Anti‐counterfeit labels protect many commercial goods, drugs, and currencies from counterfeiting activities. Recently, the designs of anti‐counterfeit labels have emerged utilizing surface‐enhanced ...Raman scattering (SERS) as a powerful technique, in which SERS‐active materials provide strong Raman signals of probe molecules. These signals are unique and, so far, have rarely been used in practical anti‐counterfeit labels applications. In this review, the general methodology of using Raman and SERS in designing anti‐counterfeit labels is first introduced. Then, two types of secret information in SERS labels, spectroscopic information and graphical information, are detailed and discussed with a focus on how the molecular information is encoded with SERS labels. Later, several advanced SERS labels are presented which combine existing security features such as barcode, quick response code, fluorescence, and unclonable features. Finally, the challenges in building usable SERS anti‐counterfeit labels are discussed and possible research directions are described.
Surface‐enhanced Raman scattering (SERS)‐based anti‐counterfeit labels are a new type of anti‐counterfeit label that has a high potential for future use in security applications. This review discusses various efforts and strategies in the development of SERS labels. These works enable the high novelty and high information capacity, which is of great importance to satisfy the need for security protection in the future.
Catalysts of oxygen reduction reaction (ORR) play key roles in renewable energy technologies such as metal-air batteries and fuel cells. Despite tremendous efforts, highly active catalysts with low ...cost remain elusive. This work used metal-organic frameworks to synthesize non-precious bimetallic carbon nanocomposites as efficient ORR catalysts. Although carbon-based Cu and Ni are good candidates, the hybrid nanocomposites take advantage of both metals to improve catalytic activity. The resulting molar ratio of Cu/Ni in the nanocomposites can be finely controlled by tuning the recipe of the precursors. Nanocomposites with a series of molar ratios were produced, and they exhibited much better ORR catalytic performance than their monometallic counterparts in terms of limited current density, onset potential and half-wave potential. In addition, their extraordinary stability in alkaline is superior to that of commercially-available Pt-based materials, which adds to the appeal of the bimetallic carbon nanocomposites as ORR catalysts. Their improved performance can be attributed to the synergetic effects of Cu and Ni, and the enhancement of the carbon matrix.
Sharp branches of gold nanostars are critical in tuning the plasmonic properties of these nanostars and maximizing the activities in surface-enhanced Raman scattering (SERS). The interaction between ...the capping ligands and nanostars plays an essential role in determining the morphology of the branches on the gold nanostars. In this Article, we show that 4-mercapto benzoic acid can effectively control the morphology of branched gold nanostars, and these gold nanostars can be used for the colloidal SERS detection of probe molecules at a nanomolar concentration. We also find that the sharp branches on gold nanostars will provide extra SERS activities as compared to the ones with a rough surface. Using the method of principal component analysis, we can easily distinguish the addition of 4-mercapto pyridine molecules at a concentration of 2 nM. Our work indicated the promising applications of these gold nanostars in colloidal SERS studies for various ultrasensitive chemical analyses.
A novel mixed matrix membrane (MMM) was prepared by incorporating polydopamine-coated metal organic framework (MOF) crystals of CAU-1-NH2 into a PMMA (polymethylmethacrylate) matrix. The MMM ...possesses the advantages of high O2 permeability, high capability of carbon dioxide capture, and excellent hydrophobic behavior. The MMM was assembled in the Li-air batteries which displayed promising electrochemical performance in the real ambient air with 30% relative humidity.
It remains challenging to prepare highly active and stable catalysts from earth-abundant elements for the oxygen reduction reaction (ORR). Herein we report a facile method to synthesize ...cost-effective heterogeneous C/α-MoC/Ag electrocatalysts. Rotating disc electrode (RDE) experiments revealed that the obtained C/α-MoC/Ag exhibited much superior catalytic performance for ORR than that of C/Ag, C/α-MoC, or even the conventional Pt/C. First-principles calculations indicated that the enhanced activity could be attributed to the efficient synergistic effects between Ag and α-MoC/C by which the energy barrier for O2 dissociation has been substantially reduced. Furthermore, Li–air and Al–air cells were assembled to demonstrate the unprecedented electrochemical performance of C/α-MoC/Ag nanocomposites surpassing the Pt/C. Thus experimental results and theoretical calculations together showed that the heterogeneous C/α-MoC/Ag nanocomposites are a promising alternative to platinum for applications in industrial metal-air batteries.
