This work presents a lecture and lab series that focuses on teaching the concept of nanophytotoxicity to undergraduate students in a relatively simple experiment. In this experiment, students evaluated the phytotoxicity of engineered nanomaterials (ENMs) using mung beans (i.e., Vigna radiata) and industrially relevant, commercially available ENMs, silicon dioxide (SiO2) and zinc oxide (ZnO) nanoparticles (NPs). In comparison to the control system using solutions of Nanopure water, the growth of mung beans in solutions of ZnO NPs with a concentration of 20 mg/L was severely stunted, showing clear evidence of a high level of nanophytotoxicity. The growth of mung beans in solutions of SiO2 NPs with the same concentration was intermediate to, though statistically separate from, the aforementioned solutions, showing clear evidence of a lower level of nanophytotoxicity than for the ZnO NPs. The simplicity of the experiment and the clear phytotoxic results should make this experiment of interest to many types of students including science majors, nonmajors, and high school students.Keywords: Collaborative/Cooperative Learning; First-Year Undergraduate/General; Hands-On Learning/Manipulatives; High School/Introductory Chemistry; Laboratory Instruction; Nanotechnology; Plant Chemistry; Toxicology;

Three-dimensional (3D) printing has been a very active area of research and development due to its capability to produce 3D objects by design. Miniaturization and improvement of spatial resolution are major challenges in current 3D printing technology development. This work reports advances in miniaturizing 3D printing to the nanometer scale using scanning probe microscopy in conjunction with local material delivery. Using polyelectrolyte polymers and complexes, we have demonstrated the concept of layer-by-layer nanoprinting by design. Nanometer precision is achieved in all three dimensions, as well as in interlayer registry. The approach enables production of designed functional 3D materials with nanometer resolution and, as such, creates a platform for conducting scientific research in designed 3D nanoenvironments as well. In doing so, it enables production of nanomaterials and scaffolds for photonics devices, biomedicine, and tissue engineering.Keywords: atomic force microscopy (AFM); layer-by-layer; nanostructure; polyelectrolyte; scanning probe lithography (SPL); scanning probe microscopy (SPM); three-dimensional (3D) printing

Single-cell mechanics, derived from atomic force microscopy-based technology, provides a new and effective means to investigate nanomaterial–cell interactions upon in vivo exposure. Lung macrophages represent initial and important responses upon introducing nanoparticles into the respiratory tract, as well as particle clearance with time. Cellular mechanics has previously proven effective to probe in vitro nanomaterial–cell interactions. This study extends technology further to probe the interactions between primary alveolar macrophages (AM) and silver nanoparticles (AgNPs) upon in vivo exposure. Two types of AgNPs, 20 and 110 nm, were instilled to rat lung at 0.5 mg AgNPs/kg body weight, and allowed 24 h interaction. The consequences of these interactions were investigated by harvesting the primary AMs while maintaining their biological status. Cellular mechanics measurements revealed the diverse responses among AM cells, due to variations in AgNP uptake and oxidative dissolving into Ag+. Three major responses are evident: zero to low uptake that does not alter cellular mechanics, intracellular accumulation of AgNPs trigger cytoskeleton rearrangement resulting in the stiffening of mechanics, and damage of cytoskeleton that softens the mechanical profile. These effects were confirmed using confocal imaging of F-actin and measurements of reactive oxygen species production. More detailed intracellular interactions will also be discussed on the basis of this study in conjunction with prior knowledge of AgNP toxicity.

Incorporating single-electron tunneling (SET) of metallic nanoparticles (NPs) into modern electronic devices offers great promise to enable new properties; however, it is technically very challenging due to the necessity to integrate ultrasmall (<10 nm) particles into the devices. The nanosize requirements are intrinsic for NPs to exhibit quantum or SET behaviors, for example, 10 nm or smaller, at room temperature. This work represents the first observation of SET that defies the well-known size restriction. Using polycrystalline Au NPs synthesized via our newly developed solid-state glycine matrices method, a Coulomb Blockade was observed for particles as large as tens of nanometers, and the blockade voltage exhibited little dependence on the size of the NPs. These observations are counterintuitive at first glance. Further investigations reveal that each observed SET arises from the ultrasmall single crystalline grain(s) within the polycrystal NP, which is (are) sufficiently isolated from the nearest neighbor grains. This work demonstrates the concept and feasibility to overcome orthodox spatial confinement requirements to achieve quantum effects.

