Abstract A comprehensive study of the antibacterial (bacteriostatic and bactericidal) properties of non-doped carbon nanodots (CNDs), nitrogen-doped (N-doped), and nitrogen/sulfur co-doped (N,S-doped) CNDs against Escherichia coli (a model organism) is discussed herein. The CNDs, with a size of ca. 5 nm, were found to be capable of inhibiting the growth of the bacterial biofilm but not significantly the growth of planktonic bacteria. Heteroatom doping was found to considerably improve the potential of CNDs as bactericidal agents. Further experiments were conducted to shed light on the potential mechanism of the antibacterial activity of the CNDs. The results showed that the CNDs do not interact with the cellular membrane via electrostatic forces. Following a simple metabolomic workflow, no alterations of the bacterial metabolome were observed except for the activation of the metabolism of α-linolenic acid. The CNDs neither oxidize cell membrane lipids and intracellular proteins nor elevate the concentration of reactive oxygen species in cells. Finally, the interactions of CNDs with genomic DNA and RNA revealed that CNDs are able to intercalate into their structure. The different affinities of the three kinds of CNDs for DNA/RNA account for the differences in their antibacterial activity and constitute the main mechanism via which CND activity is achieved. Graphical abstract

Abstract The use of magnetic nanoparticles in nanomedicine keeps expanding and, for most applications, the nanoparticles are internalized in cells then left within, bringing the need for accurate, fast, and easy to handle methodologies to assess their behavior in the cellular environment. Herein, a benchtop-size magnetic sensor is introduced to provide real-time precise measurement of nanoparticle magnetism within living cells. The values obtained with the sensor, of cells loaded with different doses of magnetic nanoparticles, are first compared to conventional vibrating sample magnetometry (VSM), and a strong correlation remarkably validates the use of the magnetic sensor as magnetometer to determine the nanoparticle cellular uptake. The sensor is then used to monitor the progressive intracellular degradation of the nanoparticles, over days. Importantly, this real-time in situ measure is performed on a stem cell-spheroid tissue model and can run continuously on a same spheroid, with cells kept alive within. Besides, such continuous magnetic measurement of cell magnetism at the tissue scale does not impact either tissue formation, viability, or stem cell function, including differentiation and extracellular matrix production.

Abstract The remarkable ability of biological systems to sense and adapt to complex environmental conditions has inspired the design of next-generation electronics with advanced functionalities. This review focuses on emerging bio-inspired strategies for the development of flexible and stretchable electronics that can accommodate mechanical deformations and integrate seamlessly with biological systems. We will provide an overview of the practical considerations in the materials and structure designs of flexible and stretchable electronics. Recent progress in bio-inspired pressure/strain sensors, stretchable electrodes, mesh electronics, and flexible energy devices are then discussed, with an emphasis on their unconventional micro/nanostructure designs and advanced functionalities. Finally, current challenges and future perspectives are identified and discussed.

Abstract There is a compelling need for delicate nanomaterial design with various intricate functions and applications. Electrohydrodynamics applies electrostatic force to overcome the surface tension of a. liquid jet, shrinking the jet through intrinsic jetting instability into submicron fibers or spheres, with versatility from a. huge selection of materials, feasibility of extracellular matrix structure mimicry and multi-compartmentalization for tissue engineering and drug delivery. The process typically involves the collection and drying of fibers at a. solid substrate, but the introduction of a. liquid phase collection by replacing the solid collector with a. coagulation bath can introduce a. variety of new opportunities for both chemical and physical functionalizations in one single step. The so-called wet electrohydrodynamics is an emerging technique that enables a. facile, homogeneous functionalization of the intrinsic large surface area of the submicron fibers/spheres. With a. thorough literature sweep, we herein highlight the three main engineering features integrated through the single step wet electrospinning process in terms of creating functional biomaterials: (i) The fabrication of 3D macrostructures, (ii) in situ chemical functionalization, and (iii) tunable nano-topography. Through an emerging technique, wet electrohydrodynamics has demonstrated a. great potential in interdisciplinary research for the development of functional 3D interfaces and materials with pertinent applications in all fields where secondary structured, functional surface is desired. Among these, engineered biomaterials bridging materials science with biology have already shown particular potential.

