Solar heat management & green air-conditioning are among the major technologies that could mitigate heat islands phenomenon while minimizing significantly the CO 2 global foot-print within the building & automotive sectors. Chromogenic materials in general, and thermochromic smart coatings especially are promising candidates that consent a noteworthy dynamic solar radiation Infrared (NIR-IR) regulation and hence an efficient solar heat management especially with the expected increase of the global seasonal temperature. Within this contribution, two major challenging bottlenecks in vanadium oxide based smart coatings were addressed. It is validated for the first time that the NIR-IR modulation of the optical transmission (∆T TRANS = T (T〈TMIT) − T (T〉TMIT ) of Vanadium oxide based smart coatings can be controlled & tuned. This upmost challenging bottle-neck controllability/tunability is confirmed via a genuine approach alongside to a simultaneous drastic reduction of the phase transition temperature T MIT from 68.8 °C to nearly room temperature. More precisely, a substantial thermochromism in multilayered V 2 O 5 /V/V 2 O 5 stacks equivalent to that of standard pure VO 2 thin films but with a far lower transition temperature, is reported. Such a multilayered V 2 O 5 /V/V 2 O 5 thermochromic system exhibited a net control & tunability of the optical transmission modulation in the NIR-IR (∆T TRANS ) via the nano-scaled thickness’ control of the intermediate Vanadium layer. In addition, the control of ∆T TRANS is accompanied by a tremendous diminution of the thermochromic transition temperature from the elevated bulk value of 68.8 °C to the range of 27.5–37.5 ºC. The observed remarkable and reversible thermochromism in such multilayered nano-scaled system of V 2 O 5 /V/V 2 O 5 is likely to be ascribed to a noteworthy interfacial diffusion, and an indirect doping by alkaline ions diffusing from the borosilicate substrate. It is hoped that the current findings would contribute in advancing thermochromic smart window technology and their applications for solar heat management in glass windows in general, skyscraper especially & in the automotive industry. If so, this would open a path to a sustainable green air-conditioning with zero-energy input.

In this work, we demonstrate a metal-wire-based plasmonic signal processor, which can simultaneously act as a broadband terahertz polarization-division multiplexer and as a novel platform to realize the independent manipulation of polarization-division multiplexed terahertz signals. Such a device opens up new exciting perspectives for exploiting the polarization degree of freedom and ultimately boosting the capacity and spectral efficiency of future terahertz networks.

In this contribution, we report, for the first time, on the surface bio-sulfurisation of metallic surfaces at room temperature via natural sativum annilin . More precisely, this bio-sulfurisation is validated on bioengineered nanostructured Cu 2-X S surfaces using natural organosulfur compounds emitted from Sativum allium L. as efficient sulfurisation chemical agents. It is validated that virgin copper surfaces can be sulfurised at room temperature without adding any extra chemical or physical processes. In addition to the validation of the green sulfurisation process of the copper surface, the bioengineered Cu 2-X S exhibited a multiscale 1-D tubular morphology with Cu 2-X S nanotubules and nanocones. Such a nanostructured Cu 2-X S surface exhibited an excessive optical selectivity, a superhydrophobicity response in addition to a remarkable site selective mercury adsorption.

In this contribution, we validate for the first time that the near infrared-infrared (NIR-IR) modulation of the optical transmission (DTTRANS = T(TTMIT)) of vanadium oxide-based nanomaterials can be controlled or tuned via a genuine approach with a simultaneous drastic reduction of its Mott transition temperature TMIT. More accurately, we report a significant thermochromism in multilayered V2O5/V/V2O5 stacks equivalent to that of pure VO2 thin films but with a far lower transition temperature TMIT. Such a multilayered V2O5/V/V2O5 thermochromic system exhibited a net control or tunability of the optical transmission modulation in the NIR-IR (DTTRANS) via the nano-scaled thickness of the intermediate vanadium layer. In addition, the control of DTTRANS is accompanied by a noteworthy diminution of the Mott transition temperature TMIT from the bulk value of 68.8 °C to the range of 27.5–37.5 °C. The observed peculiar thermochromism in the multilayered V2O5/V/V2O5 is likely to be ascribed to a significant interfacial diffusion or an excessive interfacial stress/strain, and/or to an effective halide (Na, K, Ca) doping. This doping is driven by a significant diffusion from the borosilicate substrate surface towards the V2O5/V/V2O5 stacks. If the upscaling of this approach is validated, the current findings would contribute to advancing thermochromic nanomaterials and their applications in smart windows for managing solar heat and green air-conditioning technologies.