A recent finding reports that co-stimulation of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the chemokine receptor 1 (CCR1) triggered formation of membrane nanotubes among bone-marrow-derived mast cells. The co-stimulation was attained using corresponding ligands: IgE binding antigen and macrophage inflammatory protein 1α (MIP1 α), respectively. However, this approach failed to trigger formation of nanotubes among rat basophilic leukemia (RBL) cells due to the lack of CCR1 on the cell surface (Int. Immunol. 2010, 22 (2), 113–128). RBL cells are frequently used as a model for mast cells and are best known for antibody-mediated activation via FcεRI. This work reports the successful formation of membrane nanotubes among RBLs using only one stimulus, a hapten of 2,4-dinitrophenyl (DNP) molecules, which are presented as nanostructures with our designed spatial arrangements. This observation underlines the significance of the local presentation of ligands in the context of impacting the cellular signaling cascades. In the case of RBL, certain DNP nanostructures suppress antigen-induced degranulation and facilitate the rearrangement of the cytoskeleton to form nanotubes. These results demonstrate an important scientific concept; engineered nanostructures enable cellular signaling cascades, where current technologies encounter great difficulties. More importantly, nanotechnology offers a new platform to selectively activate and/or inhibit desired cellular signaling cascades.Keywords: atomic force microscopy (AFM); haptens; mast cells; membrane nanotubes; particle lithography; rat basophilic leukemia (RBL) cells; scanning electron microscopy (SEM);

Current in vitro methods to assess nanomaterial cytotoxicity involve various assays to monitor specific cellular dysfunction, such as metabolic imbalance or inflammation. Although high throughput, fast, and animal-free, these in vitro methods suffer from unreliability and lack of relevance to in vivo situations. New approaches, especially with the potential to reliably relate to in vivo studies directly, are in critical need. This work introduces a new approach, single cell mechanics, derived from atomic force microscopy-based single cell compression. The single cell based approach is intrinsically advantageous in terms of being able to directly correlate to in vivo investigations. Its reliability and potential to measure cytotoxicity is evaluated using known systems: zinc oxide (ZnO) and silicon dioxide (SiO2) nanoparticles (NP) on human aortic endothelial cells (HAECs). This investigation clearly indicates the reliability of single cell compression. For example, ZnO NPs cause significant changes in force vs relative deformation profiles, whereas SiO2 NPs do not. New insights into NPs–cell interactions pertaining to cytotoxicity are also revealed from this single cell mechanics approach, in addition to a qualitative cytotoxicity conclusion. The advantages and disadvantages of this approach are also compared with conventional cytotoxicity assays.

Oligothiophene thin films have been considered as promising material for molecular electronics due to their desirable electronic properties and high structural stability under ambient conditions. To ensure performance in devices the functional structures, such as individual ordered domains, must be stable under practical and operational conditions or environments including exposure to various media. This work investigates the structure of oligothiophene Langmuir–Blodgett (LB) films upon exposure to liquid media such as water, ethanol (EtOH), and mixed tetrahydrofuran (THF)/EtOH solutions. The LB films form islands ranging from 500 nm up to 1 μm consisting of densely packed oligothiophene molecules. These islands are surrounded by bare substrate and loosely packed adsorbates. In situ and time-dependent AFM images were acquired to reveal the structural evolution, from which degradation pathways and kinetics are extracted. Degradation of these LB films initiates and propagates from intraisland defect sites, such as cracks and pin holes, whereas the edges of islands remain intact on the surface. The observations appear to be in contrast to the known degradation mechanism among self-assembled monolayers, such as alkanethiols on gold, which initiates and progresses at domain boundaries. Rationale for the observed degradation processes will also be discussed.

Hematite prepared by atomic layer deposition (ALD) was found to exhibit photocurrents when illuminated by near-infrared light (λ = 830 nm), whose energy is smaller than the band gap of hematite. The phenomenon was inferred to be a result of valence band to surface state transition. The influence of surface states on the thermodynamics of the hematite/water interface was studied under open-circuit conditions. It was discovered that the equilibrium potential of the hematite surface was more negative than water oxidation potential by at least 0.4 V. With a NiFeOx coating by photochemical decomposition of organometallic precursors, the equilibrium potential of hematite was restored to water oxidation potential, and the photoresponse under 830 nm illumination was annihilated. Therefore, the states were rationalized by the chemical status at the electrode surfaces, and this hypothesis was supported by similar observations on other metal oxide electrodes such as TiO2.

Multicomponent nanostructures with individual geometries have attracted much attention because of their potential to carry out multiple functions synergistically. The current work reports a simple method using particle lithography to fabricate multicomponent nanostructures of metals, proteins, and organosiloxane molecules, each with its own geometry. Particle lithography is well-known for its capability to produce arrays of triangular-shaped nanostructures with novel optical properties. This paper extends the capability of particle lithography by combining a particle template in conjunction with surface chemistry to produce multicomponent nanostructures. The advantages and limitations of this approach will also be addressed.

This article focuses on surfaces containing nanoparticles and self-assembled monolayers (SAMs). These surfaces provide a simple and reliable platform for measurements of single electron tunneling (SET) properties of metal nanoparticles at room temperature. This approach of interfacial chemistry allows for the elimination of lateral motion of the individual nanoparticles during electronic property studies. The scanning tunneling microscopy (STM) in ultra-high vacuum is used as an accurate and reproducible probe for imaging and I–V characterization of individual or aggregated Au nanoparticles, revealing a large Coulomb gap (1.0 eV) and fine Coulomb staircases (0.2–0.3 eV) at room temperature. The surrounding decanethiol SAM provides an ideal reference for the imaging and I–V measurements of nanoparticles. These measurements provide a quantitative guide for regulating current and voltage, at which individual Au nanoparticles may be detached and manipulated with the STM tip.