Joseph H Dumont

Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

Removal of intercalated water within graphitic sheets is critical to achieving high-performing oxygen reduction reaction catalysts. Graphitic materials are essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Further, durability testing showed E½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.

A graphite oxide (GO)-based remote readable tamper evident seal

This paper presents a prototype of a remotely readable graphite oxide (GO) paper-based tamper evident seal. The proposed device combines the tunable electrical properties offered by reduced graphite oxide (RGO) with a compressive sampling scheme. The benefit of using RGO as a tamper evident seal material is the sensitivity of its electrical properties to the common mechanisms adopted to defeat tamper-evident seals. RGOs electrical properties vary upon local stress or cracks induced by mechanical action (e.g., produced by shimming or lifting attacks). Further, modification of the seals electrical properties can result from the incidence of other defeat mechanisms, such as temperature changes, solvent treatment and steam application. The electrical tunability of RGO enables the engraving of a circuit on the area of the tamper evident seal intended to be exposed to malicious attacks. The operation of the tamper evident seal, as well as its remote communication functionality, is supervised by a microcontroller unit (MCU). The MCU uses the RGO-engraved circuitry to physically implement a compressive sampling acquisition procedure. The compressive sampling scheme provides the seal with self-authentication and self-state-of-health awareness capabilities. The prototype shows potential for use in low-power, embedded, remote-operation non-proliferation security related applications.

Performance assessment of a remotely readable graphite oxide (GO)-based tamper-evident seal

Tamper-evident seals are commonly used for non-proliferation applications. A properly engineered tamper-evident seal enables the detection of unauthorized access to a protected item or a secured zone. Tamper-evident seals must be susceptible to malicious attacks. These attacks should cause irreversible and detectable damage to the seals. At the same time, tamper-evident seals must demonstrate robustness to environmental changes in order to minimize false-positive and false-negative rates under real operating conditions. The architecture of the tamper-evident seal presented in this paper features a compressive sampling (CS) acquisition scheme, which provides the seal with a means for self- authentication and self-state of health awareness. The CS acquisition scheme is implemented using a micro-controller unit (MCU) and an array of resistors engraved on a graphite oxide (GO) film. CS enables compression and encryption of messages sent from the seal to the remote reader in a non-bit sensitive fashion. As already demonstrated in our previous work through the development of a simulation framework, the CS non-bit sensitive property ensures satisfactory reconstruction of the encrypted messages sent back to the reader when the resistance values of the resistor array are simultaneously affected by modest changes. This work investigates the resistive behavior of the reduced GO film to changes in temperature and humidity when tested in an environmental chamber. The goal is to characterize the humidity and temperature range for reliable operation of a GO-based seal.

A Remotely Readable, Self-authenticating Tamper Evident Seal Based on Graphene-based Materials and Compressive Sensing

Low-cost, high-precision patterning of flexible electrical components have gained special attention in many applications where multi-functional materials fuse structural support with electrical sensing. In particular, a number of structural health monitoring (SHM) applications call for the development of “sensing skin” technologies. One application that uses these technologies includes the development of next-generation tamper-evident seals (TES) that are capable of being read remotely. In our design, the state of the TES’s physical structure is monitored through an electrical circuit based on a conductive material. Electrical changes in the TES’s circuit correspond to material property changes induced by humidity, temperature, or chemical changes. Intrinsically unifying material and electrical properties, graphene and graphite derivatives promote simplistic manufacturing of flexible materials with unique electrical properties that are attractive for sensing skin applications. In addition to developing a functional graphenebased material, an encryption scheme to transmit the state of the material is devised utilizing compressive sensing. Our work focuses on the production of printable graphene-based materials and graphene-based/polymeric composites proficient for sensing environmental changes. Printing of functional complex graphene-based materials requires specific formulation while balancing electrical conductivity, formulation simplicity, solution viscosity, and printing compatibility. Production of electrically stable components on flexible substrates with programmable electrical properties will be key to using printed graphene-based materials in sensing skin applications. doi: 10.12783/SHM2015/269

A remote-readable graphite oxide (GO) based tamper-evident seal with self-reporting and self-authentication capabilities

The blossoming of sensing solutions based on the use of carbon materials and the pervasive exploration of compressed sensing (CS) for developing structural health monitoring applications suggest the possibility of combining these two research areas in a novel family of smart structures. Specifically, the authors propose an architecture for security-related applications that leverages the tunable electrical properties of a graphite oxide (GO) paper-based tamper-evident seal with a compressed-sensing (CS) encryption/authentication protocol. The electrical properties of GO are sensitive to the traditional methods that are commonly used to remove and replace paper-based tamper-evident seals (mechanical lifting, solvents, heat/cold temperature changes, steam). The sensitivity of the electro-chemical properties of GO to such malicious insults is exploited in this architecture. This is accomplished by using GO paper to physically realize the measurement matrix required to implement a compressive sampling procedure. The proposed architecture allows the seal to characterize its integrity, while simultaneously providing an encrypted/authentication feature making the seal difficult to counterfeit, spoof, or remove/replace. Traditional digital encryption/authentication techniques are often bit sensitive making them difficult to implement as part of a measurement process. CS is not bit sensitive and can tolerate deviation caused by noise and allows the seal to be robust with respect to environmental changes that can affect the electrical properties of the GO paper during normal operation. Further, the reduced amount of samples that need to be stored and transmitted makes the proposed solution highly attractive for power constrained applications where the seal is interrogated by a remote reader.

Prototyping and Testing of a Graphene-Oxide Tamper Evident Seal

Structural Health Monitoring (SHM) technology has great unexplored potential in security applications. Specifically breakthroughs in graphene-oxide (GO) damage-detecting skins coupled with nonlinear, sparse signal processing techniques being used for SHM lend themselves to addressing the need for low-power remotely-readable tamper-evident seals. Assessing the integrity of a tamper-evident seal is inherently an SHM problem. In this case damage is caused by a human adversary, not the environment. This paper presents a novel architecture that leverages the tunable electrical properties of a GO-paper-based seal with a compressed-sensing (CS) acquisition protocol. This architecture allows the seal to characterize its integrity, while simultaneously providing an encrypted authentication feature making the seal difficult to counterfeit and/or spoof. The electrical properties of GO are sensitive to the traditional methods used to attack paper-based seals (mechanical lifting, solvents, heat/cold, steam). This property of GO allows us to determine if a seal has been tampered with simply by measuring its electrical properties. Specific areas of focus addressed by this work include the quantitative analysis of the encryption/authentication capabilities provided by CS, and methods for enhancing the detection of cracks/cuts propagating through the sensitive GO paper.