Anti-counterfeiting materials have received increasing attention due to their importance in the prevention of counterfeit activities and for the protection of intellectual properties. ...Surface-enhanced Raman scattering (SERS) has demonstrated excellent potential for anti-counterfeiting applications due to its ability to reveal molecular fingerprints, which is very suitable to encode secret information. The key materials to ensure strong SERS signals are the SERS-active plasmonic nanoparticles, which can possess SERS “hot spots” by their nanoscale curvatures or forming aggregates. However, the syntheses of plasmonic nanoparticles and their applications for SERS-based anti-counterfeiting labels are less explored. In this dissertation, I will first present a comprehensive review of the various types of SERS-based anti-counterfeit labels. Then, I will discuss a unique type of material, gold nanostars, about their syntheses and the morphology-dependent SERS properties. After that, a method of fabricating and recognizing SERS-based anti-counterfeit labels will be presented, where molecular mixtures were used to generate unique SERS spectra to encode secret information. These SERS-based labels could then be decoded by principal component analysis. Versatile forms of labels, including colloidal solutions, polymeric thin films, and writable inks, were developed to facilitate the practical applications of these labels. Furthermore, a fundamental study on the colloidal SERS substrates was implemented by investigating the surface adsorption of probe molecules on gold nanoparticles using an adsorption-centrifugation approach. Adsorbate-induced nanoparticle aggregations were explored, and the impact on SERS performance was studied. We found that certain dyes, such as methyl orange, can prevent the formation of nanoparticle aggregation and stabilize the existing aggregates. This discovery provides a great tool in developing stable colloidal SERS substrates for next-generation anti-counterfeit SERS labels.
Recently, surface-enhanced Raman scattering (SERS) joined other optical methods in making novel anticounterfeiting materials due to the fact that abundant molecular fingerprints in Raman spectra can ...be less susceptible to fraud. Using these molecular features, it is critical to make novel nanostructures with increased SERS enhancement and stability. Herein, we synthesized star-shaped gold nanoparticles as SERS substrates and applied various Raman probes with these gold nanostars to make SERS tags. The encoded molecular information was successfully decoded using principal component analysis (PCA). These colloidal tags can be further stabilized when embedded in a polymer matrix. We made a prototype ballpoint pen that can do simple writing with these secret SERS inks.
Star-shaped gold nanoparticles with encoded molecular information can be used in security inks for anticounterfeiting applications.
Counterfeiting has been a serious problem for the world’s economy and security. There is an urgent demand for the development of new approaches in anti-counterfeiting. In this study, we used ...surface-enhanced Raman scattering (SERS) spectra of desired molecules as anti-counterfeiting information. Gold nanostars (AuNSs) were used due to their controllable morphology and strong SERS activities. AuNSs were synthesized using a seed-mediated growth method and characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy and scanning electron microscopy (SEM). Compared to spherical gold nanoparticles, AuNSs have high SERS enhancements due to their branched morphology. We then explored a unique approach that can produce various SERS spectra with a “secret” combination of various Raman probe molecules. Furthermore, we demonstrated that principal component analysis (PCA) can be applied for information decoding. Our work indicated that this method has the capacity to make over a thousand anti-counterfeiting materials by using ten types of probe molecules. This capacity could be easily expanded by adding new types of Raman probe molecules or introducing concentration gradients. The stabilities of these anti-counterfeiting materials were further improved by the fabrication of nanocomposite thin films, in which the AuNSs and the Raman probe molecules were embedded into a polymer matrix. Overall, this approach of using SERS-active materials for anti-counterfeiting has a good stability and a high capacity toward information storage. Most importantly, such anti-counterfeiting approach is new, thus it is extremely hard for counterfeiters. With further optimization, we believe that our gold nanostar-based SERS-active nanocomposite materials could be very promising novel functional materials in the field of anti-counterfeiting.
A novel mixed matrix membrane (MMM) was prepared by incorporating polydopamine-coated metal organic framework (MOF) crystals of CAU-1-NH
2
into a PMMA (polymethylmethacrylate) matrix. The MMM ...possesses the advantages of high O
2
permeability, high capability of carbon dioxide capture, and excellent hydrophobic behavior. The MMM was assembled in the Li-air batteries which displayed promising electrochemical performance in the real ambient air with 30% relative humidity.
A novel oxygen selective membrane was prepared and assembled in Li-air batteries operating under real air conditions with 30% RH. Due to its high O
2
permeability, remarkable CO
2
capture ability and excellent hydrophobic behavior, extremely stable cycling performance was achieved.
A novel mixed matrix membrane (MMM) was prepared by incorporating polydopamine-coated metal organic framework (MOF) crystals of CAU-1-NH sub(2) into a PMMA (polymethylmethacrylate) matrix. The MMM ...possesses the advantages of high O sub(2) permeability, high capability of carbon dioxide capture, and excellent hydrophobic behavior. The MMM was assembled in the Li-air batteries which displayed promising electrochemical performance in the real ambient air with 30% relative humidity.
PDF
