The emerging field of bionanotechnology aims at revolutionizing biomedical research and clinical practice via introduction of nanoparticle-based tools, expanding capabilities of existing investigative, diagnostic, and therapeutic techniques as well as creating novel instruments and approaches for addressing challenges faced by medicine. Quantum dots (QDs), semiconductor nanoparticles with unique photo-physical properties, have become one of the dominant classes of imaging probes as well as universal platforms for engineering of multifunctional nanodevices. Possessing versatile surface chemistry and superior optical features, QDs have found initial use in a variety of in vitro and in vivo applications. However, careful engineering of QD probes guided by application-specific design criteria is becoming increasingly important for successful transition of this technology from proof-of-concept studies towards real-life clinical applications. This review outlines the major design principles and criteria, from general ones to application-specific, governing the engineering of novel QD probes satisfying the increasing demands and requirements of nanomedicine and discusses the future directions of QD-focused bionanotechnology research (critical review, 201 references).

Designing multifunctional quantum dots for bioimaging, detection, and drug delivery

Semiconductor nanowires (NWs) have been studied extensively for over two decades for their novel electronic, photonic, thermal, electrochemical and mechanical properties. This comprehensive review article summarizes major advances in the synthesis, characterization, and application of these materials in the past decade. Developments in the understanding of the fundamental principles of "bottom-up" growth mechanisms are presented, with an emphasis on rational control of the morphology, stoichiometry, and crystal structure of the materials. This is followed by a discussion of the application of nanowires in i) electronic, ii) sensor, iii) photonic, iv) thermoelectric, v) photovoltaic, vi) photoelectrochemical, vii) battery, viii) mechanical, and ix) biological applications. Throughout the discussion, a detailed explanation of the unique properties associated with the one-dimensional nanowire geometry will be presented, and the benefits of these properties for the various applications will be highlighted. The review concludes with a brief perspective on future research directions, and remaining barriers which must be overcome for the successful commercial application of these technologies.

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25th Anniversary Article: Semiconductor Nanowires – Synthesis, Characterization, and Applications

The decontamination of bisphenol A (BPA) from aqueous solution by graphene adsorption was investigated. The maximum adsorption capacity (qm) of graphene for BPA obtained from a Langmuir isotherm was 182 mg/g at 302.15 K, which was among the highest values of BPA adsorption compared with other carbonaceous adsorbents according to the literature. Both π–π interactions and hydrogen bonds might be responsible for the adsorption of BPA on graphene, and the excellent adsorption capacity of graphene was due to its unique sp2-hybridized single-atom-layer structure. Therefore, graphene could be regarded as a promising adsorbent for BPA removal in water treatment. The kinetics and isotherm data can be well described by the pseudo-second-order kinetic model and the Langmuir isotherm, respectively. The thermodynamic studies indicated that the adsorption reaction was a spontaneous and exothermic process. Besides, the presence of NaCl in the solution could facilitate the adsorption process, whereas the alkaline pH rang...

Decontamination of Bisphenol A from Aqueous Solution by Graphene Adsorption

Adsorptive remediation of environmental pollutants using novel graphene-based nanomaterials

Simultaneous removal of Cd(II) and ionic dyes from aqueous solution using magnetic graphene oxide nanocomposite as an adsorbent

The quite efficient adsorption of methylene blue dye from an aqueous solution by graphene oxide was studied. The favorable electrostatic attraction is the main interaction between methylene blue and graphene oxide. As graphene oxide has the special nanostructural properties and negatively charged surface, the positively charged methylene blue molecules can be easily adsorbed on it. In the aqueous solution of methylene blue at 293 K, the adsorption data could be fitted by the Langmuir equation with a maximum adsorption amount of 1.939 mg/mg and a Langmuir adsorption equilibrium constant of 18.486 mL/mg. The adsorption amount increased with the increase of the solution pH (3-11), was not affected significantly by KCl under the examined condition and the adsorption process was exothermic in nature. The fast and considerable adsorption of graphene oxide could be regarded as a potential adsorbent for cationic dye removal in wastewater treatment process.

