Multifunctional Nano Device Research Articles

Smart nanomaterials for biomedics.

Nanotechnology has become important in various disciplines of technology and science. It has proven to be a potential candidate for various applications ranging from biosensors to the delivery of genes and therapeutic agents to tissue engineering. Scaffolds for every application can be tailor made to have the appropriate physicochemical properties that will influence the in vivo system in the desired way. For highly sensitive and precise detection of specific signals or pathogenic markers, or for sensing the levels of particular analytes, fabricating target-specific nanomaterials can be very useful. Multi-functional nano-devices can be fabricated using different approaches to achieve multi-directional patterning in a scaffold with the ability to alter topographical cues at scale of less than or equal to 100 nm. Smart nanomaterials are made to understand the surrounding environment and act accordingly by either protecting the drug in hostile conditions or releasing the "payload" at the intended intracellular target site. All of this is achieved by exploiting polymers for their functional groups or incorporating conducting materials into a natural biopolymer to obtain a "smart material" that can be used for detection of circulating tumor cells, detection of differences in the body analytes, or repair of damaged tissue by acting as a cell culture scaffold. Nanotechnology has changed the nature of diagnosis and treatment in the biomedical field, and this review aims to bring together the most recent advances in smart nanomaterials.

Multifunctional enveloped mesoporous silica nanoparticles for subcellular co-delivery of drug and therapeutic peptide.

A multifunctional enveloped nanodevice based on mesoporous silica nanoparticle (MSN) was delicately designed for subcellular co-delivery of drug and therapeutic peptide to tumor cells. Mesoporous silica MCM-41 nanoparticles were used as the core for loading antineoplastic drug topotecan (TPT). The surface of nanoparticles was decorated with mitochondria-targeted therapeutic agent (Tpep) containing triphenylphosphonium (TPP) and antibiotic peptide (KLAKLAK)2 via disulfide linkage, followed by coating with a charge reversal polyanion poly(ethylene glycol)-blocked-2,3-dimethylmaleic anhydride-modified poly(L-lysine) (PEG-PLL(DMA)) via electrostatic interaction. It was found that the outer shielding layer could be removed at acidic tumor microenvironment due to the degradation of DMA blocks and the cellular uptake was significantly enhanced by the formation of cationic nanoparticles. After endocytosis, due to the cleavage of disulfide bonds in the presence of intracellular glutathione (GSH), pharmacological agents (Tpep and TPT) could be released from the nanoparticles and subsequently induce specific damage of tumor cell mitochondria and nucleus respectively with remarkable synergistic antitumor effect.

Introducing the Triangular Defect to Effectively Engineer the Wide Band Gap of Boron Nitride Nanoribbons with Zigzag and Even Armchair Edges

By means of the first-principles computations, we investigated the electronic and magnetic properties of zigzag and armchair boron nitride nanoribbons (BNNRs) with triangular vacancy defects, where two series of triangular defects with different sizes are considered by sampling the N-vacancies VN, V3N+B, and V6N+3B and B-vacancies VB, V3B+N, and V6B+3N, respectively. It is revealed that introducing the triangular defect can effectively conquer the bottleneck of the wide band gap for the zigzag and even armchair BNNRs, which severely hinders the application of BN-based nanomaterials in the nanodevices. Particularly, independent of the edge chirality, the triangular defects (e.g., VB, V6B+3N and VN, V6N+3B) with the dangling bonds on N/B atoms in two series can convert the originally nonmagnetic to magnetic behaviors and more effectively engineer the wide band gap of BNNRs, even achieving the intriguing spin-gapless semiconducting and half-metallic behaviors. Additionally, the type and size of the triangular defect can also play a crucial role in affecting the electronic and magnetic properties of BNNRs. Obviously, beyond most of the approaches reported, introducing the triangular defect can be an effective strategy to engineer the rather robust wide band gap of BNNRs with the armchair edge, besides the zigzag-edged ones. These fascinating findings can promote the practical applications of the BN-based nanomaterials in multifunctional and spintronic nanodevices.

