Gold nanocages: Photothermal related applications

Gold Nanocages (AuNCs) are made up with a ultra-thin and porous walls of Au or Au-based alloys. It is the class of hollow, porous gold nanoparticles ranging in the size from 10 to over 150 nm. Generally, AuNCs are created by reacting silver nanoparticles with chloroauric acid (HAuCl₄) in boiling water. When AuNCs are irradiated with light, it exhibit a high efficiency for light-to-heat conversion and a large absorption cross section, making them effective photothermal transducers. Tuned AuNCs significantly absorb visible and near-infrared regions to optimize their interaction with the light at different wavelengths. AuNCs exhibits better photo-stability compared to the conventional organic dyes. These perspectives are of AuNCs synthesis and their use in applications involving photothermal conversion.

Figure 1. Structure of NanoRod, NanoShell, NanoCage and AuNCs.

Recently, Qiu et al., have reviewed the synthetic methods of AuNCs and their photothermal related applications, was reported in Chemical Sciences. In the synthesis part of view, they have mentioned that the specific attention of the strategies need to be developed for tuning their size, shape, composition, thickness and porosity of the walls. AuNCs are used in various photothermal related applications such as water evaporation, phase transition, controlled release, and photothermal therapy. It is also widely used as light sensors, imaging contrast agents, photothermal transducers, and drug carriers, which are related to optics, plasmonics, and nanomedicine applications [1].

Two main general methods used for the synthesis of AuNCs

(i) A template-engaged galvanic replacement reaction: This is one of the most commonly used methods for the fabrication of AuNCs are based upon the galvanic replacement reaction between Ag nanocubes and HAuCl₄ in an aqueous medium [2].

(ii) Seed-mediated growth, followed by selective etching: In this new approach, a strong reducing agent like ascorbic acid was introduced to reduce HAuCl₄ while suppressing the galvanic replacement reaction between HAuCl₄ and Ag [3]. The gold over layers were deposited on top of Ag₂O patches would be peeled off, exposing the Ag at the corner sites during this process. Finally, the Ag core could be completely etched away with an aqueous H₂O₂ solution, generating an AuNC with a uniform wall thickness and well defined pores at the corner sites.

Photothermal behavior of AuNCs: One of the most fascinating properties of AuNCs is Localized Surface Plasmon Resonance (LSPR), which refers to the scattering and absorption of incident light at a resonant frequency due to the collective oscillation of conduction electrons at the surface of the nanostructure [4]. LSPR peak position of AuNCs can be readily tuned by the composition, thickness, porosity of the walls and controlling the extent of the galvanic replacement reaction. At same time, the LSPR peak of AuNCs can be easily tuned into the transparent window (700–900 nm) of soft tissues, enabling an array of biomedical applications ranging from photothermal therapy to temperature-controlled drug release.

Applications of AuNCs

Drug delivery: The pores are very important to present in the cage formation, the pores in the walls of AuNCs offer easy and a quick a venue for the release and loading of various types of payloads. These kinds of pores can be designed in advance with the “open or close” gating capability by integration with stimuli-responsive materials to enable on-demand release for the applications in drug delivery [5].

Light detection: AuNCs can be used as a photo-sensitive electrical switch. These kind of devices can also be adapted for the detection of NIR light and light detection through integration with poly(vinylidenefluoride), due to its capability to convert thermal energy to electricity.

Water evaporation: One of the great applications, find in this field are seawater desalination and waste water purification through photothermal evaporation of water [6].

Phase transition: The photothermal effect associated with AuNCs has also been used to trigger the phase-transition of thermo-responsive materials. The phase transferred micropatterned ferroelectric film holds promise for application in NIR sensing and imaging [7].

Controlled release: The AuNC-triggered phase-transition of thermo-responsive materials can also be utilized to manage the release of therapeutic agents used for disease treatment. Thermo-responsive materials can be applied as a coating around or a filler inside AuNCs to serve as an “on or off” gate to regulate the release of payloads under NIR irradiation [8].

Release and decomposition: The photothermal effect associated with AuNCs can also be employed to decompose organic compounds for the production of reactive species such as radicals. For example, 2,2’-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) was encapsulated in AuNCs for the generation of reactive radicals and thereby eradication of cancer cells [9]. More significantly, the generation of reactive species with AuNCs through thermal decomposition of AIPH was oxygen independent, making this system suitable for cancer treatment under both normoxic and hypoxic conditions.

Photothermal therapy and potential image-guided treatment: AuNCs have received considerable attention indirectly eradicating cancer cells through localized hypothermia. Tuning their LSPR peaks into the transparent window of soft tissues in the NIR region makes this technique particularly viable for the treatment of malignance occurring deeply below the skin. Generally, AuNCs have bio-inertness, good biocompatibility and photo-stability, making them particularly attractive for the photothermal destruction of solid tumors. Encapsulation of therapeutic drugs into AuNCs will further allow for the combination therapy of photothermal treatment and temperature-controlled drug release. This type of nano sized material with multi-functional properties includes the imaging, drug delivery, controlled release, and photothermal therapy will be of great interest in nanomedicine.

