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It is a challenge to determine selenium in acid aqueous for environmental monitoring and selenium-rich agricultural diagnosis. Herein, we developed a novel localized surface plasmon resonance (LSPR) sensor to detect Se(IV) ions based on the extraordinary laterals etching of gold nanorods (AuNRs). The etching started from the laterals in the low amount of Se(IV) ions, and accompanied by an apparent red shift of the longitudinal plasmon band (LPB), and then transformed to the tips etching with the upward of Se(IV) ions, the LPB band immediately shifted to the shorter wavelength. The red shift change (Δλ) of LPB band was utilized to quantitative analysis instead of blue shift or absorbance intensity, which gave a high selectivity for the proposed sensor. More importantly, this sensor could be performed in 0.1 mol/L of HCl solution, which achieved the seamlessly jointing with the pretreatment of complex samples, without time-consuming pH adjustment.Successful selenium detection was demonstrated in complex soybean samples that collected from the maturity after spraying organic chelated selenium at full flower period. The sensor provided a promising way to monitor and diagnose selenium in complex environmental samples and selenium-rich crops., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Lipopolysaccharide (LPS), as the major component of the outer membrane of Gram-negative bacteria, can trigger a variety of biological effects such as sepsis, septic shock, and even multiorgan failure. Herein, we developed a near-infrared-fluorescent probe for fluorescent turn-on analysis of LPS based on plasmon-enhanced fluorescence (PEF). Gold nanorods (Au NRs) modified polyethylene glycol (PEG) was used as PEF materials. Au NRs were prepared with different longitudinal surface plasmon resonance (LSPR), and their fluorescence enhancement was investigated. Three kinds of molecular weights (1000, 5000, and 10000) of polyethylene glycol (PEG) were employed to control the distance between the Au NRs and the fluorescence substances of cyanine 7 (Cy7). Experimental analysis showed that the enhancement was related to the spectral overlap between the plasmon resonance of Au NRs and the extinction/emission of fluorophore. The three-dimensional finite-difference time-domain (3D-FDTD) simulation further revealed that the enhancement was caused by local electric field enhancement. Furthermore, the probe was used for the ultrasensitive analysis of LPS with a detection limit of 3.85 ng/mL and could quickly distinguish the Gram-negative bacterium- Escherichia coli ( E. coli ) (with LPS in the membrane) from Gram-positive bacterium- Staphylococcus aureus ( S. aureus ) (without LPS), as well as quantitative determination of E. coli with a detection limit of 1.0 × 10 6 cfu/mL. These results suggested that the prepared probe has great potential for biomedical diagnosis and selective detection of LPS from different bacterial strains.

MicroRNAs, as one kind of significant biomarkers, play indispensable roles in the diagnosis and treatment of cancers. Yet, owing to low expression and high sequence homology, high sensitivity and specificity for microRNA detection are greatly challenging. Herein, a sensitive sensing platform with high specificity was developed for microRNA-27a (miRNA-27a) based on the miRNA-27a-triggered chemical etching of gold nanorods to a smaller size, which was accompanied by a significant blue shift and a large decrease of intensity in the localized surface plasmon resonance (LSPR) scattering and remarkable color variability from red to green. When combined with strand displacement reactions as well as liposome signal amplification and transduction, the proposed bioassay presented high selectivity toward miRNA-27a in a dynamic range from 100 fM to 3 pM and a low limit of detection of 16.5 fM (3σ/ k ) by dark-field microscopy. Additionally, the remarkable discrimination of single nucleotide difference suggested superior selectivity and was able to detect miRNA-27a extracted from breast cancer cells. The strategy put forward is universal, presenting amusing application prospects in the early diagnosis of various cancers by adapting the corresponding nucleotide sequences.

A biosensor based on localized surface plasmon resonance (LSPR) was developed to detect the antibody of Mycobacterium tuberculosis using the fusion protein CFP10-ESAT6 as an antigen. To explore the diagnostic potential of the biosensor for tuberculosis (TB), the fusion protein CFP10-ESAT6 was immobilized on gold nanorods (Au NRs) by chemical modification, and the functionalized Au NRs were subsequently incubated with serums collected from TB patients, non-tuberculous pulmonary disease patients or healthy individuals. The change in the LSPR properties of Au NRs from the specific interaction between the antigen and antibody was monitored, and detection of the target antibody was completed based on the proposed biosensor. Serum analysis showed that the sensitivity of the biosensor was 79% and the specificity was 92%. Therefore, the LSPR biosensor is a valuable tool for serodiagnosis of TB., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A simplified approach for the fabrication of localised surface plasmon resonance (LSPR) sensors based on gold nanorods (GNRs) is described and validated in a model immunoassay for the activated leukocyte cell adhesion molecule (ALCAM) cancer biomarker. Towards improving on standard bottom-up LSPR sensor fabrication methodologies, we demonstrate that GNRs bioconjugated with monoclonal antibodies can be readily covalently immobilized onto silanized glass substrates to yield highly sensitive LSPR sensors. To maximise the performance of the proposed sensors, mixed polyethylene glycol adlayers were optimized in regards to the bioconjugation of monoclonal antibodies using the standard carbodiimide chemistry. In the optimal condition, the ALCAM GNR LSPR sensors yielded a sensitivity of 330 nm per refractive index and allowed the detection of the ALCAM antigen concentration down to 15 pM. This simple fabrication method could foster the implementation of LSPR sensors in the immunoassay field., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Although it has been revealed that astrocytes, generally known as star-shaped glial cells, play critical roles in the functions of central nervous system, there have been few efforts to directly modulate their activities and responses. In this study, an optical stimulation strategy for producing intracellular Ca 2+ transients of astrocytes is demonstrated using near-infrared (NIR) light and localized surface plasmon resonance. It is presented that NIR stimulation of micro-second duration combined with gold nanorods (GNRs) efficiently produces stronger Ca 2+ transients of astrocytes, which seems to be associated with a local heat generation by photothermal effects of GNRs. Since the proposed scheme can directly activate astrocytes with a high reliability, it is expected that GNR-mediated NIR stimulation could be utilized to facilitate minimally invasive physiological studies on the astrocyte functions. Photos of intracellular Ca 2+ transient of astrocytes with membrane-bound GNRs after optical stimulation at 30 s., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mycobacterium tuberculosis is a serious global infectious pathogen causing tuberculosis (TB). The development of an easy and sensitive method for the detection of M. tuberculosis is in urgent need due to complex and low specificity of the current assays. Herein, we present a novel method for M. tuberculosis detection based on a sandwich assay via antigen-antibody interaction using silica-coated quantum dots (SiQDs) and gold nanorods (AuNRs). A genetically engineered recombinant antibody (GBP-50B14 and SiBP-8B3) was bound to surfaces of AuNRs and SiQDs respectively, without any surface modification. The antigen-antibody interaction was revealed using M. tuberculosis-specific secretory antigen, Ag85B. Two biocomplexes showed a quenching effect in the presence of the target antigen through a sandwich assay. The assay response was in the range of 1×10 -3 -1×10 -10 μgmL -1 (R=0.969) and the limit of detection for Ag85B was 13.0pgmL -1 . The Ag85B was selectively detected using three different proteins (CFP10, and BSA), and further specifically confirmed by the use of spiked samples. Compared with existing methods, a highly sensitive and selective method for Ag85B-expressing M. tuberculosis detection has been developed for better diagnosis of TB., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Plasmonic photothermal therapy (PPTT) is a cancer therapy in which gold nanorods are injected at the site of a tumor before near-infrared light is transiently applied to the tumor causing localized cell death. Previously, PPTT studies have been carried out on xenograft mice models. Herein, we report a study showing the feasibility of PPTT as applied to natural tumors in the mammary glands of dogs and cats, which more realistically represent their human equivalents at the molecular level. We optimized a regime of three low PPTT doses at 2-week intervals that ablated tumors mainly via apoptosis in 13 natural mammary gland tumors from seven animals. Histopathology, X-ray, blood profiles, and comprehensive examinations were used for both the diagnosis and the evaluation of tumor statuses before and after treatment. Histopathology results showed an obvious reduction in the cancer grade shortly after the first treatment and a complete regression after the third treatment. Blood tests showed no obvious change in liver and kidney functions. Similarly, X-ray diffraction showed no metastasis after 1 year of treatment. In conclusion, our study suggests the feasibility of applying the gold nanorods-PPTT on natural tumors in dogs and cats without any relapse or toxicity effects after 1 year of treatment.

