Assembly Of Nanorods Research Articles

Kinetically Controlled Site-Specific Self-assembly of Hairy Colloids.

The solvophobicity-driven directional self-assembly of polymer-coated gold nanorods is a well-established phenomenon. Yet, the kinetics of this process, the origin of site-selectivity in the self-assembly, and the interplay of (attractive) solvophobic brush interactions and (repulsive) electrostatic forces are not fully understood. Herein, we use a combination of time-resolved (vis/NIR) extinction spectroscopy and finite-difference time-domain (FDTD) simulations to determine conversion profiles for the assembly of gold nanorods with polystyrene shells of distinct thicknesses into their (tip-to-tip) self-assembled structures. In particular, we demonstrate that the assembly process is highly protracted compared with diffusion-controlled rates, and we find that the assembly rate varies for different thickness values of the polymer shell. Our findings were rationalized using coarse-grained molecular dynamics simulations, which also corroborated the tip-to-tip preference in the self-assembly process, albeit with a uniform polymer coating. Utilizing the knowledge of quantified conversion rates for distinct colloidal species, we designed coassembling systems with different brush thicknesses, featuring "narcissistic" self-sorting behavior. This provides new perspectives for high-level supracolloidal self-assembly.

BODIPY directed one-dimensional self-assembly of gold nanorods.

The assembly of anisotropic nanomaterials into ordered structures is challenging. Nevertheless, such self-assembled systems are known to have novel physicochemical properties and the presence of a chromophore within the nanoparticle ensemble can enhance the optical properties through plasmon-molecule electronic coupling. Here, we report the end-to-end assembly of gold nanorods into micrometer-long chains using a linear diamino BODIPY derivative. The preferential binding affinity of the amino group and the steric bulkiness of BODIPY directed the longitudinal assembly of gold nanorods. As a result of the linear assembly, the BODIPY chromophores positioned themselves in the plasmonic hotspots, which resulted in efficient plasmon-molecule coupling, thereby imparting photothermal properties to the assembled nanorods. This work thus demonstrates a new approach for the linear assembly of gold nanorods resulting in a plasmon-molecule coupled system, and the synergy between self-assembly and electronic coupling resulted in an efficient system having potential biomedical applications.

Small CdS nanorods via sacrificial synthesis on perovskite nanocrystals – synthesis and hierarchical assembly

Precise control of the size and assembly of semiconductor nanorods (NRs) will enhance emerging photonic technologies.

Anisotropic ZSM-5 nanorod assemblies: facile synthesis, epitaxial growth, and strikingly enhanced stability in benzene alkylation

A novel bundle-like ZSM-5 nanorod assembly was facilely synthesized by adopting a CTAB-aided seed-induced strategy for highly efficient alkylation of benzene with ethanol.

HARNESSING GOLD NANORODS FOR NON-ENZYMATIC GLUCOSE SENSING

This study presents a straightforward and non-enzymatic approach for glucose detection utilizing aggregated gold nanorods (GNRs) based on surface plasmon resonance (SPR). The GNRs exhibited enhanced sensitivity toward glucose concentrations of up to 10 mM. The LSPR-based glucose detection method demonstrated superior sensitivity, stability, ease of use, and a convenient readout. Moreover, the LSPR detection technique can be seamlessly integrated with various sensing platforms, offering the potential to expand the sensor's range and applicability. This study highlights the promising prospects of LSPR-based non-enzymatic glucose detection and its potential for integration into diverse sensing systems. For the 10 mM glucose solution, the addition of 5.85x109 GNRs caused a 136 nm shift. On the other hand, when 50 mM glucose is added, the shift amounted to 82 nm, while adding 100 mM glucose resulted in a shift of 71 nm. This implies that at lower glucose concentrations, the degree of aggregation is greater, suggesting a heightened sensitivity to smaller concentrations. TEM images depicted the formation of the gold nanorod aggregates upon the introduction of 10 mM glucose.

