Unified Methodology for Fabrication and Quantification of Gold Nanorods, Gold Core Silver Shell Nanocuboids, and Their Polymer Nanocomposites

Synthesis of gold nanorods and their performance in the field of cancer cell imaging and photothermal therapy

Cancer is one of the most common incident in the world, with malignant tumors having a death rate of up to 19%. A new method of treating cancer cells effectively with minimal cytotoxicity is needed. In the field of biomedicine with unique shape-dependent optical properties, gold nanorods (GNRs) have attracted worldwide interest. These nanorods have two distinct plasmon bands. One is transverse plasmon band in the area of visible light, and the other is longitudinal band of plasmons in near infrared region. These specific characters provide promise for the design of new optically active reagents that simultaneously perform light-mediated imaging and photothermal cancer treatment. We begin our review by summarizing the latest developments in gold nanorods synthesis with a focus on seed-mediated growth method. Nanorods spontaneous self-assembly, polymer-based alignment and its applications as a novel agent for simultaneous bioimaging and photothermal cancer therapy are listed in particular.

Optimized 3D Finite-Difference-Time-Domain Algorithm to Model the Plasmonic Properties of Metal Nanoparticles with Near-Unity Accuracy

The finite difference time domain (FDTD) method is a grid-based, robust, and straightforward method to model the optical properties of metal nanoparticles (MNPs). Modelling accuracy and optical properties can be enhanced by increasing FDTD grid resolution; however, the resolution of the grid size is limited by the memory and computational requirements. In this paper, a 3D optimized FDTD (OFDTD) was designed and developed, which introduced new FDTD approximation terms based on the physical events occurring during the plasmonic oscillations in MNP. The proposed method not only required ~52% less memory than conventional FDTD, but also reduced the calculation requirements by ~9%. The 3D OFDTD method was used to model and obtain the extinction spectrum, localized surface plasmon resonance (LSPR) frequency, and the electric field enhancement factor (EF) for spherical silver nanoparticles (Ag NPs). The model’s predicted results were compared with traditional FDTD as well as experimental results to validate the model. The OFDTD results were found to be in excellent agreement with the experimental results. The EF accuracy was improved by 74% with respect to FDTD simulation, which helped reaching a near-unity OFDTD accuracy of ~99%. The λLSPR discrepancy reduced from 20 nm to 3 nm. The EF peak position discrepancy improved from ±5.5 nm to only ±0.5 nm.

Small and large scale plasmonically enhanced luminescent solar concentrator for photovoltaic applications: modelling, optimisation and sensitivity analysis

Hybrid 3D Finite difference time domain-Monte Carlo ray tracing (FDTD-MCRT) algorithm has been developed to model and optimise small and large scale plasmonically-enhanced luminescent solar concentrator (pLSC) devices for photovoltaic (PV) applications. The configuration parameters (for example, dimensions, shape, and optical properties of metal nanoparticles, luminescent species, and host material) were used to characterise the probability of optical energy transfer and loss processes, as well as reflection, refraction, absorption, emission enhancement, and total internal reflection (TIR) in the pLSC. The algorithm was validated through modelling of various doping concentrations of CdSe/ZnS quantum dots (QD) and gold nano spheres (Au NS) where ∼50% enhancement in optical conversion efficiency (OCE) was observed for a plasmonic composite of 2 ppm Au NS and 0.008 wt. % QD.

Poly(L-DOPA)-mediated bimetallic core-shell nanostructures of gold and silver and their employment in SERS, catalytic activity, and cell viability

Core-shell gold nanorod (AuNR)@silver (Ag) nanostructures with their unique properties have gained enormous interest and are widely utilized in various applications including sensor systems, catalytic reactions, diagnosis, and therapy. Despite the recent progress, simple, effective, low-cost, and easy-to-tune strategies are heavily required to fabricate these nanoparticles (NP) systems. For this, we propose the employment of the polymer of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) as a ligand molecule. A conformal thin layer of polymer of L-DOPA (PLDOPA) with its various functional groups enabled the reduction of silver ions onto the AuNRs and stabilization of the resultant NPs without using any surfactant, reducing agent, and seed material. The shape and growth model of the AuNR@Ag nanostructures was manipulated by simply tuning the amount of silver ions. This procedure created different NP morphologies ranging from concentric to acentric/island shape core-shell nanostructures. Also, even at the highest Ag deposition, the PLDOPA layer is still conformally present onto the Au@Ag core-shell NRs. The unique properties of NP systems provided remarkable characteristics in surface-enhanced Raman spectroscopy, catalytic activity, and cell viability tests.

A new approach for synthesizing plasmonic polymer nanocomposite thin films by combining a gold salt aerosol and an atmospheric pressure low-temperature plasma

The proof of the concept of a new, onestep and safe by design process to synthesize metal-polymer nanocomposites thin films on a large surface is presented. It is based on the injection of an aerosol of a solution of metal (gold) salts dissolved in a polymerizable solvent (isopropanol) into an argon atmospheric pressure dielectric barrier discharge. The main novelty of this method resides in the fact that the nanoparticles are formed in situ, inside the plasma reactor, in the gas phase. Consequently, the nanoparticle synthesis and deposition are concomitant with the solvent polymerization used to produce the matrix, which makes it possible to obtain homogeneous layers of non-agglomerated nanoparticles (NPs) with high NPs density. By toggling between low and high-frequency discharges, gold/polymer nanocomposites with different morphologies and optical properties are synthesized. The effect of the concentration of gold in the aerosol and the gas residence time in the plasma as well as the ratio of high and low-frequency discharge and their repetition rate are presented. The thin films are systematically characterized by AFM and UV-visible spectroscopy to analyze their morphologies along with their plasmonic resonances.