This article investigates the flow injection analysis of mercury (II) ions in tap water samples via surface Plasmon resonance detection. Quantitative analysis of mercury (II) is based on the chemical interaction of metallic mercury with gold nanorods immobilized on a glass substrate. A new flow cell design is presented with the ability to accommodate the detecting substrate in the sample compartment of commercial spectrometers. Two alternatives are here considered for mercury (II) detection, namely stop-flow and continuous flow injection analysis modes. The best limit of detection (2.4 ng mL(-1)) was obtained with the continuous flow injection analysis approach. The accurate determination of mercury (II) ions in samples of unknown composition is demonstrated with a fortified tap water sample., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Printable multi-marker biochips that enable simultaneous quantitative detection of multiple target biomarkers in point-of-care and resource-limited settings are a holy grail in the field of biodiagnostics. However, preserving the functionality of biomolecules, which are routinely employed as recognition elements, during conventional printing approaches remains challenging. In this article, we introduce a simple yet powerful approach, namely plasmonic calligraphy, for realizing multiplexed label-free bioassays. Plasmonic calligraphy involves a regular ballpoint pen filled with biofunctionalized gold nanorods as plasmonic ink for creating isolated test domains on paper substrates. Biofriendly plasmonic calligraphy approach serves as a facile method to miniaturize the test domain size to few mm(2), which significantly improves the sensitivity of the plasmonic biosensor compared to bioplasmonic paper fabricated using immersion approach. Furthermore, plasmonic calligraphy also serves as a simple and efficient means to isolate multiple test domains on a single test strip, which facilitates multiplexed biodetection and multi-marker biochips. Plasmonic calligraphy, which can be potentially automated by implementing with a robotic arm, serves as an alternate path forward to overcome the limitations of conventional ink-jet printing., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this study, gold nanorods (GNRs) and graphene oxide (GO) were used to enhance the sensitivity of wavelength modulation surface plasmon resonance (SPR) biosensor to detect bovine IgG. GNRs were prepared by a method of seed-mediated growth and immobilized on the Au film through 1,6-hexanedithiol by covalent attachment. GO was prepared by a modified Hummers and Offeman's method and can be assembled on the sensor surface through electrostatic interaction with GNRs. Meanwhile, GO was used as a support to immobilize antibody directly. The biosensor based on GNRs/GO sensing membrane exhibits a satisfactory response for bovine IgG in the concentration range of 0.075-40.00 µg mL(-1). For comparison, the biosensor based on 3-mercaptopropinic acid (MPA) and the biosensor based on GNRs/MPA sensing membrane were also studied for the detection of bovine IgG. The biosensor based on MPA shows a response for bovine IgG in the concentration range of 2.50-40.00 µg mL(-1). The biosensor based on GNRs/MPA sensing membrane shows a response for bovine IgG in the concentration range of 0.30-40.00 µg mL(-1). As a result, the biosensor based on GNRs/GO sensing membrane was found to be the most sensitive of the three types of biosensors., (© 2013 Elsevier B.V. All rights reserved.)

Surface plasmon resonance of precious metal gold nanorods can be tuned by controlling the aspect ratio, and they find widespread applications in biotechnology, imaging, sensing, optoelectronics, photonics, and catalysis. Here, a method is proposed for the controlled etching of gold nanorods within mesoporous silica shells by using a certain concentration of H2O2 at room temperature. In the experiments, the amount of HCl is varied to adjust the acidity and/or change the amount of H2O2 to control the speed of corrosion, achieving controllable adjustment of the aspect ratio of the gold nanorods. The extinction spectra show that under the action of H2O2 and HCl, the longitudinal plasmonic resonance of the gold nanorods shifted to shorter wavelengths, and the intensity of the longitudinal plasmonic resonance decreased. The more hydrochloric acid or hydrogen peroxide added, the faster the corrosion rate of the gold nanorods, and the faster the blue shift of the longitudinal plasmonic resonance. In addition, the intensity of the extinction spectra at 320 nm increased linearly versus time, which can also be used to monitor the etching process. By corroding gold nanorods to control the plasmonic resonances, gold nanorods can find broader applications. [ABSTRACT FROM AUTHOR]

