Innovations in nanotechnology and materials science

Nanoscience, the study of materials and phenomena at the nanometer scale, is an emerging discipline at the intersection of physics, chemistry, biology, and engineering that has profound implications across many industries. Nanoparticles, those that are between 1-100 nm, are driving research in this field. Their potential uses are so varied that it can be difficult to see where research efforts should be focused or in which field the next breakthrough may happen.

From drug delivery to environmental remediation, the possible applications of nanomaterials seem endless. This breadth presents challenges for researchers seeking to understand the most relevant discoveries and important new directions. To reveal the most significant trends in nanotechnology research, we applied a novel combination of natural language processing (NLP) and extensive manual curation by subject matter experts to the CAS Content Collection^TM, the largest human-curated repository of scientific publications. 

This allowed us to develop unique visualizations, termed CAS TrendScape^TM, of nanotechnology research trends and topics. With a deeper understanding of how nanotechnology is evolving, researchers can focus their efforts, learn from their fellow colleagues, and find their next innovation faster.

The advantages of nanomaterials

At the nanoscale, materials exhibit unique properties and behaviors that are distinct from their bulk or macroscale counterparts. Researchers can tailor their key properties by varying size, shape, and composition to achieve specific functions or make them suitable for applications in electronics, medicine, energy, and environmental remediation.

For example, nanomaterials’ high surface-to-volume ratio enhances catalytic activity, charge storage capacity, and ion storage capacity, which are important in energy conversion and storage applications. When developing nanomaterials, researchers can specify their conductivity, catalytic activity, optical properties, melting point, band gap, and more. The ability to customize properties, combined with their small size, makes nanomaterials valuable for biomedical applications like drug delivery and sensors.

CAS TrendScape of nanomaterials

Given their many possible applications,  the volume of research publications relating to nanomaterials is large — our analysis identified 3 million journals, patents, preprints, and conference proceedings published since 2003 containing nanoscale topics. Given this volume, manual analysis to find trends would be daunting. Instead, we used NLP analysis to more quickly and efficiently identify concepts growing significantly in the literature and visualize them in CAS TrendScape maps.

The CAS TrendScape is a useful tool that provides readers with a bird's eye view of the enormous landscape of a given field — in this instance, nanoscience. By organizing vast quantities of information into a structured hierarchy, it provides an easy-to-read visualization overview of the field. 

To develop these maps, our first step was to simplify the keyword analysis by reducing word variations (think of “dancing,” “dances,” and “danced,” which are different words in English but convey the same concept). We then used stemming and lemmatization text preprocessing techniques in Natural Language Toolkit (NLTK) on all word sequences, known as n-grams, containing two to six words from the abstract and title of all documents. Additionally, we only considered phrases found in over 100 documents.

This process narrowed the field to just over 300,000 candidate phrases. From there, we determined the number of documents in which each phrase appeared annually and calculated the year-over-year publication growth rate for each. A high publication growth rate often indicates that a topic is gaining interest or investment. 

Our team of scientists focused on the 20,000 phrases with the highest publication rates averaged over 2020-2022 for in-depth manual evaluation. In this way, we were able to analyze a large amount of information and narrow down from millions of documents to a clear picture of the most active research areas. The result is the CAS TrendScape visualization of topics with associated numbers of publications (see Figures 1, 2, and 4).

‍

Novel applications of nanotechnology

Our analysis revealed several important applications notable for their relative growth and publication volume over the last few years (see Figure 2).

One example is nanogenerators, which generate electrical energy from motion through charge separation that takes place when two surfaces interact or through deformation. Their growing frequency in literature seems to be driven by their ability to power wearable devices like sensors. 

We also see nanomaterials being studied in the context of catalysis to reduce CO₂ to useful chemicals or to capture and store it. CO₂ reduction is carried out via electrocatalytic, photocatalytic, and heterogeneous thermal catalytic processes.

Life sciences and biomedical applications have also driven significant growth in nanotechnology, notably in vaccines, nanozymes, and bioinks. Nanoparticle-based vaccines are an emerging area of research using liposomes, nanogels, micelles, and other nanoparticles as delivery vehicles for antigens and adjuvants. Nanovaccines can also be valuable as immunotherapeutic formulations against cancer.

Nanozymes are synthetic nanostructures that mimic natural enzymes, but their stability, tunable catalytic properties, and large-scale production capabilities provide advantages over their natural counterparts. Bioinks containing nanoparticles can be used in 3D bioprinting — an exciting range of applications that includes building cell culture scaffolds and 3D printing of organs. These use cases demonstrate the immense potential for nanoparticles in biomedicine.

To further visualize the interest in these applications, we plotted them based on their growth rates since 2019 (see Figure 3). The fastest-growing concepts are found in the upper left section — these are referenced in fewer publications but have a high growth rate. The gap between the relatively low number of publications and seemingly sudden and rapid increase in publications can be indicative of emergence. More mature concepts with lower growth rates are in the bottom right.

Critical materials in nanotechnology

When we examine the Materials branch of the CAS TrendScape in more detail, several key concepts emerge (see Figure 4).

MXenes are 2D inorganic materials growing in interest because of their uses in electrocatalysis, photocatalysis, and batteries. They’re well-suited to these applications due to their high surface area, electrical conductivity, and ability to be combined with other nanoscale materials such as carbon nanotubes.

We also observed covalent organic frameworks (COFs) as emerging materials in nanotechnology. COFs are 2D and 3D porous polymeric networks made of one or more covalently bonded monomers that act as catalysts. Since catalysts are a key application of nanotechnology, it makes sense that COFs would see complementary growth in this field. 

Related to biomedical applications, we see a number of materials emerging in the literature. Nanovesicles composed of lipids, polymers, proteins, or a combination thereof are an active area of research for delivering therapeutic or imaging contrast agents. 

Two natural materials used in nanoparticles are also gaining traction. The first is lignin, a complex organic polymer found in plant cells that provides structural support and rigidity. Lignin nanoparticles can be used as drug delivery carriers by encapsulating pharmaceutical ingredients. 

The second natural material is biochar, which is made through the pyrolysis of biomass. Its most prominent application is in the removal of pollutants from water, including heavy metals and organics. The adsorptive capacity of biochar can be enhanced by modifying it with metals or other chemicals. 

Similar to our analysis of applications, we plotted materials based on their growth rates to visualize new topics with high growth and more mature topics (see Figure 5).

Finding the information that matters

The future of nanomaterials research is extremely promising, and it’s clear that applications ranging from energy to medicine can benefit from breakthroughs in nanotechnology. However, the volume and diversity of materials science research also demonstrates why technology combined with human expertise is needed to effectively spot trends and emerging ideas.

Utilizing NLP and human curation together is more efficient and provides more relevant answers than either method on its own. In a field as varied as nanotechnology, the ability to cut through the noise and analyze millions of documents is critical. The next breakthrough application or material is hiding within the emerging research landscape, and every day CAS is working with innovators to apply knowledge management expertise and the latest technology to reveal them.