Aggregation Of Gold Nanoparticles Research Articles

Colorimetric bacteria sensing of Pseudomonas aeruginosa using gold nanoparticle probes

BackgroundDue to the advantages of molecular methods over biochemical methods, the use of molecular methods for diagnosing nosocomial infections such as Pseudomonas can be an appropriate and rapid way to choose the right diagnosis and treatment of infection and prevent further complications caused by the infection. The present article provides a description of the development of a nanoparticle-based detection technique for sensitive and specific deoxyribonucleic acid-based diagnostic of Pseudomonas aeruginosa. Specific thiolated oligonucleotide probes for one of the hypervariable regions of the 16S rDNA gene were designed and applied for colorimetric detection of the bacteria. ResultsThe results of gold nanoprobe-nucleic sequence amplification indicated the probe attached to gold nanoparticles in the presence of the target deoxyribonucleic acid. It caused aggregation of gold nanoparticles in the form of connected networks resulting in color change and indicating the presence of the target molecule in the sample, which could be observed by the naked eye. In addition, the wavelength of gold nanoparticles changed from 524 to 558 nm. Multiplex polymerase chain reactions were performed using four specific genes of Pseudomonas aeruginosa (oprL, oprI, toxA, and 16S rDNA). The sensitivity and specificity of the two techniques were assessed. According to the observations, the specificity of both techniques was 100%, and the sensitivity was 0.5 ng/μL and 0.01 ng/μL of genomic deoxyribonucleic acid for multiplex polymerase chain reaction and colorimetric assay, respectively. ConclusionsThe sensitivity of colorimetric detection was about 50 times higher than the polymerase chain reaction using the 16SrDNA gene. The results of our study proved to be highly specific with potential use for early detection of Pseudomonas aeruginosa.

Rapid and naked-eye colorimetric detection of ultra trace sumatriptan in drinking water, saliva, and human urine samples based on the aggregation of gold nanoparticles

In this study, the determination of sumatriptan (SUM) was performed using a simple, rapid, and precise colorimetric method based on the surface plasmon resonance (SPR) feature of gold nanoparticles (AuNPs). By adding SUM, the aggregation was observed in AuNPs with red-to-blue color shifts. The size distribution of NPs was estimated before and after adding SUM via dynamic light scattering (DLS), which was found to be 15.34 and 97.45 nm, respectively. Characterization of AuNPs, SUM, and AuNPs in combination with SUM was investigated using transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Examining the effect of pH, the volume of buffer, the concentration of AuNPs, interaction time, and ionic strength revealed that their optimal values were 6, 100 μL, 5 μM, 14 min, and 12 μg L-1, respectively. The suggested method was able to determine the amount of SUM in a linear range of 10 to 250 μg L-1 with a limit of detection (LOD) and limit of quantification (LOQ) of 0.392 and 1.03 μg L-1, respectively. This approach was successfully applied to determine SUM in drinking water, saliva, and human urine samples with relative standard deviations (RSD) lower than 0.03%, 0.3%, and 1.0%, respectively.

A visual colorimetric assay based on phage T156 and gold nanoparticles for the sensitive detection of Salmonella in lettuce

In this study, a new technique was developed for visual and precise identification of Salmonella using phage T156-mediated aggregation of gold nanoparticles. The phage binds to gold nanoparticles in a dispersed and stable state under high NaCl concentrations. When Salmonella is introduced, the phage specifically recognizes and adsorbs the targeted bacteria, causing the AuNPs to undergo a discoloration reaction resulting in aggregation, which enables Salmonella visualization. The method has a detection range of 3.8 × 101–3.8 × 109 CFU/mL and a limit of detection of 38 CFU/mL and can produce results in approximately 80 min. The technique was also tested on field samples, including spiked lettuce, and was found to be accurate with a recovery rate of 81.0–119.2% and relative standard deviations ranging from 3.3% to 14.7%. Notably, this technique utilizes phages as recognition elements in colorimetric methods, offering simplicity, speed, and the ability to effectively distinguish between live and dead Salmonella. It demonstrates remarkable sensitivity, specificity, and accuracy. Furthermore, it presents a novel avenue for the rapid detection of other pathogenic bacteria.