Achieving precise spatiotemporal control over the release of proangiogenic factors is crucial for vasculogenesis, the process of de novo blood vessel formation. Although various strategies have been explored, there is still a need to develop cell-laden biomaterials with finely controlled release of proangiogenic factors at specific locations and time points. We report on the developed of a near-infrared (NIR) light-responsive collagen hydrogel comprised of gold nanorods (GNRs)-conjugated liposomes containing proangiogenic growth factors (GFs). We demonstrated that this system enables on-demand dual delivery of GFs at specific sites and over selected time intervals. Liposomes were strategically formulated to encapsulate either platelet-derived growth factor (PDGF) or vascular endothelial growth factor (VEGF), each conjugated to gold nanorods (GNRs) with distinct geometries and surface plasmon resonances at 710 nm (GNR710) and 1064 nm (GNR1064), respectively. Using near infrared (NIR) irradiation and two-photon (2P) luminescence imaging, we successfully demonstrated the independent release of PDGF from GNR710 conjugated liposomes and VEGF from GNR1064-conjugated liposomes. Our imaging data revealed rapid release kinetics, with localized PDGF released in approximately 4 min and VEGF in just 1 and a half minutes following NIR laser irradiation. Importantly, we demonstrated that the release of each GF could be independently triggered using NIR irradiation with the other GF formulation remaining retained within the liposomes. This light-responsive collagen hydrogels holds promise for various applications in regenerative medicine where the establishment of a guided vascular network is essential for the survival and integration of engineered tissues. In this study, we have developed a light-responsive system with gold nanorods (GNRs)-conjugated liposomes in a collagen hydrogel, enabling precise dual delivery of proangiogenic growth factors (GFs) at specific locations and timepoints. Liposomes, containing platelet-derived growth factor (PDGF) or vascular endothelial growth factor (VEGF), release independently under near- infrared irradiation. This approach allows external activation of desired GF release, ensuring high cell viability. Each GF can be triggered independently, retaining the other within the liposomes. Beyond its application in establishing functional vascular networks, this dual delivery system holds promise as a universal platform for delivering various combinations of two or more GFs. [Display omitted] [ABSTRACT FROM AUTHOR]

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 LSPRbased 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. [ABSTRACT FROM AUTHOR]

Simple Summary: Colorectal cancer cells exhibited superior dark-field imaging results in the near-infrared II (NIR-II) wavelength range (900–1880 nm) compared to the visible light region. Subsequently, we synthesized gold nanorods (GNRs) for dark-field scattering imaging of colorectal cancer cells in the NIR-II spectrum. The results demonstrated that imaging with GNRs significantly improved the signal-to-background ratio (SBR) and showed enhanced performance, particularly in the 1425–1475 nm wavelength range. Finally, we conducted dark-field imaging of cell nuclei in the NIR-II range utilizing GNRs for specific labeling of colorectal cancer cell nuclei. The resulting nuclear images were highly accurate in localization and exhibited higher SBR compared to non-specifically-labeled cell imaging. Dark-field microscopy offers several advantages, including high image contrast, minimal cell damage, and the absence of photobleaching of nanoprobes, which make it highly advantageous for cell imaging. The NIR-II window has emerged as a prominent research focus in optical imaging in recent years, with its low autofluorescence background in biological samples and high imaging SBR. In this study, we initially compared dark-field imaging results of colorectal cancer cells in both visible and NIR-II wavelengths, confirming the superior performance of NIR-II imaging. Subsequently, we synthesized gold nanorods with localized surface plasmon resonance (LSPR) absorption peaks in the NIR-II window. After bio-compatible modification, we non-specifically labeled colorectal cancer cells for NIR-II dark-field scattering imaging. The imaging results revealed a sixfold increase in SBR, especially in the 1425–1475 nm wavelength range. Finally, we applied this imaging system to perform dark-field imaging of cell nuclei in the NIR-II region and used GNRs for specific nuclear labeling in colorectal cancer cells. The resulting images exhibited higher SBR than non-specifically-labeled cell imaging, and the probe's labeling was precise, confirming the potential application of this system in photothermal therapy and drug delivery for cancer cells. [ABSTRACT FROM AUTHOR]

Herein, we investigated the photoreduction of silver (Ag) ions on gold nanorods coated with mesoporous silica shell (AuNRs@mSiO2) induced by hot electrons generated in Au via localized surface plasmon resonance (LSPR) excitation. In addition, we investigated chemical interface damping (CID) using pyridine as the adsorbate in single Ag‐coated AuNRs@mSiO2. The Ag deposition caused a blue shift and linewidth broadening of the LSPR peak of the AuNRs@mSiO2. The subsequent chemisorption of pyridine on Ag‐coated AuNRs@mSiO2 resulted in a red shift and additional LSPR linewidth broadening. Finally, we demonstrated real‐time time‐dependent changes in LSPR peak wavelength and linewidth during the sequential processes of hot electron‐mediated Ag deposition and pyridine adsorption on a single AuNR@mSiO2 in a flow cell. Therefore, we provided a deep understanding of hot electron‐triggered Ag coating and CID induced by pyridine adsorption in single AuNRs@mSiO2 coated with Ag. [ABSTRACT FROM AUTHOR]

Synthesizing gold nanorods (AuNRs) by seed‐mediated growth method results in the presence of undesired size and shape particles by‐products occupying 10–90% of the population. In this study, AuNRs are synthesized by the seed‐mediated growth method using cetyltrimethylammonium bromide (CTAB) as a surfactant. AuNRs with redshifted longitudinal localized surface plasmon resonance (LLSPR) peak, localized in the biological "transparency window" (650–1350 nm), are synthesized after optimizing seed solution, silver nitrate solution, and hydrochloric acid solution volumes, based on the published protocols. A two‐step purification method, dialysis followed by centrifugation, is applied to remove excess CTAB and collect LLSPR‐redshifted AuNRs with high rod purity (>90%). CTAB is subsequently exchanged with polyethylene glycol (PEG) to improve AuNRs biocompatibility. PEGylated AuNRs are confirmed innocuous to both SN4741 cells and B16F10 cells by the modified MTT assay and the modified lactate dehydrogenase (LDH) assay up to 1 nm and 24 h incubation. In this study, a combined facile synthesis, purification, and surface functionalization approach is proposed to obtain water‐dispersible monodispersed AuNRs for drug delivery applications. [ABSTRACT FROM AUTHOR]

Low-energy electrons (Auger electrons) can be produced via the interaction of photons with gold atoms in gold nanorods (AuNRs). These electrons are similar to those emitted during the decay of technetium-99m (99mTc), a radioactive nuclide widely used for diagnostics in nuclear medicine. Auger and internal conversion (IC) electron emitters appropriately targeted to the DNA of tumors cells may, therefore, represent a new radiotherapeutic approach. 99mTc radiopharmaceuticals, which are used for diagnosis, could indeed be used in theragnostic fields when loaded on AuNRs and delivered to a tumor site. This work aims to provide a proof of concept (i) to evaluate AuNRs as carriers of 99mTc-based radiopharmaceuticals, and (ii) to evaluate the efficacy of Auger electrons emitted by photon-irradiated AuNRs in inducing radio-induced damage in T98G cells, thus mimicking the effect of Auger electrons emitted during the decay of 99mTc used in clinical settings. Data are presented on AuNRs' chemical characterization (with an aspect ratio of 3.2 and Surface Plasmon Resonance bands at 520 and 680 nm) and the loading of pharmaceuticals (after 99mTc decay) on their surface. Spectroscopic characterizations, such as UV-Vis and synchrotron radiation-induced X-ray photoelectron (SR-XPS) spectroscopies, were performed to investigate the drug–AuNR interaction. Finally, preliminary radiobiological data on cell killing with AuNRs are presented. [ABSTRACT FROM AUTHOR]