In this study, we report on the valence control of vanadium oxidation states towards stabilising VO2 thin films. X-ray diffraction measurements indicate that up to 300 kGy of gamma-ray radiation the VO2 phase remains monoclinic, with the crystallite size only varying slightly with the dose. X-ray photoemission spectroscopy indicates the presence of three oxide phases (VO2, V2O3 and V2O5) on the samples. A decrease in the oxidation states of V3+ and V5+ and an increase in the valence state V4+ are observed for irradiations up to 300 kGy, which favours the vanadium dioxide VO2 formation.

This contribution reports, for the first time, on an entirely green bio-engineering approach for the biosynthesis of single phase crystalline 1-D nano-scaled calcite CaCO3. This was validated using H2O as the universal solvent and natural extract of Hyphaene thebaica fruit as an effective chelating agent. In this room temperature green process, CaCl2 and CO2 are used as the unique source of Ca and CO3 respectively in view of forming nano-scaled CaCO3 with a significant shape anisotropy and an elevated surface to volume ratio. In terms of novelty, and relatively to the reported scientific and patented literature in relation to the fabrication of CaCO3 by green nano-chemistry, the current cost effective room temperature green process can be singled out as per the following specificities: only water as universal solvent is used, No additional base or acid chemicals for pH control, No additional catalyst, No critical or supercritical CO2 usage conditions, Only natural extract of thebaica as a green effective chelating agent through its phytochemicals and proper enzematic compounds, room Temperature processing, atmospheric pressure processing, Nanoscaled size particles, and Nanoparticles with a significant shape anisotropy (1-D like nanoparticles). Beyond and in addition to the validation of the 1-D synthesis aspect, the bio-engineered CaCO3 exhibited a wide-ranging functionalities in terms of highly reflecting pigment, an effective nanofertilizer as well as a potential binder in cement industry.

We demonstrate a new metal-wire waveguide topology, namely a four-wire waveguide, which simultaneously acts as a broadband terahertz polarization-division multiplexer and as a novel platform to realize the independent manipulation of polarization-division multiplexed terahertz signals.

The multiferroic and the rotating magnetocaloric properties of Nd0.8Tb0.2Mn2O5 are investigated by microscopic optical probes and macroscopic magnetic measurements. Raman-active phonons as a function of temperature, and Nd3+ and Tb3+ infrared active crystal-field (CF) excitations as a function of temperature and under magnetic fields up to 11 T have been studied in Nd0.8Tb0.2Mn2O5. The obtained results are compared to those of NdMn2O5 and TbMn2O5 reference compounds. The observation of one set of Raman-active phonons and CF excitations rule out possible twinning while their energy positions and thermal evolutions indicate noticeable changes of Mn1-O3-Mn1 and TbO8 structural units. This would explain the nature of separated magnetic phases in Nd0.8Tb0.2Mn2O5. The degeneracy of the ground-state Kramers doublet is lifted (???0 ??? 9 cm???1), indicating that the Nd3+???Mn3+ interaction impacts the magnetic and ferroelectric properties of Nd0.8Tb0.2Mn2O5. The Zeeman splitting of excited crystal-field levels of the Nd3+ ions at low temperatures shows that the gz factor is weak compared to that in NdMn2O5. This indicates that the R3+ spins in Nd0.8Tb0.2Mn2O5 are mostly aligned within the ab-plane. The nature of magnetocrystalline anisotropy in Nd0.8Tb0.2Mn2O5 as well as in all RMn2O5 compounds is quantitatively investigated by studying the anisotropy of paramagnetic Curie temperatures along (??||) and perpendicular (?????) to the c axis, (??|| ??? ?????), as a function of the rare-earth atomic number. It is particularly found that the magnetocrystalline anisotropy is mainly determined by the quadrupolar charge distribution of 4 f shells. The rotating magnetocaloric effect in Nd0.8Tb0.2Mn2O5 is also evaluated and compared to that in NdMn2O5 and TbMn2O5. Our findings show that Nd- and Tb- separated magnetic phases independently contribute to the magnetocaloric effect of Nd0.8Tb0.2Mn2O5.