Well-absorbed iron-based nanoparticulated materials are a promise for the oral management of iron deficient anemia. In this work, a battery of in vitro and in situ experiments are combined for the evaluation of the uptake, distribution and toxicity of new synthesized ultrasmall (4 nm core) Fe2O3 nanoparticles coated with tartaric/adipic acid with potential to be used as oral Fe supplements. First, the in vitro simulated gastric acid solubility studies by TEM and HPLC-ICP-MS reveal a partial reduction of the core size of about 40% after 90 min at pH 3. Such scenario confirms the arrival of the nanoparticulate material in the small intestine. In the next step, the in vivo absorption through the small intestine by intestinal perfusion experiments is conducted using the sought nanoparticles in Wistar rats. The quantification of Fe in the NPs suspension before and after perfusion shows Fe absorption levels above 79%, never reported for other Fe treatments. Such high absorption levels do not seem to compromise cell viability, evaluated in enterocytes-like models (Caco-2 and HT-29) using cytotoxicity, ROS production, genotoxicity and lipid peroxidation tests. Moreover, regional differences in terms of Fe concentration are obtained among different parts of the small intestine as duodenum > jejunum > ileum. Complementary transmission electron microscopy (TEM) images show the presence of the intact particles around the intestinal microvilli without significant tissue damage. These studies show the high potential of these NP preparations for their use as oral management of anemia.

Potential health hazards of nanomaterials on male reproductive system have received raising concerns. Even though Mn3O4 nanoparticles (Mn3O4-NPs) is highly effective in clinical diagnostic and therapeutic applications of human disease, its potential toxic effect on the male reproductive system has not been reported. In this study, the testis damage and fertility decrease of male rats were conducted to testify the experimental reproductive injury induced by Mn3O4-NPs. After repeated tail vein injection with 10 mg/kg/week Mn3O4-NPs for 0, 60 and 120 days, Mn3O4-NPs accumulated in the testes resulted in oxidative stress and disorder of normal serum sex hormones. Experiments in vivo and in vitro indicated that mitochondria-mediated cell apoptosis were triggered via oxidative stress, demonstrated by the upregulation of malondialdehyde (MDA) and the depolarization of mitochondrial membrane potential. Notably, Mn3O4-NPs significantly resulted in a reduction of the quantity/quality of sperm and finally caused astonishing fertility decrease. Our preliminary result implied that the application of Mn3O4-NPs could be a double-edged sword and careful consideration should be given to the clinical uses.

A three‐step fabrication process for optically transparent, conducting ITO thin films with an intrinsic inverse opal structure is described. The preparation is based on colloidal crystal templating using polystyrene microspheres (100 nm ‐ 600 nm). For the realization of varying periodicities in this structure, different sphere sizes were assembled to monolayers on a substrate by spin coating and infiltrated afterwards similarly. The influence of rotation parameters as well as dispersion concentration was studied. Using this approach different geometries of the surface are accessible by systematically varying the rotation parameters and infiltration volume. The thin films show excellent anti‐reflection behavior, good transmission (>80% in the visible range) as well as a low resistance of 200 Ω/sq compared to other porous ITO interfaces. The properties are very promising for several optoelectronic applications such as in‐ or out‐coupling structures in solar cells and organic light emitting diodes.

Mitochondrion, as the energy provider for cells, plays a key role in cell physiological processes. Mitochondrion‐targeted imaging is of great significance for understanding the physiological functions and pathology involved in various diseases. Herein, we report the fabrication of 6‐triphenylphosphinehexanoic acid (TPP) conjugated near‐infrared persistent luminescence nanoparticles (PLNP) (PLNP‐TPP) for mitochondria‐targeted imaging in cancer cells. The PLNP was prepared by doping Cr(III) into gallogermanate through a hydrothermal method. The as‐prepared PLNP showed small size, monodispersity, excellent near‐infrared (NIR) luminescence and visible light renewable NIR luminescence. The grafted TPP facilitated the transportation of PLNP‐TPP across the mitochondrial membrane and enabled staining of the mitochondrial region in live cancer cells. This work provides a promising strategy for fabricating PLNP nanoprobes to realize mitochondrial‐targeting bioimaging.

Preserving the quality of carbon nanotubes (CNT) is essential to fully utilize the characteristics in the dispersions and other forms. To fabricate CNT dispersions retaining the quality, we propose to reduce CNT aggregate size distributions by viscous liquids at the initial stage from as-grown CNT powders originally possessing a wide aggregate size distribution. Higher viscosity solvents were found to highly disentangle the CNT powder and give a narrower CNT aggregate size distribution without impairing the quality. To show the advantages of these CNT dispersions, we demonstrated a 10^4-fold increased electrical conductivity of CNT rubber composite based on the predispersion step of CNT powder in the rubber base compound with high viscosity. Our method can afford a high quality of CNT and avoid a long, heavy dispersion, which was conventionally carried out to decrease entangled, large size CNT aggregates, furthermore, applicable for fabrication of conducting polymer composites.