High-Performance Photoconductivity and Electrical Transport of ZnO/ZnS Core/Shell Nanowires for Multifunctional Nanodevice Applications

We report the electrical and optical properties of ZnO/ZnS core/shell nanowire (NW) devices. The spatial separation of charge carriers due to their type II band structure together with passivation effect on ZnO/ZnS core/shell NWs not only enhanced their charge carrier transport characteristics by confining the electrons and reducing surface states in the ZnO channel but also increased the photocurrent under ultraviolet (UV) illumination by reducing the recombination probability of the photogenerated charge carriers. Here the efficacy of the type-II band structure and the passivation effect are demonstrated by showing the enhanced subthreshold swing (150 mV/decade) and mobility (17.2 cm2/(Vs)) of the electrical properties, as well as the high responsivity (4.4×10(6) A/W) in the optical properties of the ZnO/ZnS core/shell NWs, compared with the subthreshold swing (464 mV/decade), mobility (8.9 cm2/(Vs)) and responsivity (2.5×10(6) A/W) of ZnO NWs.

Ultra-flexibility and unusual electronic, magnetic and chemical properties of waved graphenes and nanoribbons.

Two-dimensional materials have attracted increasing attention because of their particular properties and potential applications in next-generation nanodevices. In this work, we investigate the physical and chemical properties of waved graphenes/nanoribbons based on first-principles calculations. We show that waved graphenes are compressible up to a strain of 50% and ultra-flexible because of the vanishing in-plane stiffness. The conductivity of waved graphenes is reduced due to charge decoupling under high compression. Our analysis of pyramidalization angles predicts that the chemistry of waved graphenes can be easily controlled by modulating local curvatures. We further demonstrate that band gaps of armchair waved graphene nanoribbons decrease with the increase of compression if they are asymmetrical in geometry, while increase if symmetrical. For waved zigzag nanoribbons, their anti-ferromagnetic states are strongly enhanced by increasing compression. The versatile functions of waved graphenes enable their applications in multi-functional nanodevices and sensors.

Real-time imaging of intracellular drug release from mesoporous silica nanoparticles based on fluorescence resonance energy transfer.

In this study, a targeted cancer therapy imaging and sensing system is designed based on doxorubicin (DOX)-loaded green fluorescent mesoporous silica nanoparticles (FMSN) conjugated with folic acid (FA), by linking with α-amine-ω-propionic acid hexaethylene glycol (NH2-PEG-COOH). An in situ formation method is adopted to prepare luminescent MSNs, which then act as the donor for the fluorescence resonance energy transfer (FRET), as their emission at 500 nm overlaps with the absorption of the acceptor DOX at 485 nm. NH2-PEG-COOH is conjugated to the outer surface of the FMSN at one end and modified by folic acid at the other, so that the formed mesoporous silica composite has the merits of fluorescence imaging, mesoporous nanostructure for drug loading, receptor-mediated targeting and real-time monitoring of intracellular drug release. It was found that the FA-grafted and PEGlated nanocomposite has excellent biocompatibility towards Hep2 cells, and that the cytotoxicity of the loaded-DOX nanoparticles, containing the folate targeting units in the folate-receptor-rich Hep2 cancer cells, is higher than that without folate targeting units, under the same conditions. When the resultant nanoparticles enter into the cells, the green fluorescence of FMSN gradually recovers along with the release of DOX, to achieve the purpose of real-time monitoring of intracellular drug release.

Nearly lattice matched all wurtzite CdSe/ZnTe type II core–shell nanowires with epitaxial interfaces for photovoltaics

Achieving a high-quality interface is of great importance in core-shell nanowire solar cells, as it significantly inhibits interfacial recombination and thus improves the photovoltaic performance. Combining thermal evaporation of CdSe and pulsed laser deposition of ZnTe, we successfully synthesized nearly lattice matched all wurtzite CdSe/ZnTe core-shell nanowires on silicon substrates. Comprehensive morphological and structural characterizations revealed that a wurtzite ZnTe shell layer epitaxially grows over a wurtzite CdSe core nanowire with an abrupt interface. Further optical studies confirmed a high-quality interface and demonstrated efficient charge separation induced by the type-II band alignment. A representative photovoltaic device has been demonstrated and yielded an energy-conversion efficiency of 1.7% which can be further improved by surface passivation. The all-wurtzite core-shell nanowire with an epitaxial interface offers an attractive platform to explore the piezo-phototronic effect and promises an efficient hybrid nano-sized, energy harvesting system.

