Hyper-Cross-linked Porous MoS₂–Cyclodextrin-Polymer Frameworks: Durable Removal of Aromatic Phenolic Micropollutant from Water

A reasonable and efficient strategy for the construction of hyper-cross-linked porous MoS₂–CD-polymer frameworks (MoS₂CDPFs) was demonstrated. Here, MoS₂ nanosheets (NSs) can be decorated with amino functionalized β-cyclodextrin, producing a nanoscale structural motif (MoS₂@CD) for the synthesis of MoS₂CDPFs. We demonstrated that CD polymer (CDP) as linker can be uniformly incorporated into the frameworks. Except for the pores created between MoS₂ NSs, polymer doping generates extra interspace between MoS₂ NSs and CD monomer. Interestingly, the resultant MoS₂CDPFs can rapidly sequester aromatic phenolic micropollutant bisphenol A (0.1 mM) from water with 93.2% adsorption capacity, which is higher than that of MoS₂, MoS₂@CD, and CDP. The intercalation between MoS₂ sheets with CDP imparts the frameworks durability in adsorption/desorption of aromatic phenolic micropollutants. Remarkably, the removal efficiency reduced only 3% after 10 regeneration–reuse cycles. These findings demonstrated that the porous MoS₂–CD-polymer-based frameworks are promising adsorbents for rapid, flow-through water remediation

Scalable Fabrication of Self-Aligned Graphene Transistors and Circuits on Glass

Graphene transistors are of considerable interest for radio frequency (rf) applications. High-frequency graphene transistors with the intrinsic cutoff frequency up to 300 GHz have been demonstrated. However, the graphene transistors reported to date only exhibit a limited extrinsic cutoff frequency up to about 10 GHz, and functional graphene circuits demonstrated so far can merely operate in the tens of megahertz regime, far from the potential the graphene transistors could offer. Here we report a scalable approach to fabricate self-aligned graphene transistors with the extrinsic cutoff frequency exceeding 50 GHz and graphene circuits that can operate in the 1–10 GHz regime. The devices are fabricated on a glass substrate through a self-aligned process by using chemical vapor deposition (CVD) grown graphene and a dielectrophoretic assembled nanowire gate array. The self-aligned process allows the achievement of unprecedented performance in CVD graphene transistors with a highest transconductance of 0.36 mS/μm. The use of an insulating substrate minimizes the parasitic capacitance and has therefore enabled graphene transistors with a record-high extrinsic cutoff frequency (> 50 GHz) achieved to date. The excellent extrinsic cutoff frequency readily allows configuring the graphene transistors into frequency doubling or mixing circuits functioning in the 1–10 GHz regime, a significant advancement over previous reports (∼20 MHz). The studies open a pathway to scalable fabrication of high-speed graphene transistors and functional circuits and represent a significant step forward to graphene based radio frequency devices

Fixed-Gap Tunnel Junction for Reading DNA Nucleotides

Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition. Reactive ion etching is used to drill a hole through the layers so that the tunnel junction can be exposed to molecules in solution. When the metal electrodes are functionalized with recognition molecules that capture DNA nucleotides <i>via</i> hydrogen bonds, the identities of the individual nucleotides are revealed by characteristic features of the fluctuating tunnel current associated with single-molecule binding events