Purpose: This study aims to reveal the landscape and trends of graphene research in the world by using data from Chemical Abstracts Service (CAS).
Design/methodology/approach: Index data from CAS have been retrieved on 78,756 papers and 23,057 patents on graphene from 1985 to March 2016, and scientometric methods were used to analyze the growth and distribution of R&D output, topic distribution and evolution, and distribution and evolution of substance properties and roles.
Findings: In recent years R&D in graphene keeps in rapid growth, while China, South Korea and United States are the largest producers in research but China is relatively weak in patent applications in other countries. Research topics in graphene are continuously expanding from mechanical, material, and electrical properties to a diverse range of application areas such as batteries, capacitors, semiconductors, and sensors devices. The roles of emerging substances are increasing in Preparation and Biological Study. More techniques have been included to improve the preparation processes and applications of graphene in various fields.
Research limitations: Only data from CAS is used and some R&D activities solely reported through other channels may be missed. Also more detailed analysis need to be done to reveal the impact of research on development or vice verse, development dynamics among the players, and impact of emerging terms or substance roles on research and technology development.
Practical implications: This will provide a valuable reference for scientists and developers, R&D managers, R&D policy makers, industrial and business investers to understand the landscape and trends of graphene research. Its methodologies can be applied to other fields or with data from other similar sources.
Originality/value: The integrative use of indexing data on papers and patents of CAS and the systematic exploration of the distribution trends in output, topics, substance roles are distinctive and insightful.
Today, R&D plays important roles in enhancing national competitiveness and sustainability. Many traditionally scientifically under-developed countries are now catching up and the global R&D landscape has seen dramatic changes. Facing the continuing competition, researchers, technology innovators, and policy makers all need to grasp the structure and developments of global research and innovation, so dynamical monitoring and dignosing of research fields become a strategic endeavor at higher levels of research planning and policy making.
Materials science is the foundation for many emerging industries. Graphene (Novoselovl et al., 2004), due to its outstanding electrical, thermal, and optical properties, has great potential for applications in energy, environment, electronics, biology and other fields. As a result, graphene research is gaining intensive attention world-wide. Many countries have embarked on R&D prgrams on graphene to position themselves among the leaders.
Scientometric analysis has recently been applied to map global trends of graphene research using publications or patent data. Evidence from such analysis shows that graphene research increased over past 20 years and saw an up-ward burst in recent 5 years (Lv et al., 2011). However, exponential growth in published articles has met with a decreasing average citation per article and diminishing share of highly-cited publications (Klincewicz, 2016; Zheng, 2016). Some attributed recent rising number of publications on graphene to the fact that researchers working in carbon nanotubes gradually move towards study of graphene (Etxebarria, Gomez-Uranga, & Barrutia, 2012). The growth complexity may also be due to graphene’s growing applications in non-electronics areas, such as health, environment, and energy (Klincewicz, 2016).
Some bibliometric analysis studies on global graphene research also included patent data. Researchers investigated graphane-related patents, with parameters like the time of application, the technology fields the patents belong to, applicants (Zhao & Chen, 2016), subjects, patentee’s technical strength, and Highly Cited Patents, to reveal the innovation trends (Zheng, 2016; Le & Polytechnic, 2017). A few papers compared the publications and patents on graphene to reveal the relationship between research and innovation (Peng, 2016). Still, a detailed and large scale analysis of graphene R&D is needed to fully reveal the landscape (Li, 2015).
The current paper uses publication data for research and patent data for innovation to study the trends of graphene R&D. Both types of data are provided by Chemical Abstracts Service (Perianes-Rodriguez, Waltman, & Eck, 2016; Retrieved from http://www.cas.org/) (CAS) of the American Chemical Society. Using structured index data from CAS databases, this study focuses on the growth and distribution of R&D outputs, topic distribution and evolution, distribution and evolution of substance properties and applications, and other aspects of the global graphene R&D.
CAplus database was searched for documents including “graphene” (case insensitive) in their subject or concept metadata, along with documents using the CAS Registry number for substance of graphene in CAS Registry. A set of 78,756 articles wereretrieved by April 5, 2016 for those published from 1985 to March 2016. Types of publications include journal articles, preprints, conference articles, dissertations, and books. 23,057 patents were obtained by April 5, 2016 for those applied from 1997 to March 2016. XML data files from CAS weremapped into an internal processing file format. Then, CAS indexing terms for topic, concept, substance, commercial or government entity, source of publication, and various other data entities, were extracted for analysis.
