Core-shell NaHoF4@TiO2 NPs: A labelling method to trace engineered nanomaterials of ubiquitous elements in the environment

Understanding the fate and behavior of nanoparticles (NPs) in the natural environment is important to assess their potential risk. Single particle inductively coupled plasma mass spectrometry (spICP-MS) allows for the detection of NPs at extremely low concentrations, but the high natural background of the constituents of many of the most widely utilized nanoscale materials makes accurate quantification of engineered particles challenging. Chemical doping, with a less naturally abundant element, is one approach to address this; however, certain materials with high natural abundance, such as TiO2 NPs, are notoriously difficult to label and differentiate from natural NPs. Using the low abundance rare earth element Ho as a marker, Ho-bearing core -TiO2 shell (NaHoF4@TiO2) NPs were designed to enable the quantification of engineered TiO2 NPs in real environmental samples. The NaHoF4@TiO2 NPs were synthesized on a large scale (gram), at relatively low temperatures, using a sacrificial Al(OH)3 template that confines the hydrolysis of TiF4 within the space surrounding the NaHoF4 NPs. The resulting NPs consist of a 60 nm NaHoF4 core and a 5 nm anatase TiO2 shell, as determined by TEM, STEM-EDX mapping, and spICPMS. The NPs exhibit excellent detectability by spICP-MS at extremely low concentrations (down to 1 × 10−3 ng/L) even in complex natural environments with high Ti background

New Pathway for Heterogenization of Molecular Catalysts by Non-covalent Interactions with Carbon Nanoreactors

A novel approach to heterogenization of catalytic molecules is demonstrated using the nanoscale graphitic step edges inside hollow graphitized carbon nanofibers (GNFs). The presence of the fullerene C₆₀ moiety within a fullerene–salen Cu^II complex is essential for anchoring the catalyst within the GNF nanoreactor as demonstrated by comparison to the analogous catalyst complex without the fullerene group. The presence of the catalyst at the step edges of the GNFs is confirmed by high-resolution transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) with ultraviolet/visible (UV/vis) spectroscopy, demonstrating only negligible (ca. 3%) desorption of the fullerene–salen Cu^II complex from the GNFs into solution under typical reaction conditions. The catalyst immobilized in GNFs shows good catalytic activity and selectivity toward styrene epoxidation, comparable to the analogous catalyst in solution. Moreover, the fullerene–salen Cu^II complex in GNFs demonstrates excellent stability and recyclability because it can be readily separated from the reaction mixture and employed in multiple reaction cycles with minimal loss of activity, which is highly advantageous compared to catalysts not stabilized by the graphitic step edges that desorb rapidly from GNFs

Interactions and Reactions of Transition Metal Clusters with the Interior of Single-Walled Carbon Nanotubes Imaged at the Atomic Scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal–carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal–nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed

Interactions and Reactions of Transition Metal Clusters with the Interior of Single-Walled Carbon Nanotubes Imaged at the Atomic Scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal–carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal–nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed

Interactions and Reactions of Transition Metal Clusters with the Interior of Single-Walled Carbon Nanotubes Imaged at the Atomic Scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal–carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal–nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed

Interactions and Reactions of Transition Metal Clusters with the Interior of Single-Walled Carbon Nanotubes Imaged at the Atomic Scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal–carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal–nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed

Interactions and Reactions of Transition Metal Clusters with the Interior of Single-Walled Carbon Nanotubes Imaged at the Atomic Scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal–carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal–nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed

Interactions and Reactions of Transition Metal Clusters with the Interior of Single-Walled Carbon Nanotubes Imaged at the Atomic Scale

Clusters of transition metals, W, Re, and Os, upon encapsulation within a single-walled carbon nanotube (SWNT) exhibit marked differences in their affinity and reactivity with the SWNT, as revealed by low-voltage aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). Activated by an 80 keV electron beam, W reacts only weakly with the SWNT, Re creates localized defects on the sidewall, and Os reacts readily causing extensive defect formation and constriction of the SWNT sidewall followed by total rupture of the tubular structure. AC-HRTEM imaging at the atomic level of structural transformations caused by metal–carbon bonding of π- and σ-character demonstrates what a crucial role these types of bonds have in governing the interactions between the transition metal clusters and the SWNT. The observed order of reactivity W < Re < Os is independent of the metal cluster size, shape, or orientation, and is related to the metal to nanotube bonding energy and the amount of electronic density transferred between metal and SWNT, both of which increase along the triad W, Re, Os, as predicted by first-principles density functional theory calculations. By selecting the appropriate energy of the electron beam, the metal–nanotube interactions can be controlled (activated or precluded). At an electron energy as low as 20 keV, no visible transformations in the nanotube in the vicinity of Os-clusters are observed

Size, Structure, and Helical Twist of Graphene Nanoribbons Controlled by Confinement in Carbon Nanotubes

Carbon nanotubes (CNTs) act as efficient nanoreactors, templating the assembly of sulfur-terminated graphene nanoribbons (S-GNRs) with different sizes, structures, and conformations. Spontaneous formation of nanoribbons from small sulfur-containing molecules is efficiently triggered by heat treatment or by an 80 keV electron beam. S-GNRs form readily in CNTs with internal diameters between 1 and 2 nm. Outside of this optimum range, nanotubes narrower than 1 nm do not have sufficient space to accommodate the 2D structure of S-GNRs, while nanotubes wider than 2 nm do not provide efficient confinement for unidirectional S-GNR growth, thus neither can support nanoribbon formation. Theoretical calculations show that the thermodynamic stability of nanoribbons is dependent on the S-GNR edge structure and, to a lesser extent, the width of the nanoribbon. For nanoribbons of similar widths, the polythiaperipolycene-type edges of zigzag S-GNRs are more stable than the polythiophene-type edges of armchair S-GNRs. Both the edge structure and the width define the electronic properties of S-GNRs which can vary widely from metallic to semiconductor to insulator. The encapsulated S-GNRs exhibit diverse dynamic behavior, including rotation, translation, and helical twisting inside the nanotube, which offers a mechanism for control of the electronic properties of the graphene nanoribbon <i>via</i> confinement at the nanoscale

Size, Structure, and Helical Twist of Graphene Nanoribbons Controlled by Confinement in Carbon Nanotubes

Carbon nanotubes (CNTs) act as efficient nanoreactors, templating the assembly of sulfur-terminated graphene nanoribbons (S-GNRs) with different sizes, structures, and conformations. Spontaneous formation of nanoribbons from small sulfur-containing molecules is efficiently triggered by heat treatment or by an 80 keV electron beam. S-GNRs form readily in CNTs with internal diameters between 1 and 2 nm. Outside of this optimum range, nanotubes narrower than 1 nm do not have sufficient space to accommodate the 2D structure of S-GNRs, while nanotubes wider than 2 nm do not provide efficient confinement for unidirectional S-GNR growth, thus neither can support nanoribbon formation. Theoretical calculations show that the thermodynamic stability of nanoribbons is dependent on the S-GNR edge structure and, to a lesser extent, the width of the nanoribbon. For nanoribbons of similar widths, the polythiaperipolycene-type edges of zigzag S-GNRs are more stable than the polythiophene-type edges of armchair S-GNRs. Both the edge structure and the width define the electronic properties of S-GNRs which can vary widely from metallic to semiconductor to insulator. The encapsulated S-GNRs exhibit diverse dynamic behavior, including rotation, translation, and helical twisting inside the nanotube, which offers a mechanism for control of the electronic properties of the graphene nanoribbon <i>via</i> confinement at the nanoscale