/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Gold nanoparticles have been used in biomedical applications since their first colloidal syntheses more than three centuries ago. However, over the past two decades, their beautiful colors and unique electronic properties have also attracted tremendous attention due to their historical applications in art and ancient medicine and current applications in enhanced optoelectronics and photovoltaics. In spite of their modest alchemical beginnings, gold nanoparticles exhibit physical properties that are truly different from both small molecules and bulk materials, as well as from other nanoscale particles. Their unique combination of properties is just beginning to be fully realized in range of medical diagnostic and therapeutic applications. This critical review will provide insights into the design, synthesis, functionalization, and applications of these artificial molecules in biomedicine and discuss their tailored interactions with biological systems to achieve improved patient health. Further, we provide a survey of the rapidly expanding body of literature on this topic and argue that gold nanotechnology-enabled biomedicine is not simply an act of ‘gilding the (nanomedicinal) lily’, but that a new ‘Golden Age’ of biomedical nanotechnology is truly upon us. Moving forward, the most challenging nanoscience ahead of us will be to find new chemical and physical methods of functionalizing gold nanoparticles with compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term term effects on human health and reproduction (472 references).

The golden age: gold nanoparticles for biomedicine

A revolution in novel nanoparticles and colloidal building blocks has been enabled by recent breakthroughs in particle synthesis These new particles are poised to become the ‘atoms’ and ‘molecules’ of tomorrow’s materials if they can be successfully assembled into useful structures Here, we discuss the recent progress made in the synthesis of nanocrystals and colloidal particles and draw analogies between these new particulate building blocks and better-studied molecules and supramolecular objects We argue for a conceptual framework for these new building blocks based on anisotropy attributes and discuss the prognosis for future progress in exploiting anisotropy for materials design and assembly

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Anisotropy of building blocks and their assembly into complex structures

Gold nanorods with aspect ratios of 4.6 ± 1.2, 13 ± 2, and 18 ± 2.5 (all with 16 ± 3 nm short axis) are prepared by a seeding growth approach in the presence of an aqueous miceller template. Citrate-capped 3.5 nm diameter gold particles, prepared by the reduction of HAuCl4 with borohydride, are used as the seed. The aspect ratio of the nanorods is controlled by varying the ratio of seed to metal salt. The long rods are isolated from spherical particles by centrifugation.

Wet Chemical Synthesis of High Aspect Ratio Cylindrical Gold Nanorods

±COOAr, m to ±CH2O±, m to ArCOO± and m to ±OOCAr), 7.25±7.32 (m, 4 Ar±H, o to ±CH2O± and o to ArCOO±), 6.96±7.04 (m, 4 Ar±H, o to ±OCH2(CH2)11± and o to ±OOCAr), 4.20 (t, 2H, ArOCH2CH2O±), 4.05 (t, 2 H, ArOCH2(CH2)10±, J=6.6 Hz), 3.54±4.00 (m, 68 H, ±CH2O±), 3.37 (s, 3 H, CH3O±), 1.77±1.85 (m, 2 H, ±CH2(CH2)9±), 1.14±1.47 (m, 18 H, ±CH2(CH2)9±), 0.87 (t, 3 H, CH3(CH2)11±, J=6.8 Hz). C-NMR (62.5 MHz, CDCl3) d 165.6, 165.4 164.0, 159.6, 151.0, 150.9, 146.4, 138.7, 138.4, 132.7, 131.2, 128.8, 128.6, 128.5, 127.9, 127.1, 122.6, 122.5, 121.9, 115.5, 114.7, 72.3, 71.3, 71.1, 71.0, 68.8, 68.0, 59.4, 32.3, 30.04, 29.99, 29.97, 29.8, 29.5, 26.4, 23.7, 23.1, 14.5: Anal. calcd for C79H116O23: C, 66.18; H, 8.15. Found: C, 66.72, H, 8.33. MW/Mn=1.03 (gel permeation chromatography).