The investigations were conducted as follows:
(1) Country/region distribution of publications and patents
A global map was drawn to illustrate the numbers of patents and publications of each country/region, using the country/region of the first author affiliation as the basis. Top five producer countries were identified for both publications and patents. Then, for top 5 countries, the ratio of patents applied in other four countries to the total patents in each country was calculated, to demonstrate the patent flow in major countries.
(2) Description of the leading organizations in R&D
Based on the number of papers or patents, we selected the top 20 research institutions with each assigned accordingly as university, research institute, or enterprise. In addition, we measured the year ranges that each organization has been active in research in graphene, and the percentage of output in the last three years to indicate the activeness of the institution. Moreover, using the concept indicators in publication metadata, we extracted the high-frequency concepts as top terms and high frequency concepts in last three years as recent terms, to demonstrate the hot research areas of the top 20 organizations. The IPC categories of patent applications are listed to show the technology area distribution in detail.
(3) Substaces and application roles distributions
Substances are indexed for papers and patents by CAS, and the roles of substances are identified and divided into super roles and specific roles. This enables exploration of the substances role distribution in graphene research. For the specific roles, the distribution by year of the top 20 roles were analyzed; for the super roles, role evolutions from 2010 to 2016 were studied via three time slices, respectively 2010-2011, 2012-2013, and 2014-2016 where data for 2016 was incomplete. Because the role change was not obvious before 2009, data for 2008-2009 was added only for reference.
(4) Subject clustering of publications and patents
Clustering of the publications and patents were conducted using the indexed concepts by CAS using the sofeware VOSviewer (Eck & Waltman, 2010, 2011). A visualized bibliometric network based on co-occurence (Eck & Waltman, 2009) was produced. Then, experts were invited to interpret the topics for each cluster. Furthermore, timelines were introduced to reveal the topics evolution. In addition, emerging terms, defined as those appering first time compared to all the early times, were detected for each of the periods of pre-2010, 2010-2011, 2012-2013, 2014-2016.
Figure 1 gives the overall growth of grapheme R&D. Publications or patents before 2000 were very limited, 336 and 2 respectively, so only data since 2000 were shown. The growth seemed very slow until the groundbreaking isolation of graphene for the first time in 2004 sparked a global explosion in graphene research. Both papers and patents started rapid increase since 2005, especially after 2010. Over 50 percent of papers and patents output were during 2014-2016, and the increase looks still strong, though some leveling-off may be ahead.
3.2.1 Overall country/region distribution
The country/region distribution of publications was produced as Figure 2. Those with total numbers of over 2000 are shown in red. Five top producers are China (excluding Hong Kong, Macao and Taiwan, similarly hereinafter), United States, South Korea, Japan and India. They together accounted for 64.3 percent of the global total. The distribution of patent applicant countries was also analyzed where the top five countries are China, South Korea, United States, Japan and Germany. They together accounted for over 90 percent of the global patents in graphene.
3.2.2 R&D distribution of top five countries by year
Figure 3 gives the relative outputs of the top five countries from 2000 to 2015. From the retrieved data, we know that the United States and Japan published their first papers in graphene in 1985 and 1992, respectively, and went strong until around 2010 when their publications began level-off and even began to decline after 2013. In contrast, publications from China has grown dramatically after 2010, surpassing the United States. The publications from South Korea overtook Japan since 2010, but increased only slowly afterwards, to be in similar strength as India in recent years. Nearly half of the publications from China and South Korea were produced during 2013-2015.
As for patent applications, data since 2001 were shown in Figure 4 for the top five countries identified in Figure 2. The United States and Japan applied their first patents in 1997 and 1999, respectively, but their applications began to drop considerably around 2008-2010. In contrast, the number of patents applied from China started since 2007 and increased dramatically ever since, with 2012 saw that China applied more than 50% of the world total, while the other four countries faced steady declination.
