Controlled synthesis of highly-branched plasmonic gold nanoparticles through peptoid engineering

Revisiting the Growth Mechanism of Hierarchical Semiconductor Nanostructures: The Role of Secondary Nucleation in Branch Formation

Although there have been advances in synthesizing hierarchical semiconductor materials,  few studies have investigated the fundamental nucleation mechanisms to explain the origins of such complex structures. Resolving these nucleation and growth pathways is technically challenging but  critical for developing predictive synthetic capabilities for the synthesis and application of new materials. In this Letter, we use state-of-the-art in situ liquid phase scanning electron microscopy (SEM) and high-resolution transmission electron microscopy in a combination with classical density functional theory (cDFT) to study the nucleation of highly branched wurtzite ZnO nanostructures via a facile, room-temperature aqueous synthesis route. Using a range of precursor concentrations, we systematically vary the hierarchical organization of these nanostructures. In situ liquid phase SEM demonstrates that all branches form through secondary nucleation and grow by classical processes. Neither random aggregation nor oriented attachment is observed. cDFT results imply that the morphological evolution with increasing [Zn²⁺] arises from an interplay between a rising thermodynamic driving force, which promotes branch number and variability of orientation, and increasing barriers to interfacial transport due to ion correlation forces that alter the anisotropic kinetics of growth. These findings provide a quantitative picture of branching that sets to rest past controversies and advances efforts to decipher growth mechanisms of hierarchical structures in real solution environments.

Peptoids as tools and sensors

A review of molecular tools and sensors assembled on N-substituted glycine, or α-peptoid, oligomers between 2013 and November 2018 with the following sections: (a) Peptoids as crystal growth modifiers, (b) Peptoids as catalysts, (c) Ion and molecule sequestration and transport, (d) Peptoid sensors, (e) Macromolecule recognition, (f) Cellular transporters, (g) Medical imaging, (h) Future direction and (i) Summary and outlook. Peptoids are a promising class of peptide mimic making them an excellent platform for functional molecule preparation. Attributes of peptoid oligomers include: (a) the ease of precise sequence definition and mono-dispersity; (b) access to a vast chemical space within simple and repeating chemical preparative steps and (c) thermal, chemical and biological stability all lending support for their application in a number of areas, with some that have been realised to date. The peptoid tool and sensor examples selected have realised practical utility. They serve to illustrate the rapidity of new insight that can generate in many disparate areas of science and technology, enabling the quick assembly of design criteria for efficient peptoid molecular tools and sensors.

Design of plasmonic nanomaterials for diagnostic spectrometry

Molecular diagnostics relies on the efficient extraction of biomarker information from the given bio-systems. Plasmonic nanomaterials with tailored structural parameters are promising for the development of biomarker assays due to enrichment effect and signal enhancement. Herein, we overview the recent progress on the development of plasmonic nanomaterials for diagnostic spectrometry, encompassing the interface, mechanism, and application of these materials. For interface, we summarized the types of plasmonic nanomaterials used as interfaces between different materials and light. For mechanism, we descirbe the key parameters (e.g., hot carriers and heat) that characterize the plasmonic effect of materials. For application, we highlighted recent advances in matrix assisted laser desorption/ionization mass spectrometry (MALDI MS) and surface enhanced Raman spectroscopy (SERS) toward precision in in vitro and in vivo diagnostics. We foresee the upcoming era of precision diagnostics by nano-assisted spectrometry methods in both academy and industry, which will require the interest and effort of scientists with diverse backgrounds.

Sequence-Specific Control of Inorganic Nanomaterials Morphologies by Biomolecules

Controlling morphologies of nanomaterials such as their shapes and surface features has been a major endeavor in the field of nanoscale science and engineering, because the morphology is a major determining factor for functional properties of nanomaterials. Compared with conventional capping ligands based on organic molecules or polymers, the programmability of biomolecules makes them attractive alternatives for morphology-controlled nanomaterials synthesis. Towards the goal of predictable control of the synthesis, many studies have been performed on using different sequences of biomolecules to generate specific nanomaterial morphology. In this review, we summarize recent studies in the past few years on using DNA and peptide sequences to control inorganic nanomaterial morphologies, focusing on both case studies and mechanistic investigations. The functional properties resulting from such a sequence-specific control are also discussed, along with strengths and limitations of different approaches to achieving the goal.

Anisotropic Gold Nanoparticles in Biomedical Applications

Gold nanoparticles (AuNPs) play a crucial role in the development of nanomedicine, principally due to their unique photophysical properties and high biocompatibility. The possibility to tune and customize the localized surface plasmon resonance (LSPR) toward near-infrared region by modulating the AuNP shape is one of the reasons for the huge widespread use of AuNPs. The controlled synthesis of no-symmetrical nanoparticles, named anisotropic, is an exciting goal achieved by the scientific community which explains the exponential increase of the number of publications related to the synthesis and use of such type of AuNPs. Even with such steps forward and the AuNP translation in clinic being done, some key issues are still remain and they are related to a reliable and scalable production, a full characterization, and to the development of nanotoxicology studies on the long run. In this review we highlight the very recent advances on the synthesis of the main classes of anisotropic AuNPs (nanorods, nanourchins and nanocages) and their use in the biomedical fields, in terms of diagnosis and therapeutics.