Orthogonal Self‐Assembly on Colloidal Gold‐Platinum Nanorods

Thin films were grown on amine-primed Si and glass substrates by sequential adsorption reactions of polyallylamine hydrochloride (PAH) and anionic colloids derived from HTiNbO5 and HCa2Nb3O10. The acid−base chemistry of polycation/polyanion adsorption was studied in detail for PAH/HTiNbO5. The pKa of PAH, defined as the pH at which it is half protonated, is 8.7. Titanoniobate colloids, prepared by reaction of HTiNbO5 with tetra(n-butylammonium) hydroxide, TBA+OH-, are unilamellar at pH ≥ 8.5 and restack below pH 7.0. Efficient tiling of a PAH-terminated surface by a layer of unilamellar titanoniobate sheets occurs only at intermediate pH values (8.5−9.0). At lower pH, the colloid restacks on the surface, and at higher pH, only partial coverage by single sheets is observed by atomic force microscopy (AFM). At pH 8.5, high-quality multilayer films can be grown by sequentially adsorbing PAH with either the titanoniobate or niobate colloid. TGA/DTA studies of bulk PAH/titanoniobate intercalation compounds sho...

Layer-by-Layer Growth and Condensation Reactions of Niobate and Titanoniobate Thin Films

Multilayer thin films consisting of anionic α-zirconium phosphate (α-ZrP) sheets, tetrameric zirconium hydroxide cations [Zr4(OH)8(H2O)16]8+ (Zr48+), and alkanediylbis(phosphonic acid) (CnBPA) have been grown on silicon and gold surfaces by sequential adsorption reactions. The thin films were characterized by ellipsometry, X-ray diffraction, reflectance infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Alternately dipping cationic substrates into exfoliated α-ZrP-containing suspensions, aqueous zirconium oxychloride, and ethanolic C16BPA solutions generates a mixed ionic/covalent multilayer structure. The tetrameric Zr48+ cation adsorbs onto the α-ZrP surface, providing a covalent anchoring point for the growth of the C16BPA layer. Adsorbing a second layer of zirconium ions onto the C16BPA layer allows one to continue the layer growth sequence using either covalent (metal/phosphonate) or ionic (α-ZrP/polycation) interlayer connections. A multilayer film with...

A “Mix and Match” Ionic−Covalent Strategy for Self-Assembly of Inorganic Multilayer Films

The dielectric properties of layer perovskites in the Dion−Jacobson (KCa2Nb3O10, HCa2Nb3O10, CsPb2Nb3O10, HPb2Nb3O10, KCa2NaNb4O13, KLa2NbTi2O10) and Ruddlesden−Poppper (K2La2Ti3O10) series, and of...

Dielectric properties of the lamellar niobates and titanoniobates AM2Nb3O10 and ATiNbO5 (A = H, K, M = Ca, Pb), and their condensation products Ca4Nb6O19 and Ti2Nb2O9

TiO2, Ta2O5, and mixed TiO2/Ta2O5 ultrathin films were grown layer-by-layer using a surface sol–gel deposition technique. The technique allows one to prepare smooth films of mixed composition with angstrom-level control of thickness. The thickness increases per adsorption/hydrolysis cycle were 4.5, 2.1, and 2.5 A, respectively, for TiO2, Ta2O5, and mixed TiO2/Ta2O5 (1.6sol;1) films. By combining X-ray diffraction and ellipsometric analysis, it was determined that the as-deposited TiO2 films are less dense than bulk TiO2, and do not adhere persistently to Si/SiO2 or Au/2-mercaptoethanol substrates. These ‘green’ films were annealed at 400°C to produce denser and highly adherent films. Patterning the surface by microcontact printing of siloxane polymer thin films allows one to prepare patterned sol–gel oxide thin films.

Mingming Fang

Papers

Orthogonal Self‐Assembly on Colloidal Gold‐Platinum Nanorods

Layer-by-Layer Growth and Condensation Reactions of Niobate and Titanoniobate Thin Films

A “Mix and Match” Ionic−Covalent Strategy for Self-Assembly of Inorganic Multilayer Films

Dielectric properties of the lamellar niobates and titanoniobates AM2Nb3O10 and ATiNbO5 (A = H, K, M = Ca, Pb), and their condensation products Ca4Nb6O19 and Ti2Nb2O9

Surface Sol–gel Synthesis of Ultrathin Titanium and Tantalum Oxide Films