We present the deterministic linkage of short and long gold nanorods into one‐dimensional (1D) alternating nanorod chains in a head‐to‐head manner using click reactions. By precisely controlling the surface chemistry, we achieve orientation‐specific and robust covalent linkage between nanorods with high‐product yield. The optical response of the alternating nanorod chains exhibits Fano‐like resonances. This method enables the high‐throughput production of covalently linked plasmonic particle networks consisting of heterogeneous nanoparticles with specifically chosen spectral responses. [ABSTRACT FROM AUTHOR]

Gold nanorods (GNRs) have emerged as the most efficient photothermal agent in cancer therapy and photocatalysis. Understanding the influence of the surrounding medium, particle size, and excitation wavelength is critical to optimising the photothermal conversion rate. Here, three pairs of large and small gold nanorods of different aspect ratios and their heat generation under laser radiation at on and off surface plasmon resonance wavelengths in aqueous solution and gel‐like media are investigated. In the aqueous solution, the temperature rise of the large gold nanorods is more than with small gold nanorods at resonance excitation. In contrast to the large gold nanorods (LGNRs), the small gold nanorods (SGNRs) were less sensitive to excitation wavelength. At off‐resonance excitation, the temperature rise of the SGNRs is larger than that of the LGNRs. In the agarose gel, the photothermal effect of the SGNRs is greater than LGNRs excited at the wavelength near their solution phase longitudinal surface plasmon resonance wavelength. The temperature increase of LGNRs in gel is significantly less than in aqueous solution. These findings suggest that SGNRs could be more beneficial than the LGNRs for photothermal applications in biological systems and provides further insight when selecting GNRs. [ABSTRACT FROM AUTHOR]

An effective, selective, and multicolor colorimetric assay for Cu2+ detection based on the regulation of peroxidase-like nanozyme-mediated etching of gold nanorods (Au NRs) is proposed. Cu2+-creatinine complex is selected as the nanozyme that exhibits excellent peroxidase-like activity even in the case of low concentration of Cu2+, which can catalyze 3,3,5,5-tetramethylbenzidine (TMB) to produce oxidized TMB (TMB+) in the presence of hydrogen peroxide, and TMB+ is oxidized to generate TMB2+ after adding H+, and the TMB2+ can etch Au NRs. The determination of Cu2+ is achieved based on the blue shift of the longitudinal localized surface plasmon resonance peak of Au NRs. Under the optimal conditions, the developed colorimetric assay exhibits high sensitivity for the detection of Cu2+ (limit of detection is 0.034 μM) with a wide linear range of 0.05–4.0 μM (R2 = 0.987). The solution shows a rainbow-like color in response to the increase of Cu2+ concentration, which can realize the semi-quantitative detection of Cu2+ by naked eyes. In addition, the developed method exhibits excellent selectivity for Cu2+-detection. The established method was used for the determination of Cu2+ in lake water, soil, and normal human serum with satisfactory recovery of spiked samples. [ABSTRACT FROM AUTHOR]

In this work, a heterojunction composite of HOFs/g-C 3 N 4 was synthesized using solution-plasticized self-assembly of g-C 3 N 4 nanosheet on hydrogen-bonded organic frameworks (HOFs). HOFs/g-C 3 N 4 was then used as a substrate material to construct a novel photoelectrochemical/electrochemiluminescent (PEC/ECL) biosensor for the detection of amyloid β oligomer (Aβo). HOFs/g-C 3 N 4 composites were first drop-coated on the electrode surface. Subsequently, the Aβ aptamer was modified on the electrode surface via amide bonding. The target Aβo and the gold nanorods (Au NRs)-labeled Aβ recognition peptide (Au NRs-KLVFF) were simultaneously dropped onto the electrode surface, thus a "sandwich" dual-mode biosensor was constructed. In the PEC detection of the Aβo, the surface plasmon resonance effect of Au NRs enhanced the visible absorption of HOF/g-C 3 N 4 , and the sensor exhibited a "signal-on" photocurrent signal. Meanwhile, the ECL emission spectrum of HOF/g-C 3 N 4 in ECL mode overlaps with the ultraviolet-visible (UV) absorption of Au NRs, and the sensor signal showed a "signal-off" ECL response. Under the optimal conditions experiments, the constructed dual-mode biosensor showed a wide detection range and low detection limit for Aβo. The proposed dual-mode detection method has a detection range of 10 fM to 10 nM with a detection limit of 5.97 fM for PEC detection and a detection range of 0.1 pM to 1.0 μM with a detection limit of 0.051 pM for ECL detection respectively. Additionally, the detection method achieved satisfactory results in the analysis of real samples. Dual-mode sensing platform provides a new strategy for HOFs application in PEC/ECL assay and sensitive detection of Aβ O. • Novel photoelectrically active materials of HOFs/g-C 3 N 4 were synthesized. • The PEC/ECL dual mode signal response from HOFs/g-C 3 N 4 is achieved by utilizing the Au NRs. • Dual-mode sensing platform provides a new strategy for detection of Aβ O. [ABSTRACT FROM AUTHOR]

Gold nanorods (AuNRs) possess a high optical nonlinear coefficient, ultrafast optical response speed and widely tunable localized surface plasmon resonance (LSPR) wavelength covering the visible and near infrared region. Therefore, they are extensively investigated for many optical applications. However, the poor thermal stability of the AuNRs seriously restricts their practical performance. In addition, for many applications, such as optical communication or laser modulation, AuNRs have to be combined with transparent solids, for example polymers, glass or crystals to make devices. Here, we report on the preparation of 0.23 mg AuNR dispersed methyl silicone resin (MSR) with longitudinal LSPR (L-LSPR) wavelength (1450 nm) in the optical communication window. We found that AuNR-silicone composites possess high thermal stability. After calcination in ambient environment at a temperature of 250 °C for 10 h, the L-LSPR peak of the sample can remain longer than 1380 nm, implying that the NR shape of the Au particles was well maintained. Using the open-aperture Z-scan technique, the nonlinear absorption coefficient of the composites was measured as âˆ'11.71 cm GWâˆ'1, higher than many nonlinear materials. Thus, the thermally stable AuNR@SiO2-MSR composite with high nonlinearity is promising for practical applications in the optical communication window. [ABSTRACT FROM AUTHOR]

