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Photosynthetic biomaterials have attracted considerable attention at different levels of the biological organisation, from molecules to the biosphere, due to a variety of artificial application possibilities. During photosynthesis, the first steps of the conversion of light energy into chemical energy take place in a pigment–protein complex, called reaction centre (RC). In our experiments photosynthetic reaction centre protein, purified from Rhodobacter sphaeroides R-26 purple bacteria, was bound to porous silicon pillars (PSiP) after the electropolymerisation of aniline onto the surface. This new type of biohybrid material showed remarkable photoactivity in terms of measured photocurrent under light excitation in an electrochemical cell. The photocurrent was found to increase considerably after the addition of ubiquinone (UQ-0), an e−-acceptor mediator of the RC. The photoactivity of the complex was found to decrease by the addition of terbutryn, the chemical which inhibits the e−-transport on the acceptor side of the RC. In addition to the generation of sizeable light-induced photocurrents, using the PSiP/RC photoactive hybrid nanocomposite material, the system was found to be sensitive towards RC inhibitors and herbicides. This highly ordered patterned 3D structure opens new solution for designing low-power (bio-)optoelectronic, biophotonic and biosensing devices. Graphical abstract

International audience; Most porous silicon-based interferometric sensors targeting biosensing applications consist of vertical porous silicon layers created into a silicon wafer by electrochemical anodization and operate in a flow-over configuration. In this work, we present an alternative porous silicon interferometer based on porous silicon with horizontally oriented pores. This architecture permits the integration of flow-through porous silicon membranes within planar microfluidics. Fourier-transform infrared spectroscopy was used to obtain interference spectra from fabricated lateral porous silicon membranes and red shifts were observed upon filling microfluidic chips integrating the porous membranes with solvents of higher optical indices. This work proves that lateral porous silicon membranes are typical Fabry-Pérot interferometers with a sensitivity of more than 150 nm/RIU and a limit of detection less than 10−3 RIU, that is comparable to vertical porous silicon layers. Moreover, we have conducted simulation studies showing that the addition of Bragg mirrors on the membranes results in spectra with narrower fringes and lateral porous silicon interferometers with improved performances. After appropriate biofunctionalization of the porous silicon surface, lateral porous silicon membrane interferometers should offer alternative solutions for the development of porous silicon flow-through biosensors monolithically integrated on-chip.

Photosynthetic biomaterials have attracted considerable attention at different levels of the biological organisation, from molecules to the biosphere, due to a variety of artificial application possibilities. During photosynthesis, the first steps of the conversion of light energy into chemical energy take place in a pigment-protein complex, called reaction centre (RC). In our experiments photosynthetic reaction centre protein, purified from Rhodobacter sphaeroides R-26 purple bacteria, was bound to porous silicon pillars (PSiP) after the electropolymerisation of aniline onto the surface. This new type of biohybrid material showed remarkable photoactivity in terms of measured photocurrent under light excitation in an electrochemical cell. The photocurrent was found to increase considerably after the addition of ubiquinone (UQ-0), an e

A parametric shrinking-core model is used to quantify the dechlorination rate of chlorinated pollutants dissolved in water by zero-valent iron nanoparticles (nZVI). The mass-transfer processes are coupled with the instantaneous reaction occurring in the solid/liquid interface to compute the transient changes of dissolved pollutant concentration in bulk and suspended nZVI concentration. A sensitivity analysis is carried out to identify the dominant parameters governing the overall reaction rate for a system of uniform nanoparticles. The model is extended to assemblages of non-uniform ZVI nanoparticles with sizes following a distribution function. The statistical shrinking-core model is used to estimate the PCE dechlorination kinetic parameters along with the mass-transfer coefficients with inverse modeling of batch experiments. The observed discrepancy between numerical predictions and experimental datasets may be attributed to uncertainties associated with the nZVI oxidation by other species, and PCE adsorbed on oxidized iron. An approximate analysis of model equations allows the development of an analytic phenomenological model providing the overall reaction rate as a function of dissolved PCE concentration.