Real-Time Probing of Melamine-Induced Gold Nanoparticle Aggregation Kinetics via Evanescent-Wave Coupled Cavity Ring-down Spectroscopy.

Insight into the aggregation kinetics of gold nanoparticles (GNPs) is critical for developing a colorimetric assay extensively used in chemical and biomolecular sensing. The aggregation of NPs plays a significant role in many natural and industrial processes, demanding comprehensive perceptions of the aggregation kinetics at a solid-liquid interface. However, the direct observation of the melamine-induced aggregation process of GNPs in the time-domain still remains a challenge. There is little to no information on the fundamental mechanisms of such kinetics using evanescent waves. Total internal reflection (TIR) has been applied to generate the evanescent field (EF), exploring aggregation kinetics near the solid-liquid interface. Here, we utilized a precise optical cavity-based method, an evanescent-wave coupled cavity ring-down spectroscopy (EW-CRDS), that can probe the melamine-induced aggregation kinetics of GNPs. The key feature of the present method is that the evanescent field generated by TIR illumination harnesses the power of CRDS to study 2D fractals via the collision and attachment of the GNPs and their melamine-induced aggregates at the interfacial region in real-time. This kinetic study reveals a critical point for diffusion-limited aggregation and provides insights into the design and optimization of colorimetric sensors that exploit the aggregation of GNPs. Furthermore, the EW-CRDS is a unique analytical approach that helps to deepen our understanding in probing the real-time aggregation process, detecting the presence of aggregator as compared to UV-vis and dynamic light scattering (DLS) spectroscopy.

Reversible Microscale Assembly of Nanoparticles Driven by the Phase Transition of a Thermotropic Liquid Crystal.

The arrangement of nanoscale building blocks into patterns with microscale periodicity is challenging to achieve via self-assembly processes. Here, we report on the phase-transition-driven collective assembly of gold nanoparticles in a thermotropic liquid crystal. A temperature-induced transition from the isotropic to the nematic phase under anchoring-driven planar alignment leads to the assembly of individual nanometer-sized particles into arrays of micrometer-sized agglomerates, whose size and characteristic spacing can be tuned by varying the cooling rate. Phase field simulations coupling the conserved and nonconserved order parameters exhibit a similar evolution of the morphology as the experimental observations. This fully reversible process offers control over structural order on the microscopic level and is an interesting model system for the programmable and reconfigurable patterning of nanocomposites with access to micrometer-sized periodicities.

Quaternization-Assisted Assembly of Polymer-Tethered Gold Nanoparticles into Superlattices with a Tunable Structure

Programmable organization of functional inorganic nanoparticles (NPs) into well-defined hierarchical superstructures has raised considerable concern due to the enhanced magnetic, electronic, and optical properties arising from the strong plasmonic coupling effect. However, the spontaneous self-assembly of inorganic NPs into uniform superlattices with the desired or tunable shape remains a formidable challenge. Herein, we report the quaternization-assisted hierarchical assembly of gold nanoparticles (AuNPs) tethered with polystyrene (PS) and quaternized poly(2-vinylpyridine) (P2VP) ligands into controllable superstructures in emulsion droplets. The quaternization interaction between bromoalkyl molecular additives (e.g., CnH2n+1Br) and P2VP ligands results in the increase of the hydrophilicity degree of quaternized P2VP ligands and triggers the interfacial instability of emulsion droplets, achieving the continuous transformation of generated superstructures from solid assemblies to hollow colloidosomes and then to the multilayer sheet-like superlattices. Furthermore, the degree of quaternization can be readily tuned by the added content of additives and the length of the alkyl chain, providing a unique and promising approach to prepare contrivable superstructures and functional materials.