Silver nanoparticles: Synthesis, investigation techniques, and properties

The unique silver properties, especially in the form of nanoparticles (NPs), allow to utilize them in numerous applications. For instance, Ag NPs can be utilized for the production of electronic and solar energy harvesting devices, in advanced analytical techniques (NALDI, SERS), catalysis and photocatalysis. Moreover, the Ag NPs can be useful in medicine for bioimaging, biosensing as well as in antibacterial and anticancer therapies. The Ag NPs utilization requires comprehensive knowledge about their features regarding the synthesis approaches as well as exploitation conditions. Unfortunately, a large number of scientific articles provide only restricted information according to the objects under investigation. Additionally, the results could be affected by artifacts introduced with exploited equipment, the utilized technique or sample preparation stages. However, it is rather difficult to get information about problems, which may occur during the studies. Thus, the review provides information about novel trends in the Ag NPs synthesis, among which the physical, chemical, and biological approaches can be found. Basic information about approaches for the control of critical parameters of NPs, i.e. size and shape, was also revealed. It was shown, that the reducing agent, stabilizer, the synthesis environment, including trace ions, have a direct impact on the Ag NPs properties. Further, the capabilities of modern analytical techniques for Ag NPs and nanocomposites investigations were shown, among other microscopic (optical, TEM, SEM, STEM, AFM), spectroscopic (UV-Vis, IR, Raman, NMR, electron spectroscopy, XRD), spectrometric (MALDI-TOF MS, SIMS, ICP-MS), and separation (CE, FFF, gel electrophoresis) techniques were described. The limitations and possible artifacts of the techniques were mentioned. A large number of presented techniques is a distinguishing feature, which makes the review different from others. Finally, the physicochemical and biological properties of Ag NPs were demonstrated. It was shown, that Ag NPs features are dependent on their basic parameters, such as size, shape, chemical composition, etc. At the end of the review, the modern theories of the Ag NPs toxic mechanism were shown in a way that has never been presented before. The review should be helpful for scientists in their own studies, as it can help to prepare experiments more carefully.

Albumin-Based Nanotheranostic Probe with Hypoxia Alleviating Potentiates Synchronous Multimodal Imaging and Phototherapy for Glioma

Highly infiltrative and invasive glioma cells obscure the boundary between tumor and normal brain tissue, making it extremely difficult to precisely diagnose and completely remove. The combination of multimodal imaging with effective treatments to diagnose precisely and guide surgery and therapy accurately is desperately needed for glioma in the brain. Here, we report a biomimetic catalase-integrated-albumin phototheranostic nanoprobe (ICG/AuNR@BCNP) to realize multimodal imaging, amplify phototherapy, and guide surgery for glioma after penetrating the blood-brain barrier, accumulating into deep-seated glioma via albumin-binding protein mediated transportation. The phototheranostic nanoprobe enabled fluorescence, photoacoustic, and infrared thermal imaging with desirable detecting depth and high signal-to-background ratio for clearly differentiating brain tumors from surrounding tissues. Meanwhile, the nanoprobe could effectively induce local hyperthermia and promote the level of singlet oxygen based on alleviated hypoxic glioma microenvironment by decomposing endogenous hydrogen peroxide to oxygen to amplify phototherapy. Thus, significant inhibition of glioma growth, extended survival time, alleviated tumor hypoxia, improved apoptosis, and antiangiogenesis effects were exhibited in several animal models including the periphery and the brain through intravenous or intratumoral injection, meanwhile with low toxicity to normal tissue. The phototherapy was also guided by the assistance of external bioluminescence, magnetic resonance, and positron emission tomography imaging. Moreover, the nanoprobe could accurately guide the glioma resection. These results suggest that the phototheranostic nanoprobe is a promising nanoplatform specifically for glioma to achieve multimodal diagnosis, effective phototherapy, and accurate imaging-guided surgery.

Status of BIPV and BAPV System for Less Energy-Hungry Building in India—A Review

The photovoltaic (PV) system is one of the most promising technologies that generate benevolent electricity. Therefore, fossil fuel-generated electric power plants, that emit an enormous amount of greenhouse gases, can be replaced by the PV power plant. However, due to its lower efficiency than a traditional power plant, and to generate equal amount of power, a large land area is required for the PV power plant. Also, transmission and distribution losses are intricate issues for PV power plants. Therefore, the inclusion of PV into a building is one of the holistic approaches which reduce the necessity for such large land areas. Building-integrated and building attached/applied are the two types where PV can be included in the building. Building applied/attached PV(BAPV) indicates that the PV system is added/attached or applied to a building, whereas, building integrated PV (BIPV) illustrates the concept of replacing the traditional building envelop, such as window, wall, roof by PV. In India, applying PV on a building is growing due to India’s solar mission target for 2022. In 2015, through Jawaharlal Nehru National Solar Mission, India targeted to achieve 100 GW PV power of which 40 GW will be acquired from roof-integrated PV by 2022. By the end of December 2019, India achieved 33.7 GW total installed PV power. Also, green/zero energy/and sustainable buildings are gaining significance in India due to rapid urbanization. However, BIPV system is rarely used in India which is likely due to a lack of government support and public awareness. This work reviewed the status of BIPV/BAPV system in India. The BIPV window system can probably be the suitable BIPV product for Indian context to reduce the building’s HVAC load.

In situ synthesis of gold nanoparticles in polymer films under concentrated sunlight: control of nanoparticle size and shape with solar flux

We proposed a one step, green and efficient approach to synthesize plasmonic nanocomposites over large surfaces and with controlled morphologies.