3.2.3 Patent application flows in the top five countries
Figure 5 illustrates the flows of patent applications among the top five countries. The width of the arrows is proportional to the patent applications originated from one country to be applied in other countries. The majority of patent applications flew to United States and China. Although the total number of patent applications of China is high, only 2.3 percent of them are done in other countries. In contrast, the ratios that Korea, United States, Japan and Germany applied patents in other four countries are 27.8%, 24.8%, 32.3% and 45.3%, respectively. While Chinese institutes applied the largest number of patents, most were applied only in China.
3.3.1 Top research organizations
Table 1 lists the top 20 organizations in terms of publications, 11 are in China, three in the United States, two in South Korea, two in Singapore, one each from Japan and Russia. 18 out of the 20 are universities, while the remaining two are research institutes, indicating that graphene research is dominated by universities and research institutes.
Major research topics for each of the top 20 were obtained using methods described in Section 2. It shows that Chinese organizations mainly focus on sensors, electronics and photovoltaics, and batteries, while US ones concentrated more on photoelectric properties, electronic structure, thin film transistors and semiconductors. Organizations from South Korea deal more on capacitors while the Japanes one focuses on electric properties.
3.3.2 Top patent applicants
20 top global graphene patent applicants are listed in Table 2. Among them, 14 were from China, four from South Korea and two from the United States. In addition, 15 assignees were universities or research institutes while the other five were enterprises.The top five were Chinese Academy of Sciences, Samsung Electronics, Ocean’s King Lighting Science & Technology, Zhejiang University, and LG Electronics. The major technology topics of patent applications for the top 20 organizations indicated that Chinese assignees applied patents more in preparation, batteries and composites, while the assignees from South Korea focused mainly in semiconductors devices and batteries and those from the United States primarily in semiconductors devices.
The Discipline/Specialty Sections assigned by CAS to each indexed paper and patent were used to give an overview of the research areas of graphene. As shown in Figures 6, graphene R&D have scattered in many Sections such as Electric Phenomena, Electrochemical, Radiational, and Thermal Energy Technology, Optical, Electron, and Mass Spectroscopy and Other Related Properties, Surface Chemistry and Colloids, Ceramics, General Physical Chemistry, Biochemical Methods, Plastics Manufacture and Processing, Electrochemistry and Magnetic Phenomena. Of these, there is a gradual increase in R&D effort in Electrochemical, Radiational, and Thermal Energy Technology, Optical, Electron, and Mass Spectroscopy and Other Related Properties, Biochemical Methods, Plastics Manufacture and Processing, and Electrochemistry, as indicated by the percentage change of coverage in these areas over the years.
Analysis of technological areas was made using IPC (International Patent Classifications) data of the patents data, as shown in Figure 7. The highest concentrations are in graphene preparation, composites and batteries.
In 2013-2015, innovation in the following IPC categories are active: C08K0013/06 (Pretreated ingredients), C09D0007/12 (Other additives), H01M0010/0525 (Lithium batteries), and H01G0011/86 (Capacitors, specially adapted for electrodes), while the number of applications in the following IPC categories are relatively low: H01B0001/04 (Mainly consisting of carbon-silicon compounds, carbon, or silicon), and H01B0013/00 (Apparatus or processes specially adapted for manufacturing conductors or cables). The patents in the nanocomposites related IPC B82Y0030/00 (Nanotechnology for materials or surface science) and B82Y0040/00 (Manufacture or treatment of nanostructures) declined since 2012.
3.5.1 Research topics evolution
The evolution of graphene research topics was analyzed using the concepts of papers and patents indexed by CAS. Considering the dramatic increase after 2010, the data set was divided into two time windows, 1985-2009 and 2010-2016 (Figure 8 and 9, respectively). Two networks show that before 2009, graphene research mainly focused on the mechanical and other properties and electrical properties. But since 2010, it has extended continuously into a diverse range of potential applications, such as batteries, capacitors, semiconductors, and sensorsdevices.
3.5.2 Emerging terms in graphene R&D
Indexed concepts in papers and patents were analyzed to detect emerging concepts and their percentages among all the indexed terms, in four periods: before 2009, 2010-2011, 2012-2013, and 2014 and after, as in Figure 10. The sizes of the pie charts are proportional to the numbers of concepts and the orange color parts represent the percentages of emerging terms. Emerging concepts increased remarkably after 2010 and the trend correlated with widening of research and innovation into diverse fields, indicating the vitality of graphene R&D and potential for new break-throughs.