Nanoplasmonic Decoration of Sacrificial Bacteria: Directing Interparticle Coupling Toward Multiplex Analysis of Antiseptic Alcohols

Engineering interparticle plasmon coupling through controlling the assembly of plasmonic NPs onto the surface of sacrificial substrates is quite promising for establishing inherently absent selectivity or sensitivity toward a particular analyte. Herein, we introduce a robust sensor array strategy based upon the assembly of gold nanoparticles (AuNPs) on the cysteamine-modified surface of two Gram-positive probiotic bacteria, i.e., Lactobacillus reuteri (LBR) and Bifidobacterium lactis (BFL), as potential sacrificial substrates, for discrimination and quantification of antiseptic alcohols (AAs) comprising methanol, ethanol, and isopropanol. In fact, the damage of the bacterial membrane upon exposure to the foregoing alcohols inhibits the assembly of AuNPs, thereby precluding color variations from red to blue. Unequal resistance of the bacterial membranes against damage by the alcohols underlies independent response patterns for each analyte. The supervised classification of visible spectra and RGB data by Linear Discriminant Analysis (LDA) revealed the remarkable potential of the designed sensor array in differentiating single-component and multicomponent samples of AAs. Moreover, the Partial Least Square Regression (PLSR) technique exhibited excellent applicability to multivariate calibration of both spectral and RGB data. The intriguing attributes of the implemented approach not only hold great potential in the authentication and quality assessment of alcohol-based products but open up a new prospect for deployment of sacrificial substrates in the design of interparticle coupling-based sensors.

One-pot rapid and ultrasensitive sensing strategy for endocrine disruptor bisphenol A using cationic AuNPs and aptamer

A novel Cys-Lys-Arg-Lys-Arg-Lys-Arg peptide-capped cationic gold nanoparticles were synthesized by the utilization of microwave irradiation. The prepared gold nanoparticles along with bisphenol A aptamer have been employed for the development of a colorimetric aptasensor for bisphenol A based on the electrostatic interactions among them and the specific recognizing ability of aptamer. The presence of bisphenol A initiated the formation of bisphenol A-aptamer complex, thus added gold nanoparticles remain stable in the reaction mixture, and corresponding to this very less charge occurs into the surface plasmon resonance peak. Depending on the concentration of bisphenol A, a particular amount of free aptamer was present in the reaction which causes the aggregation of gold nanoparticles, and corresponding to this bisphenol A was detected. Under the optimized conditions, bisphenol A concentrations from 200 to 1000 pM exhibited a good linear correlation (R2 = 0.99581) with a detection limit of 87.04 pM in 7 min. The aptameric ability was studied by replacing the bisphenol A with its other analogues such as bisphenol B, bisphenol F, phenol, and benzophenone, and also in the mixture of all these. The obtained results have shown that the developed aptasensor exhibited five-fold selectivity towards bisphenol A as compared to its other analogues. Utilization of the proposed aptasensor was carried out in mineral water, tap water, and packed juice where the percentage recovery was found from 96.61 to 101.23. Thus, the developed colorimetric aptasensor exhibits excellent advantages of rapidity, simplicity, cost-effectiveness, high selectivity, and sensitivity for bisphenol A.

Simultaneous Sensing of Cd(II), Pb(II), and Cu(II) Using Gold Nanoparticle-Modified APTES-Functionalized Indium Tin Oxide Electrode: Effect of APTES Concentration.

In this work, indium tin oxide (ITO) electrodes were functionalized with varying 3-aminopropyltriethoxysilane (APTES) concentration percentages (0.5, 0.75, 1.0, and 2.0 wt %) to obtain the optimum conditions for the assembly of the as-synthesized gold nanoparticles (AuNPs). The AuNP coverage, wettability, and electrochemical performance of the modified electrodes were evaluated. The AuNP/0.75% APTES-ITO-modified electrode exhibited uniform coverage of AuNPs and high electrochemical performance for the simultaneous detection of Cd(II), Pb(II), and Cu(II) ions. Under the optimum conditions, the AuNP/0.75% APTES-ITO-modified electrode showed a linear detection range of 5-120 ppb and limit of detection of 0.73, 0.90, and 0.49 ppb for the simultaneous detection of Cd(II), Pb(II), and Cu(II) ions, respectively, via square wave anodic stripping voltammetry. The modified electrode demonstrated good anti-interference toward other heavy metal ions, good reproducibility, and suitability for application in environmental sample analysis.