(Invited) Surface and Structural Dependent Reactivity of Alkylphosphonic Acids-Modified Titanium Oxide Nanostructures with 2-Chloroethyl Ethyl Sulfide Under Visible Light Excitation

Synthesizing novel TiO2 nanomaterials are valuable for heterogeneous reactivity to address toxic chemical remediation. Titanium oxide nanoflowers (comprising assemblies of nanorods) and nanowires have been synthesized in which photocatalytic reactivity with 2-chloroethyl ethyl sulfide (2-CEES) has been significantly enhanced under visible light (1000 nm > λ > 400 nm) excitation. Enhancement of photooxidation with reaction rates of 99 and 168 µmol/g/h (quantum yields of 5.07 x 10-4 and 8.58 x 10-4 molecules/photon) were observed for TiO2 synthesized in the presence of two different alkylphosphonic acids (C14H29PO3H2 and C9H19PO3H2). Additionally, H2Ti2O5‧H2O nanowires were synthesized and capable of highly efficient hydrolysis of the carbon-chlorine (C-Cl) bond of 2-CEES without light at a reaction rate of 279.2 µmol/g/h due to high surface area and chemical nature of the titanate structure. These observations are correlated with: 1) generation of new surface defects/states (i.e. oxygen vacancies) as a result of TiO2 grafting by alkyl phosphonic acid that may serve as reaction active sites; 2) better light absorption by assemblies of nanorods in comparison to individual nanorods, 3) surface area differences, and 4) the exclusion of OH groups due to the formation surface functionalization with alkylphosphonic acids via Ti-O-P bonds on the TiO2. These robust materials can be used for highly efficient surface decontamination.

Work function analysis of photo-enhanced triethylamine adsorption impact on Au embedded CeO2 coated ZnO hybrid nanostructures: An investigation by scanning kelvin probe

This article utilizes a scanning kelvin probe to examine the impact of visible light and volatile organic compounds (VOCs) on an organic/inorganic/noble metal hybrid sensing layer. ZnO/Poly/CeO2/Poly/Au hybrid nanostructures were prepared on ITO substrate by layer-by-layer coating technique. In this case, PAH and DS polymers act as binders. The assembly of Au nanorods (NRs) on the polymer-coated ZnO NRs incorporated with CeO2 nanoparticles (NPs) and its maximum absorbance in the visible light region were studied by the structural and optical characterizations, respectively. The hybrid sensor's optical properties allowed for sizable changes in contact potential difference (CPD) when exposed to light. Although a non-selective interaction was observed, the increased responsiveness to Triethylamine (TEA) under visible light creates coordination bonds between the hybrid molecules. Notably, the surface charge was tuned in the surface of the sensing layer by varying the surfactant to explore the TEA responsiveness. Intriguingly, ZnO/Poly/CeO2 (+) has demonstrated improved adsorption capability towards TEA under irradiation due to the surface oxygen vacancies compared to ZnO/Poly/CeO2 (-). Also, ZnO/Poly/CeO2 (+) exhibited higher selectivity at adsorbing TEA than either ethanol or n-hexane.

Au nanorod assembly for sensitive SERS detection of airway inflammatory factors in sputum.

In this paper, we demonstrate a surface-enhanced Raman spectroscopy (SERS) biosensor based on the self-assembly of gold nanorods (AuNRs) for the specific detection of airway inflammatory factors in diluted sputum. The AuNR surface was modified with an antibody that was able to specifically recognize an airway inflammatory factor, interleukin-5 (IL-5), so that a end-to-end self-assembly system could be obtained, resulting in an order of magnitude amplification of the Raman signal and greatly improved sensitivity. Meanwhile, the outer layer of the biosensor was coated with silicon dioxide, which improved the stability of the system and facilitated its future applications. When the detected concentration was in the range of 0.1-50pg/mL, the SERS signal generated by the sensor showed a good linear relationship with the IL-5 concentration. Moreover, it had satisfactory performance in diluted sputum and clinical subjects with asthma, which could achieve sensitive detection of the airway inflammatory factor IL-5. Overall, the developed biosensor based on the SERS effect exhibited the advantages of rapid and sensitive detecting performance, which is suitable for monitoring airway inflammatory factors in sputum.

