RESUMEN
Hexavalent chromium removal from the environment remains a crucial worldwide challenge. To address this issue, microbiological approaches are amongst the straightforward strategies that rely mainly on the bacteria's and fungi's survival mechanisms upon exposure to toxic metals, such as reduction, efflux system, uptake, and biosorption. In this work, scanning electron microscopy, energy-dispersive X-ray spectrophotometry, Fourier transform infrared spectroscopy, and zeta potential measurements were used to investigate the ability of chromium adsorption by Bacillus licheniformis, Bacillus megaterium, Byssochlamys sp., and Candida maltosa strains isolated from tannery wastewater. Scanning electron microscopy combined with energy dispersive X-ray spectroscopy revealed alterations in the cells treated with hexavalent chromium. When exposed to 50 mg/L Cr6+, Bacillus licheniformis and Candida maltosa cells become rough, extracellular secretions are reduced in Bacillus megaterium, and Byssochlamys sp. cells are tightly bound and exhibit the greatest Cr weight percentage. In-depth analysis of Fourier transform infrared spectra of control and Cr-treated cells unveiled Cr-microbial interactions involving proteins, lipids, amino acids, and carbohydrates. These findings were supported by zeta potential measurements highlighting significant variations in charge after treatment with Cr(VI) with an adsorption limit of 100 mg/L Cr6+ for all the strains. Byssochlamys sp. showed the best performance in Cr adsorption, making it the most promising candidate for treating Cr-laden wastewater.
RESUMEN
Manufacturing custom three-dimensional (3D) carbon functional materials is of utmost importance for applications ranging from electronics and energy devices to medicine, and beyond. In lieu of viable eco-friendly synthesis pathways, conventional methods of carbon growth involve energy-intensive processes with inherent limitations of substrate compatibility. The yearning to produce complex structures, with ultra-high aspect ratios, further impedes the quest for eco-friendly and scalable paths toward 3D carbon-based materials patterning. Here, we demonstrate a facile process for carbon 3D printing at room temperature, using low-power visible light and a metal-free catalyst. Within seconds to minutes, this one-step photocatalytic growth yields rod-shaped microstructures with aspect ratios up to ~500 and diameters below 10 µm. The approach enables the rapid patterning of centimeter-size arrays of rods with tunable height and pitch, and of custom complex 3D structures. The patterned structures exhibit appealing luminescence properties and ohmic behavior, with great potential for optoelectronics and sensing applications, including those interfacing with biological systems.
RESUMEN
Tailoring two-dimensional (2D) materials functionalities is closely intertwined with defect engineering. Conventional methods do not offer the necessary control to locally introduce and study defects in 2D materials, especially in non-vacuum environments. Here, an infrared pulsed laser focused under the metallic tip of an atomic force microscope cantilever is used to create nanoscale defects in hexagonal boron nitride (h-BN) and to subsequently investigate the induced lattice distortions by means of nanoscale infrared (nano-IR) spectroscopy. The effects of incoming light power, exposure time, and environmental conditions on the defected regions are considered. Nano-IR spectra complement the morphology maps by revealing changes in lattice vibrations that distinguish the defects formed under various environments. This work introduces versatile experimental avenues to trigger and probe local reactions that functionalize 2D materials through defect creation with a higher level of precision for applications in sensing, catalysis, optoelectronics, quantum computing, and beyond.