Experimental and Quantum Chemical Studies of the Inhibition of Copper with Sodium Dodecyl Sulphate (SDS) in Acidic Medium

This work investigates the inhibitive properties of sodium dodecyl sulphate (SDS) on the corrosion of copper (Cu) in nitric acid using gasometric methods. The inhibition efficiency increases with time and concentration of SDS. The corrosion rate of copper decreases as concentration of SDS increases. Adsorption of the SDS on the surface obeyed the Langmuir adsorption isotherm. The high negative values of the kinetic parameter B suggest that the inhibitor’s effectiveness increases with temperature. The equilibrium constant and the free energy of adsorption of SDS to copper are negative and large. This observation implies that the adsorption mechanism maybe chemisorption. The quantum chemical calculation of copper dodecyl sulphate shows that the energy change in the HOMO-LUMO energy of the moiety is positive and small. This observation implies that the SDS is an efficient inhibitor. The high dipole moment obtained implies that corrosion inhibition of Cu is enhanced by adsorption of SDS and this observation correlates with the observed experimental inhibition efficiency.

Spatial and Temporal Variation of Normalized Difference Vegetation Index (NDVI) and Rainfall in the North East Arid Zone of Nigeria

This study examines the spatial and temporal variation of onset and cessation of rainfall and greenness in the North East Arid Zone of Nigeria. Onset and cessation of greenness dates were determined from mean monthly time series of Normalized Difference Vegetation Index (NDVI) using Advance Very High Resolution Radiometer (AVHRR) data for five meteorological stations in the zone for a period of nineteen years (1981-1999). Lowest growing days of six weeks were observed in Nguru (12.53°N, 10.28°E, alt.343 m), Potiskum (11.42°N, 11.02°E, alt.415 m) and Maiduguri (11.51°N, 13.05°E, alt. 354 m), while Yola (12.28°N, 9.14°E, alt.174 m) and Bauchi (10.17°N, 9.49°E, alt.609 m) have growing days of 15 and 16 weeks respectively. Highest rate of greenness of 0.18/month was observed inMaiduguriwhile the lowest rate of green-up of 0.07/month was observed in Bauchi. Similarly, highest rate of senescence (0.08/month) was observed in Bauchi while lowest rate of senescence (0.04/month) was observed in Nguru.

Trends of Temperature and Signature of Solar Activity in Selected Stations in Nigeria

This study investigates the variability and periodicity of minimum temperature, maximum temperature and sunspot number—a solar activity index in selected synoptic stations across Nigeria from 1946 to 2010. Annual and semiannual effect of solar activity on minimum temperature was observed in all the six stations. This was indicated in the occurrence of modal periodicities of 6-month and 12-month observed across the six synoptic stations. The synoptic stations are Sokoto (13.01°N, 5.15°E), Ilorin (8.29°N, 4.35°E), Ikeja (6.35°N, 3.20°E), Enugu (6.28°N, 7.33°E), Port-Harcourt (4.51°N, 7.01°E) and Maiduguri (11.51°N, 13.05°E). Similarly, the trends of inter-decadal va-riability of minimum and maximum temperature show a non-uniformity increase over the analyzed period with a slight decrease before 1960. The long term behavior of minimum and maximum temperature shows a warming rate which ranges from 0.1°C/decade to 0.2°C/ decade across the six stations except for maximum temperature at Ilorin and minimum temperature at Sokoto which is at -0.2°C/decade and 0.3°C/decade respectively.

Water-induced hydrogenation of graphene/metal interfaces at room temperature:Insights on water intercalation and identification of sites for water splitting

Though it is well recognized that the space between graphene cover and the metal substrate canact as a two-dimensional(2D)nanoreactor,several issues are still unresolved,including the role of the metal substrate,the mechanisms ruling water intercalation and the identification ofsites at which water is decomposed.Here,we solve these issues by means of density functional theory and high-resolution electron energyloss spectroscopy experiments carried out on graphene grown on(111)-oriented Cu foils.Specifically,we observe decomposition of H2O atroom temperature with only H atoms forming bonds with graphene and with buried OH groups underneath the graphene cover.Ourtheoretical model discloses physicochemical mechanisms ruling the migration and decomposition of water on graphene/Cu.We discover thatthe edge of graphene can be easily saturated by H through decomposition of H2O,which allows H2O to migrate in the subsurface region from thedecoupled edge,where H2O decomposes at room temperature.Hydrogen atoms produced by the decomposition of H2O initially form a chemicalbond with graphene for the lower energy barrier compared with other routes.These findings are essential to exploit graphene/Cu interfaces incatalysis and in energy-related applications.