Fast and Considerable Adsorption of Methylene Blue Dye onto Graphene Oxide

Controllable ZnO architectures with different morphologies were synthesized via an ethanolamine-assisted one-pot hydrothermal method. By adjusting reaction conditions such as the molar ratio between Zn(OAc)2 and NaOH and the volume ratio of the ethanolamine/water, the flowerlike, spindlelike, swordlike, and umbellarlike ZnO architectures of the hexagonal phase have been obtained. The as-prepared ZnO products were characterized by FE-SEM, TEM, XRD, BET, PL, and Raman spectroscopy. The ethanolamine significantly influenced the morphology of ZnO products, which is related to the competitive adsorption between ethanolamine and [Zn(OH)4]2− to ZnO nuclei. Their PL spectra depend on their morphologies and phase structures. The morphology-dependent photocatalytic performances in the degradation of methylene blue under UV illumination were observed, in which the flowerlike ZnO structures exhibit highest activity for their most irregular surface Zn sites.

Controllable ZnO Architectures by Ethanolamine-Assisted Hydrothermal Reaction for Enhanced Photocatalytic Activity

Core-shell-structured CdSe/SiOx nanowires were synthesized on an equilateral triangle Si (111) substrate through a simple one-step thermal evaporation process. SEM, TEM, and XRD investigations confirmed the core-shell structure; that is, the core zone is single crystalline CdSe and the shell zone is SiOx amorphous layer and CdSe core was grown along (001) direction.Two-stage growth process was present to explain the growth mechanism of the core/shell nanwires. The silicon substrate of designed equilateral triangle providing the silicon source is the key factor to form the core-shell nanowires, which is significant for fabrication of nanowire-core sheathed with a silica system. The PL of the product studied at room temperature showed two emission bands around 715 and 560 nm, which originate from the band-band transition of CdSe cores and the amorphous SiOxshells, respectively.

https://downloads.hindawi.com/journals/jnm/2010/427689.pdf

Simple synthesis and growth mechanism of core/shell cdse/SiO x nanowires

Compact wavelength-sensitive optical components are desirable for optical information processing and communication in photonic integrated system. In this work, optical waveguiding along single composition-graded CdSxSe1-x nanowires were systematically investigated. Under a focused laser excitation, the excited light can be guided passively along the bandgap-increased direction of the nanowire, keeping the photonic energy of the guided light almost unchanged during the whole propagation. In comparison, the excited light is guided actively through incessantly repeated band-to-band reabsorption and re-emitting processes along the bandgap-decreased direction, resulting in a gradual wavelength conversion during propagation. On the basis of this wavelength-converted waveguiding, a concept of nanoscale wavelength splitter is demonstrated by assembling a graded nanowire with several composition-uniform nanowires into branched nanowire structure. Our study indicates that composition-graded semiconductor nanowires ...

Wavelength-converted/selective waveguiding based on composition-graded semiconductor nanowires.

The optical-transport properties of 1D Se-doped CdS nanostructures with different doping contents and/or crystallization degrees are reported. The locally excited photoluminescence shows a significant redshift during the transport along the long axis of the 1D structures and can leave enough PL intensity for detection. The magnitude of the redshift is found to be highly dependent on the content of doping and the crystallization degree. The experimental results are compared with theoretical calculations based on the fundamental absorption rule of the semiconductor, which demonstrates that the redshift is related to the optical reabsorption effects induced by the local structural disorder in the semiconductors. Such optical properties of 1D semiconductor structures might be of interest for potential applications in color-tunable nanosized light-emitting and/or frequency-converting devices.

Qiang Wan

Papers

Fast and Considerable Adsorption of Methylene Blue Dye onto Graphene Oxide

Controllable ZnO Architectures by Ethanolamine-Assisted Hydrothermal Reaction for Enhanced Photocatalytic Activity

Simple synthesis and growth mechanism of core/shell cdse/SiO x nanowires

Wavelength-converted/selective waveguiding based on composition-graded semiconductor nanowires.

Color-Changeable Optical Transport through Se-Doped CdS 1D Nanostructures