The marine ecosystem, which makes up around two-thirds of the planet’s sur-
face, suffers from aggressive heavy metal contamination, especially in the last
few years. This pollution causes shifting in many marine life forms threatening
our fisheries and human health. The natural sources of marine heavy metal pol-
lution are rock erosion, and volcanic dust, while the artificial sources are related
to human attitudes like sewage, ship accidents, industrial wastes, and agricultural
wastes. Because they are so common in nature, microorganisms also predomi-
nate in locations where heavy metals have been contaminated. Heavy metals are
easily changed by them into harmless forms. Microorganisms have two respond-
ing mechanisms of heavy metal contamination that comprise enzymatic break-
down of the target contaminants and/or heavy metal resistance. In this chapter we
will discuss marine heavy metal contamination sources, their risks to the marine
life forms, and different responses of marine fungi to heavy metal
contamination.

There is an increasing need for environmentally friendly and sustainable energy sources that rely on efficient and abundant electrocatalysts for the oxygen evolution reaction (OER). OER plays a key role in energy conversion and storage applications. Using a vacuum kinetic spray technique operating at room temperature, electrocatalysts based on nano-sized Ni(OH)₂–MoS₂ nanocomposites (NCs) on nickel foam are fabricated from the corresponding micron powders. The Ni(OH)₂–MoS₂ NC modified working electrodes were exploited to investigate the OER at different weight ratios of MoS₂ (25, 50, and 75 wt%). To comprehensively investigate and elucidate the surface state and morphology of the electrode, x-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were assessed. SEM images showed that the micro-sized particles were fragmented into smaller nanoscale particles. XPS spectra revealed the synergy enhancement in the Ni(OH)₂–MoS₂ NCs that resulted in a strong improvement in the OER activity. Ni(OH)₂–MoS₂ hybrid NCs with 75 wt% MoS₂ exhibited the lowest overpotential of 282 mV at 10 mA cm⁻² and a small Tafel slope of 54 mV⋅dec⁻¹. Alongside, the prolonged OER durability at 50 mA cm⁻² is verified for up to 50 h.

In the present study, the structural, optical, and magnetic properties of (ZnSn)_1-xCo_xO nanocomposites (NCs) were reported. The transmission electron microscope (TEM) images of ZnSnO NCs showed mixed nanorods and nanosheets morphologies that completely transformed to mostly nanocubes with Co-ions incorporation. The optical band gap (E_g) of nanostructured ZnO, SnO, and ZnSnO NCs was 3.2, 4.5, and 3.9 eV, respectively. The estimated E_g value of all (ZnSn)_1-xCo_xO NCs was lower than the undoped ZnSnO NCs. The nanostructured ZnO revealed poor room-temperature ferromagnetic (RTFM) behavior whereas nanostructured SnO exhibited paramagnetic behavior at low magnetic field strength followed by diamagnetic behavior at high magnetic field strength. The (ZnSn)_1-xCo_xO NCs exhibited strong improvement in the RTFM, where the hybrid (ZnSn)₆₀Co₄₀O NCs exhibited the highest saturation magnetization (M_s) of 2 emu·g⁻¹. This value was 5-times higher than the undoped ZnSnO NCs and 2-orders of magnitude higher than the pure ZnO phase. However, with increasing Co-content up to 50 %, the M_s was reduced to 1.16 emu·g⁻¹ demonstrating the corruption of RTFM. The present study indicated the importance of composition utilization for tuning physical properties of (ZnSn)_1-xCo_xO NCs and improving the performance of these NCs in optoelectronic and spintronics applications.