Polymer-Grafted, Gold Nanoparticle-Based Nano-Capsules as Reversible Colorimetric Tensile Strain Sensors.

Colloidal colorimetric microsensors enable the in-situ detection of mechanical strains within materials. Enhancing the sensitivity of these sensors to small scale deformation while enabling reversibility of the sensing capability would expand their utility in applications including biosensing and chemical sensing. In this study,weintroduce the synthesis of colloidal colorimetric nano-sensors using a simple and readily scalable fabrication method. Colloidal nano sensors are prepared by emulsion-templated assembly of polymer-grafted gold nanoparticles (AuNP). To direct the adsorption of AuNP to the oil-water interface of emulsion droplets, AuNP (≈11nm) are functionalized with thiol-terminated polystyrene (PS, Mn =11k). These PS-grafted gold nanoparticles are suspended in toluene and subsequently emulsified to form droplets with a diameter of ≈30µm. By evaporating the solvent of the oil-inwater emulsion, weform nanocapsules (AuNC) (diameter < 1µm) decorated by PS-grafted AuNP. To test mechanical sensing, the AuNC are embedded in an elastomer matrix. The addition of a plasticizer reduces the glass transition temperature of the PS brushes, and in turn imparts reversible deformability to the AuNC. The plasmonic peak of the AuNC shifts towards lower wavelengths upon application of uniaxial tensile tension, indicating increased inter-nanoparticle distance, and reverts back as the tension is released.

Plasmonic gold nanoparticles aggregate based on charge neutralization for the convenient detection of fumonisin B1 by colorimetry and SERS

A novel charge neutralization strategy with positively charged SYBR Green I was used for the convenient detection of fumonisin B1. In the absence of the fumonisin B1, the aggregation of gold nanoparticles would appear in less than 2 min. In the presence of the fumonisin B1, the positive charge of SYBR Green I was neutralized by the negatively charged fumonisin B1. As a result, the aggregation of gold nanoparticles could not be achieved. Based on the charge neutralization strategy, the colorimetry and surface enhanced Raman spectroscopy (SERS) dual-channel methods were developed for the detection of fumonisin B1 in corn. The naked eye sensitivity was 500 μg kg−1 in the colorimetric method. The limit of detection was 54.86 μg kg−1 in the SERS method. The developed methods had a high stability (coefficient of variation <8.3%).

Fully Aqueous Self-Assembly of a Gold-Nanoparticle-Based Pathogen Sensor.

Surface plasmon resonance (SPR) is a very sensitive measure of biomolecular interactions but is generally too expensive for routine analysis of clinical samples. Here we demonstrate the simplified formation of virus-detecting gold nanoparticle (AuNP) assemblies on glass using only aqueous buffers at room temperature. The AuNP assembled on silanized glass and displayed a distinctive absorbance peak due to the localized SPR (LSPR) response of the AuNPs. Next, assembly of a protein engineering scaffold was followed using LSPR and a sensitive neutron reflectometry approach, which measured the formation and structure of the biological layer on the spherical AuNP. Finally, the assembly and function of an artificial flu sensor layer consisting of an in vitro-selected single-chain antibody (scFv)-membrane protein fusion was followed using the LSPR response of AuNPs within glass capillaries. In vitro selection avoids the need for separate animal-derived antibodies and allows for the rapid production of low-cost sensor proteins. This work demonstrates a simple approach to forming oriented arrays of protein sensors on nanostructured surfaces that uses (i) an easily assembled AuNP silane layer, (ii) self-assembly of an oriented protein layer on AuNPs, and (iii) simple highly specific artificial receptor proteins.