Characterization and stability measurement of deployed multicore fibers for quantum applications

Multicore fibers are expected to be a game-changer in the coming decades thanks to their intrinsic properties,allowing a larger transmission bandwidth and a lower footprint in optical communications.In addition,multicore fibers have recently been explored for quantum communication,attesting to their uniqueness in transporting high-dimensional quantum states.However,investigations and experiments reported in literature have been carried out in research laboratories,typically making use of short fiber links in controlled environments.Thus,the possibility of using long-distance multicore fibers for quantum applications is still to be proven.We characterize here for the first time,to the best of our knowledge,in terms of phase stability,multiple strands of a four-core multicore fiber installed underground in the city of L’Aquila,with an overall fiber length up to about 25 km.In this preliminary study,we investigate the possibility of using such an infrastructure to implement quantumenhanced schemes,such as high-dimensional quantum key distribution,quantum-based environmental sensors,and more,in general,quantum communication protocols.

Electric field and charge doping induced superconducting transition in 2D freestanding perovskite barium bismuthate

We present an ab-initio study of monolayer BaBiO_(3) focused on how to harness the insulator-metal transition through suppression of the charge density wave(CDW)phase in this material.After the determination of the most stable structure for the freestanding monolayer,we investigate the effects of an applied electric field and of charge doping on the electronic properties of the system.Our results show that external electric fields of the order of 0.1-0.3 V/A are able to stabilize the metallic phase,destroy the CDW phase and,in addition,lead to a metallic metastable phase.On this same footing,we show that hole doping could also suppress the CDW phase and drive the system toward a metallic phase with large electron-phonon coupling.To this end,we also study the dependence of the electron-phonon coupling on hole-doping concentration and show that this could drive the onset of superconductivity.Indeed,low-dimensional BaBiO3 is an extremely flexible material with electronic properties that could be tuned using different and possibly combined external tools such as electric fields and charge doping,paving the way to achieve effective control on the transition from the CDW,to the metallic and then superconducting phase.

Tunable spin textures in polar antiferromagnetic hybrid organic–inorganic perovskites by electric and magnetic fields

The hybrid organic–inorganic perovskites(HOIPs)have attracted much attention for their potential applications as novel optoelectronic devices.Remarkably,the Rashba band splitting,together with specific spin orientations in k-space(i.e.,spin texture),has been found to be relevant for the optoelectronic performances.In this work,by using first-principles calculations and symmetry analysis,we study the electric polarization,magnetism.

Hybrid Dirac semimetal-based photodetector with efficient low-energy photon harvesting

Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small active areas with efficient conversion into an electrical signal.Here,we provide an alternative strategy by efficiently integrating and manipulating at the nanoscale the optoelectronic properties of topological Dirac semimetal PtSe_(2)and its van der Waals heterostructures.Explicitly,we realize strong plasmonic antenna coupling to semimetal states near the skin-depth regime(λ/10^(4)),featuring colossal photoresponse by in-plane symmetry breaking.The observed spontaneous and polarization-sensitive photocurrent are correlated to strong coupling with the nonequilibrium states in PtSe_(2)Dirac semimetal,yielding efficient light absorption in the photon range below 1.24 meV with responsivity exceeding∼0.2 A/W and noise-equivalent power(NEP)less than~38 pW/Hz^(0.5),as well as superb ambient stability.Present results pave the way to efficient engineering of a topological semimetal for high-speed and low-energy photon harvesting in areas such as biomedical imaging,remote sensing or security applications.

Closing the THz gap with Dirac semimetals

High-performance THz photodetection is unprecedentedly accessed by integrating a topological Dirac(Weyl)semimetal in a carefully designed antenna at deep-subwavelength scales.

Phase-matching-free parametric oscillators based on two-dimensional semiconductors

Optical parametric oscillators are widely used as pulsed and continuous-wave tunable sources for innumerable applications,such as quantum technologies,imaging,and biophysics.A key drawback is material dispersion,which imposes a phase-matching condition that generally entails a complex design and setup,thus hindering tunability and miniaturization.Here we show that the burden of phase-matching is surprisingly absent in parametric microresonators utilizing mono-layer transition-metal dichalcogenides as quadratic nonlinear materials.By the exact solution of nonlinear Maxwell equations and first-principle calculations of the semiconductor nonlinear response,we devise a novel kind of phase-matching-free miniaturized parametric oscillator operating at conventional pump intensities.We find that different two-dimensional semiconductors yield degenerate and non-degenerate emission at various spectral regions due to doubly resonant mode excitation,which can be tuned by varying the incidence angle of the external pump laser.In addition,we show that high-frequency electrical modulation can be achieved by doping via electrical gating,which can be used to efficiently shift the threshold for parametric oscillation.Our results pave the way for the realization of novel ultra-fast tunable micron-sized sources of entangled photons—a key device underpinning any quantum protocol.Highly miniaturized optical parametric oscillators may also be employed in lab-on-chip technologies for biophysics,detection of environmental pollution and security.

Switchable Rashba anisotropy in layered hybrid organic-inorganic perovskite by hybrid improper ferroelectricity

Hybrid organic–inorganic perovskites(HOIPs)are introducing exotic directions in the photovoltaic materials landscape.The coexistence of inversion symmetry breaking and spin–orbit interactions play a key role in their optoelectronic properties.We perform a detailed study on a recently synthesized ferroelectric layered HOIP,(AMP)PbI_(4)(AMP=4-aminomethyl-piperidinium).The calculated polarization and Rashba parameters are in excellent agreement with experimental values.