In this minireview, we intend to shed light on relatively recent examples related to the size and shape effects on materials at the nanoscale and their usage to test a set of quantum mechanics governed phenomena.

The development of advanced electrode materials derived from biomass for the next generation of energy storage devices, such as supercapacitors with high specific energy and specific power coupled with a good cycle stability, is required to meet the high demand for electric vehicles and portable devices. In this study, sustainable binary vanadium pentoxide carbon-graphene foam composites (V 2 O 5 @C-R 2 HS/GF) were synthesized using a solvothermal method. The X-ray diffraction, Raman and FTIR techniques were used to study the structural properties of the composites (V 2 O 5 @C-R 2 HS/20 mg GF and V 2 O 5 @C-R 2 HS/40 mg GF). The SEM micrographs displayed an accordion-like morphology resulting from the graphene foam-modified V 2 O 5 @C-R 2 HS composite. The V 2 O 5 @C-R 2 HS, V 2 O 5 @C-R 2 HS/20 mg GF and V 2 O 5 @C-R 2 HS/40 mg GF composites were evaluated in a three-electrode configuration using 6 M potassium hydroxide (KOH) as an aqueous electrolyte. Furthermore, a two-electrode device was carried out by fabricating an asymmetric device (V 2 O 5 @C-R 2 HS/GF//AC) where V 2 O 5 @C-R 2 HS/20 mg GF was used as a positive electrode and activated carbon (AC) as a negative electrode at a cell voltage of 1.6 V in 6 M KOH. The V 2 O 5 @C-R 2 HS/GF//AC showed a high specific energy and specific power values of 55 W h kg −1 and 707 W kg −1 , respectively, at a specific current of 1 A g −1 . The asymmetric device presented a good stability test showing 99% capacity retention up to 10 000 cycles and was confirmed by the floating time up to 150 h with specific energy increasing 23.6% after the first 10 h. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)’.

Platinum nanoparticles were deposited onto Highly Oriented Pyrolitic Graphite (HOPG) substrate by laser ablating a Pt target at room temperature into a vacuum chamber. By varying the helium background pressure (from 10−5 to 0.5 Torr) and the target-to-substrate distance (from 3 to 6 cm), we were able to explore a large range of kinetic energies (i.e., from ~4 to ~130 eV/atom) of the Pt ablated neutrals species impinging on the HOPG substrates. Thus, the effect of the kinetic energy on the size and the surface density of Pt nanoparticles has been investigated ex-situ by means of scanning tunneling microscopy (STM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The pulsed laser deposition technique is shown to produce Pt nanoparticles (of which diameter in the 1–4 nm range) with a relatively narrow size distribution. While the size of the PLD Pt nanoparticles is shown to be mainly influenced by the number of laser pulses, their shape is found to be more sensitive to kinetic energy of the Pt ablated species.

We present the solid-state-biased coherent detection technique for ultra-broadband THz pulses operated via a homodyne configuration. This makes our detection method of easy implementation, suitable for cost-effective and portable THz systems.

This study reports on the effect of neutron irradiation at different fluences on the properties of VO2 thin films. The irradiations were performed at NUR research reactor, Algiers at a temperature of about 40 degrees C, with fast neutron fluence (En > 1 MeV) up to 1.9 x 10(18) n.cm(-2). The induced defects have been investigated using structural, optical and electrical measurements. Both bulk sensitive characterization techniques, Raman and grazing incident angle X-ray diffraction (GIXRD) analysis, show that no structural transformation is induced by neutron irradiation, although strain induced defect production are generated throughout the films while surface sensitive techniques, X-ray photoelectron spectroscopy (XPS) and work function measurements, show that the charge carrier (electron) concentration at room temperature decreases after irradiation. Potentially due to fast neutron irradiation induced defects, mainly in the form of Frenkel pairs, swelling and color center formation occurs in VO2 thin films without amorphization. This is further corroborated by an increase of the room temperature resistivity through the irradiated films. Temperature-dependent electrical and optical transmission measurements confirm that the characteristic semiconductor-to-metal transition of the VO2 films is preserved upon irradiation. We therefore conclude that VO2 is an excellent candidate for thermal shielding and thermal management of small satellites.

