We report the synthesis of luminescent crystals based on hexagonal-phase NaYF4 upconversion microrods. The synthetic procedure involves an epitaxial end-on growth of upconversion nanocrystals comprising different lanthanide activators onto the NaYF4 microrods. This bottom-up method readily affords multicolor-banded crystals in gram quantity by varying the composition of the activators. Importantly, the end-on growth method using one-dimensional microrods as the template enables facile multicolor tuning in a single crystal, which is inaccessible in conventional upconversion nanoparticles. We demonstrate that these novel materials offer opportunities as optical barcodes for anticounterfeiting and multiplexed labeling applications.

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We devised iron-based catalysts with honeycomb-structured graphene (HSG) as the support and potassium as the promoter for CO direct hydrogenation to light olefins (CO-FTO). Over the optimal FeK1.5/HSG catalyst, the iron time yield of light olefins amounted to 73 μmol g s with high selectivity of 59%. No obvious deactivation occurred within 120 h on stream. The excellent catalytic performance is attributed to the confinement effect of the porous HSG on the sintering of the active sites and the promotion effect of potassium on the activation of inert CO and the formation of iron carbide active for CO-FTO.

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Growing interest in lanthanide-doped nanoparticles for biological and medical uses has brought particular attention to their safety concerns. However, the intrinsic toxicity of this new class of optical nanomaterials in biological systems has not been fully evaluated. In this work, we systematically evaluate the long-term cytotoxicity of lanthanide-doped nanoparticles (NaGdF4 and NaYF4) to HeLa cells by monitoring cell viability (mitochondrial activity), adenosine triphosphate (ATP) level, and cell membrane integrity (lactate dehydrogenase release), respectively. Importantly, we find that ligand-free lanthanide-doped nanoparticles induce intracellular ATP deprivation of HeLa cells, resulting in a significant decrease in cell viability after exposure for 7 days. We attribute the particle-induced cell death to two distinct cell death pathways, autophagy and apoptosis, which are primarily mediated via the interaction between the nanoparticle and the phosphate group of cellular ATP. The understanding gained from the investigation of cytotoxicity associated with lanthanide-doped nanoparticles provides keen insights into the safe use of these nanoparticles in biological systems.

Recent research suggests that biochar amendment is a promising approach to mitigate soil contamination via immobilizing heavy metals and organic pollutants. Through intensive literature review, this paper was aimed to better understand the processes, mechanisms, and effectiveness of biochar in immobilizing chemical contaminants in soil. The quality characteristics of biochar as a soil amendment varied greatly with the feedstock materials and the pyrolysis conditions. Biochar products from different sources demonstrated remarkably diversified capacities and efficiencies for stabilizing soil contaminants. Soil-incorporated biochar was able to stabilize Cd, Cu, Ni, Pb, and Zn and reduce their bioavailability through enhanced sorption (based on electrostatic attraction, ion exchange, and surface complexation) and chemical precipitation (incurred from soil pH elevation and ash addition of carbonates and phosphates). The stabilization efficacy was largely determined by cation exchange capacity, pH, and ash content of the biochar. Biochar amendment increased the mobility of anionic toxic elements [e.g., CrO 2− 4 , AsO − 3 , and Sb(OH) − 6 ] in soil. Soil-incorporated biochar was also able to adsorb non-polar organic compounds (through pore filling, partition, and hydrophobic effect) and polar organic compounds (via H-bonding, electrostatic attraction, specific interaction, and surface precipitation). The adsorption efficiency was controlled by the biochar surface properties specific surface area, microporosity, and hydrophobicity. Biochar may facilitate the mineralization of organic pollutants by enhancing soil microbial activities. The effectiveness of biochar-facilitated soil remediation was case specific, changing with the biochar source, amendment rate, placement, soil type, and pollutant species. More field studies are needed to evaluate the long-term effectiveness of biochar-facilitated soil remediation under practical circumstances.

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