Carbon dots (CDs) are low-cost light-absorbers in photocatalytic multicomponent systems, but their wide size distribution has hampered rational design and the identification of the factors that... Show moreCarbon dots (CDs) are low-cost light-absorbers in photocatalytic multicomponent systems, but their wide size distribution has hampered rational design and the identification of the factors that lead to their best performance. To address this challenge, we report herein the use of gel filtration size exclusion chromatography to separate amorphous, graphitic, and graphitic N-doped CDs depending on their lateral size to study the effect of their size on photocatalytic H2 evolution with a DuBois-type Ni cocatalyst. Transmission electron microscopy and dynamic light scattering confirm the size-dependent separation of the CDs, whereas UV-vis and fluorescence spectroscopy of the more monodisperse fractions show a distinct response which computational modelling attributes to a complex interplay between CD size and optical properties. A size-dependent effect on the photocatalytic H2 evolution performance of the CDs in combination with a molecular Ni cocatalyst is demonstrated with a maximum activity at approximately 2-3 nm CD diameter. Overall, size separation leads to a two-fold increase in the specific photocatalytic activity for H2 evolution using the monodisperse CDs compared to the as synthesized polydisperse samples, highlighting the size-dependent effect on photocatalytic performance. Show less
Zeng, Y.; Shen, M.; Pattipeiluhu, R.; Zhou, X.; ZHANG, Y.; Bakkum, T.; ... ; Kros, A. 2023
Confinement of biopolymers inside volumes with micro- or nanoscale lateral dimensions is ubiquitous in nature. Investigating the behavior of biopolymers in a confined environment is essential to... Show moreConfinement of biopolymers inside volumes with micro- or nanoscale lateral dimensions is ubiquitous in nature. Investigating the behavior of biopolymers in a confined environment is essential to improve our basic understanding in life sciences. In this work, we present a nanopore gated sub-attoliter silicon nanocavity device, which allows DNA compaction similar to that in virus capsids. Single DNA molecules can be electrically driven into the nanocavity, and then get compacted inside the nanocavity under certain conditions. The dynamic fluctuations of the compacted DNA can be monitored via ionic current measurements. The mechanism for the DNA compaction is elucidated by varying the DNA length or concentration, voltage polarity, nanocavity dimensions and ionic strength. Furthermore, Brownian dynamics simulations reveal the dynamic fluctuations of the compacted DNA, which are reflected in the measured ionic current. Our nanocavity device is anticipated to provide a controlled environment in extremely small volumes for investigating the physics of confined biopolymers. Show less
Hierarchically built-up multicompartment nanoaggregate systems are of interest for, e.g., novel materials and medicine. Here we present a versatile strategy to generate and unambiguously... Show moreHierarchically built-up multicompartment nanoaggregate systems are of interest for, e.g., novel materials and medicine. Here we present a versatile strategy to generate and unambiguously characterize complex coacervate-core micelles by exploiting four different dendrimeric subcomponents as core-units. The resulting mesoscale structures have a hydrodynamic diameter of 50 nm and a core size of 33 nm, and host about thirty 6th generation polyamidoamine (PAMAM) dendrimers. We have used FRET (efficiency of similar to 0.2) between fluorescein and rhodamine moieties immobilized on separate PAMAM dendrimers (G6-F and G6-R, respectively) to prove synchronous encapsulation in the micelle core. Tuning the proximity of the FRET pair molecules either by varying the G6-F : G6-R ratio, or by co-assembling non-functionalized dendrimer (G6-E) in the core, reveals the optimal FRET efficiency to occur at a minimum of 70% loading with G6-F and G6-R. Additional co-encapsulation of 6th generation gold dendrimer-encapsulated nanoparticles (G6-Au) in the micelle core shows a dramatic reduction of the FRET efficiency, which can be restored by chemical etching of the gold nanoparticles from within the micellar core with thiols, leaving the micelle itself intact. This study reveals the controlled co-assembly of up to four different types of subcomponents in one single micellar core and concomitantly shows the wide variety of structures that can be made with a well-defined basic set of subcomponents. It is straightforward to design related strategies, to incorporate inside one micellar core, e.g., even more than 4 different dendrimers, or other classes of (macro)molecules, with different functional groups, other FRET pairs or different encapsulated metal nanoparticles. Show less