We study the nonlinear, field dependent properties of stacked nano-slit array structures. Specifically, by measuring the field dependent THz transmission, we are able to resolve the insulator-to-metal transition of VO2 embedded in nano-slits. 2D simulations support the experimental data and allow for the calibration of the enhanced THz fields in the nano-slit volume.

In orthorhombic SmMn2O5 single crystals, Sm3+ crystal-field (CF) excitations are studied by infrared transmission as a function of temperature and under applied magnetic field up to 10 T. These measurements are complemented with the study of Raman-active phonon frequency shifts as a function of temperature between 300 and 5 K. The frequencies of all H-6(j) crystal-field levels of Sm3+ were determined as well as those of H-6(j). At high temperatures, the evolutions of Sm3+ CF excitations exhibit anomalies around the characteristic temperatures, T* similar to 60 K and T-s similar to 120 K and reflect the thermal disorder induced by splitting of the Sm-O bonds in SmMn2O5 that contribute to the frequency and linewidth phonon shifting. At low temperatures, the degeneracy of the ground-state Kramers doublet is lifted (Delta(0) similar to 36 cm(-1)) due to the Sm3(+)-Mn3+ interaction in the ferroelectric phase and strongly enhanced below T c similar to 26 K. The Sm-Mn exchange interaction J(6) is determined and compared to that of Gd-Mn interaction in GdMn2O5. The Sm magnetic moment m(sm )(T) and the Sm contribution to the magnetic susceptibility are also evaluated from Delta(0)(T), indicating that the Sm-Mn interaction is strongly implicated in the magnetic and the ferroelectric orderings below similar to 26 K. The study of the Sm3+ CF excitations as a function of magnetic field reveals twinning in SmMn2O5. This twinning could affect its electric polarization behavior versus magnetic field.

Vanadium dioxide thin films are considered as smart functional coatings for thermal shielding, and are attractive as a passive thermal shield for spacecrafts. In space they would, however, be subjected to bombardment by interstellar dust particles and electromagnetic radiation. Materials subjected to irradiation will suffer damages induced by the displacement cascades initiated by nuclear reaction. Such cosmic radiation can severely impact the structure and function of materials. To study this effect in the laboratory, we have deposited VO_2 films on silicon wafers and exposed them to γ-radiation of doses up to 100 kGy by using a ^60Co nuklid source with 1.17 and 1.33 MeV photon energy. We anticipate that the γ-radiation causes local structural perturbations which can amount to defects with a corresponding change in electronic structure and thermal shielding property. We report on the photo emission spectroscopy of gamma irradiated VO_2 thin films.

Vanadium dioxide thin film nanostructures were synthesized by pulsed laser deposition on soda lime glass at a substrate temperature of 600°C and an oxygen ambient pressure of 15 mTorr. The effect of cooling pressure on the crystalline orientation of VO2 nanostructures was investigated. As the cooling oxygen pressure is increased, the VO2 nanostructures exhibit sharp a-axis diffraction peaks, showing the growth of (1 0 0) oriented VO2 on glass, which is characteristic of the VO2 monoclinic phase and implies that pure highly a-axis textured VO2 was formed. We found that the growth mechanism and substrate–film interaction play important roles in the development of these well-textured films via the formation of an interlayer of SiO2.

We observe a nearly instantaneous triggering of the phase transition in VO2 using transient, time-resolved absorption techniques from few-cycle, infrared (1.8 mu m) laser pulses. The results are in agreement with the Mott-Hubbard insulator model, characterized by electronic holon-doublon pair creation that initiates the insulatorto-metal phase transition within the material. The spectral resolution provided by this technique can be exploited to measure the chirp of the probe pulses. Effects from probing above and below the band gap of the material are also discussed.

In this Section, we present the detailed description of the simulations carried out to accurately estimate the THz field enhancement (FE) induced by the SiN-embedded slit. We start by modeling the emission pattern of the ultrabroadband two-color THz plasma source. Then, by considering simple geometrical principles, which include the analytical description of the frequency dependent collimation and subsequent focusing of the THz beam via two parabolic mirrors, we define the initial condition of the profiles associated to different beam spectral components. We then employ those values in the simulations.