Broadband Near-Infrared Photothermal Response of Tissue-Mimicking Phantoms Embedded with Plasmonic Gold Nanorod Aggregates: Implications for the Non-invasive Eradication of Malignant Tumors

Broadband Near-Infrared Photothermal Response of Tissue-Mimicking Phantoms Embedded with Plasmonic Gold Nanorod Aggregates: Implications for the Non-invasive Eradication of Malignant Tumors

ZnO Deposition on Silicon and Porous Silicon Substrate via Radio Frequency Magnetron Sputtering

Nanostructured Zinc Oxide (ZnO) was deposited on silicon (c-Si) and macroporous silicon (m-PS) using a radio frequency (RF) reactive magnetron sputtering technique. Two RF powers of 60 and 80 W were selected for ZnO deposition on the substrates. Furthermore, the c-Si and m-PS substrate temperatures were kept at 500 and 800 °C, respectively. The morphological, structural, and optical characteristics of the samples were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The SEM images revealed the formation of ZnO nanorods on the c-Si and ZnO nanostructures constituted by the assembly of nanorods. It has been found that the increasing RF sputtering power caused the rise in the residual stress. In addition, the increase in the deposition temperature caused an improvement in the arrangement of the crystals, which was attributed to the decrease in crystal defects.

Interfacial Profiling of MicroRNAs at Patterned Nanogaps for an Integrated Microfluidic-SERS Liquid Biopsy.

A versatile microfluidic-SERS barcoding system is developed for sensitive and multiplexed imaging of circulating microRNAs through interfacial probing of encoded nanorod aggregates at diverse patterned nanogaps. The use of a single-layer, vertically oriented nanorod array creates a plasmonic coupling-based electromagnetic field with enormously enhanced Raman outputs. The introduction of the herringbone micromixer with circulated microflow sampling accelerates the hybridization and capture of nanorod aggregates on the plasmonic substrate. The method is able to achieve ideal sensitivities at subfemtomolar levels for four miRNAs, with multiplexed assay capability for an integrated liquid biopsy. The on-chip digital profiling of serum miRNAs in mapping and barcoding formats enable both clear discrimination of untreated cancer patients from the healthy cohort and precise classification of tumor stages, metastatic conditions, and subtypes, with an overall accuracy of 94%. The SERS-based microfluidic barcoding system therefore holds great promise in early cancer screening, diagnosis, and prognosis.

Nanorod reassembling on a sprayed SERS substrate under confined evaporation inducing ultrasensitive TPhT detection

Triphenyltin is an estrogen like pollutant that poses significant environmental threats due to its highly accumulative toxicity. To improve regulation, a fast and sensitive detection method is urgently needed. SERS can capture fingerprint information and is capable of trace detection, making it an ideal solution. Here, we present a sprayed substrate comprised of lightconfining structures and gold nanorod assemblies that are easy to prepare, low-cost, and can form dense hotspots under confined evaporation. The substrates are three-layered: initially, a gold nanorod layer is sprayed as a support, then sputter Ag film on the surface to form a lightconfining structure, followed by another gold nanorod layer sprayed on the Ag film. The coupling of nanorod assembly with lightconfining Ag films leads to 10-fold sensitivity. In addition, sample droplet evaporation in a limited area called confined evaporation contributes to nanorod migration and reassembly on the corner of the substrate, enhancing analytes absorption, and substantially lowered the detection limits. By systematically evaluating the substrate performance, we were able to obtain an average enhancement factor of 3.31 × 106. After confined evaporation, the detection limit reached 10−18 M for R6G and for triphenyltin, it achieved 10−9 M. This novel method represents a significant advancement toward SERS application in detecting trace pollutants.

Dual-Responsive Fe3O4@Polyaniline Chiral Superstructures for Information Encryption.

Incorporating stimuli-responsive mechanisms into chiral assemblies of nanostructures offers numerous opportunities to create optical materials capable of dynamically modulating their chiroptical properties. In this study, we demonstrate the formation of chiral superstructures by assembling Fe3O4@polyaniline hybrid nanorods by using a gradient magnetic field. The resulting superstructures exhibit a dual response to changes in both the magnetic field and solution pH, enabling dynamic regulation of the position, intensity, and sign of its circular dichroism peaks. Such responsiveness allows for convenient control over the optical rotatory dispersion properties of the assemblies, which are further integrated into the design of a chiroptical switch that can display various colors and patterns when illuminated with light of different wavelengths and polarization states. Finally, an optical information encryption system is constructed through the controlled assembly of the hybrid nanorods to showcase the potential opportunities for practical applications brought by the resulting responsive chiral superstructures.