MINI REVIEW: PENGEMBANGAN BIOSENSOR KOLORIMETRI BERBASIS AGREGASI NANOPARTIKEL EMAS

&lt;p class="abstrak"&gt;Gold nanoparticle (AuNP) is a material commonly used in colorimetric detection for biological sensors due to its low production cost, simplicity, and ease use. AuNP is known to generate different colors depending on the particle aggregation level. In the last two decades, changes in AuNP aggregation status have become the basis for developing a sensor to detect analytes in the sample. The solution color changes could be observed without sophisticated equipment, allowing ,more straightforward interpretation of the detection result. This review focuses on developing AuNP aggregation-based colorimetric tests for detecting various biological analytes. It discusses multiple mechanisms, strategies, functionalization, the latest research, and perspectives of AuNP use in colorimetric detection, which could be considered for future biosensor development. The concept of colloidal gold nanoparticle aggregation and stabilization is emphasized in this review. &lt;/p&gt;

Robust Rules for Optimal Colorimetric Sensing Based on Gold Nanoparticle Aggregation.

Spurred by outstanding optical properties, chemical stability, and facile bioconjugation, plasmonic metals have become the first-choice materials for optical signal transducers in biosensing. While the design rules for surface-based plasmonic sensors are well-established and commercialized, there is limited knowledge of the design of sensors based on nanoparticle aggregation. The reason is the lack of control over the interparticle distances, number of nanoparticles per cluster, or multiple mutual orientations during aggregation events, blurring the threshold between positive and negative readout. Here we identify the geometrical parameters (size, shape, and interparticle distance) that allow for maximizing the color difference upon nanoparticle clustering. Finding the optimal structural parameters will provide a fast and reliable means of readout, including unaided eye inspection or computer vision.

The charge transfer pathway of g-C3N4 decorated Au/Bi(VO4) composites for highly efficient photocatalytic hydrogen evolution

In this report, a novel g-C3N4/Au/BiVO4 photocatalyst has been prepared successfully by assembling gold nanoparticles on the interface of super-thin porous g-C3N4 and BiVO4, which exhibits outstanding photocatalytic performance toward hydrogen evolution and durable stability in the absence of cocatalyst. FESEM micrograph analysis suggested that the intimate contact between Au, BiVO4, and g-C3N4 in the as-developed photocatalyst allows a smooth migration and separation of photogenerated charge carriers. In addition, the XRD, EDX and XPS analysis further confirmed the successful formation of the as-prepared g-C3N4/Au/BiVO4 photocatalyst. The photocatalytic hydrogen production activity of the developed photocatalyst was evaluated under visible-light irradiation (λ > 420 nm) using methanol as a sacrificial reagent. By optimizing the 5-CN/Au/BiVO4 composite shows the highest H2 evolution rate (2986 μmolg−1h−1), which is 15 times higher than that of g-C3N4 (199 μmolg−1h−1) and 10 time better than bare BiVO4 (297 μmolg−1h−1). The enhancement in photocatalytic activity is attributed to efficient separation of the photoexcited charges due to the anisotropic junction in the g-C3N4/Au/BiVO4 system. The enhancement in photocatalytic activity is attributed to efficient separation of the photoexcited charges due to the anisotropic junction in the g-C3N4/Au/BiVO4 system.

Single-Particle Hyperspectral Imaging for Monitoring of Gold Nanoparticle Aggregates in Macrophages.

Gold nanoparticles (Au NPs) have a promising future in the diagnosis and therapy of diseases owing to their unique photoelectric properties. In the body, monodisperse Au NPs may aggregate extracellularly and intracellularly, which influences their in vivo fate and physiological effects. However, due to the lack of a rapid, precise, and high throughput method for characterizing Au NP aggregates, the intricate aggregation process of Au NPs has not yet been fully understood. In order to overcome this obstacle, we develop a single-particle hyperspectral imaging method to identify Au NP aggregates, making use of the outstanding plasmonic properties of monodisperse and aggregated Au NPs. This method enables us to monitor the dynamic formation of Au NP aggregates in biological mediums and cells. Further single-particle hyperspectral imaging analysis reveals that following exposure to 100 nm Au NPs, the formation of Au NP aggregates in macrophages highly depends on exposure dosage and is less affected by exposure duration. In particular, surface coating, including PEGylation and protein corona, can considerably mitigate the intracellular aggregation of Au NPs. Our findings highlight that single-particle hyperspectral imaging is an efficient way for studying how Au NPs aggregate in biological scenarios.

