The adsorption of biomolecules to the surface of engineered nanomaterials, known as corona formation, defines their biological identity by altering their surface properties and transforming the physical, chemical, and biological characteristics of the particles. In the first decade since the term protein corona was coined, studies have focused primarily on biomedical applications and human toxicity. The relevance of the environmental dimensions of the protein corona are still emerging. Often referred to as the eco-corona, a biomolecular coating forms upon nanomaterials as they enter the environment and may include proteins, as well as a diverse array of other biomolecules such as metabolites from cellular activity and/or natural organic matter. Proteins remain central in studies of eco-coronas because of the ease of monitoring and structurally characterising proteins, as well as their crucial role in receptor engagement and signaling. The proteins within the eco-corona are optimal targets to establish the biophysicochemical principles of corona formation and transformation, as well as downstream impacts on nanomaterial uptake, distribution, and impacts on the environment. Moreover, proteins appear to impart a biological identity leading to cellular or organismal recognition of nanomaterials, a unique characteristic in comparison to natural organic matter. We contrast insights into protein corona formation from clinical samples with those in environmentally relevant systems. Principles specific to the environment are also explored to gain insights into dynamics of interaction with / exchange by other biomolecules, including changes during trophic transfer and ecotoxicity. With many challenges remaining, we also highlight key opportunities for method development and impactful systems on which to focus the next phase of eco-corona studies. By interrogating these environmental dimensions of the protein corona, we offer a perspective on how mechanistic insights into protein coronas in the environment can lead to more sustainable, environmentally safe nanomaterials, as well as enhance the efficacy of nanomaterials used in remediation and in the agri-sector.

Silver nanoparticles (AgNPs) are widely incorporated into consumer products and used medically for their biocidal properties, [1] with applications in biosensing, imaging, and therapies. As concerns of frequent and cumulative exposures increase, AgNP toxicity has drawn considerable attention. [2,3] Most exposure studies to date involve atypical high-dose concentrations Silver nanoparticles (AgNPs) are widely incorporated into consumer and biomedical products for their antimicrobial and plasmonic properties with limited risk assessment of low-dose cumulative exposure in humans. To evaluate cellular responses to low-dose AgNP exposures across time, human liver cells (HepG2) are exposed to AgNPs with three different surface charges (1.2 µg mL −1 ) and complete gene expression is monitored across a 24 h period. Time and AgNP surface chemistry mediate gene expression. In addition, since cells are fed, time has marked effects on gene expression that should be considered. Surface chemistry of AgNPs alters gene transcription in a timedependent manner, with the most dramatic effects in cationic AgNPs. Universal to all surface coatings, AgNP-treated cells responded by inactivating proliferation and enabling cell cycle checkpoints. Further analysis of these universal features of AgNP cellular response, as well as more detailed analysis of specific AgNP treatments, time points, or specific genes, is facilitated with an accompanying application. Taken together, these results provide a foundation for understanding hepatic response to low-dose AgNPs for future risk assessment.

Understanding heterogeneous catalysts is a challenging pursuit due to surface site nonuniformity and aperiodicity in traditionally used materials. One example is sulfated metal oxides, which function as highly active catalysts and as supports for organometallic complexes. These applications are due to traits such as acidity, ability to act as a weakly coordinating ligand, and aptitude for promoting transformations via radical cation intermediates. Research is ongoing about the structural features of sulfated metal oxides that imbue the aforementioned properties, such as sulfate geometry and coordination. To better understand these materials, metal−organic frameworks (MOFs) have been targeted as structurally defined analogues. Composed of inorganic nodes and organic linkers, MOFs possess features such as high porosity and crystallinity, which make them attractive for mechanistic studies of heterogeneous catalysts. In this work, Zr 6 -based MOF NU-1000 is sulfated and characterized using techniques such as single crystal X-ray diffraction in addition to diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The dynamic nature of the sulfate binding motif is found to transition from monodentate, to bidentate, to tridentate depending on the degree of hydration, as supported by density functional theory (DFT) calculations. Heightened Brønsted acidity compared to the parent MOF was observed upon sulfation and probed through trimethylphosphine oxide physisorption, ammonia sorption, in situ ammonia DRIFTS, and DFT studies. With the support structure benchmarked, an organoiridium complex was chemisorbed onto the sulfated MOF node, and the efficacy of this supported catalyst was demonstrated for stoichiometric and catalytic activation of benzene-d 6 and toluene with structure−activity relationships derived.

The interplay of primary organic ligands and inorganic secondary building units (SBUs) has led to a continual boom of reticular chemistry, particularly metal−organic frameworks (MOFs). Subtle variations of organic ligands can have a significant impact on the ultimate structural topology and consequently, the material's function. However, the role of ligand chirality in reticular chemistry has rarely been explored. In this work, we report the organic ligand chirality-controlled synthesis of two zirconium-based MOFs (Spiro-1 and Spiro-3) with distinct topological structures as well as a temperature-controlled formation of a kinetically stable phase (Spiro-4) based on the carboxylate-functionalized inherently axially chiral 1,1′-spirobiindane-7,7′-phosphoric acid ligand. Specifically, Spiro-1 is a homochiral framework comprising only enantiopure S-spiro ligands and has a unique 4,8-connected sjt topology with large 3D interconnected cavities, while Spiro-3 contains equal amounts of S-and R-spiro ligands, resulting in a racemic framework of 6,12-connected edgetransitive alb topology with narrow channels. Interestingly, the kinetic product Spiro-4 obtained with racemic spiro ligands is built of both hexa-and nona-nuclear zirconium clusters acting as 9-and 6-connected nodes, respectively, giving rise to a newly discovered azs net. Notably, the preinstalled highly hydrophilic phosphoric acid groups combined with large cavity, high porosity, and outstanding chemical stability endow Spiro-1 with remarkable water vapor sorption performance, whereas Spiro-3 and Spiro-4 show poor performances due to inappropriate pore systems and structural fragility upon the water adsorption/desorption process. This work highlights the important role of ligand chirality in manipulating the framework topology and function and would further enrich the development of reticular chemistry.

Titanium dioxide is the most extensively used heterogeneous catalyst for the photooxidation of toluene and other hydrocarbons, but it has low utility for the synthesis of benzyl alcohol, of which little is produced, or benzaldehyde, due to further oxidation to benzoic acid and cresol, among other oxidation products, and eventually complete mineralization to CO 2. Et 4 N[FeCl 4 ] functions as a photocatalyst through the dissociation of chlorine atoms, which abstract hydrogen from toluene, and the photooxidation of toluene proceeds only as far as benzyl alcohol and benzaldehyde. Unlike TiO 2 , which requires ultraviolet (UV) irradiation, Et 4 N[FeCl 4 ] catalyzes the photooxidation of toluene with visible light alone. Even under predominantly UV irradiation, the yield of benzyl alcohol plus benzaldehyde is greater with Et 4 N[FeCl 4 ] than with TiO 2. Et 4 N[FeCl 4 ] photocatalysis yields benzyl chloride as a side product, but it can be minimized by restricting irradiation to wavelengths above 360 nm and by the use of long irradiation times. The photonic efficiency of oxidation in one experiment was found to be 0.042 mol/einstein at 365 nm. The use of sunlight as the irradiation source was explored.