Application of technical developments in biology and vice versa or biological samples in technology led to the development of new types of functional, so-called “biohybrid” materials. These types of materials can be created at any level of the biological organization from molecules through tissues and organs to the individuals. Macromolecules and/or molecular complexes, membranes in biology, are inherently good representatives of nanosystems since they fall in the range usually called “nano.” Nanohybrid materials provide the possibility to create functional bionanohybrid complexes which also led to new discipline called “nanobionics” in the literature and are considered as materials for the future. In this publication, the special characteristics of photosynthetic reaction center proteins, which are “nature’s solar batteries,” will be discussed in terms of their possible applications for creating functional molecular biohybrid materials.

A variety of aqueous suspensions (nanofluids) of zero-valent nano-particles (nZVI) are prepared by wet chemistry techniques, their stability and longevity is evaluated by physic-chemical methods of characterization, and their reactivity toward the dechlorination of per-chloro-ethylene (PCE) is examined with tests in batch reactors. For assessing the mobility, longevity and reactivity of nZVI suspensions (nanofluids), under flow-through conditions, visualization multiphase flow and transport tests are performed on a glass-etched pore network. The nZVI breakthrough curves are constructed by measuring the transient variation of the iron concentration in the effluent with atomic absorption spectroscopy. The capacity of nZVI to remediate the bulk phase of PCE is quantified by detecting the mass loss rate of PCE ganglia trapped in glass-etched pore networks during the continuous injection of nZVI suspension or pure water. The nZVI injection in porous media is simulated as an advection- dispersion process by accounting for the attachment/detachment of nanoparticles on the pore-walls, and describing the kinetics of PCE dissolution and reaction by 1st order equations. Visualization experiments reveal that the gradual elimination of PCE ganglia by the injected nZVI is associated with the preferential "erosion" of the upstream interfacial regions. The step controlling the overall process kinetics might be either (i) the enhanced PCE dissolution or (ii) the direct reaction of bulk PCE with the nZVI deposited upon the ganglia interfaces. Inverse modeling of the experiments under the simplifying assumption of one active mechanism indicates that the estimated kinetic coefficients are increasing functions of the flow rate.

The accurate and sensitive determination of H2O2 is very important in many cases because it is a product of reactions catalysed by several oxidase enzymes in living cells and it is essential in environmental and pharmaceutical analyses. The fabrication of enzyme protein activity based biosensors is a very promising way for this purpose because the function of biological molecules is very specific, sensitive, and selective. Horseradish peroxidase (HRP) is the most commonly used enzyme for H2O2 detection because it can oxidize hydrogen atoms and, for example, xenobiotics in the presence of H2O2. In order to define the limit of detection (LOD) of H2O2 we made calibrations with guaiacol and amplex red (AR), which are hydrogen donors of HRP. The accumulation of the reaction products, tetraguaiacol, and resorufin, respectively, then can be easily detected by absorption or emission (fluorescence) spectroscopy. In our experiments an enzyme electrode was fabricated from ITO (indium tin oxide), functionalized multiwalled carbon nanotubes (f-MWCNTs), and HRP. Although the enzyme activity was smaller by about two orders of magnitude when the enzyme was bound to the f-MWCNTs (ca. 10−2 M H2O2/(M HRP·sec) compared to ca. 2 M H2O2/(M HRP·sec) and 5 M H2O2/(M HRP·sec) with AR and guaiacol in buffer solution), LOD of the H2O2 decomposition was about 6 pM H2O2/sec and 10 pM H2O2/sec in the case of AR and guaiacol, respectively.