Hybrid micro/nanostructures and light-absorbing pigment of melanin are two keys for the excellent antireflective properties of butterfly wings of Ornithoptera goliath. In this work, femtosecond laser ablation of metals in organic solvent (FLAMOS) was used to generate hybird micro/nanostructures cross-linked ultrahigh/low spatial frequency laser-induced periodic surface structures (UHSFLs/LSFLs), which well mimic the antireflective architecture of Ornithoptera goliath. Simultaneous deposition of carbon or transition metal carbide (TMC) constructed biomimetic antireflective metasurfaces. Thirteen transition metals and one transition metal alloy (Ti, V, Nb, Ta, Mo, W, Fe, Pd, Pt, Ni, Au, Ag, Cu, and CuZn) were systematically investigated by FLAMOS to demonstrate the material-dependent formation of cross-linked UHSFLs/LSFLs nanostructures and metal carbonization. Hybrid UHSFLs/LSFLs were only found to be achievable when using group IVB-VIB transition metals (e.g., Ti, V, Nb, Ta, Mo, and W), while LSFLs and hole-rich microstructures were obtained with group VIII (e.g., Fe, Pd, Pt, and Ni) and IB/IB-IIB (e.g., Au, Ag, Cu, and CuZn) transition metals or alloy. This work represents the first-ever demonstration that the orientations of UHSFLs are perpendicular to the curvatures of LSFLs due to Marangoni bursting rather than parallel to the direction of light polarization, as is commonly thought to be the case. The surface chemistry and exceptional multi-optical properties of structured metasurfaces were assessed, including thermally resistant antireflectance in the UV- near infrared (NIR) range, enhanced selective absorbance in the NIR-mid IR (MIR) range, and polarization-dependent NIR-MIR reflectance. Synergistic effects from TMCs/C-networks and surface nanostructures, resulted in the reflectance of Fe, CuZn, Ni, Ta, Mo, Ti, V, Nb, and W metasurfaces below 1% in the UV-NIR range (less than 0.2% over the entire UV-NIR range for Ni, Ti, V, and W metasurfaces).

The Wiedemann-Franz (WF) law is a fundamental result in solid-state physics that relates the thermal and electrical conductivity of a metal. It is derived from the predominant transport mechanism in metals: the motion of quasi-free charge-carrying particles. Here, an equivalent WF relationship is developed for molecular systems in which charge carriers are moving not as free particles but instead hop between redox sites. We derive a concise analytical relationship between the electrical and thermal conductivity generated by electron hopping in molecular systems and find that the linear temperature dependence of their ratio as expressed in the standard WF law is replaced by a linear dependence on the nuclear reorganization energy associated with the electron hopping process. The robustness of the molecular WF relation is confirmed by examining the conductance properties of a paradigmatic molecular junction. This result opens a new way to analyze conductivity in molecular systems, with possible applications advancing the design of molecular technologies that derive their function from electrical and/or thermal conductance.

CAR T cell therapy relies on the ex vivo manipulation of patient T cells to create a potent, cancer-targeting therapy, shown to be capable of inducing remission in patients with acute lymphoblastic leukemia and large B cell lymphoma. However, current CAR T cell engineering methods use viral delivery, which induces permanent CAR expression that leads to severe adverse effects. mRNA has been explored as a promising strategy for inducing transient CAR expression in T cells to mitigate the adverse effects associated with viral expression, but it most commonly requires electroporation for T cell transfection which can be cytotoxic. Here, ionizable lipids nanoparticles (LNPs) were designed for ex vivo mRNA delivery to human T cells. A library of 24 ionizable lipids was synthesized, formulated into LNPs, and screened for luciferase mRNA delivery to Jurkat cells, revealing seven formulations capable of enhanced mRNA delivery over lipofectamine. The top-performing LNP formulation, C14-4, was selected for CAR mRNA delivery to primary human T cells. This platform induced CAR expression equivalent to electroporation with substantially improved cytotoxicity. CAR T cells engineered via C14-4 LNP treatment were then compared to electroporated CAR T cells in a co-culture assay with Nalm-6 acute lymphoblastic leukemia cells, and we show that both CAR T cell engineering methods elicit potent cancer killing activity. These results demonstrate the ability of ionizable LNPs to deliver mRNA to primary human T cells for functional protein expression and indicate the potential of LNPs to enhance mRNA-based CAR T cell engineering methods.