Insight into the Lysozyme-Induced Aggregation of Aromatic Amino Acid-Functionalized Gold Nanoparticles: Impact of the Protein Conjugation and Lipid Corona on the Aggregation Phenomena.

The aggregation and subsequent precipitation of gold nanoparticles (Au NPs) in the presence of protein molecules restrict the usefulness of NPs in biomedical applications. Till now, the influence of different properties of Au NPs (size, surface charge, surface coatings) and proteins (surface charge, chemical modification, folded and unfolded states) and pH and ionic strength of the solution on the aggregation of both Au NPs and proteins has been thoroughly discussed in the literature. However, the underlying different mechanistic pathways of the protein concentration-dependent aggregation of both Au NPs and proteins are poorly understood. The impact of the lipid corona on the protein-induced Au NP aggregation has remained an unresolved issue. In this context, we investigate the interaction of the negatively charged aromatic amino acid (phenylalanine and tyrosine)-functionalized gold nanoparticles (Au-AA NPs) with the positively charged globular protein lysozyme at different protein concentrations and compare the results with those of conventional citrate-functionalized Au NPs (Au-Cit NPs). Next, we conjugate lipids and proteins to Au NPs to impede the aggregation of Au NPs induced by the lysozyme. Our results reveal that the aggregation mechanism of the Au-AA NPs is distinctly different at low and high protein concentrations with the uniqueness of the Au-AA NPs over the Au-Cit NPs. Furthermore, we find that human serum albumin (HSA) protein-conjugated Au-AA and Au-Cit NPs are more effective in preventing the lysozyme-induced Au NP aggregation than bovine serum albumin (BSA)-conjugated Au NPs. For the first time, we also report the significant role of "hard" and "soft" lipid coronas in the aggregation of amino acid (phenylalanine)-functionalized gold nanoparticles in the presence of lysozyme protein.

Ethanol and NaCl-Induced Gold Nanoparticle Aggregation Toxicity toward DNA Investigated with a DNA/GCE Biosensor

Engineered nanomaterials are becoming increasingly common in commercial and consumer products and pose a serious toxicological threat. Exposure of human organisms to nanomaterials can occur by inhalation, oral intake, or dermal transport. Together with the consumption of alcohol in the physiological environment of the body containing NaCl, this has raised concerns about the potentially harmful effects of ingested nanomaterials on human health. Although gold nanoparticles (AuNPs) exhibit great potential for various biomedical applications, there is some inconsistency in the case of the unambiguous genotoxicity of AuNPs due to differences in their shape, size, solubility, and exposure time. A DNA/GCE (DNA/glassy carbon electrode) biosensor was used to study ethanol (EtOH) and NaCl-induced gold nanoparticle aggregation genotoxicity under UV light in this study. The genotoxic effect of dispersed and aggregated negatively charged gold nanoparticles AuNP1 (8 nm) and AuNP2 (30 nm) toward salmon sperm double-stranded dsDNA was monitored by cyclic and square-wave voltammetry (CV, SWV). Electrochemical impedance spectroscopy (EIS) was used for a surface study of the biosensor. The aggregation of AuNPs was monitored by UV-vis spectroscopy. AuNP1 aggregates formed by 30% v/v EtOH and 0.15 mol·L-1 NaCl caused the greatest damage to the biosensor DNA layer.