Influence of l-Dopa adsorption time and concentration on Au nanorods aggregation for SERS quantitative analysis

Levodopa (l-Dopa) is an important neurotransmitter from the amino acid family and is also associated with the treatment of Parkinson's disease. The obtention of the l-Dopa SERS signal in colloid is a challenge due to the zwitterionic charge promoting repulsion from nanoparticle surface and leading to poor or not active SERS signal. In this work, SERS signal of l-Dopa was successfully obtained using Au nanorods (AuNRs) covered with a cationic lipid bilayer and using the 785 nm laser line. The UV–Vis extinction, dynamic light scattering, and zeta potential results indicated an influence of l-Dopa adsorption time and l-Dopa concentration on AuNRs aggregation. The SERS signal followed this time dependence, being the characteristic l-Dopa band observed only after 30 min. The l-Dopa quantitative analysis using the standard addition method presented a linear SERS signal at 439 cm−1 with a limit of detection of 6.7 × 10−7 mol L−1 for peak intensity, and 7.9 × 10−7 mol L−1 for band integrated area.

3D modeling of in vivo MRI-guided nano-photothermal therapy mediated by magneto-plasmonic nanohybrids

BackgroundNano-photothermal therapy (NPTT) has gained wide attention in cancer treatment due to its high efficiency and selective treatment strategy. The biggest challenges in the clinical application are the lack of (i) a reliable platform for mapping the thermal dose and (ii) efficient photothermal agents (PTAs). This study developed a 3D treatment planning for NPTT to reduce the uncertainty of treatment procedures, based on our synthesized nanohybrid.MethodsThis study aimed to develop a three-dimensional finite element method (FEM) model for in vivo NPTT in mice using magneto-plasmonic nanohybrids, which are complex assemblies of superparamagnetic iron oxide nanoparticles and gold nanorods. The model was based on Pennes' bio-heat equation and utilized a geometrically correct mice whole-body. CT26 colon tumor-bearing BALB/c mice were injected with nanohybrids and imaged using MRI (3 Tesla) before and after injection. MR images were segmented, and STereoLithography (STL) files of mice bodies and nanohybrid distribution in the tumor were established to create a realistic geometry for the model. The accuracy of the temperature predictions was validated by using an infrared (IR) camera.ResultsThe photothermal conversion efficiency of the nanohybrids was experimentally determined to be approximately 30%. The intratumoral (IT) injection group showed the highest temperature increase, with a maximum of 17 °C observed at the hottest point on the surface of the tumor-bearing mice for 300 s of laser exposure at a power density of 1.4 W/cm2. Furthermore, the highest level of tissue damage, with a maximum value of Ω = 0.4, was observed in the IT injection group, as determined through a simulation study.ConclusionsOur synthesized nanohybrid shows potential as an effective agent for MRI-guided NPTT. The developed model accurately predicted temperature distributions and tissue damage in the tumor. However, the current temperature validation method, which relies on limited 2D measurements, may be too lenient. Further refinement is necessary to improve validation. Nevertheless, the presented FEM model holds great promise for clinical NPTT treatment planning.

Small Molecules Mediated the Chirality Transfer in Self-Assembled Nanocomposites with Strong Circularly Polarized Luminescence.

Manipulation of the chirality at all scales has a cross-disciplinary importance and may address key challenges at the heart of physical sciences. One critical question in this field is how the chirality of one entity can be transferred to the asymmetry of another entity. Here, we find that small molecules play a crucial role in the chirality transfer from chiral organic molecules to CdSe/CdS nanorods, where the handedness of the nanorod assemblies either agrees or disagrees with that of the molecular assemblies, leading to the positive or inverse chirality transfer. The assembling mode of nanorods on the molecular assemblies, where the nanorods are either lying or standing, is closely associated with the handedness of the nanorod assemblies, resulting in opposite chirality. Furthermore, we have found that circularly polarized emission from chiral assemblies of nanorods is dependent on molecular additives. The promoted luminescence dissymmetry factor (glum) of the nanocomposites with a high value of ∼0.3 could be attained under optimal conditions.

Effect of Polymeric Ligand Grafting Region on Confined Assembly of Gold Nanorods in cylindrical nanopores.