In this article, we show how advanced hierarchical structures of topological defects in the so-called smectic oily streaks can be used to sequentially transfer their geometrical features to gold nanospheres. We use two kinds of topological defects, 1D dislocations and 2D ribbon-like topological defects. The large trapping efficiency of the smectic dislocation cores not only surpasses that of the elastically distorted zones around the cores but also the one of the 2D ribbon-like topological defect. This enables the formation of a large number of aligned NP chains, within the dislocation cores that can be quasi-fully filled without any significant aggregation outside the cores. When the NP concentration is large enough to entirely fill the dislocation cores, the LC confinement varies from 1D to 2D. We demonstrate that the 2D topological defect cores induce a confinement that leads to planar hexagonal networks of NPs. We then draw the phase diagram driven by NP concentration, associated with the sequential confinements induced by these two kinds of topological defects. Owing to the excellent large-scale order of these defect cores, not only the NP chains but also the NP hexagonal networks can be oriented along the desired direction, suggesting a possible new route for the creation of either 1D or 2D highly anisotropic NP networks. In addition, these results open rich perspectives based on the possible creation of coexisting NP assemblies of different kinds, localized in different confining areas of a same smectic film that would thus interact thanks to their proximity but also would interact via the surrounding soft matter matrix.

X-ray tomography has become an indispensable tool for studying complex 3D interior structures with high spatial resolution. 3D imaging using soft X-rays offers powerful contrast mechanisms, but has seen limited success with tomography due to the restrictions imposed by the much lower energy of the probe beam. The generalized geometry of laminography, characterized by a tilted axis of rotation, provides nm-scale 3D resolution for the investigation of extended (mm range) but thin (μm to nm) samples that are well suited to soft X-ray studies. This work reports on the implementation of soft X-ray laminography (SoXL) at the scanning transmission X-ray spectromicroscope of the PolLux beamline at the Swiss Light Source, Paul Scherrer Institut, which enables 3D imaging of extended specimens from 270 eV to 1500 eV. Soft X-ray imaging provides contrast mechanisms for both chemical sensitivity to molecular bonds and oxidation states and magnetic dichroism due to the much stronger attenuation of X-rays in this energy range. The presented examples of applications range from functionalized nanomaterials to biological photonic crystals and sophisticated nanostructured magnetic domain patterns, thus illustrating the wide fields of research that can benefit from SoXL.

Due to its in-plane structural anisotropy and highly polymorphic nature, borophene has been shown to form a diverse set of linear superlattice structures that are not observed in other two-dimensional materials. Here, we show both theoretically and experimentally that concentric superlattice structures can also be realized in borophene via the energetically preferred self-assembly of coherent twin boundaries. Since borophene twin boundaries do not require the creation of additional lattice defects, they are exceptionally low in energy and thus easier to nucleate and migrate than grain boundaries in other two-dimensional materials. Due to their high mobility, borophene twin boundaries naturally self-assemble to form novel phases consisting of periodic concentric loops of filled boron hexagons that are further preferred energetically by the rotational registry of borophene on the Ag(111) surface. Compared to defect-free borophene, concentric superlattice borophene phases are predicted to possess enhanced mechanical strength and localized electronic states. Overall, these results establish defect-mediated self-assembly as a pathway to unique borophene structures and properties.

Two-dimensional (2D) materials have recently been incorporated into resistive memory devices due to their atomically thin nature, but their switching mechanism is not yet well understood. Here we study bipolar switching in MoTe2-based resistive memory of varying thickness and electrode area. Using scanning thermal microscopy (SThM), we map the surface temperature of the devices under bias, revealing clear evidence of localized heating at conductive “plugs” formed during switching. The SThM measurements are correlated to electro-thermal simulations, yielding a range of plug diameters (250 to 350 nm) and temperatures at constant bias and during switching. Transmission electron microscopy images reveal these plugs result from atomic migration between electrodes, which is a thermally-activated process. However, the initial forming may be caused by defect generation or Te migration within the MoTe2. This study provides the first thermal and localized switching insights into the operation of such resistive memory, and demonstrates a thermal microscopy technique that can be applied to a wide variety of traditional and emerging memory devices.