Herein, we performed single‐particle studies to reveal three‐dimensional spatial orientational changes in the AuNR cores coated with mesoporous silica shell (AuNRs@mSiO2) following mercury (Hg) amalgamation. Defocused orientation imaging technique was used to determine the tilting angle of single AuNR cores after Au–Hg amalgam formation. Single amalgamated AuNR cores inside the silica shell were randomly tilted between 0° and 20° with respect to the glass slide on which they were deposited; no orientational changes were observed for AuNRs@mSiO2 following Hg amalgamation. This study will help in better understanding the effect of silica shell on the morphological and orientation alterations of single AuNRs@mSiO2 induced by Hg amalgamation. [ABSTRACT FROM AUTHOR]

Gold nanorods (AuNRs) are ideal inorganic nanophotothermal agents with unique characteristics, including local surface plasmon resonance effects, easy scale preparation and functional modification, and good biocompatibility. This review summarizes several recent advances in AuNRs-based photothermal therapy (PTT) research. Functionalized AuNRs photothermal agents have optimized biocompatibility and targeting properties. The multifunctional AuNRs nanoplatform composite structure meets the requirements for synergistic effects of PTT, photoacoustic imaging, and other therapeutic methods. Photothermal therapy with AuNRs (AuNRs-PTT) is widely used to treat tumors and inflammatory diseases; its tumor-targeting, tumor metastasis inhibition, and photothermal tumor ablation abilities have remarkable curative effects. An in-depth study of AuNRs in living systems and the interactions between biological structure, nanomaterial, and near-infrared irradiation could lay the foundation for further clinical research and the broad application of AuNRs in PTT. [ABSTRACT FROM AUTHOR]

Plasmonic nanoparticle assemblies are promising functional materials for surface‐enhanced Raman spectroscopy (SERS). Gold nanorod (AuNR) assemblies are of particular interest due to the large, shape‐induced local field enhancement and the tunable surface plasmon resonance of the AuNRs. Designing the optimal assembly structure for SERS, however, is challenging and requires a delicate balance between the interparticle distance, porosity, and wetting of the assembly. Here, a new type of functional assemblies–called supraparticles–fabricated through the solvent‐evaporation driven assembly of silica‐coated gold nanorods into spherical ensembles, in which the plasmonic coupling and the mass transport is tuned through the thickness and porosity of the silica shells are introduced. Etching of the AuNRs allowed fine‐tuning of the plasmonic response to the laser excitation wavelength. Using a correlative SERS‐electron microscopy approach, it is shown that all supraparticles successfully amplified the Raman signal of the crystal violet probe molecules, and that the Raman signal strongly increased when decreasing the silica shell thickness from 35 to 3 nm, provided that the supraparticles have a sufficiently high porosity. The supraparticles introduced in this study present a novel class of materials for sensing, and open up a wide parameter space to optimize their performance. [ABSTRACT FROM AUTHOR]

The ligand exchange process on gold nanorods (Au NRs) was explored by using laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS). Cetyltrimethylammonium bromide (CTAB) adsorbed on Au NRs was replaced with alkanethiol derivatives presenting different functional groups. The ligand exchange process was investigated under various conditions, such as in the presence of different functional groups in the ligands and with different concentrations of CTAB. The ligand-exchanged Au NRs were characterized by using a combination of UV–Vis spectroscopy and LDI-TOF-MS. Based on the results, it was revealed that LDI-TOF-MS analysis can provide crucial and distinct information about the degree of ligand exchange on Au NRs. [ABSTRACT FROM AUTHOR]

Any excess or lack of human serum albumin (HSA) in urine should be considered a warning for renal or cardiovascular diseases. This report proposes a rapid and straightforward method for detecting HSA based on the surface plasmon resonance characteristics and sensitivity of antibody-functionalized gold nanorods (GNRs) to trace changes in the local environment. The role of potential parameters (e.g., pH, the concentration of antibody, and the blocking agent) was also studied to optimize the sensor performance. The nanobiosensor determined HSA in the 30–300 μg·mL−1 concentration range with a detection limit of 1 μg·mL−1 and exhibited high selectivity towards HSA. This nanobiosensor has a detection limit within the reference range required to detect microalbuminuria or macroalbuminuria. The developed nanobiosensor also showed the possibility of tracing HSA in urine samples with 95–100% accuracy. This investigation introduces a potential application of gold nanorod-based sensors as promising alternatives for conventional methods in the form of a new generation of facile, rapid, and "lab-in-a-vial" nanodiagnostic technique. [ABSTRACT FROM AUTHOR]

Chemical interface damping (CID) is the most recently suggested plasmon damping pathway induced by adsorbate molecules in gold nanoparticles. Despite recent advances in this field, CID has not been studied in gold nanorods coated with mesoporous silica shells (AuNRs@mSiO2). Herein, we conducted a single‐particle correlation study to elucidate CID using p‐nitrothiophenol (p‐NTP) as adsorbates in single AuNRs@mSiO2. Through surface‐enhanced Raman spectroscopy studies, we confirmed that p‐NTP with a strong electron‐withdrawing group was effectively adsorbed on the AuNR cores. Following the chemisorption of p‐NTP, a strong CID was observed with localized surface plasmon resonance (LSPR) linewidth broadening through the preferred interaction between sulfur and the Au surfaces. Furthermore, we presented the molecular binding effect on the LSPR linewidth of single AuNRs@mSiO2 during the reaction with p‐NTP in real‐time. Thus, the result further supported that the CID could be used to develop LSPR sensors having low sensitivity to the medium dielectric constant. [ABSTRACT FROM AUTHOR]

Photothermal application of gold nanorods (AuNRs) is widely increasing because of their good photothermal conversion efficiency (PCE) due to local surface plasmon resonance. However, the high concentration of hexadecyltrimethylammonium bromide used in the synthesis is a concern. Moreover, the mild and commonly used reducing agent-ascorbic acid does not reduce the Au(I) to A(0) entirely, resulting in a low yield of gold nanorods. Herein we report for the first time the PCE of large-scaled synthesized AuNRs using the binary surfactant seed-mediated method with hydroquinone (HQ) as the reducing agent. The temporal evolution of the optical properties and morphology was investigated by varying the Ag concentration, HQ concentration, HCl volumes, and seed solution volume. The results showed that the seed volume, HQ concentration, and HCl volume played a significant role in forming mini-AuNRs absorbing in the 800 nm region with a shape yield of 87.7%. The as-synthesized AuNRs were successfully up-scaled to a larger volume based on the optimum synthetic conditions followed by photothermal profiling. The photothermal profiling analysis showed a temperature increase of more than 54.2 °C at 2.55 W cm−2 at a low optical density (OD) of 0.160 after 630 s irradiation, with a PCE of approximately 21%, presenting it as an ideal photothermal agent. [ABSTRACT FROM AUTHOR]