The grafting region of polymeric ligands exhibit a significant influence on the assembly behavior of polymer tethered gold nanorods (AuNRs) in confined space. In this work, the effect of core size, molecular weight and grafting region of ligands on the assembly structure in cylindrical nanopores was investigated. It is found that polystyrene end-tethered AuNR (AuNR@End-PS) exhibits a dumbbell-like shape, while the AuNR with PS tethered on the entire surface (AuNR@Full-PS) shows a rod-like morphology that gradually transforms into a spherical shape as the molecular weight increases. AuNR@End-PS is affected by the special steric hindrance at both ends, and prefers to form special structures such as inclination arrangement, whereas AuNR@Full-PS prefers to be arranged shoulder-to-shoulder in a chain-like assembly. The confinement effect was studied as well by varying the diameter of pores. The results show that the nanoparticles prefer to arrange into a regular and ordered assembly structure in the strong confinement spaces. Under the synergy of confined spaces and ligands at both ends, the AuNRs@End-PS are more likely to form a tilted order-assembly structure. The results of this work could provide new ideas and guidance for the preparation of ordered assembly of AuNRs with novel structures.

Iron‐incorporated Ni4Mo Hierarchical Nanorod Arrays for Promoted Electrocatalytic Oxygen Evolution Reaction

AbstractIt is great significance to explore rich and efficient transition metal‐based electrocatalysts for the electrolysis of water. Nickel‐molybdenum (Ni−Mo) alloy is considering as one of the most promising electrocatalysts for hydrogen evolution reactions (HER) in alkaline electrolyte, but its catalytic performance for oxygen evolution reaction (OER) is still unsatisfactory. Heteroatom doping by interfering with the electronic structure of the catalysts has been considered to be an effective method to enhance electrocatalytic activities. Herein, we report the synthesis of iron (Fe)‐doped Ni4Mo intermetallic compound with hierarchical nanorod assemblies on nickel foam by hydrothermal and hydrogen‐induced methods, which significantly improve the catalytic performance for OER. The as‐prepared Fe−Ni4Mo/NF shows remarkable activity for alkaline oxygen evolution reaction, requiring only a low overpotential of 271 mV to achieve a current density of 100 mA cm−2. Such performance is significantly better than that of pristine Ni4Mo/NF with overpotential of 400 mV. Density functional theory (DFT) calculation shows that the addition of Fe can significantly reduce the adsorption energy of the intermediate on the catalyst surface, thus facilitating the OER activity. Moreover, an alkaline electrolyzer composed of Fe−Ni4Mo/NF as cathode and anode can provide 10 mA cm−2 current density with only 1.48 V extremely low voltage, and shows excellent long‐term durability of 24 h. These results highlight a heteroatom incorporation engineering strategy into metallic alloys for electrochemical applications.

3D Printing‐Assisted Self‐Assembly to Bio‐Inspired Bouligand Nanostructures (Small 19/2023)

Bio-Inspired Bouligand Nanostructures In article number 2206847, Monirosadat Sadati and co-workers present a 3D printing method for replicating intricate self-assemblies in biomaterials. Using the flow in the 3D printer's nozzle, helical assemblies of cellulose nanorods are arranged in a uniform and long-range concentric pattern that resembles Bouligand nanostructures found in mammalian cortical bones. By incorporating embedded printing and in-situ photo-polymerization techniques, Bouligand-type nanostructures are immobilized in self-supporting 3D constructs.

Regulation of Chirality Transfer and Amplification from Chiral Cysteine to Gold Nanorod Assemblies using Nonchiral Surface Ligands

AbstractOwing to large chiroptical activity and high tunability, dynamic chiral superstructures of plasmonic nanoparticles have attracted great attention. A useful strategy has been developed to obtain strong plasmonic chiroptical responses (plasmonic circular dichroism, PCD) by adding small chiral thiols on achiral side‐by‐side assemblies of gold nanorods (AuNRs). Despite the critical role of chiral thiols, the impact of achiral surface ligands is yet to be revealed. Herein, the effects of achiral surface ligands are systematically investigated from the viewpoints of counter ion, hydrocarbon chain length, and head group of surfactants. A well‐packed ligand shell is found to be beneficial for the chirality transfer and amplification from adsorbed chiral thiols to rod assemblies. The PCD temperature amplification effect is observed by using different surfactant ligands and reflects the energy cost of rod‐twisting in the assemblies. This study deepens the understanding of chiral plasmonic assemblies driven by small chiral molecules and provides rational design to fabricate such assembly structures.