Two-dimensional (2D) membranes featuring arrays of sub-nanometer pores have applications in purification, solvent separation and water desalination. Compared to channels in bulk membranes, 2D... Show moreTwo-dimensional (2D) membranes featuring arrays of sub-nanometer pores have applications in purification, solvent separation and water desalination. Compared to channels in bulk membranes, 2D nanopores have lower resistance to transmembrane transport, leading to faster passage of ions. However, the formation of nanopores in 2D membranes requires expensive post-treatment using plasma or ion bombardment. Here, we study bottom-up synthesized porous carbon nanomembranes (CNMs) of biphenyl thiol (BPT) precursors. Sub-nanometer pores arise intrinsically during the BPT-CNM synthesis with a density of 2 ± 1 pore per 100 nm2. We employ BPT-CNM based pore arrays as efficient ion sieving channels, and demonstrate selectivity of the membrane towards ion transport when exposed to a range of concentration gradients of KCl, CsCl and MgCl2. The selectivity of the membrane towards K+ over Cl− ions is found be 16.6 mV at a 10 : 1 concentration ratio, which amounts to ∼30% efficiency relative to the Nernst potential for complete ion rejection. The pore arrays in the BPT-CNM show similar transport and selectivity properties to graphene and carbon nanotubes, whilst the fabrication method via self-assembly offers a facile means to control the chemical and physical properties of the membrane, such as surface charge, chemical nature and pore density. CNMs synthesized from self-assembled monolayers open the way towards the rational design of 2D membranes for selective ion sieving. Show less
Tewari, S.; Sabater, C.; Ruitenbeek, J.M. van 2019
Two-dimensional (2D) membranes featuring arrays of sub-nanometer pores have applications in purification, solvent separation and water desalination. Compared to channels in bulk membranes, 2D... Show moreTwo-dimensional (2D) membranes featuring arrays of sub-nanometer pores have applications in purification, solvent separation and water desalination. Compared to channels in bulk membranes, 2D nanopores have lower resistance to transmembrane transport, leading to faster passage of ions. However, the formation of nanopores in 2D membranes requires expensive post-treatment using plasma or ion bombardment. Here, we study bottom-up synthesized porous carbon nanomembranes (CNMs) of biphenyl thiol (BPT) precursors. Sub-nanometer pores arise intrinsically during the BPT-CNM synthesis with a density of 2 ± 1 pore per 100 nm2. We employ BPT-CNM based pore arrays as efficient ion sieving channels, and demonstrate selectivity of the membrane towards ion transport when exposed to a range of concentration gradients of KCl, CsCl and MgCl2. The selectivity of the membrane towards K+ over Cl− ions is found be 16.6 mV at a 10 : 1 concentration ratio, which amounts to ∼30% efficiency relative to the Nernst potential for complete ion rejection. The pore arrays in the BPT-CNM show similar transport and selectivity properties to graphene and carbon nanotubes, whilst the fabrication method via self-assembly offers a facile means to control the chemical and physical properties of the membrane, such as surface charge, chemical nature and pore density. CNMs synthesized from self-assembled monolayers open the way towards the rational design of 2D membranes for selective ion sieving. Show less
We tailored the size distribution of Pt nanoparticles (NPs) on graphene nanoplatelets at a given metal loading by using low-temperature atomic layer deposition carried out in a fluidized bed... Show moreWe tailored the size distribution of Pt nanoparticles (NPs) on graphene nanoplatelets at a given metal loading by using low-temperature atomic layer deposition carried out in a fluidized bed reactor operated at atmospheric pressure. The Pt NPs deposited at low temperature (100 degrees C) after 10 cycles were more active and stable towards the propene oxidation reaction than their high-temperature counterparts. Crucially, the gap in the catalytic performance was retained even after prolonged periods of time (>24 hours) at reaction temperatures as high as 450 degrees C. After exposure to such harsh conditions the Pt NPs deposited at 100 degrees C still retained a size distribution that is narrower than the one of the as-synthesized NPs obtained at 250 degrees C. The difference in performance correlated with the difference in the number of facet sites as estimated after the catalytic test. Our approach provides not only a viable route for the scalable synthesis of stable supported Pt NPs with tailored size distributions but also a tool for studying the structure-function relationship. Show less