This study aimed to determine the β-lactam antibiotics (ampicillin, amoxicillin, penicillin G, oxacillin, and carbenicillin) using conjugated antibody along with gold nanorods (AuNRs). For this purpose, XRD, ATR-FTIR spectroscopy, transmission electron microscopy, and dynamic light scattering were utilized to detect the crystallinity, to identify functional groups involved in the synthesis of AuNRs, and to measure the size of the AuNRs, respectively. In this regard, pH of 9 and a concentration of 9.6 μg of antibody at 1 mL poly(4-styrenesulfonic acid (PSS))-modified AuNRs solution were selected as the best levels of pH and concentration of antibody for the conjugation of antibody with PSS-modified AuNRs. Thereafter, the maximum wavelength rates of the PSS-modified AuNRs, conjugation of antibody with PSS-modified AuNRs, and detection of antibiotics (from 1 nM to 1 mM) with PSS-modified AuNRs–PAb were recorded using a microvolume spectrophotometer system. The results indicate that the LSPR absorption wavelength of PSS-modified AuNRs is red-shifted by increasing the concentration of β-lactam antibiotics. By increasing the concentrations of ampicillin, penicillin G, and carbenicillin, the maximum wavelength changed, and after the saturation of the antibiotic concentration, the curve reached a plateau. Correspondingly, this indicated that the antibody had a similar behavior in the detection of these antibiotics. However, regarding amoxicillin, the saturation concentration is much higher, which indicate that the antibody is more specific for its detection. In contrast, for oxacillin, saturation occurred immediately, demonstrating that the antibody had an extremely low detection capability for this antibiotic. Finally, the findings showed that the antibody was sensitive to 1 nM of five studied β-lactam antibiotics. [ABSTRACT FROM AUTHOR]

By combining photophysical measurements with transmission electron microscopy, we proved that the thickness of the silica shell around gold nanorods determines the position of the longitudinal plasmonic band when they are isolated in solution or assembled in solid. The silica thickness has been tuned by modulating the reaction time and the ratio between CTAB-coated gold nanorods and TEOS concentration, obtaining gold nanorods covered by a silica shell with a thickness varying from 3.5 to 24 nm. Considering this shell as a spacer between the gold cores, it is possible to modulate the coupling of the localized surface plasmon resonance (LSPR) of neighboring nanorods. Moreover, the comparison between the extinction spectra in solution and in solid, recorded from nanorods covered by silica shell with different thickness, can be used to estimate the inter-nanoparticles distance required for plasmon interaction. We found that LSPR coupling is effective when the distance between the gold cores is no more than 10 nm. When the distance is greater, the nanorods do not interact with each other. [ABSTRACT FROM AUTHOR]

A novel enzyme-induced metallization colorimetric assay is developed to monitor and measure beta-galactosidase (β-gal) activity, and is further employed for colorimetric bacteriophage (phage)-enabled detection of Escherichia coli (E. coli). This assay relies on enzymatic reaction-induced silver deposition on the surface of gold nanorods (AuNRs). In the presence of β-gal, the substrate p-aminophenyl β-d-galactopyranoside is hydrolyzed to produce p-aminophenol (PAP). Reduction of silver ions by PAP generates a silver shell on the surface of AuNRs, resulting in the blue shift of the longitudinal localized surface plasmon resonance peak and multicolor changes of the detection solution from light green to orange-red. Under optimized conditions, the detection limit for β-gal is 128 pM, which is lower than the conventional colorimetric assay. Additionally, the assay has a broader dynamic range for β-gal detection. The specificity of this assay for the detection of β-gal is demonstrated against several protein competitors. Additionally, this technique is successfully applied to detect E. coli bacteria cells in combination with bacteriophage infection. Due to the simplicity and short incubation time of this enzyme-induced metallization colorimetric method, the assay is well suited for the detection of bacteria in low-resource settings.

The seed-mediated method is a general procedure for the synthesis of gold nanorods (Au NRs), and reducing agents such as ascorbic acid (AA) and hydroquinone (HQ) are widely used for the growth process. Further, they are mild reducing agents; however, when AA is used, controlling the size of Au NRs with a higher aspect ratio (localized surface plasmon resonance (LSPR) peak, λLmax > 900 nm) is challenging because it results in a faster growth rate of Au NRs. In contrast, when HQ is used, Au NRs with a higher aspect ratio can be synthesized as it slows down the growth rate of the Au NRs and greatly enhanced the λLmax. However, the increase in λLmax is still needs not satisfactory due to the limited enhancement in the aspect ratio of Au NRs due to utilization of single reducing agent. The growth kinetics of the Au NRs can be modulated by controlling the reducing power of the reducing agents. In such scenario, judicious use of two reducing agents such as AA and HQ simultaneously can help us to design Au NRs of higher aspect ratio in a controlled manner due to the optimum growth rate resulting from the combined effect of both the reducing agents. In this study, we investigated the effect of the two reducing agents by controlling the volume ratios. When the growth solution contains both the reducing agents, the growth of Au NRs is first initiated by the fast reduction of Au3+ to Au+ due to stronger reducing power of the AA and when the AA in the growth solution is completely utilized, further growth of the Au NRs continues as a result of the HQ thereby resulting to high aspect ratio Au NRs. Consequently, the LSPR peak (λLmax > 1275 nm) can be tuned by controlling the volume ratios of the reducing agents. [ABSTRACT FROM AUTHOR]

Recently fashionable spintronic terahertz (THz) emission provides fresh pathways for contactless diagnosing femtosecond spin currents, opens the door for developing next‐generation high‐performance THz emitters, and accelerates the interdisciplinary of ultrafast THz optospintronics. However, one of the research highlights of ultrafast magnetism and the difficulty for further improving the spintronic THz emission productivity is how to efficiently reduce the energy consumption of all‐optical magnetitic manipulation and improve the optical spin injection efficiency. Here, it is demonstrated, for the first time, gold nanorods (GNRs) plasmonic resonances can effectively increase the THz emission from W/CoFeB/Pt heterostructures by 140%. Systematic investigations of THz yield dependences on pumping laser incidence directionality, polarization, and the GNRs dimension parameter conclusively manifest the surface plasmon resonance validity. Theoretical interpretations combined with Drude–Lorentz model and numerical simulations semiquantitatively reproduce the experimental results. The observations prove that THz efficiency can be improved by nanophotonic technologies and may also spark inspiration for developing functional nano‐THz optospintronic devices. [ABSTRACT FROM AUTHOR]

