Sensors and Actuators B 238 (2017) 880–887 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb High sensitivity bolometers from thymine functionalized multi-walled carbon nanotubes Guadalupe García-Valdivieso a , Hugo R. Navarro-Contreras a,∗ , Gustavo Vera-Reveles a,b , Francisco J. González a , Trevor J. Simmons c , Manuel Gutiérrez Hernández a , Mildred Quintana d , José G. Nieto Navarro a a Coordinación para la Innovación y Aplicación de la Ciencia y la Tecnología (CIACYT), Universidad Autónoma de San Luís Potosí, Álvaro Obregón 64, San Luis Potosí, S.L.P. 78000, Mexico b Departamento de Ciencias Básicas, Instituto Tecnológico de San Luis Potosí, Soledad de Graciano Sánchez, 78437, Mexico c Center for Future Energy Systems, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180, United States d Instituto de Física. Universidad Autónoma de San Luís Potosí, Álvaro Obregón 64, San Luis Potosí, S.L.P. 78000, Mexico a r t i c l e i n f o Article history: Received 18 April 2016 Received in revised form 27 June 2016 Accepted 16 July 2016 Available online 25 July 2016 Keywords: Bolometer Thymine Carbon nanotube TCR a b s t r a c t In this work, thin films of thymine functionalized MWNT (t-MWNT) were prepared and systematically characterized in their thermal and electrical response in order to determine the proper conditions for them to have optimum bolometric properties. It was found that t-MWNT, deposited in dried layers 5 × 6 mm and 0.53 ± 0.05 m in thickness, on top of silicon wafers, provided the best characteristics to function as bolometric materials. One of the key resultant figures of merit, the Temperature Coefficient of Resistance (TCR or ), which is measured in percent change of resistance per degree Kelvin was found to be −5.6 ± 0.1%/K. Typical measured response times of these thermal devices ranged from 0.8 to 1.6 ms. This indicates that these bolometer materials can be modulated at frequencies above 1 kHz. The responsivity (R v ) and specific detectivity (D*) at the optimal bias voltage of 1 V and at 100 Hz were R v = 252 ± 4 V/W, and D* = (2 ± 0.2) × 10 6 cmHz 1/2 /W. Both results are among the largest for MWNT based bolometer devices; however the specific detectivity observed is smaller than that for bolometric devices prepared with SWNT. The t-MWNT’s have their optimal specific detectivity response for 0.75 and 1.0 V bias voltages examined, in the frequency range above 1 kHz. © 2016 Elsevier B.V. All rights reserved. 1. Introduction The detection of terahertz (THz) and infrared radiation (IR) is of great relevance for a growing list of imaging, biomedical and indus- trial applications. Several examples are early detection of biological abnormalities in humans as well as in animals and living tissue sam- ples, night vision sensors, early warning fire detection systems, and search and rescue equipment. Bolometric detectors are primarily used for the detection of FIR and THz radiation. These devices oper- ate by absorbing incident radiation, which results in a small change of its temperature, which in turn produces a change in its electri- cal resistance. The resistance can increase or decrease depending on the Temperature Coefficient of Resistance (TCR) of the active material, which can be subsequently transduced, amplified, elec- tronically processed and digitally recorded. ∗ Corresponding author. Tel.: +52 444 8292358. E-mail address: hnavarro@uaslp.mx (H.R. Navarro-Contreras). In general, bolometers have smaller specific detectivities than optoelectronic devices, photoconductive or photovoltaic, however these last typically require cooling to operate efficiently. Therefore for many every day applications bolometers are the best practical option to detect electromagnetic FIR and THz radiation [1], where uncooled detectors are necessary. Researchers have previously reported that carbon nanotubes (CNT) have promising bolometric properties [2–4]. An excellent review of the state of the art of CNT uncooled photodetectors and bolometers, may be found in Ref. [5]. One wall CNT or SWNTs constitute quasi-one dimensional struc- tures with remarkable electric properties resulting from their fully conjugated pi network along with optical and mechanical charac- teristics advantageous for sensor technologies [3,4]. CNTs possess a large surface to volume ratio, chemical stability, tensile strength, and concomitantly large elastic response, making them attractive materials for many technological applications. The work reported herein takes advantage of the fact that CNTs have very large IR absorption coefficients, (larger than 70% in CNT layers of 100 nm in http://dx.doi.org/10.1016/j.snb.2016.07.081 0925-4005/© 2016 Elsevier B.V. All rights reserved.