Two‐dimensional bio‐dynamite: Chemically exfoliated MoS2 (ceMoS2), a water‐dispersible sheet‐like material, is an efficient near‐infrared (NIR) photothermal transducer. The superior bio‐supramolecular properties of ceMoS2 and the ability of this material to destroy biomolecular targets through near‐infrared (NIR) photothermal transduction were studied (see picture).

Establishing processing–structure–property relationships for monolayer materials is crucial for a range of applications spanning optics, catalysis, electronics and energy. Presently, for molybdenum disulfide, a promising catalyst for artificial photosynthesis, considerable debate surrounds the structure/property relationships of its various allotropes. Here we unambiguously solve the structure of molybdenum disulfide monolayers using high-resolution transmission electron microscopy supported by density functional theory and show lithium intercalation to direct a preferential transformation of the basal plane from 2H (trigonal prismatic) to 1T′ (clustered Mo). These changes alter the energetics of molybdenum disulfide interactions with hydrogen (ΔGH), and, with respect to catalysis, the 1T′ transformation renders the normally inert basal plane amenable towards hydrogen adsorption and hydrogen evolution. Indeed, we show basal plane activation of 1T′ molybdenum disulfide and a lowering of ΔGH from +1.6 eV for 2H to +0.18 eV for 1T′, comparable to 2H molybdenum disulfide edges on Au(111), one of the most active hydrogen evolution catalysts known.

We report a method for creating stimuli-responsive biomaterials in which scanning nonlinear excitation is used to photocrosslink proteins at submicrometer 3D coordinates. Proteins with differing hydration properties can be combined to achieve tunable volume changes that are rapid and reversible in response to changes in chemical environment. Protein matrices having arbitrary 3D topographies and definable density gradients over micrometer dimensions provide the ability to effect rapid (<1 sec) and precise mechanical manipulations by means of changes in hydrogel size and shape, and applicability of these materials to cell biology is shown through the fabrication of responsive bacterial cages.Escherichia coli ͉ multiphoton lithography ͉ nanobiotechnology ͉ protein hydrogels ͉ smart materials

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Lithiation-exfoliation produces single to few-layered MoS2 and WS2 sheets dispersible in water. However, the process transforms them from the pristine semiconducting 2H phase to a distorted metallic phase. Recovery of the semiconducting properties typically involves heating of the chemically exfoliated sheets at elevated temperatures. Therefore, it has been largely limited to sheets deposited on solid substrates. Here, we report the dispersion of chemically exfoliated MoS2 sheets in high boiling point organic solvents enabled by surface functionalization and the controllable recovery of their semiconducting properties directly in solution. This process connects the scalability of chemical exfoliation with the simplicity of solution processing, ultimately enabling a facile method for tuning the metal to semiconductor transitions of MoS2 and WS2 within a liquid medium.

We report the ability to modify microscopic 3D topographies within dissociated cultures, providing a means to alter the development of neurons as they extend neurites and establish interconnections. In this approach, multiphoton excitation is used to focally excite noncytotoxic photosensitizers that promote protein crosslinking, such as BSA, into matrices having feature sizes >250 nm. Barriers, growth lanes, and pinning structures comprised of crosslinked proteins are fabricated under conditions that do not compromise the viability of neurons both on short time scales and over periods of days. In addition, the ability to fabricate functional microstructures from crosslinked avidin enables submicrometer localization of controllable quantities of biotinylated ligands, such as indicators and biological effectors. Feasibility is demonstrated for using in situ microfabrication to guide the contact position of cortical neurons with micrometer accuracy, opening the possibility for engineering well defined sets of synaptic interactions.biofabrication ͉ multiphoton cell patterning ͉ growth cone S tudies of neuronal function increasingly rely on methods for precisely manipulating cellular properties. Innovations in electrophysiology, photolytic release of effectors, and inducible knockout technologies (1-3) have made it possible to explore cellular phenomena at levels of reduction few anticipated a quarter-century ago. Despite this technological revolution, approaches for influencing neuronal morphology, motility, and interconnectivity remain relatively primitive, a limitation of considerable importance to fundamental and applied neuroscience. An ability to prescribe the exact location at which an extending neurite makes contact with a target cell, or to constrain neuronal migration at a specific time point in development, would be of great value to studies of signal transduction and integration within individual cells and neural networks.Neurite orientation and growth can be modified in real time by various stimuli, including diffusible neurotrophin gradients (4), electric fields (5), and near-IR light (6), but these approaches exert relatively coarse influences over neurite pathfinding and have not been used to accurately guide cellular interactions. Finer delimitation of neurite development can be achieved by using patterned surfaces and topologies microfabricated in silicon and other materials (7-9); such structures, however, must be prepared before cells are introduced for culture when the detailed features of neurite arborization cannot be known.Multiphoton excitation provides an alternative approach for constructing 3D defined microscopic materials that, in principle, could be fabricated within cellular environments. Used extensively in 3D fluorescence imaging, multiphoton excitation also has proved useful for promoting photochemical reactions with high spatial and temporal control (10-13). Application of this strategy to ''direct-write'' material fabrication can be achieved by focusing light from a pulsed femtosec...

A strategy for rapidly printing three-dimensional (3D) microscopic replicas using multiphoton lithography directed by a dynamic electronic mask is reported. Morphological descriptions of 3D structures are encoded as stacks of 2D slices created from tomographic and computer-designed instruction sets. In this manner, digital images serve as input for a sequence of reflective photomasks on a digital micromirror device to direct replication of a structure. By scanning a laser focus across the face of the intrinsically aligned masks, tomographic and computed data can be translated into protein-based 3D reproductions with submicrometer feature sizes within 1 min. This straightforward and highly versatile approach may provide improved routes for the development of 3D cellular scaffolds, rapid prototyping of microanalytical devices, and production of custom tissue replacements.