Our SNB team have emphasize this research article to enrich our viewer's knowledge on the main synthetic approach of AuNCs and their photothermal behavior as well as related diverse applications of AuNCs. Perhaps, they will be able to find a way to move through this unique class of nanomaterials to be success for the next level.

References

J. Qiu, et al., Chem. Sci. (2020) DOI: 10.1039/d0sc05146b.
S. E. Skrabalak, et al., Nat. Protoc., 2, 2182 (2007).
X. Sun, et al., ACS Nano, 10, 8019 (2016).
E. Hutter and J. H. Fendler, Adv. Mater., 16, 1685 (2004).
S. Mura, et al., Nat. Mater., 12, 991 (2013).
T. Wu, et al., Mater. Today Energy, 12, 129 (2019).
J. Li, et al., Angew. Chem., Int. Ed., 55, 13828 (2016).
G. D. Moon, et al., J. Am. Chem. Soc., 133, 4762 (2011).
S. Shen, et al., Angew. Chem., Int. Ed., 56, 8801 (2017).

--- Dr. A. S. Ganeshraja

Author Profile

Comments

Electro-Organic Synthesis: Next Emerging Technique

Industrial developments, excessive energy consumption, sustainable technologies, environmental cleaning processes are major topics of political and social discourse. Current innovations are rated not only focusing on their benefit and utility but also concerning their eco-friendly approaches. The development of green technological processes is becoming more important and requires harmless energy sources. Particularly over the past decade, the severe limitations of fossil resources intensify the movement towards sustainable synthesis techniques with a strict cutback in the ecological footprint [ 1 ]. Electro-organic synthesis belongs to the synthetic organic chemistry discipline that facilities the direct use of electricity to generate valuable compounds. Hence, it is possible to transfer green aspects of sustainable energy sources to the whole production process [ 2 ]. Since the Kolbe’s discoveries of using electricity as a reagent for organic transformations over 170 years ago, ...

Designing of Corrosion Resistant Alloys via Percolation Theory

Canada and USA Scientists have reported on designing of corrosion-resistant alloys via percolation theory and published in Nature Materials on 01 February 2021. Nickel–chromium, Iron–chromium binary alloys can serve as the prototypical corrosion-resistant metals owing to its presence of a nanometre-thick protective passive oxide film. The main key criterion for good passive behavior is the passive film should be compromised via a scratch or abrasive wear that can be reformed with a little metal dissolution. This could be a principal reason for the stainless steels and other chromium containing alloys that are used for critical applications which ranges from nuclear reactor components to biomedical implants. A long-standing unanswered question in corrosion science is the unravelling of the compositional dependence of the electrochemical behavior of the alloys [ 1, 2 ]. The discovery of the family of these alloys were increased its rate with the advent of artificial intelligence, da...

AN ACT OF FACE MASK MATERIAL USED TO PROTECT US FROM SARS-COV-2

“ In the absence of a vaccine, or effective antiviral, one of our only remaining strategies for controlling COVID-19 is to physically block the spread of SARS-CoV-2 in the community ” On 11 March 2020, the World Health Organization (WHO) declared the COVID-19 outbreak a global pandemic [1] . In the absence of a vaccine, or effective antiviral, one of our only remaining strategies for controlling COVID-19 is to physically block the spread of SARS-CoV-2 in the community. Given that COVID-19 is a respiratory illness, the most effective physical defense likely involves widespread public use of face coverings, in conjunction with other control measures [ 2 ] . Face coverings (also variously referred to as face masks, nonmedical masks, community masks or barrier masks ) function primarily in source control; capturing droplets expelled by an infected individual [3] . Figure 1. DIY masks to protect against from viruses sounds like a crazy idea. source click here In the absence of an...

Novel Approach of Plastic Waste to Flash Graphene

Prof. Algozeeb and his research collaboration team have investigated an novel approach of upcycling plastic waste (PW) products to flash graphene (FG). This method relies on Flash Joule Heating (FJH) to convert PW into FG. A sequential direct current (DC) and alternating current (AC) flash is used in order to make a high-quality graphene. In this FJH process, they established without catalyst and works for PW mixtures that can make the process suitable for handling landfill PW. In 21 st century, PW pollution is considerable one among the various environmental issues. A very large fraction of PW ends up in the ocean, which leads to the formation of micro- and nanoplastics that threaten marine life, micro-organisms, useful bacteria, and humans. From the intense carbon footprint process, most of these synthesized plastics are used only once before dumping into landfills or water ways that terminate in the oceans. Hence, upcycling PW to higher value materials and chemicals is econ...