Strong Confined Optical Emission and Enhanced Thermoelectric Power Factor by Coupling Homologous In2O3(ZnO)m with In-Doped ZnO Channels into Heterojunction Belts

Multifunctional nanodevices integrated with excellent optoelectric and thermoelectric properties are highly demanded for developing next generation self-powered optoelectronics. In the work, we demonstrate the viability of a coupled structure of homologous In2O3(ZnO)m with In-doped ZnO into heterojunction belts synthesized by alloy-evaporation deposition, offering multiple functions with strong confined optical emissions and high power factors. Energy-filter secondary electron images reveal a five-layer contrast in the width direction of the belts due to different ionization energies corresponding to In2O3(ZnO)m/In:ZnO/ZnO/In:ZnO/In2O3(ZnO)m, as confirmed by transmission electron microscopy analysis. The indium-doped ZnO channels confined in two sides behave like quantum wells through band alignment, and become predominant in the main UV emission at 385 nm, as revealed by cathodoluminescence spectroscopic imaging. More intriguingly, this novel heterostructure provides an ideal pathway to enhance electron conduction through the indium doped ZnO layer, and the homologous In2O3(ZnO)m layer contains numerous interfaces to impede phonon transportation. In this way, the power factor of the heterostructure is greatly enhanced to be 2.07 × 10–4 W m–1 K–2 at room temperature, as compared to about 1.03 × 10–5 W m–1 K–2 for the undoped ZnO nanowires. This unique heterostructure achieved by a facile one-step growth process offers a new concept for designing devices by manipulating photons via coupling with electrons and phonons.

Nanomedicine metaphors: From war to care. Emergence of an oecological approach

• War metaphors have been widely used to describe the targeting ability and therapeutic potentials of multifunctional nanodevices against cancer. • This militaristic view overlooks the interactions of nanoparticles with the complex dynamical environment of the body. • Nanodevices should be defined by their interactions with the milieu, rather than as individual remotely-controlled entities. • Nanomedicine may take advantage of the milieu for designing new strategies of care. • The emerging oecological approach, focusing on nanoparticle relations with their environment, may prove more promising than the magic bullet concept. Images such as ‘therapeutic missile’ are commonly used to present targeted drug delivery devices. The ballistic metaphor, reminiscent of Paul Ehrlich's ‘magic bullet’, has raised great expectations. Accordingly, chemists, physicists and engineers have worked hard to design smart ‘missiles’ delivering their load of drug to the target. While paying attention to the equipment of the nanodevice for the transport and molecular recognition for the delivery, they have to face the challenges posed by the messy environment of the body. We question the relevance of the missile metaphor, and suggest that an alternative oecological metaphor would be more appropriate. Such an approach, focused on interactions between the nanovehicle and the complex, versatile, heterogeneous biological milieu, seems more heuristic and promising.

Self-powered ultraviolet photodetector based on a single ZnO tetrapod/PEDOT:PSS heterostructure

A new ultraviolet (UV) photodetector based on a single ZnO tetrapod and PEDOT:PSS heterostructure was constructed and investigated. At zero bias, the detector showed an on/off ratio of ∼1100, a rise time of ∼3.5 s and a decay time of ∼4.5 s when the 325 nm UV (0.16 mW) illuminated the p–n heterojunction. The self-powered properties were driven by the photovoltaic effect, with a short-circuit current of ∼1.1 nA, an open-circuit voltage of ∼0.2 V and a fill factor of ∼25%. Furthermore, self-powered properties were also found when the UV irradiated the ZnO tetrapod only, and the short-circuit current and the open-circuit voltage decreased with the increasing distance between the illuminated spot at the ZnO tetrapod and the heterojunction. The mechanisms for the performances of the detector were examined and discussed. In consideration of the multiterminal feature of ZnO tetrapods, our work provides a possible new approach to developing independent and multifunctional nanodevices.