Despite the great interest in inorganic halide perovskites (IHPs) for a variety of photo-electronic applications, environmentally robust nanopatterns of IHPs have hardly been developed mainly owing to the uncontrollable rapid crystallization and/or temperature and humidity sensitive polymorphs. Herein, we present a facile route for fabricating environment- and phase-stable IHP nanopatterns over large areas. Our method is based on nanoimprinting of a soft and moldable IHP adduct. A small amount of poly(ethylene oxide) was added to an IHP precursor solution to fabricate a spin-coated film that is soft and moldable in an amorphous adduct state. Subsequently, a topographically prepatterned elastomeric mold was used to nanoimprint the film to develop well-defined IHP nanopatterns of CsPbBr3 and CsPbI3 of 200 nm in width over a large area. To ensure environment- and phase-stable black CsPbI3 nanopatterns, a polymer backfilling process was employed on a nanopatterned CsPbI3. The CsPbI3 nanopatterns were overcoated with a thin poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) film, followed by thermal melting of PVDF-TrFE, which formed the air-exposed CsPbI3 nanopatterns laterally confined with PVDF-TrFE. Our polymer backfilled CsPbI3 nanopatterns exhibited excellent environmental stability over one year at ambient conditions and for 10 hours at 85 °C, allowing the development of arrays of two-terminal, parallel-type photodetectors with nanopatterned photoactive CsPbI3 channels. Our polymer-assisted nanoimprinting offers a fast, low-pressure/temperature patterning method for high-quality nanopatterns on various substrates over a large area, overcoming conventional costly time-consuming lithographic techniques.

Terahertz technology promises broad applications, which calls for terahertz electromagnetic interference (EMI) shielding materials to alleviate the radiation pollution. 2D transition metal carbides and/or nitrides (MXenes) with metallic conductivity are promising for EMI shielding but it has remained a great challenge to simultaneously realize light weight, high stability, and foldability in a MXene shielding material to meet the requirements of increasingly popular portable and wearable equipment. Herein, an ion diffusion induced gelation method is demonstrated to synthesize freestanding, lightweight, foldable, and highly stable MXene foams, in which MXene sheets are cross-linked by multivalent metal ions and graphene oxide to form an oriented porous structure. The method is highly efficient, controllable, and versatile for scalable generation of functional 3D MXene structures with arbitrary shapes and synergistic properties. The distinctive cross-linked porous structure endows the lightweight MXene foam with good foldability, outstanding durability and stability in wet environment, and an excellent terahertz shielding effectiveness of 51 dB at a small thickness of 85 μm. This work not only provides an insight for the on-target design of high-performance terahertz shielding materials but could also expands the applications of MXenes in 3D macroscopic form.

The emergent two-dimensional (2D) materials are atomically thin and ultra-flexible, promising for a variety of miniaturized, high-performance and flexible devices in applications. On one hand, the ultra-high flexibility causes problems—the prevalent wrinkles in 2D materials may undermine the ideal properties and create barriers in fabrication, processing and quality control of materials. On the other hand, in some cases the wrinkles are used for the architecturing of surface texture and the modulation of physical/chemical properties. Therefore, a thorough understanding in the mechanism and stability of wrinkles is highly needed. Herein, we report a critical length for stabilizing the wrinkles in 2D materi-als, observed in the wrinkling and wrinkle elimination processes upon thermal annealing as well as by our in situ TEM manipulations on individual wrinkles, which directly capture the evolving wrinkles with variable lengths. The experiments, mechanical modelling, and the density functional theory (DFT) simulations consistently reveal that a minimum critical length is requested for stabilizing the wrinkles in 2D materials. Wrinkles with lengths below critical value are unstable and removable by thermal an-nealing, whilst wrinkles with lengths above critical value are self-stabilized by van der Waals (vdW) interactions. It additionally confirms the pronounced frictional effects in wrinkles with lengths above critical value during the dynamical movement or sliding.

One of the major problems with phase change memory (PCM) is the high current density required for the crystal-amorphous transformation via a melt-quench process. However, alternative low-energy pathways of amorphization via a defect-assisted process have also been proposed. Here, a defect-assisted amorphization pathway in Bi-doped GeTe nanowires is utilized to establish that carrier localization effects can significantly decrease the energy costs of amorphization. We demonstrate a strategy of doping GeTe nanowires with Bismuth to engineer carrier localization effects via Fermi level/mobility edge tuning and increased atomic disorder. Enhanced carrier localization increases the carrier-lattice coupling and therefore, the energy supplied to carriers via electrical pulses can be more efficiently extracted by the lattice to induce the critical bond distortions required for amorphization without an intermediate melting process. RESET (crystal to amorphous transition) current densities as low as ~0.3 MA cm-2 are achieved for 8% Bi-doped GeTe nanowires, which is nearly a three-fold reduction compared to un-doped GeTe nanowires and is significantly less than GeTe thin film devices (~50 MA cm-2). We demonstrate good reversibility of switching in the Bi-doped GeTe nanowires and also demonstrate the existence of intermediate resistance states which can be accessed by controlled electrical pulsing. The combination of low power switching in conjunction with multiple resistance states indicates that doping strategies in PCM nanowires are beneficial for nonvolatile memory and neuromorphic computing applications.