There are several research papers and journals that can be beneficial for studying the Chemistry optional subject for UPSC. These resources provide in-depth knowledge and cover a wide range of topics in the field of Chemistry. Here are some recommended research papers and journals:

1. Journal of the American Chemical Society (JACS):
JACS is one of the most prestigious and widely recognized journals in the field of Chemistry. It publishes high-quality research articles, reviews, and perspectives covering various areas of Chemistry. This journal is known for its rigorous peer-review process and significant contributions to the advancement of the field.

2. Angewandte Chemie International Edition:
Angewandte Chemie is a leading international journal that publishes cutting-edge research in all areas of Chemistry. It features articles from different branches of Chemistry, including organic, inorganic, physical, and analytical chemistry. The journal emphasizes the practical applications of chemical research.

3. Chemical Reviews:
Chemical Reviews is a highly regarded journal that publishes comprehensive reviews on all aspects of Chemistry. It provides critical analysis, summaries, and evaluations of important research topics. This journal is an excellent resource for gaining a deep understanding of key concepts and developments in the field.

4. Accounts of Chemical Research:
Accounts of Chemical Research publishes concise and comprehensive articles that highlight recent advances and trends in various sub-disciplines of Chemistry. The journal focuses on the broader implications and significance of the research and provides insightful perspectives on the subject matter.

5. Nature Chemistry:
Nature Chemistry is a prestigious journal that publishes groundbreaking research across all areas of Chemistry. It features original research articles, reviews, and news highlighting important discoveries and advancements. This journal is known for its interdisciplinary approach and high-impact research publications.

6. Chemical Science:
Chemical Science is a flagship journal of the Royal Society of Chemistry. It publishes innovative and high-quality research across the breadth of Chemistry. The journal covers a wide range of topics and showcases the latest developments in the field.

It is important to note that these research papers and journals should be used in conjunction with standard textbooks and study materials to build a strong foundation in Chemistry. Reading and analyzing research papers can enhance critical thinking and provide a deeper understanding of the subject.