Emerging micro- and nanotechnologies in cancer diagnosis and therapy

Understanding the mechanism of cancer cell metastasis is crucial for targeted cancer diagnosis and research. But this process is still not fully understood mainly because of lack of in vitro cell culture models that precisely mimic the physiological complexities of cancer cell intravascular flows, invasion, adhesion, metastasis, angiogenesis and migration to specific sites. Microand nanoscale technologies offer a promising tool for such purpose. This special issue broadly covers the topics of cell microenvironment, biological surface modifications, multifunctional nanoparticles and nanosensors, microfluidics, molecular detection as well as multistage targeting strategies for cancer. In particular, it focuses on investigating how we can harness the power of microand nanotechnologies to radically change the way we diagnose and treat cancer. This includes both in vivo and ex vivo technologies. For in vivo applications, biosensors would have the capability of detecting tumors andmetastatic lesions that are far smaller than those detectable using conventional technologies. Novel and multi-functional nanodevices will be capable of detecting cancer at its earliest stages, pinpointing its location within the body, delivering anticancer drugs specifically to malignant cells, and determining if these drugs are effective. In addition, functionalized nanoparticles would deliver multiple therapeutic agents to tumor sites in order to simultaneously attack multiple points in the pathways involved in cancer. Such nano-therapeutics are expected to increase the efficacy of drugs while dramatically reducing potential side effects. For ex vivo application, the tumor microenvironment and circulating tumor cells can be studied. Together, such innovative approaches can provide information on potential early diagnosis as well as whether a given therapy is working as expected. The group of Fischbach et al. reviews recent efforts in modulating the tumor microenvironment to develop in vitro tumor models for cancer pathogenesis and drug discovery. The work covers some of the recent landmark efforts towards this direction or micro-tumor engineering with focus on tissue microstructure organization and surrounding mass transport behavior using biomimetic approaches. The authors thus highlight the immense potential of microfabrication techniques for such cancer pathogenesis applications. In order to understand the recent advances in microfluidic technologies for cancer research, Nagrath et al. have identified four critical areas of research: cancer cell isolation, molecular diagnostics, tumor biology, and high-throughput screening for therapeutics. Cancer cell isolation can be further subcategorized into two major techniques: immunoaffinity-based isolation and size-based separation. Other methods include hydrodynamic focusing and dielectrophoresis. For the cancer cell isolation technologies, Ohnaga et al. developed polymeric microfluidic devices for the isolation of circulating tumor cells using microposts coated with anti-epithelial cell adhesion olecule antibody, and a flow system to capture tumor cells using an esophageal cancer cell line, KYSE220, dispersed in phosphate-buffered saline or mononuclear cell separation from whole blood. Recently, He et al. developed biocompatible nano-films composed of TiO2 nanoparticles to enhance topographic interactions between the nanofilm substrate surface and cell surface. The surface of the TiO2 nanoparticles is chemically modified to enable functionalization of anti-EpCAM antibodies. The J. X. J. Zhang (*) Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA e-mail: john.zhang@engr.utexas.edu

The Effects of the Formation of Stone–Wales Defects on the Electronic and Magnetic Properties of Silicon Carbide Nanoribbons: A First‐Principles Investigation

Detailed first-principles density functional theory (DFT) computations were performed to investigate the geometries, the electronic, and the magnetic properties of both armchair-edged silicon carbide nanoribbons (aSiCNRs) and zigzag-edged silicon carbide nanoribbons (zSiCNRs) with Stone-Wales (SW) defects. SW defects in the center of aSiCNRs can remarkably reduce their band gaps, irrespective of the orientation of the defect, whereas zSiCNRs with SW defects in the center or at the edges exhibit degenerate energies of their ferromagnetic (FM) and antiferromagnetic (AFM) states, in which metallic and half-metallic behavior can be observed, respectively; half-metallic behavior can even be observed in both the FM and AFM states simultaneously. Further, it was shown that the formation energies of the SW defects in SiCNRs are orientation dependent, and the formation of edge defects is always favored over the formation of interior defects in zSiCNRs. The possible existence of SW defects in SiCNRs was further validated through exploring the kinetic process of their formation. These findings can be anticipated to provide valuable information in promoting the potential applications of SiC-based nanomaterials in multifunctional and spintronic nanodevices.

