The research on skutterudites in the last few years has contributed to a better understanding of the physical processes which play an important role in enhancing their thermoelectric performance and to the discovery of novel filled compounds, with one of the most promising zT values at intermediate temperatures. Skutterudites are still an ongoing field of research, and an improvement of their efficiencies, stabilities, contacts, industrial scalable fabrication processes and other factors are expected in the near future in order to develop viable modules for intermediate temperature range applications, such as in the automobile industry, factories or incinerators. This paper gives a review on the status of research in the field of skutterudites.

Composite films of poly(3-hexylthiophene) and single- as well as multi-walled carbon nanotubes are demonstrated to offer a competitive thermoelectric performance. The power factor significantly exceeds values obtained with either constituent alone provided that the conjugated polymer is sufficiently p-doped. The use of single-walled carbon nanotubes consistently results in a higher electrical conductivity with a maximum value above 10³ S cm⁻¹ and thus gives rise to a power factor of 25 ± 6 μW m⁻¹ K⁻² for a filler content of only 8 wt% and a maximum 95 ± 12 μW m⁻¹ K⁻² for 42–81 wt%. Moreover, a carbon nanotube content of 8–10 wt% does not compromise the low bulk thermal conductivity of the polymer matrix, which promises a high figure of merit of at least ZT > 10⁻² at room-temperature. All samples are cast on plastic substrates, emphasising their suitability for large-area, flexible thermoelectric applications.

Anodic porous alumina, –AAO– (also known as nanoporous alumina, nanohole alumina arrays, –NAA– or nanoporous anodized alumina platforms, –NAAP–) has opened new opportunities in a wide range of fields, and is used as an advanced photonic structure for applications in structural coloration and advanced optical biosensing based on the ordered nanoporous structure obtained and as a template to grow nanowires or nanotubes of different materials giving rise to metamaterials with tailored properties. Therefore, understanding the structure of nanoporous anodic alumina templates and knowing how they are fabricated provide a tool for the further design of structures based on them, such as 3D nanoporous structures developed recently. In this work, we review the latest developments related to nanoporous alumina, which is currently a very active field, to provide a solid and thorough reference for all interested experts, both in academia and industry, on these nanostructured and highly useful structures. We present an overview of theories on the formation of pores and self-ordering in alumina, paying special attention to those presented in recent years, and different nanostructures that have been developed recently. Therefore, a wide variety of architectures, ranging from ordered nanoporous structures to diameter changing pores, branched pores, and 3D nanostructures will be discussed. Next, some of the most relevant results using different nanostructured morphologies as templates for the growth of different materials with novel properties and reduced dimensionality in magnetism, thermoelectricity, etc. will be summarised, showing how these structures have influenced the state of the art in a wide variety of fields. Finally, a review on how these anodic aluminium membranes are used as platforms for different applications combined with optical techniques, together with principles behind these applications will be presented, in addition to a hint on the future applications of these versatile nanomaterials. In summary, this review is focused on the most recent developments, without neglecting the basis and older studies that have led the way to these findings. Thus, it gives an updated state-of-the-art review that should be useful not only for experts in the field, but also for non-specialists, helping them to gain a broad understanding of the importance of anodic porous alumina, and most probably, endow them with new ideas for its use in fields of interest or even developing the anodization technique.