Interfacial Colloidal Self-Assembly for Functional Materials

ConspectusSelf-assembly bridges nanoscale and microscale colloidal particles into macroscale functional materials. In particular, self-assembly processes occurring at the liquid/liquid or solid/liquid/air interfaces hold great promise in constructing large-scale two- or three-dimensional (2D or 3D) architectures. Interaction of colloidal particles in the assemblies leads to emergent collective properties not found in individual building blocks, offering a much larger parameter space to tune the material properties. Interfacial self-assembly methods are rapid, cost-effective, scalable, and compatible with existing fabrication technologies, thus promoting widespread interest in a broad range of research fields.Surface chemistry of nanoparticles plays a predominant role in driving the self-assembly of nanoparticles at water/oil interfaces. Amphiphilic nanoparticles coated with mixed polymer brushes or mussel-inspired polydopamine were demonstrated to self-assemble into closely packed thin films, enabling diverse applications from electrochemical sensors and catalysis to surface-enhanced optical properties. Interfacial assemblies of amphiphilic gold nanoparticles were integrated with graphene paper to obtain flexible electrodes in a modular approach. The robust, biocompatible electrodes with exceptional electrocatalytic activities showed excellent sensitivity and reproducibility in biosensing. Recyclable catalysts were prepared by transferring monolayer assemblies of polydopamine-coated nanocatalysts to both hydrophilic and hydrophobic substrates. The immobilized catalysts were easily recovered and recycled without loss of catalytic activity. Plasmonic nanoparticles were self-assembled into a plasmonic substrate for surface-enhanced Raman scattering, metal-enhanced fluorescence, and modulated fluorescence resonance energy transfer (FRET). Strong Raman enhancement was accomplished by rationally directing the Raman probes to the electromagnetic hotspots. Optimal enhancement of fluorescence and FRET was realized by precisely controlling the spacing between the metal surface and the fluorophores and tuning the surface plasmon resonance wavelength of the self-assembled substrate to match the optical properties of the fluorescent dye.At liquid/solid interfaces, infiltration-assisted (IFAST) colloidal self-assembly introduces liquid infiltration in the substrate as a new factor to control the degree of order of the colloidal assemblies. The strong infiltration flow leads to the formation of amorphous colloidal arrays that display noniridescent structural colors. This method is compatible with a broad range of colloidal particle inks, and any solid substrate that is permeable to dispersing liquids but particle-excluding is suitable for IFAST colloidal assembly. Therefore, the IFAST technology offers rapid, scalable fabrication of structural color patterns of diverse colloidal particles with full-spectrum coverage and unprecedented flexibility. Metal-organic framework particles with either spherical or polyhedral morphology were used as ink particles in the Mayer rod coating on wettability patterned photopapers, leading to amorphous photonic structures with vapor-responsive colors. Anticounterfeiting labels have also been developed based on the complex optical features encoded in the photonic structures.Interfacial colloidal self-assembly at the water/oil interface and IFAST assembly at the solid/liquid/air interface have proven to be versatile fabrication platforms to produce functional materials with well-defined properties for diverse applications. These platform technologies are promising in the manufacturing of value-added functional materials.

Photoexcited Plasmon-Driven Ultrafast Dynamics of the Adsorbate Probed by Femtosecond Time-Resolved Surface-Enhanced Time-Domain Raman Spectroscopy.

Metal nanoparticles have high potential in light-harvesting applications by transferring absorbed photon energy to the adsorbates. However, photoexcited plasmon-driven ultrafast dynamics of the adsorbate on metal nanoparticles have not been clearly understood. We studied ultrafast plasmon-driven processes of trans-1,2-bis(4-pyridyl)ethylene (BPE) adsorbed on gold nanoparticle assemblies (GNAs) using time-resolved surface-enhanced impulsive stimulated Raman spectroscopy (TR-SE-ISRS). After photoexciting the localized surface plasmon resonance (LSPR) band of the GNAs, we measured femtosecond time-resolved surface-enhanced Raman spectra of the adsorbate, which exhibited transient bleach in the Raman signal and following biphasic recovery that proceeds on the time scale of a few tens of picoseconds. The TR-SE-ISRS data were analyzed with singular value decomposition, and the obtained species-associated Raman spectra indicated that photoexcitation of the LSPR band alters chemical interaction between BPE and the GNAs on an ultrafast time scale; initial steady-state BPE is recovered through a precursor state that has weaker interaction with the GNAs.