Magnetic and optical properties of Cu-doped ZnO nanosheet: First-principles calculations

We performed first-principles calculations within density-functional theory to study the magnetic and optical properties of Cu-doped ZnO nanosheet (NS). We found that Cu atom prefers to substitute for Zn site and can induce a local magnetic moment of 1.00μB per unit in ZnO NS. When two Zn atoms are substituted by two Cu dopants, they tend to form a cluster and ferromagnetic (FM) ordering becomes energetically more favorable. In addition, localized states appear within the band gap due to the introduction of Cu dopant to ZnO NS. With increasing Cu concentrations, both the imaginary part of dielectric function and the absorption spectrum exhibit a red-shift behavior, which are in good agreement with the recent experimental results. The ferromagnetic coupling can be attributed to the p–d hybridization mechanism. The intriguing properties of Cu-doped ZnO NS may be promising for designing novel multifunctional nanodevice.

Gated Systems for Multifunctional Optoelectronic Devices

Paolo Samori (1971) is Distinguished Professor (PRCE) and director of the Institut de Science et d’Ingenierie Supramoleculaires (ISIS) of the Universite de Strasbourg where he is also head of the Nanochemistry Laboratory. He is also Fellow of the Royal Society of Chemistry (FRSC) and junior member of the Institut Universitaire de France (IUF). He obtained a Laurea in Industrial Chemistry at University of Bologna in 1995. In 2000 he received his Ph.D. in Chemistry from the Humboldt University Berlin (Prof. J.P. Rabe). He was permanent research scientist at Istituto per la Sintesi Organica e la Fotoreattivita of the Consiglio Nazionale delle Ricerche of Bologna and Visiting Professor at ISIS. His research activity is focussed on applications of scanning probe microscopies beyond imaging, hierarchical self-assembly of hybrid architectures at surfaces, supramolecular electronics, and the fabrication of organic-based multifunctional nanodevices.

The donor/acceptor edge-modification: an effective strategy to modulate the electronic and magnetic behaviors of zigzag silicon carbon nanoribbons

Based on first principles computations, we systematically investigated electronic and magnetic properties of zSiCNRs with unilateral/bilateral modification by employing electron donor/acceptor groups, where five chemical functional groups are sampled, namely, CH3, OH, NH2, CN and NO2. Our computed results reveal that the edge modification with donor/acceptor groups can break the magnetic degeneracy of pristine zSiCNRs, and intriguing antiferromagnetic (AFM) half-metallicity, AFM metallicity and ferromagnetic (FM) metallicity can be achieved. This overcomes the bottleneck that FM metallicity and AFM half-metallicity in pristine zSiCNRs are vulnerable under even small disturbances, due to the energy degeneracy between the FM and AFM states. Obviously, edge modification with donor/acceptor groups can be an effective strategy to modulate the electronic and magnetic behaviors of zSiCNRs, which will be advantageous for promoting SiC-based nanomaterials in the application of spintronics and multifunctional nanodevices in the near future.

First principles investigation on the stability, magnetic and electronic properties of the fully and partially hydrogenated BN nanoribbons in different conformers

Based on first-principles computations, the geometries, stabilities, electronic and magnetic properties of fully and partially hydrogenated boron nitride nanoribbons (BNNRs) were investigated. Our results from the theoretical computation revealed that the boat and stirrup configurations were the most stable ones among the boat, chair and stirrup configurations for zigzag and armchair fully hydrogenated BNNRs, respectively. The fully hydrogenated 10-zBNNRs exhibited energetically degenerated ferromagnetic (FM) and ferrimagnetic (MFM) states for the boat and chair configurations. In the FM state, they showed metallic behavior, whereas in the MFM state, only the energy levels in the spin-down channel cross the Fermi-level, indicating the corresponding half-metallic feature. Moreover, intrinsic MFM half-metallic behavior can be observed in stirrup fully hydrogenated 10-zBNNRs. However, all of the fully hydrogenated 15-aBNNRs were nonmagnetic wide-band-gap semiconductors. By hydrogenating the zigzag BNNRs (zBNNRs) from the edge(s) step by step in a boat manner, we provide an effective approach to enrich the electronic and magnetic properties of zBNNRs and the transition of NM wide-gap semiconductor → NM narrow-gap semiconductor → energetically degenerated FM/MFM(AFM) metal/half-metal → FM metal → MFM half-metal can be achieved by controlling the hydrogenation patterns and ratios. These appealing features, especially the diverse electronic and magnetic transitions, in the unitary BNNR-based nanostructures may provide tremendous potential applications for integrated multi-functional and spintronic nanodevices.