A hybrid scaffold containing gold nanorods and lysozyme amyloid fibrils has been fabricated, and the effect of surface modification on improving nanostructure assembly on the biological template has been investigated. The nanohybrid system was characterized by monitoring surface plasmon resonance bands, dynamic light scattering spectroscopy, Thioflavin-T assay, and transmission electron microscopy. Surface of gold nanorods (GNRs) was modified with polystyrene sulfonate (PSS), and possible difference in assembly of the pristine and modified nanostructures was compared upon interaction with amyloid fibrils. Analysis of transmission electron microscopy showed that changing the surface charge of GNRs with biocompatible polymer improved electrostatic interactions between the nanostructures and amyloid fibril templates. Analysis of cell viability assays also showed that surface functionalization of GNRs remarkably improved biocompatibility of the nanoscaffold. Results of this study encourage utilization of modification strategies to fabricate a new generation of nanoscaffolds with fruitful applications in regenerative medicine.

Mesenchymal stem cell therapies show great promise in regenerative medicine. However, to generate clinically relevant numbers of these stem cells, significant in vitro expansion of the cells is required before transplantation into the affected wound or defect. The current gold standard protocol for recovering in vitro cultured cells involves treatment with enzymes such as trypsin which can affect the cell phenotype and ability to interact with the environment. Alternative enzyme free methods of adherent cell recovery have been investigated, but none match the convenience and performance of enzymatic detachment. In this work we have developed a synthetically simple, low cost cell culture substrate functionalized with gold nanorods that can support cell proliferation and detachment. When these nanorods are irradiated with biocompatible low intensity near infrared radiation (785 nm, 560 mWcm−2) they generate localized surface plasmon resonance induced nanoscale heating effects which trigger detachment of adherent mesenchymal stem cells. Through simulations and thermometry experiments we show that this localized heating is concentrated at the cell-nanorod interface, and that the stem cells detached using this technique show either similar or improved multipotency, viability and ability to differentiate into clinically desirable osteo and adipocytes, compared to enzymatically harvested cells. This proof-of-principle work shows that photothermally mediated cell detachment is a promising method for recovering mesenchymal stem cells from in vitro culture substrates, and paves the way for further studies to scale up this process and facilitate its clinical translation. New non-enzymatic methods of harvesting adherent cells without damaging or killing them are highly desirable in fields such as regenerative medicine. Here, we present a synthetically simple, non-toxic, infra-red induced method of harvesting mesenchymal stem cells from gold nanorod functionalized substrates. The detached cells retain their ability to differentiate into therapeutically valuable osteo and adipocytes. This work represents a significant improvement on similar cell harvesting studies due to: its simplicity; the use of clinically valuable stem cells as oppose to immortalized cell lines; and the extensive cellular characterization performed. Understanding, not just if cells live or die but how they proliferate and differentiate after photothermal detachment will be essential for the translation of this and similar techniques into commercial devices. [Display omitted] [ABSTRACT FROM AUTHOR]

We present a precise study for coating gold nanorods (GNRs) by a silica shell layer. Different parameters like pH, reaction time, and, most importantly, the ratio between the selected surfactant and the tetraethyl orthosilicate (TEOS) are studied and discussed. This latter is the key parameter to increase reproducibility, stability, reaction time, and the control of the targeted silica shell thickness. Moreover, the silica shell growth induces an optical shift of the localized surface plasmon resonance (LSPR) bands, which is explained by the change of the local refractive index. Both extinction spectroscopy and scanning electronic microscopy (SEM) are used to characterize the growth of the silica shell in time. Based on these results, it is thus possible to follow the growth process just by extinction spectroscopy, which ensures a rapid control of the reaction and makes it possible to stop it on time depending on the targeted shell thickness. Controlling the thickness is mandatory for further GNRs functionalization and surface plasmon enhanced spectroscopies. [ABSTRACT FROM AUTHOR]

Abstract The unique photonic effect of self-assembled metal nanoparticles is widely used in many applications. In this article, we prepared self-assembled gold nanorod (GNR) vertical arrays substrate by an evaporation method and found that the morphology of the substrate can be effectively regulated by changing the immersion time in the target molecules solution to obtain different Raman enhancement effects. We separately calculated the local electromagnetic field of the GNR vertical arrays and disorder substrate by the finite element method (FEM), which was consistent with the experimental results. Based on optimal soaking time, the sensitivity, reproducibility, and stability of substrates were separately studied. The experimental results show that the GNR vertical arrays can detect Rhodamine 6G (Rh6G) at concentrations as low as 10−11 M and exhibit good reproducibility and stability due to local electromagnetic (EM) field enhancement caused by the coupling of adjacent nanorods. Thus, our work can demonstrate that the substrate has excellent surface-enhanced Raman scattering (SERS) activity and the obtained GNR vertical arrays have great potential for biosensor and biodetection.

Abstract Background Campylobacteriosis is a zoonotic infectious disease that can be mostly undiagnosed or unreported due to fastidious Campylobacter species. The aim of this study was to develop a simple, sensitive, and quick assay for the detection of Campylobacter spp. and taking advantage of the great sensitivity of gold nanorods (GNRs) to trace changes in the local environment and interparticle distance. Methods Characterized GNRs were modified by specific ssDNA probes of cadF gene. First, the biosensor was evaluated using recombinant plasmid (pTG19-T/cadF) and synthetic single-stranded 95 bp gene, followed by a collection of the extracted DNAs of the stool samples. The sensing strategy was compared by culture, PCR, and real-time PCR. Results and discussion Analysis of 283 specimens showed successful detection of Campylobacter spp. in 44 cases (16%), which was comparable to culture (7%), PCR (15%), and real-time PCR (18%). In comparison with real-time PCR, the sensitivity of the biosensor was reported 88%, while the specificity test for all assays was the same (100%). However, it was not able to detect Campylobacter in 6 positive clinical samples, as compared to real-time PCR. The limit of detection was calculated to be the same for the biosensor and real-time PCR (102 copy number/mL). Conclusions Taking high speed and simplicity of this assay into consideration, the plasmonic nanobiosensor could pave the way in designing a new generation of diagnostic kits for detection of C. jejuni and C. coli species in clinical laboratories.

