The 3D printing of articles by the effect of a directed laser beam on a plastic powder is a demanding process, and unlike injection molding, very few polymers work well enough with it. Recently, we reported that poly(ethylene terephthalate) (PET) powder has intrinsically good properties for 3D printing. Basic mechanical properties were shown earlier and it was demonstrated that unfused but heat-exposed PET powder does not degrade quickly allowing good re-use potential. In this work, we conducted a detailed comparison of the mechanical properties of PET and polyamide 12 from different build orientations. PET powders with two different molecular weights were used. With the high molecular weight powder, the processing parameters were optimized, and the printed bars showed little difference between the different orientations, which means there is low anisotropy in mechanical properties of built parts. Based on processing experience of the first powder, the second powder with a lower molecular weight was also very printable and complex parts were made with ease from the initial printing trials; since the process parameters were not optimized then, lower mechanical properties were obtained. While the intrinsic material properties of PET (melting and re-crystallization kinetics) are not the best for injection molding, PET is eminently suitable for powder bed fusion.

We have investigated a Z-scheme based on a ZnO/Pt/CdZnS photocatalyst, active in the presence of a complex medium composed of acetic acid and benzyl alcohol, the effects of which on the catalyst stability and performance are studied. Transmission electron microscopy images showed uniformly dispersed sub-nanometer Pt particles. Inductively coupled plasma and X-ray photoelectron spectroscopy analyses suggested that Pt is sandwiched between ZnO and CdZnS. An apparent quantum yield (AQY) of 34% was obtained over the [ZnO] 4 /1 wt %Pt/CdZnS system at 360 nm, 2.5-fold higher than that of 1%Pt/CdZnS (14%). Furthermore, an AQY of 16% was observed using [ZnO] 4 /1 wt %Pt/CdZnS, which was comparable to that of 1 wt %Pt/CdZnS (10%) at 460 nm. On the basis of these results, we proposed a charge transfer mechanism, which was confirmed through femtosecond transient absorption spectroscopy. Finally, we identified the two main factors that affected the stability of the catalyst, which were the sacrificial reagent and the acidic pH.

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The performance of a semiconductor photocatalyst is affected by bulk and surface doping because of changes in the charge carrier dynamics. Finding relationships between these changes upon doping and catalytic performance offers needed information for the fundamental understanding of the overall catalytic reaction. In this work, the electron transfer for the hydrogen ion reduction reaction over a prototype Pt/CdS catalyst doped with Ni2+ cations (Cd0.99Ni0.01S) was studied using fs-pump probe transient absorption spectroscopy (TAS) under photocatalytic reaction conditions. Cd0.99Ni0.01S is composed of both hexagonal and cubic phases (X-ray diffraction) with average particles of 7 nm in size (transmission electron microscopy). TAS of Cd0.99Ni0.01S in the presence and absence of a hole scavenger (benzyl alcohol) and in the presence and absence of Pt particles helped to further probe into the origin of the two most pronounced transient signals in the 400–800 nm range. These are the ground-state bleaching at ca. 480 nm and the photoinduced absorption signal at ca. 600 nm. The first is largely linked to electron de-excitation lifetime and the latter to hole lifetime. From the decay kinetics under catalytic reaction conditions, it was possible to compute for the charge transfer yields (ϕ) from the semiconductor to the Pt metal particles (electron transfer) and from the benzyl alcohol to the semiconductor (hole trapping). The rate of the photocatalytic hydrogen production shows a positive relationship with the decay kinetics obtained by fs-pump probe measurements. While the photocatalytic reaction rates were found to be constant for successive runs, X-ray photoelectron spectroscopy Pt 4f and Ni 2p lines of the used catalyst showed a decrease in their content. Thus, care needs to be taken when relying solely on reaction rate measurements to test for catalytic stability.