The reaction center protein is the unit in the photosynthetic organisms in which the primary events of the photoelectric energy conversion take place during photosynthesis. When the photochemistry following the excitation of the reaction center by light is oversaturated there is a large probability to form reactive oxygen species (ROS, e.g., singlet oxygen (O-1(2))). Because the ROS components decrease the overall yield of the photochemical energy conversion there is a considerable effort in many laboratories to find conditions to reduce these harmful compounds. The aim of our work is to create a system by using carbon nanotubes (CNTs) and RCs for efficient light-energy conversion. The role of the O-1(2) that destroys the RC structure is discussed. 1,3-Diphenylisobenzofuran was used to detect the concentration of the O-1(2). Although, O-1(2) can be sensitized by CNTs in certain conditions, in our experiments the main sources of the O-1(2) are the RCs. The concentration of the O-1(2) in the equilibrium is determined by the forward sensitization and the backward deactivation processes of the components and functions of the CNT/RC composite. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Since their discovery, carbon nanotubes (CNTs) have attracted intense attention to broad range of potential applications. In contrast to the 1D isolated single-walled carbon nanotubes (SWCNT), 2D films or bundles made of thousands of tubes have been introduced as more advantageous building blocks for new types of applications in mechanically flexible and stretchable, optically transparent electronic systems. In our experiments, we combined photosynthetic reaction centre proteins, the light energy converter units in living cells, purified from purple bacteria, with multiwalled carbon nanotube (MWCNT) bundles. The change in the conductivity of the bare MWCNT bundles and the RC/MWCNT composite after light excitation was measured and compared. We found that the electrical conductivity under light excitation depends on the intrinsic conductivity of individual tubes within the bundles and on structural characteristics, like geometry (diameter, length, spatial arrangement, interconnects, etc.) and the electronic coupling with the RCs. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Specific inhibitory reactions of herbicides with photosynthetic reaction centers bound to working electrodes were monitored in a conventional electrochemical cell and a newly designed microfluidic electrochemical flow cell. In both cases, the bacterial reaction centers were bound to a transparent conductive metal oxide, indium-tin-oxide, electrode through carbon nanotubes. In the conventional cell, photocurrent densities of up to a few μA/cm2 could be measured routinely. The photocurrent could be blocked by the photosynthetic inhibitor terbutryn (I 50 = 0.38 ± 0.14 μM) and o-phenanthroline (I 50 = 63.9 ± 12.2 μM). The microfluidic flow cell device enabled us to reduce the sample volume and to simplify the electrode arrangement. The useful area of the electrodes remained the same (ca. 2 cm2), similar to the classical electrochemical cell; however, the size of the cell was reduced considerably. The microfluidic flow control enabled us monitoring in real time the binding/unbinding of the inhibitor and cofactor molecules at the secondary quinone site.

Basic principles of structural and functional requirements of photosynthetic energy conversion in hierarchically organized machineries are reviewed. Blueprints of photosynthesis, the energetic basis of virtually all life on Earth, can serve the basis for constructing artificial light energy-converting molecular devices. In photosynthetic organisms, the conversion of light energy into chemical energy takes places in highly organized fine-tunable systems with structural and functional hierarchy. The incident photons are absorbed by light-harvesting complexes, which funnel the excitation energy into reaction centre (RC) protein complexes containing redox-active chlorophyll molecules; the primary charge separations in the RCs are followed by vectorial transport of charges (electrons and protons) in the photosynthetic membrane. RCs possess properties that make their use in solar energy-converting and integrated optoelectronic systems feasible. Therefore, there is a large interest in many laboratories and in the industry toward their use in molecular devices. RCs have been bound to different carrier matrices, with their photophysical and photochemical activities largely retained in the nano-systems and with electronic connection to conducting surfaces. We show examples of RCs bound to carbon-based materials (functionalized and non-functionalized single- and multiwalled carbon nanotubes), transitional metal oxides (ITO) and conducting polymers and porous silicon and characterize their photochemical activities. Recently, we adapted several physical and chemical methods for binding RCs to different nanomaterials. It is generally found that the P(+)(QAQB)(-) charge pair, which is formed after single saturating light excitation is stabilized after the attachment of the RCs to the nanostructures, which is followed by slow reorganization of the protein structure. Measuring the electric conductivity in a direct contact mode or in electrochemical cell indicates that there is an electronic interaction between the protein and the inorganic carrier matrices. This can be a basis of sensing element of bio-hybrid device for biosensor and/or optoelectronic applications.