The ligand exchange process on gold nanorods (Au NRs) was explored by using laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS). Cetyltrimethylammonium bromide (CTAB) adsorbed on Au NRs was replaced with alkanethiol derivatives presenting different functional groups. The ligand exchange process was investigated under various conditions, such as in the presence of different functional groups in the ligands and with different concentrations of CTAB. The ligand-exchanged Au NRs were characterized by using a combination of UV–Vis spectroscopy and LDI-TOF-MS. Based on the results, it was revealed that LDI-TOF-MS analysis can provide crucial and distinct information about the degree of ligand exchange on Au NRs.

Here, we present a high performance uncooled near-infrared (NIR) detector comprising of a giga hertz (GHz) solidly mounted resonator (SMR) and gold nanorods (GNRs) arrays. By coupling the localized surface plasmon resonances of GNRs, the resonator system exhibits optimized optical response to vis-NIR region. Both simulation and experiments demonstrate the hybrid GNRs-SMR exhibit significantly enhanced optical responsive sensitivity of NIR, the tunable aspect ratios (AR) of GNRs enable resonator respond sensitively to selected light. Specially, taking advantage of the acoustofluidic effect of SMR, the GNRs can be controllably and precisely modified on the microchip surface in an ultra-short time, which addresses one of the most fundamental challenges in the localized functionalization of micro/nano scale surface. The presented work opens new directions in development of novel miniaturized, tunable NIR detector. [ABSTRACT FROM AUTHOR]

Owing to strong and tunable surface plasmon resonance (SPR) effect and good biocompatibility, gold nanoparticles have been suggested to be a versatile platform for a broad range of biomedical applications. In this study, a new nanoplatform of thermo-responsive polymer encapsulated gold nanorods incorporating indocyanine green (ICG) was designed to couple the photothermal properties of gold nanorods (AuNRs) and the photodynamic properties of ICG to enhance the photodynamic/photothermal combination therapy (PDT/PTT). In addition to the significantly increased payload and enhancing photostability of ICG, the polymer shell in the nanoplatform also has thermo-responsive characteristics that can control the release of drugs at tumour sites upon the laser irradiation. On the basis of these improvements, the nanoplatform strongly increased drug aggregation at the tumour site and improved the photothermal/photodynamic therapeutic efficacy. These results suggest that this nanoplatform would be a great potential system for tumour imaging and antitumour therapy. [ABSTRACT FROM AUTHOR]

A simple but efficient colorimetric assay was developed for the detection and quantification of acid phosphatase (ACP) using a smartphone. This strategy is based on target-controlled iodine-mediated etching of gold nanorods (AuNRs). Due to effective hydrolysis of the substrate pyrophosphate (PPi) by ACP, chelated Cu2+ with PPi was released, which promoted the redox reaction with an iodide ion (I−), leading to the formation of I3−. As the etching agent of AuNRs, I3− caused a blueshift of the localized surface plasmon resonance peak and, more importantly, an observable color change. The vivid colors were recorded with a smartphone camera and directly analyzed using an image-processing app. On the basis of the direct correlation between ACP concentration and the etching degree of AuNRs as well as color change, this smartphone nanocolorimetry technique showed a good linear response toward ACP over the range of 0–15.0 U/L, with a detection limit of 0.97 U/L. Using the standard addition method, the practical applicability of the proposed smartphone-based assay was successfully demonstrated by determining ACP in human serum samples, with results consistent with those obtained by UV-Vis spectrophotometry. [ABSTRACT FROM AUTHOR]

Based on the etching of gold nanorods (GNRs) and enzyme-linked immunosorbent assay (ELISA), a multicolor immunosensor for visual detection of enterovirus 71 infection is proposed. Once the immunocomplex is formed, the horseradish peroxidase bound to the ELISA plate oxidizes 3,3′,5,5′-tetramethylbenzidine (TMB) into TMB2+ in the presence of hydrogen peroxide. Subsequently, TMB2+ quantitatively etches GNRs to the short GNRs, leading to a blue shift of longitudinal localized surface plasmon resonance and corresponding color responses. This change is used to develop two types of cut-off standards, which respond to the human anti-enterovirus at a concentration of 71 IgM antibody. The method has been validated with clinical serum samples and showed high sensitivity and specificity. This visual immunosensor has an important application value for point-of-care detection of EV71, especially in areas lacking detection equipment. [ABSTRACT FROM AUTHOR]

We demonstrate the structural reorganization of gold nanorods (GNRs) that could fine-tune localized surface plasmon resonance (LSPR) by using modified wet chemical synthesis on the solid substrate. Controlling the growth solution ageing time using the modifiable GNRs is an approach to overcome the limitations of rods formation due to inhomogeneous and uncontrollable size and aspect ratio. In this study, the suitable ageing time of GNRs was determined to produce optimum GNRs in terms of surface density and aspect ratio. As the ageing time was increased from 30 min to 24 h, the colour of the growth solution was changed from light to dark purple. The change is associated with the density of the nanorods formation. The optical spectral peaks of GNRs occur in a range between 500 nm and 800 nm in the visible and near-infrared region spectrum for transverse surface resonance (t-SPR) and longitudinal surface resonance (l-SPR), respectively. From the morphological analysis, it was found that 20 h ageing time resulting in high density and homogeneous GNRs with 74.81% surface density with 4.23 ± 0.04 aspect ratio. Hence, the growth ageing time of GNRs can be manipulated to control their shape evolution and dimension in terms of size and aspect ratio. The controllable aspect ratio and size GNRs can be potentially used as sensing material in plasmonic applications. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the fabrication of hybrid plasmonic solar cells using gold nanoparticles (AuNPs). Two types of AuNPs, gold nanospheres (AuNSs) and gold nanorods (AuNRs), were incorporated in a hole transport layer (HTL) (PEDOT:PSS) on a metallic grating electrode. The organic solar cells (OSCs) structure comprised an indium-tin-oxide (ITO)-coated glass substrate/PEDOT:PSS:AuNSs:AuNRs/P3HT:PCBM/Al grating electrode. Adding AuNPs induced localized surface plasmon resonance (LSPR), while grating structured Al at the interface with a photoactive layer excited the propagating surface plasmons. Compared with a flat reference device, the proposed OSCs exhibited improved photovoltaic properties by increasing both the short-circuit current density (JSC) and the power conversion efficiency (PCE) with large enhancements of 16.23% and 14.06%, respectively. The efficiency improvement was attributed to increased broadband absorption and improved electrical properties inside the thin-film devices. [ABSTRACT FROM AUTHOR]