3.6.1 Substance role distribution
Substance roles indexed by CAS in the papers and patents were examined (Figure 11). 39.9 percent are USES, including TEM (Technical or Engineered Material Use), MOA (Modifier or Additive Use), CAT (Catalyst Use), NUU (Other Use, Unclassified); 20.8 percent are Special, including PRP (Properties) and NAN (Nanoscale Substances/Materials); 18.6 percent are PROC (Process), including PEP (Physical, Engineering or Chemical Process) and REM (Removal or Disposal).
3.6.2 Subtances role distribution evolution
Time distribution for substances roles was given in Figure 12. PRP (Properties) has declined since 2006; NAN (Nanoscale Substances/Materials), IMF (Industrial Manufacture), RGT (Reagent), CAT (Catalyst Use) have decreased since 2009; PEP (Physical, Engineering or Chemical Process) has remained constant since 2011; TEM (Technical or Engineered Material Use), ANT (Analyte), BSU (Biological Study, Unclassified), POF (Polymer in Formulation) have decreased since 2012. In contrast, BUU (Biological Use, Unclassified) has increased since 2008, MOA (Modifier or Additive Use), POL (Pollutant) and REM (Removal or Disposal) grew year on year. In general, the main roles declined recently while roles in Biological Use, Modifier or Additive Use, Pollutant, Removal or Disposal have become new focuses.
3.6.3 Evolution of emerging substance roles
Time slice analysis was used to examine the evolution of emerging substance roles in graphene research (Figure 13). Based on the emerging substances, roles in USES and PROC (Process) have declined in recent years. On the contrary, the roles in PREP (Preparation) and BIOL (Biological Study) increased over time.
(1) In recent years, the numbers of both papers and patents in graphene continued their increases, indicating that R&D in graphene is still growing.
(2) China, United States, South Korea and Japan hold considerable technological advantages. United States and Japan developed their research and innovation earlier than China and South Korea, but China has become the largest R&D producer in recent years.
(3) Major Chinese graphene R&D actors are mainly universities and research institutes, while the R&D efforts in South Korea and the United States are dominated by enterprises. Chinese applications for patents concentrated mainly on preparation, batteries and composites, whereas South Korean organizations applied for patents mainly in semiconductor devices and batteries and US organizations did so primarily in semiconductor devices.
(4) The industrialized application of graphene materials is continuously expanding from mechanical, material, and electrical properties to a diverse range of potential applications such as batteries, capacitors, semiconductors, sensors, and semiconductors devices. The constant occurrences of the emerging terms in recent years also indicate a robust and diversifying R&D field.
(5) The roles of emerging substance roles tend to increase in Preparation and Biological Study over time, suggesting that the innovative application of graphene has caught the attention. And, it seems that the technology for preparing graphene materials will still be a major focus for the near future. Wide application of graphene in fields such as energy, biology, electronics and nano-composite materials, requires low-cost, green preparation processes, high-quality fine structure control and multilevel multifunctional assembly and integration. Development, improvement and optimization of preparation methods and techniques will be needed to maximize all the outstanding qualities of graphene.
In conclusion, graphene research and development has shown promising application potential across a wide range of fields, but challenges still exist in technological breakthrough in its preparation methods and processes in order to realize its industrialization for leading innovation in next-generation materials.
Lixue Zou (email@example.com, corresponding author) conceived and designed the analysis, contributed data or analysis tools, performed the analysis and wrote the paper. Li Wang (firstname.lastname@example.org) conceived and designed the analysis, contributed data or analysis tools. Yingqi Wu (email@example.com), Caroline Ma (firstname.lastname@example.org) and Sunny Yu (email@example.com) collected the data. Xiwen Liu (firstname.lastname@example.org) conceived and designed the analysis.
Special acknowledgement is to Mr. Matthew Toussant who gave us considerable guidance on project planning and implementation, Mrs. Cynthia Liu and Mr. Todd Chamberlain who supported us with data provision, and the experts in the field of graphene provided the detailed scientific interpretation.
The authors have declared that no competing interests exist.
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