Dendrimer-based nanodevices for targeted drug delivery applications.

This review reports some recent advances on the use of dendrimers as a versatile platform for targeted drug delivery applications. The unique 3-dimensional architectures and macromolecular characteristics afford dendrimers with ideal drug delivery ability through encapsulating drugs in their interior or covalently conjugating drugs on their surfaces. The adaptable surface functionalization ability enables covalent conjugation of various targeting molecules onto the surface of dendrimers, thereby allowing for generation of various multifunctional nanodevices for targeted drug delivery applications. In particular, the application of dendrimers as versatile platforms for targeted cancer therapeutics will be introduced in detail.

Synthesis of multiferroic Bi0.9La0.1Fe0.95Mn0.05O3–Ba0.7Sr0.3TiO3–Ni0.8Zn0.2Fe2O4 nanotubes with one closed end using a template-assisted sol–gel process

One-dimensional multiferroic nanostructures have received a great deal of recent attention. This paper presents the synthesis of Ba0.7Sr0.3TiO3 (BSTO) and Ni0.8Zn0.2Fe2O4 (NZFO) co-reinforced Bi0.9La0.1Fe0.95Mn0.05O3 (BLFMO) nanotubes with one closed end. The aim was to obtain one-dimensional multiferroics with higher ferroelectric and magnetic properties. It was found that these nanotubes had high aspect ratios with polycrystalline structures. Also, compared to single-phase nanotubes, they were found to possess a rougher surface and more non-uniform wall thickness. After combining BSTO and NZFO phases together, the BLFMO–BSTO–NZFO nanotubes possessed a larger saturation magnetization at 300 K. Such multiferroic nanotubes with one closed end have seldom been reported. These tubular structures are appropriate to be used as the shells of other functional nanowires or nanoparticles, and have a potential application for multifunctional nano-devices.

In situ doxorubicin–CaP shell formation on amphiphilic gelatin–iron oxide core as a multifunctional drug delivery system with improved cytocompatibility, pH-responsive drug release and MR imaging

An amphiphilic gelatin–iron oxide core/calcium phosphate shell (AGIO@CaP-DOX) nanoparticle was successfully synthesized as an efficient anti-cancer drug delivery system, where doxorubicin (DOX) as a model molecule was encapsulated by electrolytic co-deposition during CaP shell formation. The shell of CaP precipitate played a pivotal role, not only in acting as a drug depot, but also in rendering the drug release rate in a highly pH-dependent controlled manner. Together with MR imaging, highly biocompatible drug-carrying CaP shell and efficient cellular internalization, the AGIO@CaP-DOX nanoparticles developed in this study area promising multifunctional nanodevice for nanotherapeutic approaches.

Fabrication of functionalized double-lamellar multifunctional envelope-type nanodevices using a microfluidic chip with a chaotic mixer array.

Multifunctional envelope-type nanodevices (MENDs) are very promising non-viral gene delivery vectors because they are biocompatible and enable programmed packaging of various functional elements into an individual nanostructured liposome. Conventionally MENDs have been fabricated by complicated, labor-intensive, time-consuming bulk batch methods. To avoid these problems in MEND fabrication, we adopted a microfluidic chip with a chaotic mixer array on the floor of its reaction channel. The array was composed of 69 cycles of the staggered chaotic mixer with bas-relief structures. Although the reaction channel had very large Péclet numbers (>105) favorable for laminar flows, its chaotic mixer array led to very small mixing lengths (<1.5 cm) and that allowed homogeneous mixing of MEND precursors in a short time. Using the microfluidic chip, we fabricated a double-lamellar MEND (D-MEND) composed of a condensed plasmid DNA core and a lipid bilayer membrane envelope as well as the D-MEND modified with trans-membrane peptide octaarginine. Our lab-on-a-chip approach was much simpler, faster, and more convenient for fabricating the MENDs, as compared with the conventional bulk batch approaches. Further, the physical properties of the on-chip-fabricated MENDs were comparable to or better than those of the bulk batch-fabricated MENDs. Our fabrication strategy using microfluidic chips with short mixing length reaction channels may provide practical ways for constructing more elegant liposome-based non-viral vectors that can effectively penetrate all membranes in cells and lead to high gene transfection efficiency.