Lucia Fontana

Bioconjugation of gold-polymer core-shell nanoparticles with bovine serum amine oxidase for biomedical applications.

Core-shell gold nanoparticles [AuNPs], stabilized with a hydrophilic polymer, poly(3-dimethylammonium-1-propyne hydrochloride) [PDMPAHCl], have been used for the immobilization of bovine serum amine oxidase [BSAO]. The functionalized surface of the hybrid nanoparticles is pH responsive, due to the presence of aminic groups that carry out a double role: on one hand they act as ligands for the gold nanoparticle surface, allowing the colloidal stabilization and, on the other hand, they give a hydrophilic characteristic to the whole colloidal suspension. The core-shell nanoparticles [Au@PDMPAHCl] have been characterized by using UV-vis and X-ray photoelectron spectroscopy, DLS, ζ-potential measurements and by FE-TEM microscopy. BSAO enzyme can be loaded by non-covalent immobilization onto Au@PDMPAHCl nanoparticles up to 70% in weight, depending on the pH values of the environmental medium. Activity tests on Au@PDMPAHCl-BSAO bioconjugates confirm an enzymatic activity up to 40%, with respect to the free enzyme activity. Moreover, our results show that loading and enzymatic activity are rather interrelated characteristics and that, under appropriate polymer concentration and pH conditions, a satisfactory compromise can be reached. These results, as a whole, indicate that Au@PDMPAHCl-BSAO bioconjugate systems are promising for future biomedical applications.

Silver nanoparticles linked by a Pt-containing organometallic dithiol bridge: study of local structure and interface by XAFS and SR-XPS

Silver nanoparticles (AgNPs) functionalized with an organometallic bifunctional thiol containing Pt(ii) centers, generated in situ from trans-trans-[thioacetyl-bistributylphosphine-diethynylbiphenyl-diplatinum(ii)], were synthesized with different sulphur/metal molar ratios (i.e. AgNPs-1 and AgNPs-2) with the aim to obtain nanosystems of different mean size and self-organization behaviour. AgNPs spontaneously self-assemble, giving rise to 2D networks, as previously assessed. In this work a deeper insight into the chemico-physical properties of these AgNPs is proposed by means of synchrotron radiation induced X-ray photoelectron spectroscopy (SR-XPS) and X-ray absorption fine structure spectroscopy (XAFS) techniques. The results are discussed in order to probe the interaction at the interface between a noble metal and a thiol ligand at the atomic level and the aim of this study is to shed light on the chemical structure and self-organization details of nanosystems. The nature of the chemical interaction between the dithiol ligand and the Ag atoms on the nanoparticle surface was investigated by combining SR-XPS (S2p, Ag3d core levels) and XAS (S and Ag K-edges) analysis. UV-visible absorption and emission measurements were also carried out on all samples and compared with TD-DFT calculations so as to get a better understanding of their optical behavior and establish the nature of the excitation and emission processes.

FENESTRATION PEAK SOLAR HEAT GAIN: A REVIEW OF THE CLOUDLESS DAY CONDITION AS CONSERVATIVE HYPOTHESIS

Peak solar heat gain through fenestration, particularly for clear and cloudy day conditions, was estimated, using an approach based on the ASHRAE methodology and considering the correlation between hourly clearness index kT and diffuse ratio of the total radiation. Hourly SHGCLEAR and SHGCLOUDY values for surfaces facing the basic cardinal orientations and the horizontal surface, at different latitudes, on the 21st day of each month, have been computed and compared. Results show that in many cases solar heat gain for cloudy day may exceed that for clear day. For wall exposures near the North the clear day condition could not be the most conservative condition for the peak SHG evaluation.

Screening performance of pairs of diffusively reflecting traffic noise barriers: theory and experiments

An easy-to-apply computational procedure for the study of the acoustic performance of pairs of diffusively reflecting roadside barriers is described in detail, and an experimental verification of its predictions, carried out on a 1:10 scale model, is presented and discussed. It is shown that, in comparison with pairs of more traditional specularly reflecting noise barriers, significant attenuation benefits are obtained not only in the shadow zone behind the barriers, but also in the unprotected zone immediately above the barriers, which proves that diffusive traffic faces of the barriers may effectively help in counteracting multiple reflection effects.

A COMPARATIVE STUDY OF THE COOLING PERFORMANCE OF NEW HVAC SYSTEMS BASED ON THE REVERSED AIR CYCLE

A numerical study on the cooling performance of new air-conditioning systems based on the reversed air cycle is conducted through a specifi cally developed computer code. The main peculiarity of such HVAC systems is the combination of the roles traditionally played separately by the chiller and the air handling unit, as the expanded cool air is directly supplied to the indoor ambient for its environmental control. For any system proposed, simulations have been carried out for a wide variety of psychrometric states of both outdoor air and supply air, and for different effi ciencies of the heat exchangers and the turbomachinery. Among the main results obtained, it is found that for hot and dry climates, as well as for temperate climates, the values of the cooling performance of the most advanced confi gurations are of the same order as those typical for traditional HVAC systems served by vapour-compression refrigerating units.

Measurement of the Radiative Properties of Frescoed Wall Surfaces Variously Pigmented

A method of radiative heating for frescoed surfaces has recently been proposed to prevent deterioration caused by moisture condensation. A previous study has stressed the importance of the surface absorptivities, in respect both to the power required and temperature disuniformity. In the present research, these absorptivities are measured for wall surfaces, composed and painted with different colors, precisely with the same techniques used at the time of the original construction (XIV–XVI century), and heated by radiating sources with continuous nearly grey spectra and grey-body temperatures between around 3,200 K and 700 K. For temperatures high enough to permit the realization of compact radiating sources (T ≤ 1,300 K), the absorptivities result all sufficiently high, thus not requiring high radiating power, and sufficiently close not to create dangerous internal stresses.