RECENT DEVELOPMENTS IN SPINTRONIC DEVICES

Spintronics is one of the emerging fields for the next-generation nanoelectronic devices that are used to reduce their power consumption, and increase their memory and processing capabilities. Such devices used for the spin degree of freedom of electrons and/or holes, which can also interact with their orbital moments [ 1 ]. However, for spintronic devices to meet the ever-increasing demands of the industry, innovation in terms of materials, processes, and circuits are required. Figure 1. Schematic diagram for major methods to generate a spin-polarised current [ 2 ]. Spin-polarised electrons can be generated in non-magnetic (NM) materials using the following methods [ 2 ]: spin injection from a ferromagnetic (FM), a magnetic field, an electric field, an electromagnetic wave introduction, a thermal gradient, Zeeman splitting, spin motive force, and mechanical rotation (see Figure 1 ). One of the most common methods is spin injection from a FM material, e.g., conventional FM meta...

Electromagnetic Field: Non-Chemical Water Treatment Technology

An interesting review report on “A critical review of the application of electromagnetic fields for scaling control in water systems: mechanisms, characterization, and operation” was reported by Lu Lin, Wenbin Jiang, Xuesong Xu and Pei Xu published in Nature Partner Journals Clean Water published on June 2020 [1] . Water is the precious matter in the world. source U.S. General Services Administration has interested on non-chemical water treatment technologies. It has mentioned following important points: n on-chemical technology promises to increase the period between required blow-down cycles, thus reducing water consumption , minimizes associated issues of chemical storage, handling, and disposal, and may permit on-site re-use of cooling-tower “blow-down” water as “grey water” , it promises to be life cycle cost effective based solely on the reduction in chemical costs , this technology may reduce or eliminate chemical costs, it may not reduce other contractor costs ...

Postdocs Crisis: The "Last Generation" of Scientists

Postdoctoral Researchers play a vital role in the research productivity of several countries and serving as leaders, mentors, guides, teachers, and scientists. These researchers have developed their own skills and preparing themself for their scientific research careers with various research groups worldwide. Even performing in a short term, they need to spend additional years in some special cases for succession in their research careers. Senior research investigators or leaders who have promised to their younger colleagues or students for a long term contract in the academics should find a new pathway to make it possible to stay and plan for their long-term career. Also, these investigators should be more flexible, patience, and supportive for everyone in their research groups. But the main key point which they should focus on that was the researchers who want to pursue fulfilling careers in science elsewhere need to be supported in all means, whatever matters, whoever may be, the ta...

Single-Atom Catalysis in Chemistry World

The recent interest on the heterogeneous single-atom catalysts (SACs) were composed of atomically dispersed active metal cen ters in catalyst research field, because of the increased atom utilization and unique catalytic properties of such materials, which differ greatly from those of conventional nano or subnano counter parts. In this case, the fabrication of SACs are challenging, especially in the case of noble metal based catalysts and many researches are ongoing in this field for the development of improved catalysts. Many chall enges have faced for the hybridization of controlling of single atoms in suitable host materials, but it has also equally opened with unique opportunities for catalyst design. SACs with atomically dispersed active metal centers on supports represent an intermediary between heterogeneous and homogeneous catalysis. Therefore, understanding the homogeneous catalysis prototype creates a great opportunity for designing SACs and developing related applications....

A Novel Green Synthesis of Au/TiO2 Nanocomposites

Prof. Lahiru A. Wijenayaka, Sri Lanka Institute of Nanotechnology (SLINTEC), Mahenwatte, Pitipana, Homagama, Sri Lanka and his collaboration team has reported on the interesting materials for effective environmental alternative remediation via nontoxic, low cost and eco-friendly methods dedicated to the scientific community. Here, a novel, facile, and green synthetic approach to synthesize gold nanoparticle decorated over TiO 2 (Au/TiO 2 ) nanocomposites for sustainable environmental development has been discussed [ 1 ] . Based on various metal oxide semiconductor (MOS) photocatalysts, titanium dioxide (TiO 2 ) is the most widely used, owing to its effective and excellent results in optical transmittance, high refractive index, chemical stability, concurrently being stable, nontoxic, and inexpensive [ 2 ]. They are highlighted with the following points: (i) Synthesis of the Au/TiO 2 nanocomposite, (ii) Microscopic characterization, (iii) Dye adsorption on Au/TiO 2 and (iv) Photoca...

Innovations of Integrated Artificial Intelligence

Artificial intelligence (AI) is the study of methods to imitate intelligent human behavior. AI is widely heralded as an ongoing “revolution” transforming science and society altogether [ 1 , 2 ]. While approaches to AI such as machine learning, deep learning and artificial neural networks are reshaping data processing and analysis [ 3 ], healthcare, transportation and the production chain [ 4 ]. Figure 1. Integrated concept of artificial intelligence. AI Ethics Guidelines National and international organizations (European Commission, Organisation for Economic Co-operation and Development (OECD), UK House of Lords, Singapore Commission) have responded to these concerns by developing ad hoc expert committees on AI, often mandated to draft policy documents in various countries. In 2018 alone, companies such as Google and SAP publicly released AI guidelines and principles. The advisory council on the ethical use of AI scientific team have announced that results reveal a global co...

Search This Blog