCOBR, showing higher temporal stability and superior control over particle size distribution than tubular flow reactors.

Redox-active organic–inorganic hybrid polyoxometalate micelles

A redox-active hybrid organic–inorganic polyoxometalate surfactant showed solvent-dependent self-assembly to form nano-scale architectures. The supramolecular assemblies exhibited contrasting electronic structure and redox activity to their molecular building units, and were found to be stable under electrochemical reduction and re-oxidation.

Nonlinear optical characterization of new ionic liquids by a noise reduced thermally managed EZ-Scan technique

Thermal and nonlinear optical characteristics are evaluated for a novel ionic liquid, BMIOMe.NTf2, by means of the well established thermally managed eclipse Z-scan technique (EZ-scan). Nevertheless, this method still requires samples with good optical quality in order to provide a reasonable signal-noise ratio (SNR) when the material’s nonlinearity is small. Two different procedures where then introduced to improve the SNR against sample linear inhomogeneities and scattering. Both procedures are based in a subtraction of noisy background signals from the nonlinear signal of EZ-scan output. The first is applied to thermal effects and slow sample’s response, based on the perform a subtraction of the initial exposure time from the steady state signal, eliminating the linear noise. In this case, we could verify an increment of SNR from 1:2 to 40:1. The second procedure is related to fast response, e.g., arising from the electronic nonlinear polarizability. This consists in performing two sequential measurement, one with a decade of intensity higher than the first. After performing the subtraction between them, linear background suppression can be verified, with improvement of SNR to 2:1, amount about 10 times the signal value. Performing these procedures, we present a study of properties of ionic liquid BMIOMe.NTf2. This presents a steady cumulative effect of multiple pulse absorption leading to thermal lensing as measured by the thermally managed EZ-scan technique. The photoinduced conductivity effect observed for this ionic liquid is discussed based on the observed photothermal conversion. Also a fast response corresponding to a nonlinear refractive index was also registered when the time evolution is extrapolated for short times.